--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/asn1/der/bit/der_decode_bit_string.c	Wed Mar 08 13:23:58 2006 +0000
@@ -0,0 +1,101 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, [email protected], http://libtomcrypt.org
+ */
+#include "tomcrypt.h"
+
+/**
+  @file der_decode_bit_string.c
+  ASN.1 DER, encode a BIT STRING, Tom St Denis
+*/
+
+
+#ifdef LTC_DER
+
+/**
+  Store a BIT STRING
+  @param in      The DER encoded BIT STRING
+  @param inlen   The size of the DER BIT STRING
+  @param out     [out] The array of bits stored (one per char)
+  @param outlen  [in/out] The number of bits stored
+  @return CRYPT_OK if successful
+*/
+int der_decode_bit_string(const unsigned char *in,  unsigned long inlen,
+                                unsigned char *out, unsigned long *outlen)
+{
+   unsigned long dlen, blen, x, y;
+
+   LTC_ARGCHK(in     != NULL);
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+
+   /* packet must be at least 4 bytes */
+   if (inlen < 4) {
+       return CRYPT_INVALID_ARG;
+   }
+
+   /* check for 0x03 */
+   if ((in[0]&0x1F) != 0x03) {
+      return CRYPT_INVALID_PACKET;
+   }
+
+    /* offset in the data */
+    x = 1;
+
+   /* get the length of the data */
+   if (in[x] & 0x80) {
+      /* long format get number of length bytes */
+      y = in[x++] & 127;
+
+      /* invalid if 0 or > 2 */
+      if (y == 0 || y > 2) {
+         return CRYPT_INVALID_PACKET;
+      }
+
+      /* read the data len */
+      dlen = 0;
+      while (y--) {
+         dlen = (dlen << 8) | (unsigned long)in[x++];
+      }
+   } else {
+      /* short format */
+      dlen = in[x++] & 127;
+   }
+  
+   /* is the data len too long or too short? */
+   if ((dlen == 0) || (dlen + x > inlen)) {
+       return CRYPT_INVALID_PACKET;
+   }
+
+   /* get padding count */
+   blen = ((dlen - 1) << 3) - (in[x++] & 7);
+
+   /* too many bits? */
+   if (blen > *outlen) {
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+
+   /* decode/store the bits */
+   for (y = 0; y < blen; y++) {
+       out[y] = (in[x] & (1 << (7 - (y & 7)))) ? 1 : 0;
+       if ((y & 7) == 7) {
+          ++x;
+       }
+   }
+
+   /* we done */
+   *outlen = blen;
+   return CRYPT_OK;
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_decode_bit_string.c,v $ */
+/* $Revision: 1.1 $ */
+/* $Date: 2005/05/16 15:08:11 $ */