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comparison byteordering.c @ 19:5f9a40d6991b

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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
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18:021e6e0006f4 19:5f9a40d6991b
1
2 /*
3 * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
4 *
5 * This file is free software; you can redistribute it and/or modify
6 * it under the terms of either the GNU General Public License version 2
7 * or the GNU Lesser General Public License version 2.1, both as
8 * published by the Free Software Foundation.
9 */
10
11 #include "byteordering.h"
12
13 /**
14 * \addtogroup byteordering
15 *
16 * Architecture-dependent handling of byte-ordering.
17 *
18 * @{
19 */
20 /**
21 * \file
22 * Byte-order handling implementation (license: GPLv2 or LGPLv2.1)
23 *
24 * \author Roland Riegel
25 */
26
27 #if DOXYGEN || SWAP_NEEDED
28
29 /**
30 * \internal
31 * Swaps the bytes of a 16-bit integer.
32 *
33 * \param[in] i A 16-bit integer which to swap.
34 * \returns The swapped 16-bit integer.
35 */
36 uint16_t swap16(uint16_t i)
37 {
38 return SWAP16(i);
39 }
40
41 /**
42 * \internal
43 * Swaps the bytes of a 32-bit integer.
44 *
45 * \param[in] i A 32-bit integer which to swap.
46 * \returns The swapped 32-bit integer.
47 */
48 uint32_t swap32(uint32_t i)
49 {
50 return SWAP32(i);
51 }
52
53 #endif
54
55 /**
56 * Reads a 16-bit integer from memory in little-endian byte order.
57 *
58 * \param[in] p Pointer from where to read the integer.
59 * \returns The 16-bit integer read from memory.
60 */
61 uint16_t read16(const uint8_t* p)
62 {
63 return (((uint16_t) p[1]) << 8) |
64 (((uint16_t) p[0]) << 0);
65 }
66
67 /**
68 * Reads a 32-bit integer from memory in little-endian byte order.
69 *
70 * \param[in] p Pointer from where to read the integer.
71 * \returns The 32-bit integer read from memory.
72 */
73 uint32_t read32(const uint8_t* p)
74 {
75 return (((uint32_t) p[3]) << 24) |
76 (((uint32_t) p[2]) << 16) |
77 (((uint32_t) p[1]) << 8) |
78 (((uint32_t) p[0]) << 0);
79 }
80
81 /**
82 * Writes a 16-bit integer into memory in little-endian byte order.
83 *
84 * \param[in] p Pointer where to write the integer to.
85 * \param[in] i The 16-bit integer to write.
86 */
87 void write16(uint8_t* p, uint16_t i)
88 {
89 p[1] = (uint8_t) ((i & 0xff00) >> 8);
90 p[0] = (uint8_t) ((i & 0x00ff) >> 0);
91 }
92
93 /**
94 * Writes a 32-bit integer into memory in little-endian byte order.
95 *
96 * \param[in] p Pointer where to write the integer to.
97 * \param[in] i The 32-bit integer to write.
98 */
99 void write32(uint8_t* p, uint32_t i)
100 {
101 p[3] = (uint8_t) ((i & 0xff000000) >> 24);
102 p[2] = (uint8_t) ((i & 0x00ff0000) >> 16);
103 p[1] = (uint8_t) ((i & 0x0000ff00) >> 8);
104 p[0] = (uint8_t) ((i & 0x000000ff) >> 0);
105 }
106
107 /**
108 * @}
109 */
110