changeset 19:5f9a40d6991b

Import SD handling from http://www.roland-riegel.de/sd-reader/index.html Use smaller build options
author Matt Johnston <matt@ucc.asn.au>
date Tue, 25 Jun 2013 13:55:11 +0800
parents 021e6e0006f4
children 534009795508
files Makefile byteordering.c byteordering.h fat.c fat.h fat_config.h main.c partition.c partition.h partition_config.h sd-reader_config.h sd_raw.c sd_raw.h sd_raw_config.h
diffstat 14 files changed, 4927 insertions(+), 6 deletions(-) [+]
line wrap: on
line diff
--- a/Makefile	Thu Jun 13 23:44:59 2013 +0800
+++ b/Makefile	Tue Jun 25 13:55:11 2013 +0800
@@ -17,16 +17,19 @@
 #                   default_serial = "avrdoper"
 # FUSES ........ Parameters for avrdude to flash the fuses appropriately.
 
-DEVICE     = atmega328
+DEVICE     = atmega328p
 PROGDEVICE     = atmega328p
 CLOCK      = 4915200
 PROGRAMMER = #-c stk500v2 -P avrdoper
 PROGRAMMER = -c stk500 -P ~/dev/stk500 -p $(PROGDEVICE)  -B 2
 SOURCE_1WIRE = onewire.c simple_ds18b20.c crc8.c
 SOURCE_CRYPTO = hmac-sha1.c sha1-asm.S aes.c
+SOURCE_SD = byteordering.c fat.c  partition.c sd_raw.c 
 SOURCE    = main.c
-SOURCE += $(SOURCE_CRYPTO)
-LIBS       = -lm
+SOURCE += $(SOURCE_CRYPTO) $(SOURCE_SD)
+LIBS       = 
+
+OBJECTS := $(patsubst %.c,%.o,$(patsubst %.S,%.o,$(SOURCE)))
 
 # default but 2mhz
 FUSES      = -U hfuse:w:0xd9:m -U lfuse:w:0x77:m -U efuse:w:0xfd:m
@@ -61,9 +64,12 @@
 
 # Tune the lines below only if you know what you are doing:
 
+SHELL := /bin/bash
+export PATH := $(PATH):/usr/local/CrossPack-AVR/bin/
+
 AVRDUDE = avrdude $(PROGRAMMER) 
 #COMPILE = avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -g -std=c99 -mcall-prologues -fdata-sections -ffunction-sections  -Wl,--gc-sections -Wl,--relax -fwhole-program  -Wl,-u,vfprintf -lprintf_flt -lm
-COMPILE = /usr/local/CrossPack-AVR/bin/avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -g -std=c99 -Wl,-u,vfprintf -lprintf_flt -lm
+COMPILE = /usr/local/CrossPack-AVR/bin/avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -g -std=c99  -mcall-prologues -fdata-sections -ffunction-sections  -Wl,--gc-sections -Wl,--relax -fwhole-program -flto
 
 # symbolic targets:
 all:	main.hex
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/byteordering.c	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,110 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#include "byteordering.h"
+
+/**
+ * \addtogroup byteordering
+ *
+ * Architecture-dependent handling of byte-ordering.
+ *
+ * @{
+ */
+/**
+ * \file
+ * Byte-order handling implementation (license: GPLv2 or LGPLv2.1)
+ *
+ * \author Roland Riegel
+ */
+
+#if DOXYGEN || SWAP_NEEDED
+
+/**
+ * \internal
+ * Swaps the bytes of a 16-bit integer.
+ *
+ * \param[in] i A 16-bit integer which to swap.
+ * \returns The swapped 16-bit integer.
+ */
+uint16_t swap16(uint16_t i)
+{
+    return SWAP16(i);
+}
+
+/**
+ * \internal
+ * Swaps the bytes of a 32-bit integer.
+ *
+ * \param[in] i A 32-bit integer which to swap.
+ * \returns The swapped 32-bit integer.
+ */
+uint32_t swap32(uint32_t i)
+{
+    return SWAP32(i);
+}
+
+#endif
+
+/**
+ * Reads a 16-bit integer from memory in little-endian byte order.
+ *
+ * \param[in] p Pointer from where to read the integer.
+ * \returns The 16-bit integer read from memory.
+ */
+uint16_t read16(const uint8_t* p)
+{
+    return (((uint16_t) p[1]) << 8) |
+           (((uint16_t) p[0]) << 0);
+}
+
+/**
+ * Reads a 32-bit integer from memory in little-endian byte order.
+ *
+ * \param[in] p Pointer from where to read the integer.
+ * \returns The 32-bit integer read from memory.
+ */
+uint32_t read32(const uint8_t* p)
+{
+    return (((uint32_t) p[3]) << 24) |
+           (((uint32_t) p[2]) << 16) |
+           (((uint32_t) p[1]) <<  8) |
+           (((uint32_t) p[0]) <<  0);
+}
+
+/**
+ * Writes a 16-bit integer into memory in little-endian byte order.
+ *
+ * \param[in] p Pointer where to write the integer to.
+ * \param[in] i The 16-bit integer to write.
+ */
+void write16(uint8_t* p, uint16_t i)
+{
+    p[1] = (uint8_t) ((i & 0xff00) >> 8);
+    p[0] = (uint8_t) ((i & 0x00ff) >> 0);
+}
+
+/**
+ * Writes a 32-bit integer into memory in little-endian byte order.
+ *
+ * \param[in] p Pointer where to write the integer to.
+ * \param[in] i The 32-bit integer to write.
+ */
+void write32(uint8_t* p, uint32_t i)
+{
+    p[3] = (uint8_t) ((i & 0xff000000) >> 24);
+    p[2] = (uint8_t) ((i & 0x00ff0000) >> 16);
+    p[1] = (uint8_t) ((i & 0x0000ff00) >>  8);
+    p[0] = (uint8_t) ((i & 0x000000ff) >>  0);
+}
+
+/**
+ * @}
+ */
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/byteordering.h	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,188 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef BYTEORDERING_H
+#define BYTEORDERING_H
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * \addtogroup byteordering
+ *
+ * @{
+ */
+/**
+ * \file
+ * Byte-order handling header (license: GPLv2 or LGPLv2.1)
+ *
+ * \author Roland Riegel
+ */
+
+#define SWAP16(val) ((((uint16_t) (val)) << 8) | \
+                     (((uint16_t) (val)) >> 8)   \
+                    )
+#define SWAP32(val) (((((uint32_t) (val)) & 0x000000ff) << 24) | \
+                     ((((uint32_t) (val)) & 0x0000ff00) <<  8) | \
+                     ((((uint32_t) (val)) & 0x00ff0000) >>  8) | \
+                     ((((uint32_t) (val)) & 0xff000000) >> 24)   \
+                    )
+
+#if LITTLE_ENDIAN || __AVR__
+#define SWAP_NEEDED 0
+#elif BIG_ENDIAN
+#define SWAP_NEEDED 1
+#else
+#error "Endianess undefined! Please define LITTLE_ENDIAN=1 or BIG_ENDIAN=1."
+#endif
+
+/**
+ * \def HTOL16(val)
+ *
+ * Converts a 16-bit integer from host byte order to little-endian byte order.
+ *
+ * Use this macro for compile time constants only. For variable values
+ * use the function htol16() instead. This saves code size.
+ *
+ * \param[in] val A 16-bit integer in host byte order.
+ * \returns The given 16-bit integer converted to little-endian byte order.
+ */
+/**
+ * \def HTOL32(val)
+ *
+ * Converts a 32-bit integer from host byte order to little-endian byte order.
+ *
+ * Use this macro for compile time constants only. For variable values
+ * use the function htol32() instead. This saves code size.
+ *
+ * \param[in] val A 32-bit integer in host byte order.
+ * \returns The given 32-bit integer converted to little-endian byte order.
+ */
+/**
+ * \def LTOH16(val)
+ *
+ * Converts a 16-bit integer from little-endian byte order to host byte order.
+ *
+ * Use this macro for compile time constants only. For variable values
+ * use the function ltoh16() instead. This saves code size.
+ *
+ * \param[in] val A 16-bit integer in little-endian byte order.
+ * \returns The given 16-bit integer converted to host byte order.
+ */
+/**
+ * \def LTOH32(val)
+ *
+ * Converts a 32-bit integer from little-endian byte order to host byte order.
+ *
+ * Use this macro for compile time constants only. For variable values
+ * use the function ltoh32() instead. This saves code size.
+ *
+ * \param[in] val A 32-bit integer in little-endian byte order.
+ * \returns The given 32-bit integer converted to host byte order.
+ */
+
+#if SWAP_NEEDED
+#define HTOL16(val) SWAP16(val)
+#define HTOL32(val) SWAP32(val)
+#define LTOH16(val) SWAP16(val)
+#define LTOH32(val) SWAP32(val)
+#else
+#define HTOL16(val) (val)
+#define HTOL32(val) (val)
+#define LTOH16(val) (val)
+#define LTOH32(val) (val)
+#endif
+
+#if DOXYGEN
+
+/**
+ * Converts a 16-bit integer from host byte order to little-endian byte order.
+ *
+ * Use this function on variable values instead of the
+ * macro HTOL16(). This saves code size.
+ *
+ * \param[in] h A 16-bit integer in host byte order.
+ * \returns The given 16-bit integer converted to little-endian byte order.
+ */
+uint16_t htol16(uint16_t h);
+
+/**
+ * Converts a 32-bit integer from host byte order to little-endian byte order.
+ *
+ * Use this function on variable values instead of the
+ * macro HTOL32(). This saves code size.
+ *
+ * \param[in] h A 32-bit integer in host byte order.
+ * \returns The given 32-bit integer converted to little-endian byte order.
+ */
+uint32_t htol32(uint32_t h);
+
+/**
+ * Converts a 16-bit integer from little-endian byte order to host byte order.
+ *
+ * Use this function on variable values instead of the
+ * macro LTOH16(). This saves code size.
+ *
+ * \param[in] l A 16-bit integer in little-endian byte order.
+ * \returns The given 16-bit integer converted to host byte order.
+ */
+uint16_t ltoh16(uint16_t l);
+
+/**
+ * Converts a 32-bit integer from little-endian byte order to host byte order.
+ *
+ * Use this function on variable values instead of the
+ * macro LTOH32(). This saves code size.
+ *
+ * \param[in] l A 32-bit integer in little-endian byte order.
+ * \returns The given 32-bit integer converted to host byte order.
+ */
+uint32_t ltoh32(uint32_t l);
+
+#elif SWAP_NEEDED
+
+#define htol16(h) swap16(h)
+#define htol32(h) swap32(h)
+#define ltoh16(l) swap16(l)
+#define ltoh32(l) swap32(l)
+
+#else
+
+#define htol16(h) (h)
+#define htol32(h) (h)
+#define ltoh16(l) (l)
+#define ltoh32(l) (l)
+
+#endif
+
+uint16_t read16(const uint8_t* p);
+uint32_t read32(const uint8_t* p);
+void write16(uint8_t* p, uint16_t i);
+void write32(uint8_t* p, uint32_t i);
+
+/**
+ * @}
+ */
+
+#if SWAP_NEEDED
+uint16_t swap16(uint16_t i);
+uint32_t swap32(uint32_t i);
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/fat.c	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,2551 @@
+
+/* 
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#include "byteordering.h"
+#include "partition.h"
+#include "fat.h"
+#include "fat_config.h"
+#include "sd-reader_config.h"
+
+#include <string.h>
+
+#if USE_DYNAMIC_MEMORY
+    #include <stdlib.h>
+#endif
+
+/**
+ * \addtogroup fat FAT support
+ *
+ * This module implements FAT16/FAT32 read and write access.
+ * 
+ * The following features are supported:
+ * - File names up to 31 characters long.
+ * - Unlimited depth of subdirectories.
+ * - Short 8.3 and long filenames.
+ * - Creating and deleting files.
+ * - Reading and writing from and to files.
+ * - File resizing.
+ * - File sizes of up to 4 gigabytes.
+ * 
+ * @{
+ */
+/**
+ * \file
+ * FAT implementation (license: GPLv2 or LGPLv2.1)
+ *
+ * \author Roland Riegel
+ */
+
+/**
+ * \addtogroup fat_config FAT configuration
+ * Preprocessor defines to configure the FAT implementation.
+ */
+
+/**
+ * \addtogroup fat_fs FAT access
+ * Basic functions for handling a FAT filesystem.
+ */
+
+/**
+ * \addtogroup fat_file FAT file functions
+ * Functions for managing files.
+ */
+
+/**
+ * \addtogroup fat_dir FAT directory functions
+ * Functions for managing directories.
+ */
+
+/**
+ * @}
+ */
+
+#define FAT16_CLUSTER_FREE 0x0000
+#define FAT16_CLUSTER_RESERVED_MIN 0xfff0
+#define FAT16_CLUSTER_RESERVED_MAX 0xfff6
+#define FAT16_CLUSTER_BAD 0xfff7
+#define FAT16_CLUSTER_LAST_MIN 0xfff8
+#define FAT16_CLUSTER_LAST_MAX 0xffff
+
+#define FAT32_CLUSTER_FREE 0x00000000
+#define FAT32_CLUSTER_RESERVED_MIN 0x0ffffff0
+#define FAT32_CLUSTER_RESERVED_MAX 0x0ffffff6
+#define FAT32_CLUSTER_BAD 0x0ffffff7
+#define FAT32_CLUSTER_LAST_MIN 0x0ffffff8
+#define FAT32_CLUSTER_LAST_MAX 0x0fffffff
+
+#define FAT_DIRENTRY_DELETED 0xe5
+#define FAT_DIRENTRY_LFNLAST (1 << 6)
+#define FAT_DIRENTRY_LFNSEQMASK ((1 << 6) - 1)
+
+/* Each entry within the directory table has a size of 32 bytes
+ * and either contains a 8.3 DOS-style file name or a part of a
+ * long file name, which may consist of several directory table
+ * entries at once.
+ *
+ * multi-byte integer values are stored little-endian!
+ *
+ * 8.3 file name entry:
+ * ====================
+ * offset  length  description
+ *      0       8  name (space padded)
+ *      8       3  extension (space padded)
+ *     11       1  attributes (FAT_ATTRIB_*)
+ *
+ * long file name (lfn) entry ordering for a single file name:
+ * ===========================================================
+ * LFN entry n
+ *     ...
+ * LFN entry 2
+ * LFN entry 1
+ * 8.3 entry (see above)
+ * 
+ * lfn entry:
+ * ==========
+ * offset  length  description
+ *      0       1  ordinal field
+ *      1       2  unicode character 1
+ *      3       3  unicode character 2
+ *      5       3  unicode character 3
+ *      7       3  unicode character 4
+ *      9       3  unicode character 5
+ *     11       1  attribute (always 0x0f)
+ *     12       1  type (reserved, always 0)
+ *     13       1  checksum
+ *     14       2  unicode character 6
+ *     16       2  unicode character 7
+ *     18       2  unicode character 8
+ *     20       2  unicode character 9
+ *     22       2  unicode character 10
+ *     24       2  unicode character 11
+ *     26       2  cluster (unused, always 0)
+ *     28       2  unicode character 12
+ *     30       2  unicode character 13
+ * 
+ * The ordinal field contains a descending number, from n to 1.
+ * For the n'th lfn entry the ordinal field is or'ed with 0x40.
+ * For deleted lfn entries, the ordinal field is set to 0xe5.
+ */
+
+struct fat_header_struct
+{
+    offset_t size;
+
+    offset_t fat_offset;
+    uint32_t fat_size;
+
+    uint16_t sector_size;
+    uint16_t cluster_size;
+
+    offset_t cluster_zero_offset;
+
+    offset_t root_dir_offset;
+#if FAT_FAT32_SUPPORT
+    cluster_t root_dir_cluster;
+#endif
+};
+
+struct fat_fs_struct
+{
+    struct partition_struct* partition;
+    struct fat_header_struct header;
+    cluster_t cluster_free;
+};
+
+struct fat_file_struct
+{
+    struct fat_fs_struct* fs;
+    struct fat_dir_entry_struct dir_entry;
+    offset_t pos;
+    cluster_t pos_cluster;
+};
+
+struct fat_dir_struct
+{
+    struct fat_fs_struct* fs;
+    struct fat_dir_entry_struct dir_entry;
+    cluster_t entry_cluster;
+    uint16_t entry_offset;
+};
+
+struct fat_read_dir_callback_arg
+{
+    struct fat_dir_entry_struct* dir_entry;
+    uintptr_t bytes_read;
+#if FAT_LFN_SUPPORT
+    uint8_t checksum;
+#endif
+    uint8_t finished;
+};
+
+struct fat_usage_count_callback_arg
+{
+    cluster_t cluster_count;
+    uintptr_t buffer_size;
+};
+
+#if !USE_DYNAMIC_MEMORY
+static struct fat_fs_struct fat_fs_handles[FAT_FS_COUNT];
+static struct fat_file_struct fat_file_handles[FAT_FILE_COUNT];
+static struct fat_dir_struct fat_dir_handles[FAT_DIR_COUNT];
+#endif
+
+static uint8_t fat_read_header(struct fat_fs_struct* fs);
+static cluster_t fat_get_next_cluster(const struct fat_fs_struct* fs, cluster_t cluster_num);
+static offset_t fat_cluster_offset(const struct fat_fs_struct* fs, cluster_t cluster_num);
+static uint8_t fat_dir_entry_read_callback(uint8_t* buffer, offset_t offset, void* p);
+#if FAT_LFN_SUPPORT
+static uint8_t fat_calc_83_checksum(const uint8_t* file_name_83);
+#endif
+
+static uint8_t fat_get_fs_free_16_callback(uint8_t* buffer, offset_t offset, void* p);
+#if FAT_FAT32_SUPPORT
+static uint8_t fat_get_fs_free_32_callback(uint8_t* buffer, offset_t offset, void* p);
+#endif
+
+#if FAT_WRITE_SUPPORT
+static cluster_t fat_append_clusters(struct fat_fs_struct* fs, cluster_t cluster_num, cluster_t count);
+static uint8_t fat_free_clusters(struct fat_fs_struct* fs, cluster_t cluster_num);
+static uint8_t fat_terminate_clusters(struct fat_fs_struct* fs, cluster_t cluster_num);
+static uint8_t fat_clear_cluster(const struct fat_fs_struct* fs, cluster_t cluster_num);
+static uintptr_t fat_clear_cluster_callback(uint8_t* buffer, offset_t offset, void* p);
+static offset_t fat_find_offset_for_dir_entry(struct fat_fs_struct* fs, const struct fat_dir_struct* parent, const struct fat_dir_entry_struct* dir_entry);
+static uint8_t fat_write_dir_entry(const struct fat_fs_struct* fs, struct fat_dir_entry_struct* dir_entry);
+#if FAT_DATETIME_SUPPORT
+static void fat_set_file_modification_date(struct fat_dir_entry_struct* dir_entry, uint16_t year, uint8_t month, uint8_t day);
+static void fat_set_file_modification_time(struct fat_dir_entry_struct* dir_entry, uint8_t hour, uint8_t min, uint8_t sec);
+#endif
+#endif
+
+/**
+ * \ingroup fat_fs
+ * Opens a FAT filesystem.
+ *
+ * \param[in] partition Discriptor of partition on which the filesystem resides.
+ * \returns 0 on error, a FAT filesystem descriptor on success.
+ * \see fat_close
+ */
+struct fat_fs_struct* fat_open(struct partition_struct* partition)
+{
+    if(!partition ||
+#if FAT_WRITE_SUPPORT
+       !partition->device_write ||
+       !partition->device_write_interval
+#else
+       0
+#endif
+      )
+        return 0;
+
+#if USE_DYNAMIC_MEMORY
+    struct fat_fs_struct* fs = malloc(sizeof(*fs));
+    if(!fs)
+        return 0;
+#else
+    struct fat_fs_struct* fs = fat_fs_handles;
+    uint8_t i;
+    for(i = 0; i < FAT_FS_COUNT; ++i)
+    {
+        if(!fs->partition)
+            break;
+
+        ++fs;
+    }
+    if(i >= FAT_FS_COUNT)
+        return 0;
+#endif
+
+    memset(fs, 0, sizeof(*fs));
+
+    fs->partition = partition;
+    if(!fat_read_header(fs))
+    {
+#if USE_DYNAMIC_MEMORY
+        free(fs);
+#else
+        fs->partition = 0;
+#endif
+        return 0;
+    }
+    
+    return fs;
+}
+
+/**
+ * \ingroup fat_fs
+ * Closes a FAT filesystem.
+ *
+ * When this function returns, the given filesystem descriptor
+ * will be invalid.
+ *
+ * \param[in] fs The filesystem to close.
+ * \see fat_open
+ */
+void fat_close(struct fat_fs_struct* fs)
+{
+    if(!fs)
+        return;
+
+#if USE_DYNAMIC_MEMORY
+    free(fs);
+#else
+    fs->partition = 0;
+#endif
+}
+
+/**
+ * \ingroup fat_fs
+ * Reads and parses the header of a FAT filesystem.
+ *
+ * \param[in,out] fs The filesystem for which to parse the header.
+ * \returns 0 on failure, 1 on success.
+ */
+uint8_t fat_read_header(struct fat_fs_struct* fs)
+{
+    if(!fs)
+        return 0;
+
+    struct partition_struct* partition = fs->partition;
+    if(!partition)
+        return 0;
+
+    /* read fat parameters */
+#if FAT_FAT32_SUPPORT
+    uint8_t buffer[37];
+#else
+    uint8_t buffer[25];
+#endif
+    offset_t partition_offset = (offset_t) partition->offset * 512;
+    if(!partition->device_read(partition_offset + 0x0b, buffer, sizeof(buffer)))
+        return 0;
+
+    uint16_t bytes_per_sector = read16(&buffer[0x00]);
+    uint16_t reserved_sectors = read16(&buffer[0x03]);
+    uint8_t sectors_per_cluster = buffer[0x02];
+    uint8_t fat_copies = buffer[0x05];
+    uint16_t max_root_entries = read16(&buffer[0x06]);
+    uint16_t sector_count_16 = read16(&buffer[0x08]);
+    uint16_t sectors_per_fat = read16(&buffer[0x0b]);
+    uint32_t sector_count = read32(&buffer[0x15]);
+#if FAT_FAT32_SUPPORT
+    uint32_t sectors_per_fat32 = read32(&buffer[0x19]);
+    uint32_t cluster_root_dir = read32(&buffer[0x21]);
+#endif
+
+    if(sector_count == 0)
+    {
+        if(sector_count_16 == 0)
+            /* illegal volume size */
+            return 0;
+        else
+            sector_count = sector_count_16;
+    }
+#if FAT_FAT32_SUPPORT
+    if(sectors_per_fat != 0)
+        sectors_per_fat32 = sectors_per_fat;
+    else if(sectors_per_fat32 == 0)
+        /* this is neither FAT16 nor FAT32 */
+        return 0;
+#else
+    if(sectors_per_fat == 0)
+        /* this is not a FAT16 */
+        return 0;
+#endif
+
+    /* determine the type of FAT we have here */
+    uint32_t data_sector_count = sector_count
+                                 - reserved_sectors
+#if FAT_FAT32_SUPPORT
+                                 - sectors_per_fat32 * fat_copies
+#else
+                                 - (uint32_t) sectors_per_fat * fat_copies
+#endif
+                                 - ((max_root_entries * 32 + bytes_per_sector - 1) / bytes_per_sector);
+    uint32_t data_cluster_count = data_sector_count / sectors_per_cluster;
+    if(data_cluster_count < 4085)
+        /* this is a FAT12, not supported */
+        return 0;
+    else if(data_cluster_count < 65525)
+        /* this is a FAT16 */
+        partition->type = PARTITION_TYPE_FAT16;
+    else
+        /* this is a FAT32 */
+        partition->type = PARTITION_TYPE_FAT32;
+
+    /* fill header information */
+    struct fat_header_struct* header = &fs->header;
+    memset(header, 0, sizeof(*header));
+    
+    header->size = (offset_t) sector_count * bytes_per_sector;
+
+    header->fat_offset = /* jump to partition */
+                         partition_offset +
+                         /* jump to fat */
+                         (offset_t) reserved_sectors * bytes_per_sector;
+    header->fat_size = (data_cluster_count + 2) * (partition->type == PARTITION_TYPE_FAT16 ? 2 : 4);
+
+    header->sector_size = bytes_per_sector;
+    header->cluster_size = (uint16_t) bytes_per_sector * sectors_per_cluster;
+
+#if FAT_FAT32_SUPPORT
+    if(partition->type == PARTITION_TYPE_FAT16)
+#endif
+    {
+        header->root_dir_offset = /* jump to fats */
+                                  header->fat_offset +
+                                  /* jump to root directory entries */
+                                  (offset_t) fat_copies * sectors_per_fat * bytes_per_sector;
+
+        header->cluster_zero_offset = /* jump to root directory entries */
+                                      header->root_dir_offset +
+                                      /* skip root directory entries */
+                                      (offset_t) max_root_entries * 32;
+    }
+#if FAT_FAT32_SUPPORT
+    else
+    {
+        header->cluster_zero_offset = /* jump to fats */
+                                      header->fat_offset +
+                                      /* skip fats */
+                                      (offset_t) fat_copies * sectors_per_fat32 * bytes_per_sector;
+
+        header->root_dir_cluster = cluster_root_dir;
+    }
+#endif
+
+    return 1;
+}
+
+/**
+ * \ingroup fat_fs
+ * Retrieves the next following cluster of a given cluster.
+ *
+ * Using the filesystem file allocation table, this function returns
+ * the number of the cluster containing the data directly following
+ * the data within the cluster with the given number.
+ *
+ * \param[in] fs The filesystem for which to determine the next cluster.
+ * \param[in] cluster_num The number of the cluster for which to determine its successor.
+ * \returns The wanted cluster number, or 0 on error.
+ */
+cluster_t fat_get_next_cluster(const struct fat_fs_struct* fs, cluster_t cluster_num)
+{
+    if(!fs || cluster_num < 2)
+        return 0;
+
+#if FAT_FAT32_SUPPORT
+    if(fs->partition->type == PARTITION_TYPE_FAT32)
+    {
+        /* read appropriate fat entry */
+        uint32_t fat_entry;
+        if(!fs->partition->device_read(fs->header.fat_offset + (offset_t) cluster_num * sizeof(fat_entry), (uint8_t*) &fat_entry, sizeof(fat_entry)))
+            return 0;
+
+        /* determine next cluster from fat */
+        cluster_num = ltoh32(fat_entry);
+        
+        if(cluster_num == FAT32_CLUSTER_FREE ||
+           cluster_num == FAT32_CLUSTER_BAD ||
+           (cluster_num >= FAT32_CLUSTER_RESERVED_MIN && cluster_num <= FAT32_CLUSTER_RESERVED_MAX) ||
+           (cluster_num >= FAT32_CLUSTER_LAST_MIN && cluster_num <= FAT32_CLUSTER_LAST_MAX))
+            return 0;
+    }
+    else
+#endif
+    {
+        /* read appropriate fat entry */
+        uint16_t fat_entry;
+        if(!fs->partition->device_read(fs->header.fat_offset + (offset_t) cluster_num * sizeof(fat_entry), (uint8_t*) &fat_entry, sizeof(fat_entry)))
+            return 0;
+
+        /* determine next cluster from fat */
+        cluster_num = ltoh16(fat_entry);
+        
+        if(cluster_num == FAT16_CLUSTER_FREE ||
+           cluster_num == FAT16_CLUSTER_BAD ||
+           (cluster_num >= FAT16_CLUSTER_RESERVED_MIN && cluster_num <= FAT16_CLUSTER_RESERVED_MAX) ||
+           (cluster_num >= FAT16_CLUSTER_LAST_MIN && cluster_num <= FAT16_CLUSTER_LAST_MAX))
+            return 0;
+    }
+
+    return cluster_num;
+}
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_fs
+ * Appends a new cluster chain to an existing one.
+ *
+ * Set cluster_num to zero to create a completely new one.
+ *
+ * \param[in] fs The file system on which to operate.
+ * \param[in] cluster_num The cluster to which to append the new chain.
+ * \param[in] count The number of clusters to allocate.
+ * \returns 0 on failure, the number of the first new cluster on success.
+ */
+cluster_t fat_append_clusters(struct fat_fs_struct* fs, cluster_t cluster_num, cluster_t count)
+{
+    if(!fs)
+        return 0;
+
+    device_read_t device_read = fs->partition->device_read;
+    device_write_t device_write = fs->partition->device_write;
+    offset_t fat_offset = fs->header.fat_offset;
+    cluster_t count_left = count;
+    cluster_t cluster_current = fs->cluster_free;
+    cluster_t cluster_next = 0;
+    cluster_t cluster_count;
+    uint16_t fat_entry16;
+#if FAT_FAT32_SUPPORT
+    uint32_t fat_entry32;
+    uint8_t is_fat32 = (fs->partition->type == PARTITION_TYPE_FAT32);
+
+    if(is_fat32)
+        cluster_count = fs->header.fat_size / sizeof(fat_entry32);
+    else
+#endif
+        cluster_count = fs->header.fat_size / sizeof(fat_entry16);
+
+    fs->cluster_free = 0;
+    for(cluster_t cluster_left = cluster_count; cluster_left > 0; --cluster_left, ++cluster_current)
+    {
+        if(cluster_current < 2 || cluster_current >= cluster_count)
+            cluster_current = 2;
+
+#if FAT_FAT32_SUPPORT
+        if(is_fat32)
+        {
+            if(!device_read(fat_offset + (offset_t) cluster_current * sizeof(fat_entry32), (uint8_t*) &fat_entry32, sizeof(fat_entry32)))
+                return 0;
+        }
+        else
+#endif
+        {
+            if(!device_read(fat_offset + (offset_t) cluster_current * sizeof(fat_entry16), (uint8_t*) &fat_entry16, sizeof(fat_entry16)))
+                return 0;
+        }
+
+#if FAT_FAT32_SUPPORT
+        if(is_fat32)
+        {
+            /* check if this is a free cluster */
+            if(fat_entry32 != HTOL32(FAT32_CLUSTER_FREE))
+                continue;
+
+            /* If we don't need this free cluster for the
+             * current allocation, we keep it in mind for
+             * the next time.
+             */
+            if(count_left == 0)
+            {
+                fs->cluster_free = cluster_current;
+                break;
+            }
+
+            /* allocate cluster */
+            if(cluster_next == 0)
+                fat_entry32 = HTOL32(FAT32_CLUSTER_LAST_MAX);
+            else
+                fat_entry32 = htol32(cluster_next);
+
+            if(!device_write(fat_offset + (offset_t) cluster_current * sizeof(fat_entry32), (uint8_t*) &fat_entry32, sizeof(fat_entry32)))
+                break;
+        }
+        else
+#endif
+        {
+            /* check if this is a free cluster */
+            if(fat_entry16 != HTOL16(FAT16_CLUSTER_FREE))
+                continue;
+
+            /* If we don't need this free cluster for the
+             * current allocation, we keep it in mind for
+             * the next time.
+             */
+            if(count_left == 0)
+            {
+                fs->cluster_free = cluster_current;
+                break;
+            }
+
+            /* allocate cluster */
+            if(cluster_next == 0)
+                fat_entry16 = HTOL16(FAT16_CLUSTER_LAST_MAX);
+            else
+                fat_entry16 = htol16((uint16_t) cluster_next);
+
+            if(!device_write(fat_offset + (offset_t) cluster_current * sizeof(fat_entry16), (uint8_t*) &fat_entry16, sizeof(fat_entry16)))
+                break;
+        }
+
+        cluster_next = cluster_current;
+        --count_left;
+    }
+
+    do
+    {
+        if(count_left > 0)
+            break;
+
+        /* We allocated a new cluster chain. Now join
+         * it with the existing one (if any).
+         */
+        if(cluster_num >= 2)
+        {
+#if FAT_FAT32_SUPPORT
+            if(is_fat32)
+            {
+                fat_entry32 = htol32(cluster_next);
+
+                if(!device_write(fat_offset + (offset_t) cluster_num * sizeof(fat_entry32), (uint8_t*) &fat_entry32, sizeof(fat_entry32)))
+                    break;
+            }
+            else
+#endif
+            {
+                fat_entry16 = htol16((uint16_t) cluster_next);
+
+                if(!device_write(fat_offset + (offset_t) cluster_num * sizeof(fat_entry16), (uint8_t*) &fat_entry16, sizeof(fat_entry16)))
+                    break;
+            }
+        }
+
+        return cluster_next;
+
+    } while(0);
+
+    /* No space left on device or writing error.
+     * Free up all clusters already allocated.
+     */
+    fat_free_clusters(fs, cluster_next);
+
+    return 0;
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_fs
+ * Frees a cluster chain, or a part thereof.
+ *
+ * Marks the specified cluster and all clusters which are sequentially
+ * referenced by it as free. They may then be used again for future
+ * file allocations.
+ *
+ * \note If this function is used for freeing just a part of a cluster
+ *       chain, the new end of the chain is not correctly terminated
+ *       within the FAT. Use fat_terminate_clusters() instead.
+ *
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in] cluster_num The starting cluster of the chain which to free.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_terminate_clusters
+ */
+uint8_t fat_free_clusters(struct fat_fs_struct* fs, cluster_t cluster_num)
+{
+    if(!fs || cluster_num < 2)
+        return 0;
+
+    offset_t fat_offset = fs->header.fat_offset;
+#if FAT_FAT32_SUPPORT
+    if(fs->partition->type == PARTITION_TYPE_FAT32)
+    {
+        uint32_t fat_entry;
+        while(cluster_num)
+        {
+            if(!fs->partition->device_read(fat_offset + (offset_t) cluster_num * sizeof(fat_entry), (uint8_t*) &fat_entry, sizeof(fat_entry)))
+                return 0;
+
+            /* get next cluster of current cluster before freeing current cluster */
+            uint32_t cluster_num_next = ltoh32(fat_entry);
+
+            if(cluster_num_next == FAT32_CLUSTER_FREE)
+                return 1;
+            if(cluster_num_next == FAT32_CLUSTER_BAD ||
+               (cluster_num_next >= FAT32_CLUSTER_RESERVED_MIN &&
+                cluster_num_next <= FAT32_CLUSTER_RESERVED_MAX
+               )
+              )
+                return 0;
+            if(cluster_num_next >= FAT32_CLUSTER_LAST_MIN && cluster_num_next <= FAT32_CLUSTER_LAST_MAX)
+                cluster_num_next = 0;
+
+            /* We know we will free the cluster, so remember it as
+             * free for the next allocation.
+             */
+            if(!fs->cluster_free)
+                fs->cluster_free = cluster_num;
+
+            /* free cluster */
+            fat_entry = HTOL32(FAT32_CLUSTER_FREE);
+            fs->partition->device_write(fat_offset + (offset_t) cluster_num * sizeof(fat_entry), (uint8_t*) &fat_entry, sizeof(fat_entry));
+
+            /* We continue in any case here, even if freeing the cluster failed.
+             * The cluster is lost, but maybe we can still free up some later ones.
+             */
+
+            cluster_num = cluster_num_next;
+        }
+    }
+    else
+#endif
+    {
+        uint16_t fat_entry;
+        while(cluster_num)
+        {
+            if(!fs->partition->device_read(fat_offset + (offset_t) cluster_num * sizeof(fat_entry), (uint8_t*) &fat_entry, sizeof(fat_entry)))
+                return 0;
+
+            /* get next cluster of current cluster before freeing current cluster */
+            uint16_t cluster_num_next = ltoh16(fat_entry);
+
+            if(cluster_num_next == FAT16_CLUSTER_FREE)
+                return 1;
+            if(cluster_num_next == FAT16_CLUSTER_BAD ||
+               (cluster_num_next >= FAT16_CLUSTER_RESERVED_MIN &&
+                cluster_num_next <= FAT16_CLUSTER_RESERVED_MAX
+               )
+              )
+                return 0;
+            if(cluster_num_next >= FAT16_CLUSTER_LAST_MIN && cluster_num_next <= FAT16_CLUSTER_LAST_MAX)
+                cluster_num_next = 0;
+
+            /* free cluster */
+            fat_entry = HTOL16(FAT16_CLUSTER_FREE);
+            fs->partition->device_write(fat_offset + (offset_t) cluster_num * sizeof(fat_entry), (uint8_t*) &fat_entry, sizeof(fat_entry));
+
+            /* We continue in any case here, even if freeing the cluster failed.
+             * The cluster is lost, but maybe we can still free up some later ones.
+             */
+
+            cluster_num = cluster_num_next;
+        }
+    }
+
+    return 1;
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_fs
+ * Frees a part of a cluster chain and correctly terminates the rest.
+ *
+ * Marks the specified cluster as the new end of a cluster chain and
+ * frees all following clusters.
+ *
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in] cluster_num The new end of the cluster chain.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_free_clusters
+ */
+uint8_t fat_terminate_clusters(struct fat_fs_struct* fs, cluster_t cluster_num)
+{
+    if(!fs || cluster_num < 2)
+        return 0;
+
+    /* fetch next cluster before overwriting the cluster entry */
+    cluster_t cluster_num_next = fat_get_next_cluster(fs, cluster_num);
+
+    /* mark cluster as the last one */
+#if FAT_FAT32_SUPPORT
+    if(fs->partition->type == PARTITION_TYPE_FAT32)
+    {
+        uint32_t fat_entry = HTOL32(FAT32_CLUSTER_LAST_MAX);
+        if(!fs->partition->device_write(fs->header.fat_offset + (offset_t) cluster_num * sizeof(fat_entry), (uint8_t*) &fat_entry, sizeof(fat_entry)))
+            return 0;
+    }
+    else
+#endif
+    {
+        uint16_t fat_entry = HTOL16(FAT16_CLUSTER_LAST_MAX);
+        if(!fs->partition->device_write(fs->header.fat_offset + (offset_t) cluster_num * sizeof(fat_entry), (uint8_t*) &fat_entry, sizeof(fat_entry)))
+            return 0;
+    }
+
+    /* free remaining clusters */
+    if(cluster_num_next)
+        return fat_free_clusters(fs, cluster_num_next);
+    else
+        return 1;
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_fs
+ * Clears a single cluster.
+ *
+ * The complete cluster is filled with zeros.
+ *
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in] cluster_num The cluster to clear.
+ * \returns 0 on failure, 1 on success.
+ */
+uint8_t fat_clear_cluster(const struct fat_fs_struct* fs, cluster_t cluster_num)
+{
+    if(cluster_num < 2)
+        return 0;
+
+    offset_t cluster_offset = fat_cluster_offset(fs, cluster_num);
+
+    uint8_t zero[16];
+    memset(zero, 0, sizeof(zero));
+    return fs->partition->device_write_interval(cluster_offset,
+                                                zero,
+                                                fs->header.cluster_size,
+                                                fat_clear_cluster_callback,
+                                                0
+                                               );
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_fs
+ * Callback function for clearing a cluster.
+ */
+uintptr_t fat_clear_cluster_callback(uint8_t* buffer, offset_t offset, void* p)
+{
+    return 16;
+}
+#endif
+
+/**
+ * \ingroup fat_fs
+ * Calculates the offset of the specified cluster.
+ *
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in] cluster_num The cluster whose offset to calculate.
+ * \returns The cluster offset.
+ */
+offset_t fat_cluster_offset(const struct fat_fs_struct* fs, cluster_t cluster_num)
+{
+    if(!fs || cluster_num < 2)
+        return 0;
+
+    return fs->header.cluster_zero_offset + (offset_t) (cluster_num - 2) * fs->header.cluster_size;
+}
+
+/**
+ * \ingroup fat_file
+ * Retrieves the directory entry of a path.
+ *
+ * The given path may both describe a file or a directory.
+ *
+ * \param[in] fs The FAT filesystem on which to search.
+ * \param[in] path The path of which to read the directory entry.
+ * \param[out] dir_entry The directory entry to fill.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_read_dir
+ */
+uint8_t fat_get_dir_entry_of_path(struct fat_fs_struct* fs, const char* path, struct fat_dir_entry_struct* dir_entry)
+{
+    if(!fs || !path || path[0] == '\0' || !dir_entry)
+        return 0;
+
+    if(path[0] == '/')
+        ++path;
+
+    /* begin with the root directory */
+    memset(dir_entry, 0, sizeof(*dir_entry));
+    dir_entry->attributes = FAT_ATTRIB_DIR;
+
+    while(1)
+    {
+        if(path[0] == '\0')
+            return 1;
+
+        struct fat_dir_struct* dd = fat_open_dir(fs, dir_entry);
+        if(!dd)
+            break;
+
+        /* extract the next hierarchy we will search for */
+        const char* sub_path = strchr(path, '/');
+        uint8_t length_to_sep;
+        if(sub_path)
+        {
+            length_to_sep = sub_path - path;
+            ++sub_path;
+        }
+        else
+        {
+            length_to_sep = strlen(path);
+            sub_path = path + length_to_sep;
+        }
+        
+        /* read directory entries */
+        while(fat_read_dir(dd, dir_entry))
+        {
+            /* check if we have found the next hierarchy */
+            if((strlen(dir_entry->long_name) != length_to_sep ||
+                strncmp(path, dir_entry->long_name, length_to_sep) != 0))
+                continue;
+
+            fat_close_dir(dd);
+            dd = 0;
+
+            if(path[length_to_sep] == '\0')
+                /* we iterated through the whole path and have found the file */
+                return 1;
+
+            if(dir_entry->attributes & FAT_ATTRIB_DIR)
+            {
+                /* we found a parent directory of the file we are searching for */
+                path = sub_path;
+                break;
+            }
+
+            /* a parent of the file exists, but not the file itself */
+            return 0;
+        }
+
+        fat_close_dir(dd);
+    }
+    
+    return 0;
+}
+
+/**
+ * \ingroup fat_file
+ * Opens a file on a FAT filesystem.
+ *
+ * \param[in] fs The filesystem on which the file to open lies.
+ * \param[in] dir_entry The directory entry of the file to open.
+ * \returns The file handle, or 0 on failure.
+ * \see fat_close_file
+ */
+struct fat_file_struct* fat_open_file(struct fat_fs_struct* fs, const struct fat_dir_entry_struct* dir_entry)
+{
+    if(!fs || !dir_entry || (dir_entry->attributes & FAT_ATTRIB_DIR))
+        return 0;
+
+#if USE_DYNAMIC_MEMORY
+    struct fat_file_struct* fd = malloc(sizeof(*fd));
+    if(!fd)
+        return 0;
+#else
+    struct fat_file_struct* fd = fat_file_handles;
+    uint8_t i;
+    for(i = 0; i < FAT_FILE_COUNT; ++i)
+    {
+        if(!fd->fs)
+            break;
+
+        ++fd;
+    }
+    if(i >= FAT_FILE_COUNT)
+        return 0;
+#endif
+    
+    memcpy(&fd->dir_entry, dir_entry, sizeof(*dir_entry));
+    fd->fs = fs;
+    fd->pos = 0;
+    fd->pos_cluster = dir_entry->cluster;
+
+    return fd;
+}
+
+/**
+ * \ingroup fat_file
+ * Closes a file.
+ *
+ * \param[in] fd The file handle of the file to close.
+ * \see fat_open_file
+ */
+void fat_close_file(struct fat_file_struct* fd)
+{
+    if(fd)
+    {
+#if FAT_DELAY_DIRENTRY_UPDATE
+        /* write directory entry */
+        fat_write_dir_entry(fd->fs, &fd->dir_entry);
+#endif
+
+#if USE_DYNAMIC_MEMORY
+        free(fd);
+#else
+        fd->fs = 0;
+#endif
+    }
+}
+
+/**
+ * \ingroup fat_file
+ * Reads data from a file.
+ * 
+ * The data requested is read from the current file location.
+ *
+ * \param[in] fd The file handle of the file from which to read.
+ * \param[out] buffer The buffer into which to write.
+ * \param[in] buffer_len The amount of data to read.
+ * \returns The number of bytes read, 0 on end of file, or -1 on failure.
+ * \see fat_write_file
+ */
+intptr_t fat_read_file(struct fat_file_struct* fd, uint8_t* buffer, uintptr_t buffer_len)
+{
+    /* check arguments */
+    if(!fd || !buffer || buffer_len < 1)
+        return -1;
+
+    /* determine number of bytes to read */
+    if(fd->pos + buffer_len > fd->dir_entry.file_size)
+        buffer_len = fd->dir_entry.file_size - fd->pos;
+    if(buffer_len == 0)
+        return 0;
+    
+    uint16_t cluster_size = fd->fs->header.cluster_size;
+    cluster_t cluster_num = fd->pos_cluster;
+    uintptr_t buffer_left = buffer_len;
+    uint16_t first_cluster_offset = (uint16_t) (fd->pos & (cluster_size - 1));
+
+    /* find cluster in which to start reading */
+    if(!cluster_num)
+    {
+        cluster_num = fd->dir_entry.cluster;
+        
+        if(!cluster_num)
+        {
+            if(!fd->pos)
+                return 0;
+            else
+                return -1;
+        }
+
+        if(fd->pos)
+        {
+            uint32_t pos = fd->pos;
+            while(pos >= cluster_size)
+            {
+                pos -= cluster_size;
+                cluster_num = fat_get_next_cluster(fd->fs, cluster_num);
+                if(!cluster_num)
+                    return -1;
+            }
+        }
+    }
+    
+    /* read data */
+    do
+    {
+        /* calculate data size to copy from cluster */
+        offset_t cluster_offset = fat_cluster_offset(fd->fs, cluster_num) + first_cluster_offset;
+        uint16_t copy_length = cluster_size - first_cluster_offset;
+        if(copy_length > buffer_left)
+            copy_length = buffer_left;
+
+        /* read data */
+        if(!fd->fs->partition->device_read(cluster_offset, buffer, copy_length))
+            return buffer_len - buffer_left;
+
+        /* calculate new file position */
+        buffer += copy_length;
+        buffer_left -= copy_length;
+        fd->pos += copy_length;
+
+        if(first_cluster_offset + copy_length >= cluster_size)
+        {
+            /* we are on a cluster boundary, so get the next cluster */
+            if((cluster_num = fat_get_next_cluster(fd->fs, cluster_num)))
+            {
+                first_cluster_offset = 0;
+            }
+            else
+            {
+                fd->pos_cluster = 0;
+                return buffer_len - buffer_left;
+            }
+        }
+
+        fd->pos_cluster = cluster_num;
+
+    } while(buffer_left > 0); /* check if we are done */
+
+    return buffer_len;
+}
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_file
+ * Writes data to a file.
+ * 
+ * The data is written to the current file location.
+ *
+ * \param[in] fd The file handle of the file to which to write.
+ * \param[in] buffer The buffer from which to read the data to be written.
+ * \param[in] buffer_len The amount of data to write.
+ * \returns The number of bytes written (0 or something less than \c buffer_len on disk full) or -1 on failure.
+ * \see fat_read_file
+ */
+intptr_t fat_write_file(struct fat_file_struct* fd, const uint8_t* buffer, uintptr_t buffer_len)
+{
+    /* check arguments */
+    if(!fd || !buffer || buffer_len < 1)
+        return -1;
+    if(fd->pos > fd->dir_entry.file_size)
+        return -1;
+
+    uint16_t cluster_size = fd->fs->header.cluster_size;
+    cluster_t cluster_num = fd->pos_cluster;
+    uintptr_t buffer_left = buffer_len;
+    uint16_t first_cluster_offset = (uint16_t) (fd->pos & (cluster_size - 1));
+
+    /* find cluster in which to start writing */
+    if(!cluster_num)
+    {
+        cluster_num = fd->dir_entry.cluster;
+        
+        if(!cluster_num)
+        {
+            if(!fd->pos)
+            {
+                /* empty file */
+                fd->dir_entry.cluster = cluster_num = fat_append_clusters(fd->fs, 0, 1);
+                if(!cluster_num)
+                    return 0;
+            }
+            else
+            {
+                return -1;
+            }
+        }
+
+        if(fd->pos)
+        {
+            uint32_t pos = fd->pos;
+            cluster_t cluster_num_next;
+            while(pos >= cluster_size)
+            {
+                pos -= cluster_size;
+                cluster_num_next = fat_get_next_cluster(fd->fs, cluster_num);
+                if(!cluster_num_next)
+                {
+                    if(pos != 0)
+                        return -1; /* current file position points beyond end of file */
+
+                    /* the file exactly ends on a cluster boundary, and we append to it */
+                    cluster_num_next = fat_append_clusters(fd->fs, cluster_num, 1);
+                    if(!cluster_num_next)
+                        return 0;
+                }
+
+                cluster_num = cluster_num_next;
+            }
+        }
+    }
+    
+    /* write data */
+    do
+    {
+        /* calculate data size to write to cluster */
+        offset_t cluster_offset = fat_cluster_offset(fd->fs, cluster_num) + first_cluster_offset;
+        uint16_t write_length = cluster_size - first_cluster_offset;
+        if(write_length > buffer_left)
+            write_length = buffer_left;
+
+        /* write data which fits into the current cluster */
+        if(!fd->fs->partition->device_write(cluster_offset, buffer, write_length))
+            break;
+
+        /* calculate new file position */
+        buffer += write_length;
+        buffer_left -= write_length;
+        fd->pos += write_length;
+
+        if(first_cluster_offset + write_length >= cluster_size)
+        {
+            /* we are on a cluster boundary, so get the next cluster */
+            cluster_t cluster_num_next = fat_get_next_cluster(fd->fs, cluster_num);
+            if(!cluster_num_next && buffer_left > 0)
+                /* we reached the last cluster, append a new one */
+                cluster_num_next = fat_append_clusters(fd->fs, cluster_num, 1);
+            if(!cluster_num_next)
+            {
+                fd->pos_cluster = 0;
+                break;
+            }
+
+            cluster_num = cluster_num_next;
+            first_cluster_offset = 0;
+        }
+
+        fd->pos_cluster = cluster_num;
+
+    } while(buffer_left > 0); /* check if we are done */
+
+    /* update directory entry */
+    if(fd->pos > fd->dir_entry.file_size)
+    {
+#if !FAT_DELAY_DIRENTRY_UPDATE
+        uint32_t size_old = fd->dir_entry.file_size;
+#endif
+
+        /* update file size */
+        fd->dir_entry.file_size = fd->pos;
+
+#if !FAT_DELAY_DIRENTRY_UPDATE
+        /* write directory entry */
+        if(!fat_write_dir_entry(fd->fs, &fd->dir_entry))
+        {
+            /* We do not return an error here since we actually wrote
+             * some data to disk. So we calculate the amount of data
+             * we wrote to disk and which lies within the old file size.
+             */
+            buffer_left = fd->pos - size_old;
+            fd->pos = size_old;
+        }
+#endif
+    }
+
+    return buffer_len - buffer_left;
+}
+#endif
+
+/**
+ * \ingroup fat_file
+ * Repositions the read/write file offset.
+ *
+ * Changes the file offset where the next call to fat_read_file()
+ * or fat_write_file() starts reading/writing.
+ *
+ * If the new offset is beyond the end of the file, fat_resize_file()
+ * is implicitly called, i.e. the file is expanded.
+ *
+ * The new offset can be given in different ways determined by
+ * the \c whence parameter:
+ * - \b FAT_SEEK_SET: \c *offset is relative to the beginning of the file.
+ * - \b FAT_SEEK_CUR: \c *offset is relative to the current file position.
+ * - \b FAT_SEEK_END: \c *offset is relative to the end of the file.
+ *
+ * The resulting absolute offset is written to the location the \c offset
+ * parameter points to.
+ *
+ * Calling this function can also be used to retrieve the current file position:
+   \code
+   int32_t file_pos = 0;
+   if(!fat_seek_file(fd, &file_pos, FAT_SEEK_CUR))
+   {
+       // error
+   }
+   // file_pos now contains the absolute file position
+   \endcode
+ * 
+ * \param[in] fd The file decriptor of the file on which to seek.
+ * \param[in,out] offset A pointer to the new offset, as affected by the \c whence
+ *                   parameter. The function writes the new absolute offset
+ *                   to this location before it returns.
+ * \param[in] whence Affects the way \c offset is interpreted, see above.
+ * \returns 0 on failure, 1 on success.
+ */
+uint8_t fat_seek_file(struct fat_file_struct* fd, int32_t* offset, uint8_t whence)
+{
+    if(!fd || !offset)
+        return 0;
+
+    uint32_t new_pos = fd->pos;
+    switch(whence)
+    {
+        case FAT_SEEK_SET:
+            new_pos = *offset;
+            break;
+        case FAT_SEEK_CUR:
+            new_pos += *offset;
+            break;
+        case FAT_SEEK_END:
+            new_pos = fd->dir_entry.file_size + *offset;
+            break;
+        default:
+            return 0;
+    }
+
+    if(new_pos > fd->dir_entry.file_size
+#if FAT_WRITE_SUPPORT
+       && !fat_resize_file(fd, new_pos)
+#endif
+       )
+        return 0;
+
+    fd->pos = new_pos;
+    fd->pos_cluster = 0;
+
+    *offset = (int32_t) new_pos;
+    return 1;
+}
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_file
+ * Resizes a file to have a specific size.
+ *
+ * Enlarges or shrinks the file pointed to by the file descriptor to have
+ * exactly the specified size.
+ *
+ * If the file is truncated, all bytes having an equal or larger offset
+ * than the given size are lost. If the file is expanded, the additional
+ * bytes are allocated.
+ *
+ * \note Please be aware that this function just allocates or deallocates disk
+ * space, it does not explicitely clear it. To avoid data leakage, this
+ * must be done manually.
+ *
+ * \param[in] fd The file decriptor of the file which to resize.
+ * \param[in] size The new size of the file.
+ * \returns 0 on failure, 1 on success.
+ */
+uint8_t fat_resize_file(struct fat_file_struct* fd, uint32_t size)
+{
+    if(!fd)
+        return 0;
+
+    cluster_t cluster_num = fd->dir_entry.cluster;
+    uint16_t cluster_size = fd->fs->header.cluster_size;
+    uint32_t size_new = size;
+
+    do
+    {
+        if(cluster_num == 0 && size_new == 0)
+            /* the file stays empty */
+            break;
+
+        /* seek to the next cluster as long as we need the space */
+        while(size_new > cluster_size)
+        {
+            /* get next cluster of file */
+            cluster_t cluster_num_next = fat_get_next_cluster(fd->fs, cluster_num);
+            if(cluster_num_next)
+            {
+                cluster_num = cluster_num_next;
+                size_new -= cluster_size;
+            }
+            else
+            {
+                break;
+            }
+        }
+
+        if(size_new > cluster_size || cluster_num == 0)
+        {
+            /* Allocate new cluster chain and append
+             * it to the existing one, if available.
+             */
+            cluster_t cluster_count = (size_new + cluster_size - 1) / cluster_size;
+            cluster_t cluster_new_chain = fat_append_clusters(fd->fs, cluster_num, cluster_count);
+            if(!cluster_new_chain)
+                return 0;
+
+            if(!cluster_num)
+            {
+                cluster_num = cluster_new_chain;
+                fd->dir_entry.cluster = cluster_num;
+            }
+        }
+
+        /* write new directory entry */
+        fd->dir_entry.file_size = size;
+        if(size == 0)
+            fd->dir_entry.cluster = 0;
+        if(!fat_write_dir_entry(fd->fs, &fd->dir_entry))
+            return 0;
+
+        if(size == 0)
+        {
+            /* free all clusters of file */
+            fat_free_clusters(fd->fs, cluster_num);
+        }
+        else if(size_new <= cluster_size)
+        {
+            /* free all clusters no longer needed */
+            fat_terminate_clusters(fd->fs, cluster_num);
+        }
+
+    } while(0);
+
+    /* correct file position */
+    if(size < fd->pos)
+    {
+        fd->pos = size;
+        fd->pos_cluster = 0;
+    }
+
+    return 1;
+}
+#endif
+
+/**
+ * \ingroup fat_dir
+ * Opens a directory.
+ *
+ * \param[in] fs The filesystem on which the directory to open resides.
+ * \param[in] dir_entry The directory entry which stands for the directory to open.
+ * \returns An opaque directory descriptor on success, 0 on failure.
+ * \see fat_close_dir
+ */
+struct fat_dir_struct* fat_open_dir(struct fat_fs_struct* fs, const struct fat_dir_entry_struct* dir_entry)
+{
+    if(!fs || !dir_entry || !(dir_entry->attributes & FAT_ATTRIB_DIR))
+        return 0;
+
+#if USE_DYNAMIC_MEMORY
+    struct fat_dir_struct* dd = malloc(sizeof(*dd));
+    if(!dd)
+        return 0;
+#else
+    struct fat_dir_struct* dd = fat_dir_handles;
+    uint8_t i;
+    for(i = 0; i < FAT_DIR_COUNT; ++i)
+    {
+        if(!dd->fs)
+            break;
+
+        ++dd;
+    }
+    if(i >= FAT_DIR_COUNT)
+        return 0;
+#endif
+    
+    memcpy(&dd->dir_entry, dir_entry, sizeof(*dir_entry));
+    dd->fs = fs;
+    dd->entry_cluster = dir_entry->cluster;
+    dd->entry_offset = 0;
+
+    return dd;
+}
+
+/**
+ * \ingroup fat_dir
+ * Closes a directory descriptor.
+ *
+ * This function destroys a directory descriptor which was
+ * previously obtained by calling fat_open_dir(). When this
+ * function returns, the given descriptor will be invalid.
+ *
+ * \param[in] dd The directory descriptor to close.
+ * \see fat_open_dir
+ */
+void fat_close_dir(struct fat_dir_struct* dd)
+{
+    if(dd)
+#if USE_DYNAMIC_MEMORY
+        free(dd);
+#else
+        dd->fs = 0;
+#endif
+}
+
+/**
+ * \ingroup fat_dir
+ * Reads the next directory entry contained within a parent directory.
+ *
+ * \param[in] dd The descriptor of the parent directory from which to read the entry.
+ * \param[out] dir_entry Pointer to a buffer into which to write the directory entry information.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_reset_dir
+ */
+uint8_t fat_read_dir(struct fat_dir_struct* dd, struct fat_dir_entry_struct* dir_entry)
+{
+    if(!dd || !dir_entry)
+        return 0;
+
+    /* get current position of directory handle */
+    struct fat_fs_struct* fs = dd->fs;
+    const struct fat_header_struct* header = &fs->header;
+    uint16_t cluster_size = header->cluster_size;
+    cluster_t cluster_num = dd->entry_cluster;
+    uint16_t cluster_offset = dd->entry_offset;
+    struct fat_read_dir_callback_arg arg;
+
+    if(cluster_offset >= cluster_size)
+    {
+        /* The latest call hit the border of the last cluster in
+         * the chain, but it still returned a directory entry.
+         * So we now reset the handle and signal the caller the
+         * end of the listing.
+         */
+        fat_reset_dir(dd);
+        return 0;
+    }
+
+    /* reset callback arguments */
+    memset(&arg, 0, sizeof(arg));
+    memset(dir_entry, 0, sizeof(*dir_entry));
+    arg.dir_entry = dir_entry;
+
+    /* check if we read from the root directory */
+    if(cluster_num == 0)
+    {
+#if FAT_FAT32_SUPPORT
+        if(fs->partition->type == PARTITION_TYPE_FAT32)
+            cluster_num = header->root_dir_cluster;
+        else
+#endif
+            cluster_size = header->cluster_zero_offset - header->root_dir_offset;
+    }
+
+    /* read entries */
+    uint8_t buffer[32];
+    while(!arg.finished)
+    {
+        /* read directory entries up to the cluster border */
+        uint16_t cluster_left = cluster_size - cluster_offset;
+        offset_t pos = cluster_offset;
+        if(cluster_num == 0)
+            pos += header->root_dir_offset;
+        else
+            pos += fat_cluster_offset(fs, cluster_num);
+
+        arg.bytes_read = 0;
+        if(!fs->partition->device_read_interval(pos,
+                                                buffer,
+                                                sizeof(buffer),
+                                                cluster_left,
+                                                fat_dir_entry_read_callback,
+                                                &arg)
+          )
+            return 0;
+
+        cluster_offset += arg.bytes_read;
+
+        if(cluster_offset >= cluster_size)
+        {
+            /* we reached the cluster border and switch to the next cluster */
+
+            /* get number of next cluster */
+            if((cluster_num = fat_get_next_cluster(fs, cluster_num)) != 0)
+            {
+                cluster_offset = 0;
+                continue;
+            }
+
+            /* we are at the end of the cluster chain */
+            if(!arg.finished)
+            {
+                /* directory entry not found, reset directory handle */
+                fat_reset_dir(dd);
+                return 0;
+            }
+            else
+            {
+                /* The current execution of the function has been successful,
+                 * so we can not signal an end of the directory listing to
+                 * the caller, but must wait for the next call. So we keep an
+                 * invalid cluster offset to mark this directory handle's
+                 * traversal as finished.
+                 */
+            }
+
+            break;
+        }
+    }
+
+    dd->entry_cluster = cluster_num;
+    dd->entry_offset = cluster_offset;
+
+    return arg.finished;
+}
+
+/**
+ * \ingroup fat_dir
+ * Resets a directory handle.
+ *
+ * Resets the directory handle such that reading restarts
+ * with the first directory entry.
+ *
+ * \param[in] dd The directory handle to reset.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_read_dir
+ */
+uint8_t fat_reset_dir(struct fat_dir_struct* dd)
+{
+    if(!dd)
+        return 0;
+
+    dd->entry_cluster = dd->dir_entry.cluster;
+    dd->entry_offset = 0;
+    return 1;
+}
+
+/**
+ * \ingroup fat_fs
+ * Callback function for reading a directory entry.
+ *
+ * Interprets a raw directory entry and puts the contained
+ * information into a fat_dir_entry_struct structure.
+ * 
+ * For a single file there may exist multiple directory
+ * entries. All except the last one are lfn entries, which
+ * contain parts of the long filename. The last directory
+ * entry is a traditional 8.3 style one. It contains all
+ * other information like size, cluster, date and time.
+ * 
+ * \param[in] buffer A pointer to 32 bytes of raw data.
+ * \param[in] offset The absolute offset of the raw data.
+ * \param[in,out] p An argument structure controlling operation.
+ * \returns 0 on failure or completion, 1 if reading has
+ *          to be continued
+ */
+uint8_t fat_dir_entry_read_callback(uint8_t* buffer, offset_t offset, void* p)
+{
+    struct fat_read_dir_callback_arg* arg = p;
+    struct fat_dir_entry_struct* dir_entry = arg->dir_entry;
+
+    arg->bytes_read += 32;
+
+    /* skip deleted or empty entries */
+    if(buffer[0] == FAT_DIRENTRY_DELETED || !buffer[0])
+    {
+#if FAT_LFN_SUPPORT
+        arg->checksum = 0;
+#endif
+        return 1;
+    }
+
+#if !FAT_LFN_SUPPORT
+    /* skip lfn entries */
+    if(buffer[11] == 0x0f)
+        return 1;
+#endif
+
+    char* long_name = dir_entry->long_name;
+#if FAT_LFN_SUPPORT
+    if(buffer[11] == 0x0f)
+    {
+        /* checksum validation */
+        if(arg->checksum == 0 || arg->checksum != buffer[13])
+        {
+            /* reset directory entry */
+            memset(dir_entry, 0, sizeof(*dir_entry));
+
+            arg->checksum = buffer[13];
+            dir_entry->entry_offset = offset;
+        }
+
+        /* lfn supports unicode, but we do not, for now.
+         * So we assume pure ascii and read only every
+         * second byte.
+         */
+        uint16_t char_offset = ((buffer[0] & 0x3f) - 1) * 13;
+        const uint8_t char_mapping[] = { 1, 3, 5, 7, 9, 14, 16, 18, 20, 22, 24, 28, 30 };
+        for(uint8_t i = 0; i <= 12 && char_offset + i < sizeof(dir_entry->long_name) - 1; ++i)
+            long_name[char_offset + i] = buffer[char_mapping[i]];
+
+        return 1;
+    }
+    else
+#endif
+    {
+#if FAT_LFN_SUPPORT
+        /* if we do not have a long name or the previous lfn does not match, take the 8.3 name */
+        if(long_name[0] == '\0' || arg->checksum != fat_calc_83_checksum(buffer))
+#endif
+        {
+            /* reset directory entry */
+            memset(dir_entry, 0, sizeof(*dir_entry));
+            dir_entry->entry_offset = offset;
+
+            uint8_t i;
+            for(i = 0; i < 8; ++i)
+            {
+                if(buffer[i] == ' ')
+                    break;
+                long_name[i] = buffer[i];
+
+                /* Windows NT and later versions do not store lfn entries
+                 * for 8.3 names which have a lowercase basename, extension
+                 * or both when everything else is uppercase. They use two
+                 * extra bits to signal a lowercase basename or extension.
+                 */
+                if((buffer[12] & 0x08) && buffer[i] >= 'A' && buffer[i] <= 'Z')
+                    long_name[i] += 'a' - 'A';
+            }
+            if(long_name[0] == 0x05)
+                long_name[0] = (char) FAT_DIRENTRY_DELETED;
+
+            if(buffer[8] != ' ')
+            {
+                long_name[i++] = '.';
+
+                uint8_t j = 8;
+                for(; j < 11; ++j)
+                {
+                    if(buffer[j] == ' ')
+                        break;
+                    long_name[i] = buffer[j];
+
+                    /* See above for the lowercase 8.3 name handling of
+                     * Windows NT and later.
+                     */
+                    if((buffer[12] & 0x10) && buffer[j] >= 'A' && buffer[j] <= 'Z')
+                        long_name[i] += 'a' - 'A';
+
+                    ++i;
+                }
+            } 
+
+            long_name[i] = '\0';
+        }
+        
+        /* extract properties of file and store them within the structure */
+        dir_entry->attributes = buffer[11];
+        dir_entry->cluster = read16(&buffer[26]);
+#if FAT_FAT32_SUPPORT
+        dir_entry->cluster |= ((cluster_t) read16(&buffer[20])) << 16;
+#endif
+        dir_entry->file_size = read32(&buffer[28]);
+
+#if FAT_DATETIME_SUPPORT
+        dir_entry->modification_time = read16(&buffer[22]);
+        dir_entry->modification_date = read16(&buffer[24]);
+#endif
+
+        arg->finished = 1;
+        return 0;
+    }
+}
+
+#if DOXYGEN || FAT_LFN_SUPPORT
+/**
+ * \ingroup fat_fs
+ * Calculates the checksum for 8.3 names used within the
+ * corresponding lfn directory entries.
+ *
+ * \param[in] file_name_83 The 11-byte file name buffer.
+ * \returns The checksum of the given file name.
+ */
+uint8_t fat_calc_83_checksum(const uint8_t* file_name_83)
+{
+    uint8_t checksum = file_name_83[0];
+    for(uint8_t i = 1; i < 11; ++i)
+        checksum = ((checksum >> 1) | (checksum << 7)) + file_name_83[i];
+
+    return checksum;
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_fs
+ * Searches for space where to store a directory entry.
+ *
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in] parent The directory in which to search.
+ * \param[in] dir_entry The directory entry for which to search space.
+ * \returns 0 on failure, a device offset on success.
+ */
+offset_t fat_find_offset_for_dir_entry(struct fat_fs_struct* fs, const struct fat_dir_struct* parent, const struct fat_dir_entry_struct* dir_entry)
+{
+    if(!fs || !dir_entry)
+        return 0;
+
+    /* search for a place where to write the directory entry to disk */
+#if FAT_LFN_SUPPORT
+    uint8_t free_dir_entries_needed = (strlen(dir_entry->long_name) + 12) / 13 + 1;
+    uint8_t free_dir_entries_found = 0;
+#endif
+    cluster_t cluster_num = parent->dir_entry.cluster;
+    offset_t dir_entry_offset = 0;
+    offset_t offset = 0;
+    offset_t offset_to = 0;
+#if FAT_FAT32_SUPPORT
+    uint8_t is_fat32 = (fs->partition->type == PARTITION_TYPE_FAT32);
+#endif
+
+    if(cluster_num == 0)
+    {
+#if FAT_FAT32_SUPPORT
+        if(is_fat32)
+        {
+            cluster_num = fs->header.root_dir_cluster;
+        }
+        else
+#endif
+        {
+            /* we read/write from the root directory entry */
+            offset = fs->header.root_dir_offset;
+            offset_to = fs->header.cluster_zero_offset;
+            dir_entry_offset = offset;
+        }
+    }
+    
+    while(1)
+    {
+        if(offset == offset_to)
+        {
+            if(cluster_num == 0)
+                /* We iterated through the whole root directory and
+                 * could not find enough space for the directory entry.
+                 */
+                return 0;
+
+            if(offset)
+            {
+                /* We reached a cluster boundary and have to
+                 * switch to the next cluster.
+                 */
+
+                cluster_t cluster_next = fat_get_next_cluster(fs, cluster_num);
+                if(!cluster_next)
+                {
+                    cluster_next = fat_append_clusters(fs, cluster_num, 1);
+                    if(!cluster_next)
+                        return 0;
+
+                    /* we appended a new cluster and know it is free */
+                    dir_entry_offset = fs->header.cluster_zero_offset +
+                                       (offset_t) (cluster_next - 2) * fs->header.cluster_size;
+
+                    /* clear cluster to avoid garbage directory entries */
+                    fat_clear_cluster(fs, cluster_next);
+
+                    break;
+                }
+                cluster_num = cluster_next;
+            }
+
+            offset = fat_cluster_offset(fs, cluster_num);
+            offset_to = offset + fs->header.cluster_size;
+            dir_entry_offset = offset;
+#if FAT_LFN_SUPPORT
+            free_dir_entries_found = 0;
+#endif
+        }
+        
+        /* read next lfn or 8.3 entry */
+        uint8_t first_char;
+        if(!fs->partition->device_read(offset, &first_char, sizeof(first_char)))
+            return 0;
+
+        /* check if we found a free directory entry */
+        if(first_char == FAT_DIRENTRY_DELETED || !first_char)
+        {
+            /* check if we have the needed number of available entries */
+#if FAT_LFN_SUPPORT
+            ++free_dir_entries_found;
+            if(free_dir_entries_found >= free_dir_entries_needed)
+#endif
+                break;
+
+            offset += 32;
+        }
+        else
+        {
+            offset += 32;
+            dir_entry_offset = offset;
+#if FAT_LFN_SUPPORT
+            free_dir_entries_found = 0;
+#endif
+        }
+    }
+
+    return dir_entry_offset;
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_fs
+ * Writes a directory entry to disk.
+ *
+ * \note The file name is not checked for invalid characters.
+ *
+ * \note The generation of the short 8.3 file name is quite
+ * simple. The first eight characters are used for the filename.
+ * The extension, if any, is made up of the first three characters
+ * following the last dot within the long filename. If the
+ * filename (without the extension) is longer than eight characters,
+ * the lower byte of the cluster number replaces the last two
+ * characters to avoid name clashes. In any other case, it is your
+ * responsibility to avoid name clashes.
+ *
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in] dir_entry The directory entry to write.
+ * \returns 0 on failure, 1 on success.
+ */
+uint8_t fat_write_dir_entry(const struct fat_fs_struct* fs, struct fat_dir_entry_struct* dir_entry)
+{
+    if(!fs || !dir_entry)
+        return 0;
+    
+#if FAT_DATETIME_SUPPORT
+    {
+        uint16_t year;
+        uint8_t month;
+        uint8_t day;
+        uint8_t hour;
+        uint8_t min;
+        uint8_t sec;
+
+        fat_get_datetime(&year, &month, &day, &hour, &min, &sec);
+        fat_set_file_modification_date(dir_entry, year, month, day);
+        fat_set_file_modification_time(dir_entry, hour, min, sec);
+    }
+#endif
+
+    device_write_t device_write = fs->partition->device_write;
+    offset_t offset = dir_entry->entry_offset;
+    const char* name = dir_entry->long_name;
+    uint8_t name_len = strlen(name);
+#if FAT_LFN_SUPPORT
+    uint8_t lfn_entry_count = (name_len + 12) / 13;
+#endif
+    uint8_t buffer[32];
+
+    /* write 8.3 entry */
+
+    /* generate 8.3 file name */
+    memset(&buffer[0], ' ', 11);
+    char* name_ext = strrchr(name, '.');
+    if(name_ext && *++name_ext)
+    {
+        uint8_t name_ext_len = strlen(name_ext);
+        name_len -= name_ext_len + 1;
+
+        if(name_ext_len > 3)
+#if FAT_LFN_SUPPORT
+            name_ext_len = 3;
+#else
+            return 0;
+#endif
+        
+        memcpy(&buffer[8], name_ext, name_ext_len);
+    }
+    
+    if(name_len <= 8)
+    {
+        memcpy(buffer, name, name_len);
+
+#if FAT_LFN_SUPPORT
+        /* For now, we create lfn entries for all files,
+         * except the "." and ".." directory references.
+         * This is to avoid difficulties with capitalization,
+         * as 8.3 filenames allow uppercase letters only.
+         *
+         * Theoretically it would be possible to leave
+         * the 8.3 entry alone if the basename and the
+         * extension have no mixed capitalization.
+         */
+        if(name[0] == '.' &&
+           ((name[1] == '.' && name[2] == '\0') ||
+            name[1] == '\0')
+          )
+            lfn_entry_count = 0;
+#endif
+    }
+    else
+    {
+#if FAT_LFN_SUPPORT
+        memcpy(buffer, name, 8);
+
+        /* Minimize 8.3 name clashes by appending
+         * the lower byte of the cluster number.
+         */
+        uint8_t num = dir_entry->cluster & 0xff;
+
+        buffer[6] = (num < 0xa0) ? ('0' + (num >> 4)) : ('a' + (num >> 4));
+        num &= 0x0f;
+        buffer[7] = (num < 0x0a) ? ('0' + num) : ('a' + num);
+#else
+        return 0;
+#endif
+    }
+    if(buffer[0] == FAT_DIRENTRY_DELETED)
+        buffer[0] = 0x05;
+
+    /* fill directory entry buffer */
+    memset(&buffer[11], 0, sizeof(buffer) - 11);
+    buffer[0x0b] = dir_entry->attributes;
+#if FAT_DATETIME_SUPPORT
+    write16(&buffer[0x16], dir_entry->modification_time);
+    write16(&buffer[0x18], dir_entry->modification_date);
+#endif
+#if FAT_FAT32_SUPPORT
+    write16(&buffer[0x14], (uint16_t) (dir_entry->cluster >> 16));
+#endif
+    write16(&buffer[0x1a], dir_entry->cluster);
+    write32(&buffer[0x1c], dir_entry->file_size);
+
+    /* write to disk */
+#if FAT_LFN_SUPPORT
+    if(!device_write(offset + (uint16_t) lfn_entry_count * 32, buffer, sizeof(buffer)))
+#else
+    if(!device_write(offset, buffer, sizeof(buffer)))
+#endif
+        return 0;
+    
+#if FAT_LFN_SUPPORT
+    /* calculate checksum of 8.3 name */
+    uint8_t checksum = fat_calc_83_checksum(buffer);
+    
+    /* write lfn entries */
+    for(uint8_t lfn_entry = lfn_entry_count; lfn_entry > 0; --lfn_entry)
+    {
+        memset(buffer, 0xff, sizeof(buffer));
+        
+        /* set file name */
+        const char* long_name_curr = name + (lfn_entry - 1) * 13;
+        uint8_t i = 1;
+        while(i < 0x1f)
+        {
+            buffer[i++] = *long_name_curr;
+            buffer[i++] = 0;
+
+            switch(i)
+            {
+                case 0x0b:
+                    i = 0x0e;
+                    break;
+                case 0x1a:
+                    i = 0x1c;
+                    break;
+            }
+
+            if(!*long_name_curr++)
+                break;
+        }
+        
+        /* set index of lfn entry */
+        buffer[0x00] = lfn_entry;
+        if(lfn_entry == lfn_entry_count)
+            buffer[0x00] |= FAT_DIRENTRY_LFNLAST;
+
+        /* mark as lfn entry */
+        buffer[0x0b] = 0x0f;
+
+        /* set 8.3 checksum */
+        buffer[0x0d] = checksum;
+
+        /* clear reserved bytes */
+        buffer[0x0c] = 0;
+        buffer[0x1a] = 0;
+        buffer[0x1b] = 0;
+
+        /* write entry */
+        device_write(offset, buffer, sizeof(buffer));
+    
+        offset += sizeof(buffer);
+    }
+#endif
+    
+    return 1;
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_file
+ * Creates a file.
+ *
+ * Creates a file and obtains the directory entry of the
+ * new file. If the file to create already exists, the
+ * directory entry of the existing file will be returned
+ * within the dir_entry parameter.
+ *
+ * \note The file name is not checked for invalid characters.
+ *
+ * \note The generation of the short 8.3 file name is quite
+ * simple. The first eight characters are used for the filename.
+ * The extension, if any, is made up of the first three characters
+ * following the last dot within the long filename. If the
+ * filename (without the extension) is longer than eight characters,
+ * the lower byte of the cluster number replaces the last two
+ * characters to avoid name clashes. In any other case, it is your
+ * responsibility to avoid name clashes.
+ *
+ * \param[in] parent The handle of the directory in which to create the file.
+ * \param[in] file The name of the file to create.
+ * \param[out] dir_entry The directory entry to fill for the new (or existing) file.
+ * \returns 0 on failure, 1 on success, 2 if the file already existed.
+ * \see fat_delete_file
+ */
+uint8_t fat_create_file(struct fat_dir_struct* parent, const char* file, struct fat_dir_entry_struct* dir_entry)
+{
+    if(!parent || !file || !file[0] || !dir_entry)
+        return 0;
+
+    /* check if the file already exists */
+    while(1)
+    {
+        if(!fat_read_dir(parent, dir_entry))
+            break;
+
+        if(strcmp(file, dir_entry->long_name) == 0)
+        {
+            fat_reset_dir(parent);
+            return 2;
+        }
+    }
+
+    struct fat_fs_struct* fs = parent->fs;
+
+    /* prepare directory entry with values already known */
+    memset(dir_entry, 0, sizeof(*dir_entry));
+    strncpy(dir_entry->long_name, file, sizeof(dir_entry->long_name) - 1);
+
+    /* find place where to store directory entry */
+    if(!(dir_entry->entry_offset = fat_find_offset_for_dir_entry(fs, parent, dir_entry)))
+        return 0;
+    
+    /* write directory entry to disk */
+    if(!fat_write_dir_entry(fs, dir_entry))
+        return 0;
+    
+    return 1;
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_file
+ * Deletes a file or directory.
+ *
+ * If a directory is deleted without first deleting its
+ * subdirectories and files, disk space occupied by these
+ * files will get wasted as there is no chance to release
+ * it and mark it as free.
+ * 
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in] dir_entry The directory entry of the file to delete.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_create_file
+ */
+uint8_t fat_delete_file(struct fat_fs_struct* fs, struct fat_dir_entry_struct* dir_entry)
+{
+    if(!fs || !dir_entry)
+        return 0;
+
+    /* get offset of the file's directory entry */
+    offset_t dir_entry_offset = dir_entry->entry_offset;
+    if(!dir_entry_offset)
+        return 0;
+
+#if FAT_LFN_SUPPORT
+    uint8_t buffer[12];
+    while(1)
+    {
+        /* read directory entry */
+        if(!fs->partition->device_read(dir_entry_offset, buffer, sizeof(buffer)))
+            return 0;
+        
+        /* mark the directory entry as deleted */
+        buffer[0] = FAT_DIRENTRY_DELETED;
+        
+        /* write back entry */
+        if(!fs->partition->device_write(dir_entry_offset, buffer, sizeof(buffer)))
+            return 0;
+
+        /* check if we deleted the whole entry */
+        if(buffer[11] != 0x0f)
+            break;
+
+        dir_entry_offset += 32;
+    }
+#else
+    /* mark the directory entry as deleted */
+    uint8_t first_char = FAT_DIRENTRY_DELETED;
+    if(!fs->partition->device_write(dir_entry_offset, &first_char, 1))
+        return 0;
+#endif
+
+    /* We deleted the directory entry. The next thing to do is
+     * marking all occupied clusters as free.
+     */
+    return (dir_entry->cluster == 0 || fat_free_clusters(fs, dir_entry->cluster));
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_file
+ * Moves or renames a file.
+ *
+ * Changes a file's name, optionally moving it into another
+ * directory as well. Before calling this function, the
+ * target file name must not exist. Moving a file to a
+ * different filesystem (i.e. \a parent_new doesn't lie on
+ * \a fs) is not supported.
+ * 
+ * After successfully renaming (and moving) the file, the
+ * given directory entry is updated such that it points to
+ * the file's new location.
+ *
+ * \note The notes which apply to fat_create_file() also
+ * apply to this function.
+ *
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in,out] dir_entry The directory entry of the file to move.
+ * \param[in] parent_new The handle of the new parent directory of the file.
+ * \param[in] file_new The file's new name.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_create_file, fat_delete_file, fat_move_dir
+ */
+uint8_t fat_move_file(struct fat_fs_struct* fs, struct fat_dir_entry_struct* dir_entry, struct fat_dir_struct* parent_new, const char* file_new)
+{
+    if(!fs || !dir_entry || !parent_new || (file_new && !file_new[0]))
+        return 0;
+    if(fs != parent_new->fs)
+        return 0;
+
+    /* use existing file name if none has been specified */
+    if(!file_new)
+        file_new = dir_entry->long_name;
+
+    /* create file with new file name */
+    struct fat_dir_entry_struct dir_entry_new;
+    if(!fat_create_file(parent_new, file_new, &dir_entry_new))
+        return 0;
+
+    /* copy members of directory entry which do not change with rename */
+    dir_entry_new.attributes = dir_entry->attributes;
+#if FAT_DATETIME_SUPPORT
+    dir_entry_new.modification_time = dir_entry->modification_time;
+    dir_entry_new.modification_date = dir_entry->modification_date;
+#endif
+    dir_entry_new.cluster = dir_entry->cluster;
+    dir_entry_new.file_size = dir_entry->file_size;
+
+    /* make the new file name point to the old file's content */
+    if(!fat_write_dir_entry(fs, &dir_entry_new))
+    {
+        fat_delete_file(fs, &dir_entry_new);
+        return 0;
+    }
+    
+    /* delete the old file, but not its clusters, which have already been remapped above */
+    dir_entry->cluster = 0;
+    if(!fat_delete_file(fs, dir_entry))
+        return 0;
+
+    *dir_entry = dir_entry_new;
+    return 1;
+}
+#endif
+
+#if DOXYGEN || FAT_WRITE_SUPPORT
+/**
+ * \ingroup fat_dir
+ * Creates a directory.
+ *
+ * Creates a directory and obtains its directory entry.
+ * If the directory to create already exists, its
+ * directory entry will be returned within the dir_entry
+ * parameter.
+ *
+ * \note The notes which apply to fat_create_file() also
+ * apply to this function.
+ *
+ * \param[in] parent The handle of the parent directory of the new directory.
+ * \param[in] dir The name of the directory to create.
+ * \param[out] dir_entry The directory entry to fill for the new directory.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_delete_dir
+ */
+uint8_t fat_create_dir(struct fat_dir_struct* parent, const char* dir, struct fat_dir_entry_struct* dir_entry)
+{
+    if(!parent || !dir || !dir[0] || !dir_entry)
+        return 0;
+
+    /* check if the file or directory already exists */
+    while(fat_read_dir(parent, dir_entry))
+    {
+        if(strcmp(dir, dir_entry->long_name) == 0)
+        {
+            fat_reset_dir(parent);
+            return 0;
+        }
+    }
+
+    struct fat_fs_struct* fs = parent->fs;
+
+    /* allocate cluster which will hold directory entries */
+    cluster_t dir_cluster = fat_append_clusters(fs, 0, 1);
+    if(!dir_cluster)
+        return 0;
+
+    /* clear cluster to prevent bogus directory entries */
+    fat_clear_cluster(fs, dir_cluster);
+    
+    memset(dir_entry, 0, sizeof(*dir_entry));
+    dir_entry->attributes = FAT_ATTRIB_DIR;
+
+    /* create "." directory self reference */
+    dir_entry->entry_offset = fs->header.cluster_zero_offset +
+                              (offset_t) (dir_cluster - 2) * fs->header.cluster_size;
+    dir_entry->long_name[0] = '.';
+    dir_entry->cluster = dir_cluster;
+    if(!fat_write_dir_entry(fs, dir_entry))
+    {
+        fat_free_clusters(fs, dir_cluster);
+        return 0;
+    }
+
+    /* create ".." parent directory reference */
+    dir_entry->entry_offset += 32;
+    dir_entry->long_name[1] = '.';
+    dir_entry->cluster = parent->dir_entry.cluster;
+    if(!fat_write_dir_entry(fs, dir_entry))
+    {
+        fat_free_clusters(fs, dir_cluster);
+        return 0;
+    }
+
+    /* fill directory entry */
+    strncpy(dir_entry->long_name, dir, sizeof(dir_entry->long_name) - 1);
+    dir_entry->cluster = dir_cluster;
+
+    /* find place where to store directory entry */
+    if(!(dir_entry->entry_offset = fat_find_offset_for_dir_entry(fs, parent, dir_entry)))
+    {
+        fat_free_clusters(fs, dir_cluster);
+        return 0;
+    }
+
+    /* write directory to disk */
+    if(!fat_write_dir_entry(fs, dir_entry))
+    {
+        fat_free_clusters(fs, dir_cluster);
+        return 0;
+    }
+
+    return 1;
+}
+#endif
+
+/**
+ * \ingroup fat_dir
+ * Deletes a directory.
+ *
+ * This is just a synonym for fat_delete_file().
+ * If a directory is deleted without first deleting its
+ * subdirectories and files, disk space occupied by these
+ * files will get wasted as there is no chance to release
+ * it and mark it as free.
+ * 
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in] dir_entry The directory entry of the directory to delete.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_create_dir
+ */
+#ifdef DOXYGEN
+uint8_t fat_delete_dir(struct fat_fs_struct* fs, struct fat_dir_entry_struct* dir_entry);
+#endif
+
+/**
+ * \ingroup fat_dir
+ * Moves or renames a directory.
+ *
+ * This is just a synonym for fat_move_file().
+ * 
+ * \param[in] fs The filesystem on which to operate.
+ * \param[in,out] dir_entry The directory entry of the directory to move.
+ * \param[in] parent_new The handle of the new parent directory.
+ * \param[in] dir_new The directory's new name.
+ * \returns 0 on failure, 1 on success.
+ * \see fat_create_dir, fat_delete_dir, fat_move_file
+ */
+#ifdef DOXYGEN
+uint8_t fat_move_dir(struct fat_fs_struct* fs, struct fat_dir_entry_struct* dir_entry, struct fat_dir_struct* parent_new, const char* dir_new);
+#endif
+
+#if DOXYGEN || FAT_DATETIME_SUPPORT
+/**
+ * \ingroup fat_file
+ * Returns the modification date of a file.
+ *
+ * \param[in] dir_entry The directory entry of which to return the modification date.
+ * \param[out] year The year the file was last modified.
+ * \param[out] month The month the file was last modified.
+ * \param[out] day The day the file was last modified.
+ */
+void fat_get_file_modification_date(const struct fat_dir_entry_struct* dir_entry, uint16_t* year, uint8_t* month, uint8_t* day)
+{
+    if(!dir_entry)
+        return;
+
+    *year = 1980 + ((dir_entry->modification_date >> 9) & 0x7f);
+    *month = (dir_entry->modification_date >> 5) & 0x0f;
+    *day = (dir_entry->modification_date >> 0) & 0x1f;
+}
+#endif
+
+#if DOXYGEN || FAT_DATETIME_SUPPORT
+/**
+ * \ingroup fat_file
+ * Returns the modification time of a file.
+ *
+ * \param[in] dir_entry The directory entry of which to return the modification time.
+ * \param[out] hour The hour the file was last modified.
+ * \param[out] min The min the file was last modified.
+ * \param[out] sec The sec the file was last modified.
+ */
+void fat_get_file_modification_time(const struct fat_dir_entry_struct* dir_entry, uint8_t* hour, uint8_t* min, uint8_t* sec)
+{
+    if(!dir_entry)
+        return;
+
+    *hour = (dir_entry->modification_time >> 11) & 0x1f;
+    *min = (dir_entry->modification_time >> 5) & 0x3f;
+    *sec = ((dir_entry->modification_time >> 0) & 0x1f) * 2;
+}
+#endif
+
+#if DOXYGEN || (FAT_WRITE_SUPPORT && FAT_DATETIME_SUPPORT)
+/**
+ * \ingroup fat_file
+ * Sets the modification time of a date.
+ *
+ * \param[in] dir_entry The directory entry for which to set the modification date.
+ * \param[in] year The year the file was last modified.
+ * \param[in] month The month the file was last modified.
+ * \param[in] day The day the file was last modified.
+ */
+void fat_set_file_modification_date(struct fat_dir_entry_struct* dir_entry, uint16_t year, uint8_t month, uint8_t day)
+{
+    if(!dir_entry)
+        return;
+
+    dir_entry->modification_date =
+        ((year - 1980) << 9) |
+        ((uint16_t) month << 5) |
+        ((uint16_t) day << 0);
+}
+#endif
+
+#if DOXYGEN || (FAT_WRITE_SUPPORT && FAT_DATETIME_SUPPORT)
+/**
+ * \ingroup fat_file
+ * Sets the modification time of a file.
+ *
+ * \param[in] dir_entry The directory entry for which to set the modification time.
+ * \param[in] hour The year the file was last modified.
+ * \param[in] min The month the file was last modified.
+ * \param[in] sec The day the file was last modified.
+ */
+void fat_set_file_modification_time(struct fat_dir_entry_struct* dir_entry, uint8_t hour, uint8_t min, uint8_t sec)
+{
+    if(!dir_entry)
+        return;
+
+    dir_entry->modification_time =
+        ((uint16_t) hour << 11) |
+        ((uint16_t) min << 5) |
+        ((uint16_t) sec >> 1) ;
+}
+#endif
+
+/**
+ * \ingroup fat_fs
+ * Returns the amount of total storage capacity of the filesystem in bytes.
+ *
+ * \param[in] fs The filesystem on which to operate.
+ * \returns 0 on failure, the filesystem size in bytes otherwise.
+ */
+offset_t fat_get_fs_size(const struct fat_fs_struct* fs)
+{
+    if(!fs)
+        return 0;
+
+#if FAT_FAT32_SUPPORT
+    if(fs->partition->type == PARTITION_TYPE_FAT32)
+        return (offset_t) (fs->header.fat_size / 4 - 2) * fs->header.cluster_size;
+    else
+#endif
+        return (offset_t) (fs->header.fat_size / 2 - 2) * fs->header.cluster_size;
+}
+
+/**
+ * \ingroup fat_fs
+ * Returns the amount of free storage capacity on the filesystem in bytes.
+ *
+ * \note As the FAT filesystem is cluster based, this function does not
+ *       return continuous values but multiples of the cluster size.
+ *
+ * \param[in] fs The filesystem on which to operate.
+ * \returns 0 on failure, the free filesystem space in bytes otherwise.
+ */
+offset_t fat_get_fs_free(const struct fat_fs_struct* fs)
+{
+    if(!fs)
+        return 0;
+
+    uint8_t fat[32];
+    struct fat_usage_count_callback_arg count_arg;
+    count_arg.cluster_count = 0;
+    count_arg.buffer_size = sizeof(fat);
+
+    offset_t fat_offset = fs->header.fat_offset;
+    uint32_t fat_size = fs->header.fat_size;
+    while(fat_size > 0)
+    {
+        uintptr_t length = UINTPTR_MAX - 1;
+        if(fat_size < length)
+            length = fat_size;
+
+        if(!fs->partition->device_read_interval(fat_offset,
+                                                fat,
+                                                sizeof(fat),
+                                                length,
+#if FAT_FAT32_SUPPORT
+                                                (fs->partition->type == PARTITION_TYPE_FAT16) ?
+                                                    fat_get_fs_free_16_callback :
+                                                    fat_get_fs_free_32_callback,
+#else
+                                                fat_get_fs_free_16_callback,
+#endif
+                                                &count_arg
+                                               )
+          )
+            return 0;
+
+        fat_offset += length;
+        fat_size -= length;
+    }
+
+    return (offset_t) count_arg.cluster_count * fs->header.cluster_size;
+}
+
+/**
+ * \ingroup fat_fs
+ * Callback function used for counting free clusters in a FAT.
+ */
+uint8_t fat_get_fs_free_16_callback(uint8_t* buffer, offset_t offset, void* p)
+{
+    struct fat_usage_count_callback_arg* count_arg = (struct fat_usage_count_callback_arg*) p;
+    uintptr_t buffer_size = count_arg->buffer_size;
+
+    for(uintptr_t i = 0; i < buffer_size; i += 2, buffer += 2)
+    {
+        uint16_t cluster = read16(buffer);
+        if(cluster == HTOL16(FAT16_CLUSTER_FREE))
+            ++(count_arg->cluster_count);
+    }
+
+    return 1;
+}
+
+#if DOXYGEN || FAT_FAT32_SUPPORT
+/**
+ * \ingroup fat_fs
+ * Callback function used for counting free clusters in a FAT32.
+ */
+uint8_t fat_get_fs_free_32_callback(uint8_t* buffer, offset_t offset, void* p)
+{
+    struct fat_usage_count_callback_arg* count_arg = (struct fat_usage_count_callback_arg*) p;
+    uintptr_t buffer_size = count_arg->buffer_size;
+
+    for(uintptr_t i = 0; i < buffer_size; i += 4, buffer += 4)
+    {
+        uint32_t cluster = read32(buffer);
+        if(cluster == HTOL32(FAT32_CLUSTER_FREE))
+            ++(count_arg->cluster_count);
+    }
+
+    return 1;
+}
+#endif
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/fat.h	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,131 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef FAT_H
+#define FAT_H
+
+#include <stdint.h>
+#include "fat_config.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * \addtogroup fat
+ *
+ * @{
+ */
+/**
+ * \file
+ * FAT header (license: GPLv2 or LGPLv2.1)
+ *
+ * \author Roland Riegel
+ */
+
+/**
+ * \addtogroup fat_file
+ * @{
+ */
+
+/** The file is read-only. */
+#define FAT_ATTRIB_READONLY (1 << 0)
+/** The file is hidden. */
+#define FAT_ATTRIB_HIDDEN (1 << 1)
+/** The file is a system file. */
+#define FAT_ATTRIB_SYSTEM (1 << 2)
+/** The file is empty and has the volume label as its name. */
+#define FAT_ATTRIB_VOLUME (1 << 3)
+/** The file is a directory. */
+#define FAT_ATTRIB_DIR (1 << 4)
+/** The file has to be archived. */
+#define FAT_ATTRIB_ARCHIVE (1 << 5)
+
+/** The given offset is relative to the beginning of the file. */
+#define FAT_SEEK_SET 0
+/** The given offset is relative to the current read/write position. */
+#define FAT_SEEK_CUR 1
+/** The given offset is relative to the end of the file. */
+#define FAT_SEEK_END 2
+
+/**
+ * @}
+ */
+
+struct partition_struct;
+struct fat_fs_struct;
+struct fat_file_struct;
+struct fat_dir_struct;
+
+/**
+ * \ingroup fat_file
+ * Describes a directory entry.
+ */
+struct fat_dir_entry_struct
+{
+    /** The file's name, truncated to 31 characters. */
+    char long_name[32];
+    /** The file's attributes. Mask of the FAT_ATTRIB_* constants. */
+    uint8_t attributes;
+#if FAT_DATETIME_SUPPORT
+    /** Compressed representation of modification time. */
+    uint16_t modification_time;
+    /** Compressed representation of modification date. */
+    uint16_t modification_date;
+#endif
+    /** The cluster in which the file's first byte resides. */
+    cluster_t cluster;
+    /** The file's size. */
+    uint32_t file_size;
+    /** The total disk offset of this directory entry. */
+    offset_t entry_offset;
+};
+
+struct fat_fs_struct* fat_open(struct partition_struct* partition);
+void fat_close(struct fat_fs_struct* fs);
+
+struct fat_file_struct* fat_open_file(struct fat_fs_struct* fs, const struct fat_dir_entry_struct* dir_entry);
+void fat_close_file(struct fat_file_struct* fd);
+intptr_t fat_read_file(struct fat_file_struct* fd, uint8_t* buffer, uintptr_t buffer_len);
+intptr_t fat_write_file(struct fat_file_struct* fd, const uint8_t* buffer, uintptr_t buffer_len);
+uint8_t fat_seek_file(struct fat_file_struct* fd, int32_t* offset, uint8_t whence);
+uint8_t fat_resize_file(struct fat_file_struct* fd, uint32_t size);
+
+struct fat_dir_struct* fat_open_dir(struct fat_fs_struct* fs, const struct fat_dir_entry_struct* dir_entry);
+void fat_close_dir(struct fat_dir_struct* dd);
+uint8_t fat_read_dir(struct fat_dir_struct* dd, struct fat_dir_entry_struct* dir_entry);
+uint8_t fat_reset_dir(struct fat_dir_struct* dd);
+
+uint8_t fat_create_file(struct fat_dir_struct* parent, const char* file, struct fat_dir_entry_struct* dir_entry);
+uint8_t fat_delete_file(struct fat_fs_struct* fs, struct fat_dir_entry_struct* dir_entry);
+uint8_t fat_move_file(struct fat_fs_struct* fs, struct fat_dir_entry_struct* dir_entry, struct fat_dir_struct* parent_new, const char* file_new);
+uint8_t fat_create_dir(struct fat_dir_struct* parent, const char* dir, struct fat_dir_entry_struct* dir_entry);
+#define fat_delete_dir fat_delete_file
+#define fat_move_dir fat_move_file
+
+void fat_get_file_modification_date(const struct fat_dir_entry_struct* dir_entry, uint16_t* year, uint8_t* month, uint8_t* day);
+void fat_get_file_modification_time(const struct fat_dir_entry_struct* dir_entry, uint8_t* hour, uint8_t* min, uint8_t* sec);
+
+uint8_t fat_get_dir_entry_of_path(struct fat_fs_struct* fs, const char* path, struct fat_dir_entry_struct* dir_entry);
+
+offset_t fat_get_fs_size(const struct fat_fs_struct* fs);
+offset_t fat_get_fs_free(const struct fat_fs_struct* fs);
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/fat_config.h	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,128 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef FAT_CONFIG_H
+#define FAT_CONFIG_H
+
+#include <stdint.h>
+#include "sd_raw_config.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * \addtogroup fat
+ *
+ * @{
+ */
+/**
+ * \file
+ * FAT configuration (license: GPLv2 or LGPLv2.1)
+ */
+
+/**
+ * \ingroup fat_config
+ * Controls FAT write support.
+ *
+ * Set to 1 to enable FAT write support, set to 0 to disable it.
+ */
+#define FAT_WRITE_SUPPORT SD_RAW_WRITE_SUPPORT
+
+/**
+ * \ingroup fat_config
+ * Controls FAT long filename (LFN) support.
+ *
+ * Set to 1 to enable LFN support, set to 0 to disable it.
+ */
+#define FAT_LFN_SUPPORT 0
+
+/**
+ * \ingroup fat_config
+ * Controls FAT date and time support.
+ * 
+ * Set to 1 to enable FAT date and time stamping support.
+ */
+#define FAT_DATETIME_SUPPORT 0
+
+/**
+ * \ingroup fat_config
+ * Controls FAT32 support.
+ *
+ * Set to 1 to enable FAT32 support.
+ */
+#define FAT_FAT32_SUPPORT SD_RAW_SDHC
+
+/**
+ * \ingroup fat_config
+ * Controls updates of directory entries.
+ *
+ * Set to 1 to delay directory entry updates until the file is closed.
+ * This can boost performance significantly, but may cause data loss
+ * if the file is not properly closed.
+ */
+#define FAT_DELAY_DIRENTRY_UPDATE 0
+
+/**
+ * \ingroup fat_config
+ * Determines the function used for retrieving current date and time.
+ *
+ * Define this to the function call which shall be used to retrieve
+ * current date and time.
+ *
+ * \note Used only when FAT_DATETIME_SUPPORT is 1.
+ *
+ * \param[out] year Pointer to a \c uint16_t which receives the current year.
+ * \param[out] month Pointer to a \c uint8_t which receives the current month.
+ * \param[out] day Pointer to a \c uint8_t which receives the current day.
+ * \param[out] hour Pointer to a \c uint8_t which receives the current hour.
+ * \param[out] min Pointer to a \c uint8_t which receives the current minute.
+ * \param[out] sec Pointer to a \c uint8_t which receives the current sec.
+ */
+#define fat_get_datetime(year, month, day, hour, min, sec) \
+    get_datetime(year, month, day, hour, min, sec)
+/* forward declaration for the above */
+void get_datetime(uint16_t* year, uint8_t* month, uint8_t* day, uint8_t* hour, uint8_t* min, uint8_t* sec);
+
+/**
+ * \ingroup fat_config
+ * Maximum number of filesystem handles.
+ */
+#define FAT_FS_COUNT 1
+
+/**
+ * \ingroup fat_config
+ * Maximum number of file handles.
+ */
+#define FAT_FILE_COUNT 1
+
+/**
+ * \ingroup fat_config
+ * Maximum number of directory handles.
+ */
+#define FAT_DIR_COUNT 1
+
+/**
+ * @}
+ */
+
+#if FAT_FAT32_SUPPORT
+    typedef uint32_t cluster_t;
+#else
+    typedef uint16_t cluster_t;
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
--- a/main.c	Thu Jun 13 23:44:59 2013 +0800
+++ b/main.c	Tue Jun 25 13:55:11 2013 +0800
@@ -16,6 +16,12 @@
 #include "hmac-sha1.h"
 #include "aes.h"
 
+#include "fat.h"
+#include "fat_config.h"
+#include "partition.h"
+#include "sd_raw.h"
+#include "sd_raw_config.h"
+
 //#include "simple_ds18b20.h"
 //#include "onewire.h"
 
@@ -265,6 +271,56 @@
     return (unsigned char)c;
 }
 
+uint8_t find_file_in_dir(struct fat_fs_struct* fs, struct fat_dir_struct* dd, const char* name, struct fat_dir_entry_struct* dir_entry)
+{
+    while(fat_read_dir(dd, dir_entry))
+    {
+        if(strcmp(dir_entry->long_name, name) == 0)
+        {
+            fat_reset_dir(dd);
+            return 1;
+        }
+    }
+
+    return 0;
+}
+
+struct fat_file_struct* 
+open_file_in_dir(struct fat_fs_struct* fs, struct fat_dir_struct* dd, const char* name)
+{
+    struct fat_dir_entry_struct file_entry;
+    if(!find_file_in_dir(fs, dd, name, &file_entry))
+        return 0;
+
+    return fat_open_file(fs, &file_entry);
+}
+
+static void
+hmac_file(const char* fn)
+{
+    sd_raw_init();
+    struct partition_struct* partition = partition_open(sd_raw_read, sd_raw_read_interval, 0, 0, 0);
+    struct fat_fs_struct* fs = fat_open(partition);
+    struct fat_dir_entry_struct directory;
+    fat_get_dir_entry_of_path(fs, "/", &directory);
+
+    struct sd_raw_info disk_info;
+    sd_raw_get_info(&disk_info);
+    printf("diskinfo size %d", disk_info.capacity);
+
+    struct fat_dir_struct* dd = fat_open_dir(fs, &directory);
+    struct fat_file_struct* fd = open_file_in_dir(fs, dd, "fn");
+
+    char c = 0;
+    char buf[512];
+    for (int i = 0; i < 10; i++)
+    {
+        fat_read_file(fd, buf, sizeof(buf));
+        c ^= buf[0];
+    }
+    printf("total %d\n", c);
+}
+
 static void
 cmd_reset()
 {
@@ -491,8 +547,8 @@
     }
 
     uint8_t tmpbuf[256];
-    aesInit(avr_keys[key_index], tmpbuf);
-    aesDecrypt(&indata[HMACLEN], NULL);
+    //aesInit(avr_keys[key_index], tmpbuf);
+    //aesDecrypt(&indata[HMACLEN], NULL);
 
     printf_P(PSTR("DECRYPTED: "));
     printhex(output, AESLEN, stdout);
@@ -846,6 +902,8 @@
 	
 	PORT_PI_WARNING &= ~_BV(PIN_PI_WARNING);
     DDR_PI_RESET &= ~_BV(PIN_PI_RESET);	
+
+    hmac_file("stuff");
 }
 
 static void
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/partition.c	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,155 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#include "byteordering.h"
+#include "partition.h"
+#include "partition_config.h"
+#include "sd-reader_config.h"
+
+#include <string.h>
+
+#if USE_DYNAMIC_MEMORY
+    #include <stdlib.h>
+#endif
+
+/**
+ * \addtogroup partition Partition table support
+ *
+ * Support for reading partition tables and access to partitions.
+ *
+ * @{
+ */
+/**
+ * \file
+ * Partition table implementation (license: GPLv2 or LGPLv2.1)
+ *
+ * \author Roland Riegel
+ */
+
+/**
+ * \addtogroup partition_config Configuration of partition table support
+ * Preprocessor defines to configure the partition support.
+ */
+
+#if !USE_DYNAMIC_MEMORY
+static struct partition_struct partition_handles[PARTITION_COUNT];
+#endif
+
+/**
+ * Opens a partition.
+ *
+ * Opens a partition by its index number and returns a partition
+ * handle which describes the opened partition.
+ *
+ * \note This function does not support extended partitions.
+ *
+ * \param[in] device_read A function pointer which is used to read from the disk.
+ * \param[in] device_read_interval A function pointer which is used to read in constant intervals from the disk.
+ * \param[in] device_write A function pointer which is used to write to the disk.
+ * \param[in] device_write_interval A function pointer which is used to write a data stream to disk.
+ * \param[in] index The index of the partition which should be opened, range 0 to 3.
+ *                  A negative value is allowed as well. In this case, the partition opened is
+ *                  not checked for existance, begins at offset zero, has a length of zero
+ *                  and is of an unknown type. Use this in case you want to open the whole device
+ *                  as a single partition (e.g. for "super floppy" use).
+ * \returns 0 on failure, a partition descriptor on success.
+ * \see partition_close
+ */
+struct partition_struct* partition_open(device_read_t device_read, device_read_interval_t device_read_interval, device_write_t device_write, device_write_interval_t device_write_interval, int8_t index)
+{
+    struct partition_struct* new_partition = 0;
+    uint8_t buffer[0x10];
+
+    if(!device_read || !device_read_interval || index >= 4)
+        return 0;
+
+    if(index >= 0)
+    {
+        /* read specified partition table index */
+        if(!device_read(0x01be + index * 0x10, buffer, sizeof(buffer)))
+            return 0;
+
+        /* abort on empty partition entry */
+        if(buffer[4] == 0x00)
+            return 0;
+    }
+
+    /* allocate partition descriptor */
+#if USE_DYNAMIC_MEMORY
+    new_partition = malloc(sizeof(*new_partition));
+    if(!new_partition)
+        return 0;
+#else
+    new_partition = partition_handles;
+    uint8_t i;
+    for(i = 0; i < PARTITION_COUNT; ++i)
+    {
+        if(new_partition->type == PARTITION_TYPE_FREE)
+            break;
+
+        ++new_partition;
+    }
+    if(i >= PARTITION_COUNT)
+        return 0;
+#endif
+
+    memset(new_partition, 0, sizeof(*new_partition));
+
+    /* fill partition descriptor */
+    new_partition->device_read = device_read;
+    new_partition->device_read_interval = device_read_interval;
+    new_partition->device_write = device_write;
+    new_partition->device_write_interval = device_write_interval;
+
+    if(index >= 0)
+    {
+        new_partition->type = buffer[4];
+        new_partition->offset = read32(&buffer[8]);
+        new_partition->length = read32(&buffer[12]);
+    }
+    else
+    {
+        new_partition->type = 0xff;
+    }
+
+    return new_partition;
+}
+
+/**
+ * Closes a partition.
+ *
+ * This function destroys a partition descriptor which was
+ * previously obtained from a call to partition_open().
+ * When this function returns, the given descriptor will be
+ * invalid.
+ *
+ * \param[in] partition The partition descriptor to destroy.
+ * \returns 0 on failure, 1 on success.
+ * \see partition_open
+ */
+uint8_t partition_close(struct partition_struct* partition)
+{
+    if(!partition)
+        return 0;
+
+    /* destroy partition descriptor */
+#if USE_DYNAMIC_MEMORY
+    free(partition);
+#else
+    partition->type = PARTITION_TYPE_FREE;
+#endif
+
+    return 1;
+}
+
+/**
+ * @}
+ */
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/partition.h	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,212 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef PARTITION_H
+#define PARTITION_H
+
+#include <stdint.h>
+#include "sd_raw_config.h"
+#include "partition_config.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * \addtogroup partition
+ *
+ * @{
+ */
+/**
+ * \file
+ * Partition table header (license: GPLv2 or LGPLv2.1)
+ *
+ * \author Roland Riegel
+ */
+
+/**
+ * The partition table entry is not used.
+ */
+#define PARTITION_TYPE_FREE 0x00
+/**
+ * The partition contains a FAT12 filesystem.
+ */
+#define PARTITION_TYPE_FAT12 0x01
+/**
+ * The partition contains a FAT16 filesystem with 32MB maximum.
+ */
+#define PARTITION_TYPE_FAT16_32MB 0x04
+/**
+ * The partition is an extended partition with its own partition table.
+ */
+#define PARTITION_TYPE_EXTENDED 0x05
+/**
+ * The partition contains a FAT16 filesystem.
+ */
+#define PARTITION_TYPE_FAT16 0x06
+/**
+ * The partition contains a FAT32 filesystem.
+ */
+#define PARTITION_TYPE_FAT32 0x0b
+/**
+ * The partition contains a FAT32 filesystem with LBA.
+ */
+#define PARTITION_TYPE_FAT32_LBA 0x0c
+/**
+ * The partition contains a FAT16 filesystem with LBA.
+ */
+#define PARTITION_TYPE_FAT16_LBA 0x0e
+/**
+ * The partition is an extended partition with LBA.
+ */
+#define PARTITION_TYPE_EXTENDED_LBA 0x0f
+/**
+ * The partition has an unknown type.
+ */
+#define PARTITION_TYPE_UNKNOWN 0xff
+
+/**
+ * A function pointer used to read from the partition.
+ *
+ * \param[in] offset The offset on the device where to start reading.
+ * \param[out] buffer The buffer into which to place the data.
+ * \param[in] length The count of bytes to read.
+ */
+typedef uint8_t (*device_read_t)(offset_t offset, uint8_t* buffer, uintptr_t length);
+/**
+ * A function pointer passed to a \c device_read_interval_t.
+ *
+ * \param[in] buffer The buffer which contains the data just read.
+ * \param[in] offset The offset from which the data in \c buffer was read.
+ * \param[in] p An opaque pointer.
+ * \see device_read_interval_t
+ */
+typedef uint8_t (*device_read_callback_t)(uint8_t* buffer, offset_t offset, void* p);
+/**
+ * A function pointer used to continuously read units of \c interval bytes
+ * and call a callback function.
+ *
+ * This function starts reading at the specified offset. Every \c interval bytes,
+ * it calls the callback function with the associated data buffer.
+ *
+ * By returning zero, the callback may stop reading.
+ *
+ * \param[in] offset Offset from which to start reading.
+ * \param[in] buffer Pointer to a buffer which is at least interval bytes in size.
+ * \param[in] interval Number of bytes to read before calling the callback function.
+ * \param[in] length Number of bytes to read altogether.
+ * \param[in] callback The function to call every interval bytes.
+ * \param[in] p An opaque pointer directly passed to the callback function.
+ * \returns 0 on failure, 1 on success
+ * \see device_read_t
+ */
+typedef uint8_t (*device_read_interval_t)(offset_t offset, uint8_t* buffer, uintptr_t interval, uintptr_t length, device_read_callback_t callback, void* p);
+/**
+ * A function pointer used to write to the partition.
+ *
+ * \param[in] offset The offset on the device where to start writing.
+ * \param[in] buffer The buffer which to write.
+ * \param[in] length The count of bytes to write.
+ */
+typedef uint8_t (*device_write_t)(offset_t offset, const uint8_t* buffer, uintptr_t length);
+/**
+ * A function pointer passed to a \c device_write_interval_t.
+ *
+ * \param[in] buffer The buffer which receives the data to write.
+ * \param[in] offset The offset to which the data in \c buffer will be written.
+ * \param[in] p An opaque pointer.
+ * \returns The number of bytes put into \c buffer
+ * \see device_write_interval_t
+ */
+typedef uintptr_t (*device_write_callback_t)(uint8_t* buffer, offset_t offset, void* p);
+/**
+ * A function pointer used to continuously write a data stream obtained from
+ * a callback function.
+ *
+ * This function starts writing at the specified offset. To obtain the
+ * next bytes to write, it calls the callback function. The callback fills the
+ * provided data buffer and returns the number of bytes it has put into the buffer.
+ *
+ * By returning zero, the callback may stop writing.
+ *
+ * \param[in] offset Offset where to start writing.
+ * \param[in] buffer Pointer to a buffer which is used for the callback function.
+ * \param[in] length Number of bytes to write in total. May be zero for endless writes.
+ * \param[in] callback The function used to obtain the bytes to write.
+ * \param[in] p An opaque pointer directly passed to the callback function.
+ * \returns 0 on failure, 1 on success
+ * \see device_write_t
+ */
+typedef uint8_t (*device_write_interval_t)(offset_t offset, uint8_t* buffer, uintptr_t length, device_write_callback_t callback, void* p);
+
+/**
+ * Describes a partition.
+ */
+struct partition_struct
+{
+    /**
+     * The function which reads data from the partition.
+     *
+     * \note The offset given to this function is relative to the whole disk,
+     *       not to the start of the partition.
+     */
+    device_read_t device_read;
+    /**
+     * The function which repeatedly reads a constant amount of data from the partition.
+     *
+     * \note The offset given to this function is relative to the whole disk,
+     *       not to the start of the partition.
+     */
+    device_read_interval_t device_read_interval;
+    /**
+     * The function which writes data to the partition.
+     *
+     * \note The offset given to this function is relative to the whole disk,
+     *       not to the start of the partition.
+     */
+    device_write_t device_write;
+    /**
+     * The function which repeatedly writes data to the partition.
+     *
+     * \note The offset given to this function is relative to the whole disk,
+     *       not to the start of the partition.
+     */
+    device_write_interval_t device_write_interval;
+
+    /**
+     * The type of the partition.
+     *
+     * Compare this value to the PARTITION_TYPE_* constants.
+     */
+    uint8_t type;
+    /**
+     * The offset in blocks on the disk where this partition starts.
+     */
+    uint32_t offset;
+    /**
+     * The length in blocks of this partition.
+     */
+    uint32_t length;
+};
+
+struct partition_struct* partition_open(device_read_t device_read, device_read_interval_t device_read_interval, device_write_t device_write, device_write_interval_t device_write_interval, int8_t index);
+uint8_t partition_close(struct partition_struct* partition);
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/partition_config.h	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,44 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef PARTITION_CONFIG_H
+#define PARTITION_CONFIG_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * \addtogroup partition
+ *
+ * @{
+ */
+/**
+ * \file
+ * Partition configuration (license: GPLv2 or LGPLv2.1)
+ */
+
+/**
+ * \ingroup partition_config
+ * Maximum number of partition handles.
+ */
+#define PARTITION_COUNT 1
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sd-reader_config.h	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,53 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef SD_READER_CONFIG_H
+#define SD_READER_CONFIG_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * \addtogroup config Sd-reader configuration
+ *
+ * @{
+ */
+
+/**
+ * \file
+ * Common sd-reader configuration used by all modules (license: GPLv2 or LGPLv2.1)
+ *
+ * \note This file contains only configuration items relevant to
+ * all sd-reader implementation files. For module specific configuration
+ * options, please see the files fat_config.h, partition_config.h
+ * and sd_raw_config.h.
+ */
+
+/**
+ * Controls allocation of memory.
+ *
+ * Set to 1 to use malloc()/free() for allocation of structures
+ * like file and directory handles, set to 0 to use pre-allocated
+ * fixed-size handle arrays.
+ */
+#define USE_DYNAMIC_MEMORY 0
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sd_raw.c	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,998 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#include <string.h>
+#include <avr/io.h>
+#include "sd_raw.h"
+
+/**
+ * \addtogroup sd_raw MMC/SD/SDHC card raw access
+ *
+ * This module implements read and write access to MMC, SD
+ * and SDHC cards. It serves as a low-level driver for the
+ * higher level modules such as partition and file system
+ * access.
+ *
+ * @{
+ */
+/**
+ * \file
+ * MMC/SD/SDHC raw access implementation (license: GPLv2 or LGPLv2.1)
+ *
+ * \author Roland Riegel
+ */
+
+/**
+ * \addtogroup sd_raw_config MMC/SD configuration
+ * Preprocessor defines to configure the MMC/SD support.
+ */
+
+/**
+ * @}
+ */
+
+/* commands available in SPI mode */
+
+/* CMD0: response R1 */
+#define CMD_GO_IDLE_STATE 0x00
+/* CMD1: response R1 */
+#define CMD_SEND_OP_COND 0x01
+/* CMD8: response R7 */
+#define CMD_SEND_IF_COND 0x08
+/* CMD9: response R1 */
+#define CMD_SEND_CSD 0x09
+/* CMD10: response R1 */
+#define CMD_SEND_CID 0x0a
+/* CMD12: response R1 */
+#define CMD_STOP_TRANSMISSION 0x0c
+/* CMD13: response R2 */
+#define CMD_SEND_STATUS 0x0d
+/* CMD16: arg0[31:0]: block length, response R1 */
+#define CMD_SET_BLOCKLEN 0x10
+/* CMD17: arg0[31:0]: data address, response R1 */
+#define CMD_READ_SINGLE_BLOCK 0x11
+/* CMD18: arg0[31:0]: data address, response R1 */
+#define CMD_READ_MULTIPLE_BLOCK 0x12
+/* CMD24: arg0[31:0]: data address, response R1 */
+#define CMD_WRITE_SINGLE_BLOCK 0x18
+/* CMD25: arg0[31:0]: data address, response R1 */
+#define CMD_WRITE_MULTIPLE_BLOCK 0x19
+/* CMD27: response R1 */
+#define CMD_PROGRAM_CSD 0x1b
+/* CMD28: arg0[31:0]: data address, response R1b */
+#define CMD_SET_WRITE_PROT 0x1c
+/* CMD29: arg0[31:0]: data address, response R1b */
+#define CMD_CLR_WRITE_PROT 0x1d
+/* CMD30: arg0[31:0]: write protect data address, response R1 */
+#define CMD_SEND_WRITE_PROT 0x1e
+/* CMD32: arg0[31:0]: data address, response R1 */
+#define CMD_TAG_SECTOR_START 0x20
+/* CMD33: arg0[31:0]: data address, response R1 */
+#define CMD_TAG_SECTOR_END 0x21
+/* CMD34: arg0[31:0]: data address, response R1 */
+#define CMD_UNTAG_SECTOR 0x22
+/* CMD35: arg0[31:0]: data address, response R1 */
+#define CMD_TAG_ERASE_GROUP_START 0x23
+/* CMD36: arg0[31:0]: data address, response R1 */
+#define CMD_TAG_ERASE_GROUP_END 0x24
+/* CMD37: arg0[31:0]: data address, response R1 */
+#define CMD_UNTAG_ERASE_GROUP 0x25
+/* CMD38: arg0[31:0]: stuff bits, response R1b */
+#define CMD_ERASE 0x26
+/* ACMD41: arg0[31:0]: OCR contents, response R1 */
+#define CMD_SD_SEND_OP_COND 0x29
+/* CMD42: arg0[31:0]: stuff bits, response R1b */
+#define CMD_LOCK_UNLOCK 0x2a
+/* CMD55: arg0[31:0]: stuff bits, response R1 */
+#define CMD_APP 0x37
+/* CMD58: arg0[31:0]: stuff bits, response R3 */
+#define CMD_READ_OCR 0x3a
+/* CMD59: arg0[31:1]: stuff bits, arg0[0:0]: crc option, response R1 */
+#define CMD_CRC_ON_OFF 0x3b
+
+/* command responses */
+/* R1: size 1 byte */
+#define R1_IDLE_STATE 0
+#define R1_ERASE_RESET 1
+#define R1_ILL_COMMAND 2
+#define R1_COM_CRC_ERR 3
+#define R1_ERASE_SEQ_ERR 4
+#define R1_ADDR_ERR 5
+#define R1_PARAM_ERR 6
+/* R1b: equals R1, additional busy bytes */
+/* R2: size 2 bytes */
+#define R2_CARD_LOCKED 0
+#define R2_WP_ERASE_SKIP 1
+#define R2_ERR 2
+#define R2_CARD_ERR 3
+#define R2_CARD_ECC_FAIL 4
+#define R2_WP_VIOLATION 5
+#define R2_INVAL_ERASE 6
+#define R2_OUT_OF_RANGE 7
+#define R2_CSD_OVERWRITE 7
+#define R2_IDLE_STATE (R1_IDLE_STATE + 8)
+#define R2_ERASE_RESET (R1_ERASE_RESET + 8)
+#define R2_ILL_COMMAND (R1_ILL_COMMAND + 8)
+#define R2_COM_CRC_ERR (R1_COM_CRC_ERR + 8)
+#define R2_ERASE_SEQ_ERR (R1_ERASE_SEQ_ERR + 8)
+#define R2_ADDR_ERR (R1_ADDR_ERR + 8)
+#define R2_PARAM_ERR (R1_PARAM_ERR + 8)
+/* R3: size 5 bytes */
+#define R3_OCR_MASK (0xffffffffUL)
+#define R3_IDLE_STATE (R1_IDLE_STATE + 32)
+#define R3_ERASE_RESET (R1_ERASE_RESET + 32)
+#define R3_ILL_COMMAND (R1_ILL_COMMAND + 32)
+#define R3_COM_CRC_ERR (R1_COM_CRC_ERR + 32)
+#define R3_ERASE_SEQ_ERR (R1_ERASE_SEQ_ERR + 32)
+#define R3_ADDR_ERR (R1_ADDR_ERR + 32)
+#define R3_PARAM_ERR (R1_PARAM_ERR + 32)
+/* Data Response: size 1 byte */
+#define DR_STATUS_MASK 0x0e
+#define DR_STATUS_ACCEPTED 0x05
+#define DR_STATUS_CRC_ERR 0x0a
+#define DR_STATUS_WRITE_ERR 0x0c
+
+/* status bits for card types */
+#define SD_RAW_SPEC_1 0
+#define SD_RAW_SPEC_2 1
+#define SD_RAW_SPEC_SDHC 2
+
+#if !SD_RAW_SAVE_RAM
+/* static data buffer for acceleration */
+static uint8_t raw_block[512];
+/* offset where the data within raw_block lies on the card */
+static offset_t raw_block_address;
+#if SD_RAW_WRITE_BUFFERING
+/* flag to remember if raw_block was written to the card */
+static uint8_t raw_block_written;
+#endif
+#endif
+
+/* card type state */
+static uint8_t sd_raw_card_type;
+
+/* private helper functions */
+static void sd_raw_send_byte(uint8_t b);
+static uint8_t sd_raw_rec_byte();
+static uint8_t sd_raw_send_command(uint8_t command, uint32_t arg);
+
+/**
+ * \ingroup sd_raw
+ * Initializes memory card communication.
+ *
+ * \returns 0 on failure, 1 on success.
+ */
+uint8_t sd_raw_init()
+{
+    /* enable inputs for reading card status */
+    configure_pin_available();
+    configure_pin_locked();
+
+    /* enable outputs for MOSI, SCK, SS, input for MISO */
+    configure_pin_mosi();
+    configure_pin_sck();
+    configure_pin_ss();
+    configure_pin_miso();
+
+    unselect_card();
+
+    /* initialize SPI with lowest frequency; max. 400kHz during identification mode of card */
+    SPCR = (0 << SPIE) | /* SPI Interrupt Enable */
+           (1 << SPE)  | /* SPI Enable */
+           (0 << DORD) | /* Data Order: MSB first */
+           (1 << MSTR) | /* Master mode */
+           (0 << CPOL) | /* Clock Polarity: SCK low when idle */
+           (0 << CPHA) | /* Clock Phase: sample on rising SCK edge */
+           (1 << SPR1) | /* Clock Frequency: f_OSC / 128 */
+           (1 << SPR0);
+    SPSR &= ~(1 << SPI2X); /* No doubled clock frequency */
+
+    /* initialization procedure */
+    sd_raw_card_type = 0;
+    
+    if(!sd_raw_available())
+        return 0;
+
+    /* card needs 74 cycles minimum to start up */
+    for(uint8_t i = 0; i < 10; ++i)
+    {
+        /* wait 8 clock cycles */
+        sd_raw_rec_byte();
+    }
+
+    /* address card */
+    select_card();
+
+    /* reset card */
+    uint8_t response;
+    for(uint16_t i = 0; ; ++i)
+    {
+        response = sd_raw_send_command(CMD_GO_IDLE_STATE, 0);
+        if(response == (1 << R1_IDLE_STATE))
+            break;
+
+        if(i == 0x1ff)
+        {
+            unselect_card();
+            return 0;
+        }
+    }
+
+#if SD_RAW_SDHC
+    /* check for version of SD card specification */
+    response = sd_raw_send_command(CMD_SEND_IF_COND, 0x100 /* 2.7V - 3.6V */ | 0xaa /* test pattern */);
+    if((response & (1 << R1_ILL_COMMAND)) == 0)
+    {
+        sd_raw_rec_byte();
+        sd_raw_rec_byte();
+        if((sd_raw_rec_byte() & 0x01) == 0)
+            return 0; /* card operation voltage range doesn't match */
+        if(sd_raw_rec_byte() != 0xaa)
+            return 0; /* wrong test pattern */
+
+        /* card conforms to SD 2 card specification */
+        sd_raw_card_type |= (1 << SD_RAW_SPEC_2);
+    }
+    else
+#endif
+    {
+        /* determine SD/MMC card type */
+        sd_raw_send_command(CMD_APP, 0);
+        response = sd_raw_send_command(CMD_SD_SEND_OP_COND, 0);
+        if((response & (1 << R1_ILL_COMMAND)) == 0)
+        {
+            /* card conforms to SD 1 card specification */
+            sd_raw_card_type |= (1 << SD_RAW_SPEC_1);
+        }
+        else
+        {
+            /* MMC card */
+        }
+    }
+
+    /* wait for card to get ready */
+    for(uint16_t i = 0; ; ++i)
+    {
+        if(sd_raw_card_type & ((1 << SD_RAW_SPEC_1) | (1 << SD_RAW_SPEC_2)))
+        {
+            uint32_t arg = 0;
+#if SD_RAW_SDHC
+            if(sd_raw_card_type & (1 << SD_RAW_SPEC_2))
+                arg = 0x40000000;
+#endif
+            sd_raw_send_command(CMD_APP, 0);
+            response = sd_raw_send_command(CMD_SD_SEND_OP_COND, arg);
+        }
+        else
+        {
+            response = sd_raw_send_command(CMD_SEND_OP_COND, 0);
+        }
+
+        if((response & (1 << R1_IDLE_STATE)) == 0)
+            break;
+
+        if(i == 0x7fff)
+        {
+            unselect_card();
+            return 0;
+        }
+    }
+
+#if SD_RAW_SDHC
+    if(sd_raw_card_type & (1 << SD_RAW_SPEC_2))
+    {
+        if(sd_raw_send_command(CMD_READ_OCR, 0))
+        {
+            unselect_card();
+            return 0;
+        }
+
+        if(sd_raw_rec_byte() & 0x40)
+            sd_raw_card_type |= (1 << SD_RAW_SPEC_SDHC);
+
+        sd_raw_rec_byte();
+        sd_raw_rec_byte();
+        sd_raw_rec_byte();
+    }
+#endif
+
+    /* set block size to 512 bytes */
+    if(sd_raw_send_command(CMD_SET_BLOCKLEN, 512))
+    {
+        unselect_card();
+        return 0;
+    }
+
+    /* deaddress card */
+    unselect_card();
+
+    /* switch to highest SPI frequency possible */
+    SPCR &= ~((1 << SPR1) | (1 << SPR0)); /* Clock Frequency: f_OSC / 4 */
+    SPSR |= (1 << SPI2X); /* Doubled Clock Frequency: f_OSC / 2 */
+
+#if !SD_RAW_SAVE_RAM
+    /* the first block is likely to be accessed first, so precache it here */
+    raw_block_address = (offset_t) -1;
+#if SD_RAW_WRITE_BUFFERING
+    raw_block_written = 1;
+#endif
+    if(!sd_raw_read(0, raw_block, sizeof(raw_block)))
+        return 0;
+#endif
+
+    return 1;
+}
+
+/**
+ * \ingroup sd_raw
+ * Checks wether a memory card is located in the slot.
+ *
+ * \returns 1 if the card is available, 0 if it is not.
+ */
+uint8_t sd_raw_available()
+{
+    return get_pin_available() == 0x00;
+}
+
+/**
+ * \ingroup sd_raw
+ * Checks wether the memory card is locked for write access.
+ *
+ * \returns 1 if the card is locked, 0 if it is not.
+ */
+uint8_t sd_raw_locked()
+{
+    return get_pin_locked() == 0x00;
+}
+
+/**
+ * \ingroup sd_raw
+ * Sends a raw byte to the memory card.
+ *
+ * \param[in] b The byte to sent.
+ * \see sd_raw_rec_byte
+ */
+void sd_raw_send_byte(uint8_t b)
+{
+    SPDR = b;
+    /* wait for byte to be shifted out */
+    while(!(SPSR & (1 << SPIF)));
+    SPSR &= ~(1 << SPIF);
+}
+
+/**
+ * \ingroup sd_raw
+ * Receives a raw byte from the memory card.
+ *
+ * \returns The byte which should be read.
+ * \see sd_raw_send_byte
+ */
+uint8_t sd_raw_rec_byte()
+{
+    /* send dummy data for receiving some */
+    SPDR = 0xff;
+    while(!(SPSR & (1 << SPIF)));
+    SPSR &= ~(1 << SPIF);
+
+    return SPDR;
+}
+
+/**
+ * \ingroup sd_raw
+ * Send a command to the memory card which responses with a R1 response (and possibly others).
+ *
+ * \param[in] command The command to send.
+ * \param[in] arg The argument for command.
+ * \returns The command answer.
+ */
+uint8_t sd_raw_send_command(uint8_t command, uint32_t arg)
+{
+    uint8_t response;
+
+    /* wait some clock cycles */
+    sd_raw_rec_byte();
+
+    /* send command via SPI */
+    sd_raw_send_byte(0x40 | command);
+    sd_raw_send_byte((arg >> 24) & 0xff);
+    sd_raw_send_byte((arg >> 16) & 0xff);
+    sd_raw_send_byte((arg >> 8) & 0xff);
+    sd_raw_send_byte((arg >> 0) & 0xff);
+    switch(command)
+    {
+        case CMD_GO_IDLE_STATE:
+           sd_raw_send_byte(0x95);
+           break;
+        case CMD_SEND_IF_COND:
+           sd_raw_send_byte(0x87);
+           break;
+        default:
+           sd_raw_send_byte(0xff);
+           break;
+    }
+    
+    /* receive response */
+    for(uint8_t i = 0; i < 10; ++i)
+    {
+        response = sd_raw_rec_byte();
+        if(response != 0xff)
+            break;
+    }
+
+    return response;
+}
+
+/**
+ * \ingroup sd_raw
+ * Reads raw data from the card.
+ *
+ * \param[in] offset The offset from which to read.
+ * \param[out] buffer The buffer into which to write the data.
+ * \param[in] length The number of bytes to read.
+ * \returns 0 on failure, 1 on success.
+ * \see sd_raw_read_interval, sd_raw_write, sd_raw_write_interval
+ */
+uint8_t sd_raw_read(offset_t offset, uint8_t* buffer, uintptr_t length)
+{
+    offset_t block_address;
+    uint16_t block_offset;
+    uint16_t read_length;
+    while(length > 0)
+    {
+        /* determine byte count to read at once */
+        block_offset = offset & 0x01ff;
+        block_address = offset - block_offset;
+        read_length = 512 - block_offset; /* read up to block border */
+        if(read_length > length)
+            read_length = length;
+        
+#if !SD_RAW_SAVE_RAM
+        /* check if the requested data is cached */
+        if(block_address != raw_block_address)
+#endif
+        {
+#if SD_RAW_WRITE_BUFFERING
+            if(!sd_raw_sync())
+                return 0;
+#endif
+
+            /* address card */
+            select_card();
+
+            /* send single block request */
+#if SD_RAW_SDHC
+            if(sd_raw_send_command(CMD_READ_SINGLE_BLOCK, (sd_raw_card_type & (1 << SD_RAW_SPEC_SDHC) ? block_address / 512 : block_address)))
+#else
+            if(sd_raw_send_command(CMD_READ_SINGLE_BLOCK, block_address))
+#endif
+            {
+                unselect_card();
+                return 0;
+            }
+
+            /* wait for data block (start byte 0xfe) */
+            while(sd_raw_rec_byte() != 0xfe);
+
+#if SD_RAW_SAVE_RAM
+            /* read byte block */
+            uint16_t read_to = block_offset + read_length;
+            for(uint16_t i = 0; i < 512; ++i)
+            {
+                uint8_t b = sd_raw_rec_byte();
+                if(i >= block_offset && i < read_to)
+                    *buffer++ = b;
+            }
+#else
+            /* read byte block */
+            uint8_t* cache = raw_block;
+            for(uint16_t i = 0; i < 512; ++i)
+                *cache++ = sd_raw_rec_byte();
+            raw_block_address = block_address;
+
+            memcpy(buffer, raw_block + block_offset, read_length);
+            buffer += read_length;
+#endif
+            
+            /* read crc16 */
+            sd_raw_rec_byte();
+            sd_raw_rec_byte();
+            
+            /* deaddress card */
+            unselect_card();
+
+            /* let card some time to finish */
+            sd_raw_rec_byte();
+        }
+#if !SD_RAW_SAVE_RAM
+        else
+        {
+            /* use cached data */
+            memcpy(buffer, raw_block + block_offset, read_length);
+            buffer += read_length;
+        }
+#endif
+
+        length -= read_length;
+        offset += read_length;
+    }
+
+    return 1;
+}
+
+/**
+ * \ingroup sd_raw
+ * Continuously reads units of \c interval bytes and calls a callback function.
+ *
+ * This function starts reading at the specified offset. Every \c interval bytes,
+ * it calls the callback function with the associated data buffer.
+ *
+ * By returning zero, the callback may stop reading.
+ *
+ * \note Within the callback function, you can not start another read or
+ *       write operation.
+ * \note This function only works if the following conditions are met:
+ *       - (offset - (offset % 512)) % interval == 0
+ *       - length % interval == 0
+ *
+ * \param[in] offset Offset from which to start reading.
+ * \param[in] buffer Pointer to a buffer which is at least interval bytes in size.
+ * \param[in] interval Number of bytes to read before calling the callback function.
+ * \param[in] length Number of bytes to read altogether.
+ * \param[in] callback The function to call every interval bytes.
+ * \param[in] p An opaque pointer directly passed to the callback function.
+ * \returns 0 on failure, 1 on success
+ * \see sd_raw_write_interval, sd_raw_read, sd_raw_write
+ */
+uint8_t sd_raw_read_interval(offset_t offset, uint8_t* buffer, uintptr_t interval, uintptr_t length, sd_raw_read_interval_handler_t callback, void* p)
+{
+    if(!buffer || interval == 0 || length < interval || !callback)
+        return 0;
+
+#if !SD_RAW_SAVE_RAM
+    while(length >= interval)
+    {
+        /* as reading is now buffered, we directly
+         * hand over the request to sd_raw_read()
+         */
+        if(!sd_raw_read(offset, buffer, interval))
+            return 0;
+        if(!callback(buffer, offset, p))
+            break;
+        offset += interval;
+        length -= interval;
+    }
+
+    return 1;
+#else
+    /* address card */
+    select_card();
+
+    uint16_t block_offset;
+    uint16_t read_length;
+    uint8_t* buffer_cur;
+    uint8_t finished = 0;
+    do
+    {
+        /* determine byte count to read at once */
+        block_offset = offset & 0x01ff;
+        read_length = 512 - block_offset;
+        
+        /* send single block request */
+#if SD_RAW_SDHC
+        if(sd_raw_send_command(CMD_READ_SINGLE_BLOCK, (sd_raw_card_type & (1 << SD_RAW_SPEC_SDHC) ? offset / 512 : offset - block_offset)))
+#else
+        if(sd_raw_send_command(CMD_READ_SINGLE_BLOCK, offset - block_offset))
+#endif
+        {
+            unselect_card();
+            return 0;
+        }
+
+        /* wait for data block (start byte 0xfe) */
+        while(sd_raw_rec_byte() != 0xfe);
+
+        /* read up to the data of interest */
+        for(uint16_t i = 0; i < block_offset; ++i)
+            sd_raw_rec_byte();
+
+        /* read interval bytes of data and execute the callback */
+        do
+        {
+            if(read_length < interval || length < interval)
+                break;
+
+            buffer_cur = buffer;
+            for(uint16_t i = 0; i < interval; ++i)
+                *buffer_cur++ = sd_raw_rec_byte();
+
+            if(!callback(buffer, offset + (512 - read_length), p))
+            {
+                finished = 1;
+                break;
+            }
+
+            read_length -= interval;
+            length -= interval;
+
+        } while(read_length > 0 && length > 0);
+        
+        /* read rest of data block */
+        while(read_length-- > 0)
+            sd_raw_rec_byte();
+        
+        /* read crc16 */
+        sd_raw_rec_byte();
+        sd_raw_rec_byte();
+
+        if(length < interval)
+            break;
+
+        offset = offset - block_offset + 512;
+
+    } while(!finished);
+    
+    /* deaddress card */
+    unselect_card();
+
+    /* let card some time to finish */
+    sd_raw_rec_byte();
+
+    return 1;
+#endif
+}
+
+#if DOXYGEN || SD_RAW_WRITE_SUPPORT
+/**
+ * \ingroup sd_raw
+ * Writes raw data to the card.
+ *
+ * \note If write buffering is enabled, you might have to
+ *       call sd_raw_sync() before disconnecting the card
+ *       to ensure all remaining data has been written.
+ *
+ * \param[in] offset The offset where to start writing.
+ * \param[in] buffer The buffer containing the data to be written.
+ * \param[in] length The number of bytes to write.
+ * \returns 0 on failure, 1 on success.
+ * \see sd_raw_write_interval, sd_raw_read, sd_raw_read_interval
+ */
+uint8_t sd_raw_write(offset_t offset, const uint8_t* buffer, uintptr_t length)
+{
+    if(sd_raw_locked())
+        return 0;
+
+    offset_t block_address;
+    uint16_t block_offset;
+    uint16_t write_length;
+    while(length > 0)
+    {
+        /* determine byte count to write at once */
+        block_offset = offset & 0x01ff;
+        block_address = offset - block_offset;
+        write_length = 512 - block_offset; /* write up to block border */
+        if(write_length > length)
+            write_length = length;
+        
+        /* Merge the data to write with the content of the block.
+         * Use the cached block if available.
+         */
+        if(block_address != raw_block_address)
+        {
+#if SD_RAW_WRITE_BUFFERING
+            if(!sd_raw_sync())
+                return 0;
+#endif
+
+            if(block_offset || write_length < 512)
+            {
+                if(!sd_raw_read(block_address, raw_block, sizeof(raw_block)))
+                    return 0;
+            }
+            raw_block_address = block_address;
+        }
+
+        if(buffer != raw_block)
+        {
+            memcpy(raw_block + block_offset, buffer, write_length);
+
+#if SD_RAW_WRITE_BUFFERING
+            raw_block_written = 0;
+
+            if(length == write_length)
+                return 1;
+#endif
+        }
+
+        /* address card */
+        select_card();
+
+        /* send single block request */
+#if SD_RAW_SDHC
+        if(sd_raw_send_command(CMD_WRITE_SINGLE_BLOCK, (sd_raw_card_type & (1 << SD_RAW_SPEC_SDHC) ? block_address / 512 : block_address)))
+#else
+        if(sd_raw_send_command(CMD_WRITE_SINGLE_BLOCK, block_address))
+#endif
+        {
+            unselect_card();
+            return 0;
+        }
+
+        /* send start byte */
+        sd_raw_send_byte(0xfe);
+
+        /* write byte block */
+        uint8_t* cache = raw_block;
+        for(uint16_t i = 0; i < 512; ++i)
+            sd_raw_send_byte(*cache++);
+
+        /* write dummy crc16 */
+        sd_raw_send_byte(0xff);
+        sd_raw_send_byte(0xff);
+
+        /* wait while card is busy */
+        while(sd_raw_rec_byte() != 0xff);
+        sd_raw_rec_byte();
+
+        /* deaddress card */
+        unselect_card();
+
+        buffer += write_length;
+        offset += write_length;
+        length -= write_length;
+
+#if SD_RAW_WRITE_BUFFERING
+        raw_block_written = 1;
+#endif
+    }
+
+    return 1;
+}
+#endif
+
+#if DOXYGEN || SD_RAW_WRITE_SUPPORT
+/**
+ * \ingroup sd_raw
+ * Writes a continuous data stream obtained from a callback function.
+ *
+ * This function starts writing at the specified offset. To obtain the
+ * next bytes to write, it calls the callback function. The callback fills the
+ * provided data buffer and returns the number of bytes it has put into the buffer.
+ *
+ * By returning zero, the callback may stop writing.
+ *
+ * \param[in] offset Offset where to start writing.
+ * \param[in] buffer Pointer to a buffer which is used for the callback function.
+ * \param[in] length Number of bytes to write in total. May be zero for endless writes.
+ * \param[in] callback The function used to obtain the bytes to write.
+ * \param[in] p An opaque pointer directly passed to the callback function.
+ * \returns 0 on failure, 1 on success
+ * \see sd_raw_read_interval, sd_raw_write, sd_raw_read
+ */
+uint8_t sd_raw_write_interval(offset_t offset, uint8_t* buffer, uintptr_t length, sd_raw_write_interval_handler_t callback, void* p)
+{
+#if SD_RAW_SAVE_RAM
+    #error "SD_RAW_WRITE_SUPPORT is not supported together with SD_RAW_SAVE_RAM"
+#endif
+
+    if(!buffer || !callback)
+        return 0;
+
+    uint8_t endless = (length == 0);
+    while(endless || length > 0)
+    {
+        uint16_t bytes_to_write = callback(buffer, offset, p);
+        if(!bytes_to_write)
+            break;
+        if(!endless && bytes_to_write > length)
+            return 0;
+
+        /* as writing is always buffered, we directly
+         * hand over the request to sd_raw_write()
+         */
+        if(!sd_raw_write(offset, buffer, bytes_to_write))
+            return 0;
+
+        offset += bytes_to_write;
+        length -= bytes_to_write;
+    }
+
+    return 1;
+}
+#endif
+
+#if DOXYGEN || SD_RAW_WRITE_SUPPORT
+/**
+ * \ingroup sd_raw
+ * Writes the write buffer's content to the card.
+ *
+ * \note When write buffering is enabled, you should
+ *       call this function before disconnecting the
+ *       card to ensure all remaining data has been
+ *       written.
+ *
+ * \returns 0 on failure, 1 on success.
+ * \see sd_raw_write
+ */
+uint8_t sd_raw_sync()
+{
+#if SD_RAW_WRITE_BUFFERING
+    if(raw_block_written)
+        return 1;
+    if(!sd_raw_write(raw_block_address, raw_block, sizeof(raw_block)))
+        return 0;
+    raw_block_written = 1;
+#endif
+    return 1;
+}
+#endif
+
+/**
+ * \ingroup sd_raw
+ * Reads informational data from the card.
+ *
+ * This function reads and returns the card's registers
+ * containing manufacturing and status information.
+ *
+ * \note: The information retrieved by this function is
+ *        not required in any way to operate on the card,
+ *        but it might be nice to display some of the data
+ *        to the user.
+ *
+ * \param[in] info A pointer to the structure into which to save the information.
+ * \returns 0 on failure, 1 on success.
+ */
+uint8_t sd_raw_get_info(struct sd_raw_info* info)
+{
+    if(!info || !sd_raw_available())
+        return 0;
+
+    memset(info, 0, sizeof(*info));
+
+    select_card();
+
+    /* read cid register */
+    if(sd_raw_send_command(CMD_SEND_CID, 0))
+    {
+        unselect_card();
+        return 0;
+    }
+    while(sd_raw_rec_byte() != 0xfe);
+    for(uint8_t i = 0; i < 18; ++i)
+    {
+        uint8_t b = sd_raw_rec_byte();
+
+        switch(i)
+        {
+            case 0:
+                info->manufacturer = b;
+                break;
+            case 1:
+            case 2:
+                info->oem[i - 1] = b;
+                break;
+            case 3:
+            case 4:
+            case 5:
+            case 6:
+            case 7:
+                info->product[i - 3] = b;
+                break;
+            case 8:
+                info->revision = b;
+                break;
+            case 9:
+            case 10:
+            case 11:
+            case 12:
+                info->serial |= (uint32_t) b << ((12 - i) * 8);
+                break;
+            case 13:
+                info->manufacturing_year = b << 4;
+                break;
+            case 14:
+                info->manufacturing_year |= b >> 4;
+                info->manufacturing_month = b & 0x0f;
+                break;
+        }
+    }
+
+    /* read csd register */
+    uint8_t csd_read_bl_len = 0;
+    uint8_t csd_c_size_mult = 0;
+#if SD_RAW_SDHC
+    uint16_t csd_c_size = 0;
+#else
+    uint32_t csd_c_size = 0;
+#endif
+    uint8_t csd_structure = 0;
+    if(sd_raw_send_command(CMD_SEND_CSD, 0))
+    {
+        unselect_card();
+        return 0;
+    }
+    while(sd_raw_rec_byte() != 0xfe);
+    for(uint8_t i = 0; i < 18; ++i)
+    {
+        uint8_t b = sd_raw_rec_byte();
+
+        if(i == 0)
+        {
+            csd_structure = b >> 6;
+        }
+        else if(i == 14)
+        {
+            if(b & 0x40)
+                info->flag_copy = 1;
+            if(b & 0x20)
+                info->flag_write_protect = 1;
+            if(b & 0x10)
+                info->flag_write_protect_temp = 1;
+            info->format = (b & 0x0c) >> 2;
+        }
+        else
+        {
+#if SD_RAW_SDHC
+            if(csd_structure == 0x01)
+            {
+                switch(i)
+                {
+                    case 7:
+                        b &= 0x3f;
+                    case 8:
+                    case 9:
+                        csd_c_size <<= 8;
+                        csd_c_size |= b;
+                        break;
+                }
+                if(i == 9)
+                {
+                    ++csd_c_size;
+                    info->capacity = (offset_t) csd_c_size * 512 * 1024;
+                }
+            }
+            else if(csd_structure == 0x00)
+#endif
+            {
+                switch(i)
+                {
+                    case 5:
+                        csd_read_bl_len = b & 0x0f;
+                        break;
+                    case 6:
+                        csd_c_size = b & 0x03;
+                        csd_c_size <<= 8;
+                        break;
+                    case 7:
+                        csd_c_size |= b;
+                        csd_c_size <<= 2;
+                        break;
+                    case 8:
+                        csd_c_size |= b >> 6;
+                        ++csd_c_size;
+                        break;
+                    case 9:
+                        csd_c_size_mult = b & 0x03;
+                        csd_c_size_mult <<= 1;
+                        break;
+                    case 10:
+                        csd_c_size_mult |= b >> 7;
+
+                        info->capacity = (uint32_t) csd_c_size << (csd_c_size_mult + csd_read_bl_len + 2);
+                        break;
+                }
+            }
+        }
+    }
+
+    unselect_card();
+
+    return 1;
+}
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sd_raw.h	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,148 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef SD_RAW_H
+#define SD_RAW_H
+
+#include <stdint.h>
+#include "sd_raw_config.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * \addtogroup sd_raw
+ *
+ * @{
+ */
+/**
+ * \file
+ * MMC/SD/SDHC raw access header (license: GPLv2 or LGPLv2.1)
+ *
+ * \author Roland Riegel
+ */
+
+/**
+ * The card's layout is harddisk-like, which means it contains
+ * a master boot record with a partition table.
+ */
+#define SD_RAW_FORMAT_HARDDISK 0
+/**
+ * The card contains a single filesystem and no partition table.
+ */
+#define SD_RAW_FORMAT_SUPERFLOPPY 1
+/**
+ * The card's layout follows the Universal File Format.
+ */
+#define SD_RAW_FORMAT_UNIVERSAL 2
+/**
+ * The card's layout is unknown.
+ */
+#define SD_RAW_FORMAT_UNKNOWN 3
+
+/**
+ * This struct is used by sd_raw_get_info() to return
+ * manufacturing and status information of the card.
+ */
+struct sd_raw_info
+{
+    /**
+     * A manufacturer code globally assigned by the SD card organization.
+     */
+    uint8_t manufacturer;
+    /**
+     * A string describing the card's OEM or content, globally assigned by the SD card organization.
+     */
+    uint8_t oem[3];
+    /**
+     * A product name.
+     */
+    uint8_t product[6];
+    /**
+     * The card's revision, coded in packed BCD.
+     *
+     * For example, the revision value \c 0x32 means "3.2".
+     */
+    uint8_t revision;
+    /**
+     * A serial number assigned by the manufacturer.
+     */
+    uint32_t serial;
+    /**
+     * The year of manufacturing.
+     *
+     * A value of zero means year 2000.
+     */
+    uint8_t manufacturing_year;
+    /**
+     * The month of manufacturing.
+     */
+    uint8_t manufacturing_month;
+    /**
+     * The card's total capacity in bytes.
+     */
+    offset_t capacity;
+    /**
+     * Defines wether the card's content is original or copied.
+     *
+     * A value of \c 0 means original, \c 1 means copied.
+     */
+    uint8_t flag_copy;
+    /**
+     * Defines wether the card's content is write-protected.
+     *
+     * \note This is an internal flag and does not represent the
+     *       state of the card's mechanical write-protect switch.
+     */
+    uint8_t flag_write_protect;
+    /**
+     * Defines wether the card's content is temporarily write-protected.
+     *
+     * \note This is an internal flag and does not represent the
+     *       state of the card's mechanical write-protect switch.
+     */
+    uint8_t flag_write_protect_temp;
+    /**
+     * The card's data layout.
+     *
+     * See the \c SD_RAW_FORMAT_* constants for details.
+     *
+     * \note This value is not guaranteed to match reality.
+     */
+    uint8_t format;
+};
+
+typedef uint8_t (*sd_raw_read_interval_handler_t)(uint8_t* buffer, offset_t offset, void* p);
+typedef uintptr_t (*sd_raw_write_interval_handler_t)(uint8_t* buffer, offset_t offset, void* p);
+
+uint8_t sd_raw_init();
+uint8_t sd_raw_available();
+uint8_t sd_raw_locked();
+
+uint8_t sd_raw_read(offset_t offset, uint8_t* buffer, uintptr_t length);
+uint8_t sd_raw_read_interval(offset_t offset, uint8_t* buffer, uintptr_t interval, uintptr_t length, sd_raw_read_interval_handler_t callback, void* p);
+uint8_t sd_raw_write(offset_t offset, const uint8_t* buffer, uintptr_t length);
+uint8_t sd_raw_write_interval(offset_t offset, uint8_t* buffer, uintptr_t length, sd_raw_write_interval_handler_t callback, void* p);
+uint8_t sd_raw_sync();
+
+uint8_t sd_raw_get_info(struct sd_raw_info* info);
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sd_raw_config.h	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,139 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef SD_RAW_CONFIG_H
+#define SD_RAW_CONFIG_H
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * \addtogroup sd_raw
+ *
+ * @{
+ */
+/**
+ * \file
+ * MMC/SD support configuration (license: GPLv2 or LGPLv2.1)
+ */
+
+/**
+ * \ingroup sd_raw_config
+ * Controls MMC/SD write support.
+ *
+ * Set to 1 to enable MMC/SD write support, set to 0 to disable it.
+ */
+#define SD_RAW_WRITE_SUPPORT 1
+
+/**
+ * \ingroup sd_raw_config
+ * Controls MMC/SD write buffering.
+ *
+ * Set to 1 to buffer write accesses, set to 0 to disable it.
+ *
+ * \note This option has no effect when SD_RAW_WRITE_SUPPORT is 0.
+ */
+#define SD_RAW_WRITE_BUFFERING 1
+
+/**
+ * \ingroup sd_raw_config
+ * Controls MMC/SD access buffering.
+ * 
+ * Set to 1 to save static RAM, but be aware that you will
+ * lose performance.
+ *
+ * \note When SD_RAW_WRITE_SUPPORT is 1, SD_RAW_SAVE_RAM will
+ *       be reset to 0.
+ */
+#define SD_RAW_SAVE_RAM 0
+
+/**
+ * \ingroup sd_raw_config
+ * Controls support for SDHC cards.
+ *
+ * Set to 1 to support so-called SDHC memory cards, i.e. SD
+ * cards with more than 2 gigabytes of memory.
+ */
+#define SD_RAW_SDHC 1
+
+/**
+ * @}
+ */
+
+/* defines for customisation of sd/mmc port access */
+#if defined(__AVR_ATmega8__) || \
+    defined(__AVR_ATmega48__) || \
+    defined(__AVR_ATmega48P__) || \
+    defined(__AVR_ATmega88__) || \
+    defined(__AVR_ATmega88P__) || \
+    defined(__AVR_ATmega168__) || \
+    defined(__AVR_ATmega168P__) || \
+    defined(__AVR_ATmega328P__)
+    #define configure_pin_mosi() DDRB |= (1 << DDB3)
+    #define configure_pin_sck() DDRB |= (1 << DDB5)
+    #define configure_pin_ss() DDRB |= (1 << DDB2)
+    #define configure_pin_miso() DDRB &= ~(1 << DDB4)
+
+    #define select_card() PORTB &= ~(1 << PORTB2)
+    #define unselect_card() PORTB |= (1 << PORTB2)
+#elif defined(__AVR_ATmega16__) || \
+      defined(__AVR_ATmega32__)
+    #define configure_pin_mosi() DDRB |= (1 << DDB5)
+    #define configure_pin_sck() DDRB |= (1 << DDB7)
+    #define configure_pin_ss() DDRB |= (1 << DDB4)
+    #define configure_pin_miso() DDRB &= ~(1 << DDB6)
+
+    #define select_card() PORTB &= ~(1 << PORTB4)
+    #define unselect_card() PORTB |= (1 << PORTB4)
+#elif defined(__AVR_ATmega64__) || \
+      defined(__AVR_ATmega128__) || \
+      defined(__AVR_ATmega169__)
+    #define configure_pin_mosi() DDRB |= (1 << DDB2)
+    #define configure_pin_sck() DDRB |= (1 << DDB1)
+    #define configure_pin_ss() DDRB |= (1 << DDB0)
+    #define configure_pin_miso() DDRB &= ~(1 << DDB3)
+
+    #define select_card() PORTB &= ~(1 << PORTB0)
+    #define unselect_card() PORTB |= (1 << PORTB0)
+#else
+    #error "no sd/mmc pin mapping available!"
+#endif
+
+#define configure_pin_available() DDRC &= ~(1 << DDC4)
+#define configure_pin_locked() DDRC &= ~(1 << DDC5)
+
+#define get_pin_available() (PINC & (1 << PINC4))
+#define get_pin_locked() (PINC & (1 << PINC5))
+
+#if SD_RAW_SDHC
+    typedef uint64_t offset_t;
+#else
+    typedef uint32_t offset_t;
+#endif
+
+/* configuration checks */
+#if SD_RAW_WRITE_SUPPORT
+#undef SD_RAW_SAVE_RAM
+#define SD_RAW_SAVE_RAM 0
+#else
+#undef SD_RAW_WRITE_BUFFERING
+#define SD_RAW_WRITE_BUFFERING 0
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+