base64.c 6.42 KB
Newer Older
Pekka Pessi's avatar
Pekka Pessi committed
1 2 3 4 5 6 7
/*
 * This file is part of the Sofia-SIP package
 *
 * Copyright (C) 2005 Nokia Corporation.
 *
 * Contact: Pekka Pessi <pekka.pessi@nokia.com>
 *
8
 * This library is free software; you can redistribute it and/or
Pekka Pessi's avatar
Pekka Pessi committed
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 *
 */

/**@CFILE base64.c
 *
 * Implementation of BASE64 encoding and decoding functions.
 *
 * @author Pekka Pessi <Pekka.Pessi@nokia.com>
 *
 */

33 34
#include "config.h"

Pekka Pessi's avatar
Pekka Pessi committed
35 36
#include <stdio.h>
#include <string.h>
37
#include "sofia-sip/base64.h"
Pekka Pessi's avatar
Pekka Pessi committed
38

39
static unsigned char const code[] =
Pekka Pessi's avatar
Pekka Pessi committed
40 41 42 43 44 45 46 47 48 49 50
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

#define B64NOP 128
#define B64EOF  64

/**Decode a BASE64-encoded string.
 *
 * The function base64_d() decodes a string @a b64s encoded with BASE64. It
 * stores the result in the buffer @a buf of @a bsiz bytes.
 *
 * If the @a buf is NULL, the function just returns the length of decoded
51
 * data. In any case, no decoded data is stored in @a buf beyond @a bsiz.
Pekka Pessi's avatar
Pekka Pessi committed
52
 * The function always returns the full length of decodable data.
53
 *
Pekka Pessi's avatar
Pekka Pessi committed
54 55 56 57
 * @param buf  Buffer to store decoded data
 * @param bsiz Size of @a buf
 * @param b64s Base64-encoded string.
 *
58
 * @return Length of data that can be decoded in bytes.
Pekka Pessi's avatar
Pekka Pessi committed
59
 *
60
 * @sa <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>,
Pekka Pessi's avatar
Pekka Pessi committed
61 62 63 64 65
 * <i>"Multipurpose Internet Mail Extensions (MIME) Part One:
 * Format of Internet Message Bodies"</i>,
 * N. Freed, N. Borenstein, November 1996.
 *
 * @par Example
66
 * The following example code decodes a string of BASE64 data into a
Pekka Pessi's avatar
Pekka Pessi committed
67 68 69 70 71 72 73 74 75 76 77 78
 * memory area allocated from heap:
 * @code
 * int decoder(char const *encoded, void **return_decoded)
 * {
 *   int len = base64_d(NULL, 0, encoded);
 *   void *decoded = malloc(len);
 *   base64_d(decoded, len, encoded);
 *   *return_decoded = decoded;
 *   return len;
 * }
 * @endcode
 */
79
isize_t base64_d(char buf[], isize_t bsiz, char const *b64s)
Pekka Pessi's avatar
Pekka Pessi committed
80 81 82 83 84
{
  static unsigned char decode[256] = "";
  unsigned char const *s = (unsigned char const *)b64s;
  unsigned char c, b1, b2 = B64EOF, b3 = B64EOF, b4 = B64EOF;
  unsigned long w;
85 86
  isize_t i, len = 0, total_len = 0;

Pekka Pessi's avatar
Pekka Pessi committed
87 88 89 90 91 92
  if (b64s == NULL)
    return 0;

  if (decode['\0'] != B64EOF) {
    /* Prepare decoding table */
    for (i = 1; i < 256; i++)
93
      decode[i] = B64NOP;
Pekka Pessi's avatar
Pekka Pessi committed
94 95

    for (i = 0; i < 64; i++) {
96
      decode[code[i]] = (unsigned char)i;
Pekka Pessi's avatar
Pekka Pessi committed
97 98 99 100 101 102 103 104 105 106
    }
    decode['='] = B64EOF;
    decode['\0'] = B64EOF;
  }

  /* Calculate length */
  while ((c = decode[*s++]) != B64EOF) {
    if (c != B64NOP)
      len++;
  }
107

Pekka Pessi's avatar
Pekka Pessi committed
108 109 110 111 112
  total_len = len = len * 3 / 4;

  if (buf == NULL || bsiz == 0)
    return total_len;

113
  if (len > bsiz)
Pekka Pessi's avatar
Pekka Pessi committed
114
    len = bsiz;
115

Pekka Pessi's avatar
Pekka Pessi committed
116
  for (i = 0, s = (unsigned char const *)b64s; i < len; ) {
117

Pekka Pessi's avatar
Pekka Pessi committed
118 119 120 121 122 123 124 125 126 127 128
    while ((b1 = decode[*s++]) == B64NOP)
      ;
    if (b1 != B64EOF)
      while ((b2 = decode[*s++]) == B64NOP)
	;
    if (b2 != B64EOF)
      while ((b3 = decode[*s++]) == B64NOP)
	;
    if (b3 != B64EOF)
      while ((b4 = decode[*s++]) == B64NOP)
	;
129

Pekka Pessi's avatar
Pekka Pessi committed
130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165
    if (((b1 | b2 | b3 | b4) & (B64NOP|B64EOF)) == 0) {
      /* Normal case, 4 B64 chars to 3 data bytes */
      w = (b1 << 18) | (b2 << 12) | (b3 << 6) | b4;
      buf[i++] = (unsigned char)(w >> 16);
      buf[i++] = (unsigned char)(w >> 8);
      buf[i++] = (unsigned char)(w);
      continue;
    }
    else {
      /* EOF */
      if ((b1 | b2) & B64EOF) {
	/* fputs("base64dec: strange eof ===\n", stderr); */
	break;
      }
      buf[i++] = (b1 << 2) | (b2 >> 4);
      if (b3 != B64EOF) {
	buf[i++] = ((b2 & 15) << 4) | ((b3 >> 2) & 15);
	if (b4 != B64EOF) {
	  buf[i++] = ((b3 & 3) << 6) | b4;
	}
      }
      break;
    }
  }

#if 0
  printf("base64_d returns, decoded %d bytes\n", total_len);
  for (i = 0; i < len; i++)
    printf("%02x", buf[i]);
  printf("\n");
#endif

  return total_len;
}

/**Encode data with BASE64.
166 167
 *
 * The function base64_e() encodes @a dsiz bytes of @a data into @a buf.
Pekka Pessi's avatar
Pekka Pessi committed
168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185
 *
 * @note The function base64_e() uses at most @a bsiz bytes from @a buf.
 *
 * If @a bsiz is zero, the function just returns the length of BASE64
 * encoding, excluding the final @c NUL.
 *
 * If encoded string is longer than that @a bsiz, the function terminates
 * string with @c NUL at @a buf[bsiz-1], but returns the length of encoding as
 * usual.
 *
 * @param buf  buffer for encoded data
 * @param bsiz size of @a buffer
 * @param data data to be encoded
 * @param dsiz size of @a data
 *
 * @return The function base64_e() return length of encoded string,
 * excluding the final NUL.
 *
186
 * @sa <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>,
Pekka Pessi's avatar
Pekka Pessi committed
187 188 189 190 191
 * <i>"Multipurpose Internet Mail Extensions (MIME) Part One:
 * Format of Internet Message Bodies"</i>,
 * N. Freed, N. Borenstein, November 1996.
 *
 */
192
isize_t base64_e(char buf[], isize_t bsiz, void *data, isize_t dsiz)
Pekka Pessi's avatar
Pekka Pessi committed
193 194 195 196
{
  unsigned char *s = (unsigned char *)buf;
  unsigned char *b = (unsigned char *)data;
  unsigned long w;
197 198 199

  isize_t i, n, slack = (unsigned)dsiz % 3;
  isize_t dsize = dsiz - slack, bsize = bsiz;
Pekka Pessi's avatar
Pekka Pessi committed
200 201 202

  if (bsize == 0)
    s = NULL;
203

Pekka Pessi's avatar
Pekka Pessi committed
204 205 206 207 208 209 210 211 212 213
  for (i = 0, n = 0; i < dsize; i += 3, n += 4) {
    w = (b[i] << 16) | (b[i+1] << 8) | b[i+2];

    if (s) {
      if (n + 4 < bsize) {
	s[n + 0] = code[(w >> 18) & 63];
	s[n + 1] = code[(w >> 12) & 63];
	s[n + 2] = code[(w >> 6) & 63];
	s[n + 3] = code[(w) & 63];
      } else {
214
	if (n + 1 < bsize)
Pekka Pessi's avatar
Pekka Pessi committed
215
	  s[n + 0] = code[(w >> 18) & 63];
216
	if (n + 2 < bsize)
Pekka Pessi's avatar
Pekka Pessi committed
217 218 219 220 221 222 223
	  s[n + 1] = code[(w >> 12) & 63];
	if (n + 3 < bsize)
	  s[n + 2] = code[(w >> 6) & 63];
	s[bsize - 1] = '\0';
	s = NULL;
      }
    }
224 225
  }

Pekka Pessi's avatar
Pekka Pessi committed
226 227 228 229 230 231 232
  if (slack) {
    if (s) {
      if (slack == 2)
	w = (b[i] << 16) | (b[i+1] << 8);
      else
	w = (b[i] << 16);

233
      if (n + 1 < bsize)
Pekka Pessi's avatar
Pekka Pessi committed
234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251
	s[n + 0] = code[(w >> 18) & 63];
      if (n + 2 < bsize)
	s[n + 1] = code[(w >> 12) & 63];
      if (n + 3 < bsize)
	s[n + 2] = (slack == 2) ? code[(w >> 6) & 63] : '=';
      if (n + 3 < bsize)
	s[n + 3] = '=';
      if (n + 4 >= bsize)
	s[bsize - 1] = '\0', s = NULL;
    }
    n += 4;
  }

  if (s)
    s[n] = '\0';

  return n;
}