s_encoding.c

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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <ctype.h>
#include <glib.h>
#ifdef HAVE_STRING_H
#include <string.h>
#endif

static gchar s_encoding_Base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
#define s_encoding_Pad64    '='
static guchar s_encoding_Base64_rank[256] = {
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0x00-0x0f   */
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0x10-0x1f   */
    255,255,255,255,255,255,255,255,255,255,255, 62,255,255,255, 63, /* 0x20-0x2f   */
     52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,255,255,255, /* 0x30-0x3f   */
    255,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, /* 0x40-0x4f   */
     15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255,255, /* 0x50-0x5f   */
    255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, /* 0x60-0x6f   */
     41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255, /* 0x70-0x7f   */
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0x80-0x8f   */
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0x90-0x9f   */
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0xa0-0xaf   */
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0xb0-0xbf   */
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0xc0-0xcf   */
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0xd0-0xdf   */
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0xe0-0xef   */
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0xf0-0xff   */
};

gchar* s_encoding_base64_encode (gchar* src, guint srclen, 
                 guint* dstlenp, gboolean strict) 
{
  gchar* dst;
  guint dstpos;
  guchar input[3];
  guchar output[4];
  guint ocnt;
  guint i;

  if (srclen == 0) 
    return NULL;    /* FIX: Or return ""? */

  /* Calculate required length of dst.  4 bytes of dst are needed for
     every 3 bytes of src. */
  *dstlenp = (((srclen + 2) / 3) * 4)+5;
  if (strict)
    *dstlenp += (*dstlenp / 72);    /* Handle trailing \n */

  dst = g_new(gchar, *dstlenp );

  /* bulk encoding */
  dstpos = 0;
  ocnt = 0;
  while (srclen >= 3) 
    {
      /*
    Convert 3 bytes of src to 4 bytes of output

    output[0] = input[0] 7:2
    output[1] = input[0] 1:0 input[1] 7:4
    output[2] = input[1] 3:0 input[2] 7:6
    output[3] = input[1] 5:0

       */
      input[0] = *src++;
      input[1] = *src++;
      input[2] = *src++;
      srclen -= 3;

      output[0] = (input[0] >> 2);
      output[1] = ((input[0] & 0x03) << 4) + 
    (input[1] >> 4);
      output[2] = ((input[1] & 0x0f) << 2) + 
    (input[2] >> 6);
      output[3] = (input[2] & 0x3f);

      g_assert ((dstpos + 4) < *dstlenp);

      /* Map output to the Base64 alphabet */
      dst[dstpos++] = s_encoding_Base64[(guint) output[0]];
      dst[dstpos++] = s_encoding_Base64[(guint) output[1]];
      dst[dstpos++] = s_encoding_Base64[(guint) output[2]];
      dst[dstpos++] = s_encoding_Base64[(guint) output[3]];

      /* Add a newline if strict and  */
      if (strict)
    if ((++ocnt % (72/4)) == 0) 
      dst[dstpos++] = '\n';
    }

  /* Now worry about padding with remaining 1 or 2 bytes */
  if (srclen != 0) 
    {
      input[0] = input[1] = input[2] = '\0';
      for (i = 0; i < srclen; i++) 
    input[i] = *src++;

      output[0] = (input[0] >> 2);
      output[1] = ((input[0] & 0x03) << 4) + 
    (input[1] >> 4);
      output[2] = ((input[1] & 0x0f) << 2) + 
    (input[2] >> 6);

      g_assert ((dstpos + 4) < *dstlenp);

      dst[dstpos++] = s_encoding_Base64[(guint) output[0]];
      dst[dstpos++] = s_encoding_Base64[(guint) output[1]];

      if (srclen == 1)
    dst[dstpos++] = s_encoding_Pad64;
      else
    dst[dstpos++] = s_encoding_Base64[(guint) output[2]];

      dst[dstpos++] = s_encoding_Pad64;
    }

  g_assert (dstpos <= *dstlenp);

  dst[dstpos] = '\0';

  *dstlenp = dstpos + 1;

  return dst;
}

gchar *s_encoding_base64_decode (gchar* src, guint srclen, guint* dstlenp)
{

  gchar* dst;
  guint   dstidx, state, ch = 0;
  gchar  res;
  guchar pos;

  if (srclen == 0) 
    srclen = strlen(src);
  state = 0;
  dstidx = 0;
  res = 0;

  dst = g_new(gchar, srclen+1);
  *dstlenp = srclen+1;

  while (srclen > 0)
    {
      srclen--;
      ch = *src++;
      if (ch == s_encoding_Pad64) 
    break;
      if (s_encoding_Base64_rank[ch]==255) /* Skip any non-base64 anywhere */
    continue;

      pos = s_encoding_Base64_rank[ch];

      switch (state) 
    {
    case 0:
      dst[dstidx] = (pos << 2);
      state = 1;
      break;
    case 1:
      dst[dstidx] |= (pos >> 4);
      res = ((pos & 0x0f) << 4);
      dstidx++;
      state = 2;
      break;
    case 2:
      dst[dstidx] = res | (pos >> 2);
      res = (pos & 0x03) << 6;
      dstidx++;
      state = 3;
      break;
    case 3:
      dst[dstidx] = res | pos;
      dstidx++;
      state = 0;
      break;
    default:
      break;
    }
    }
  /*
   * We are done decoding Base-64 chars.  Let's see if we ended
   * on a byte boundary, and/or with erroneous trailing characters.
   */
  if (ch == s_encoding_Pad64)           /* We got a pad char. */
    {
      switch (state) 
    {
    case 0:             /* Invalid = in first position */
    case 1:             /* Invalid = in second position */
      return NULL;
    case 2:             /* Valid, means one byte of info */
                                /* Skip any number of spaces. */
      while (srclen > 0)
        {
          srclen--;
          ch = *src++;
          if (ch == s_encoding_Pad64) break;
          if (s_encoding_Base64_rank[ch] != 255) break;
        }
                                /* Make sure there is another trailing = sign. */
      if (ch != s_encoding_Pad64) 
        {
          g_free(dst);
          *dstlenp = 0;
          return NULL;
        }
                                /* FALLTHROUGH */
    case 3:             /* Valid, means two bytes of info */
                                /*
                                 * We know this char is an =.  Is there anything but
                                 * whitespace after it?
                                 */
      while (srclen > 0)
        {
          srclen--;
          ch = *src++;
          if (s_encoding_Base64_rank[ch] != 255) 
        {
          g_free(dst);
          *dstlenp = 0;
          return NULL;
        }
        }
                                /*
                                 * Now make sure for cases 2 and 3 that the "extra"
                                 * bits that slopped past the last full byte were
                                 * zeros.  If we don't check them, they become a
                                 * subliminal channel.
                                 */
      if (res != 0)
        {
          g_free(dst);
          *dstlenp = 0;
          return NULL;
        }
    default:
      break;
    }
    } else 
      {
    /*
     * We ended by seeing the end of the string.  Make sure we
     * have no partial bytes lying around.
     */
    if (state != 0) 
      {
        g_free(dst);
        *dstlenp = 0;
        return NULL;
      }
      }
  dst[dstidx]=0;
  *dstlenp = dstidx;
  return dst;
}