base64.c

穿越防火墙技术代码

/*
base64.c
Copyright (C) 1999 Lars Brinkhoff.  See COPYING for terms and conditions.
*/

#include <string.h>
#include <stdlib.h>

#include "config.h"
#include "base64.h"
#include "common.h"

static int encode[] =
{
  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
  'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
  'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
  'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
  'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
  'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
  'w', 'x', 'y', 'z', '0', '1', '2', '3',
  '4', '5', '6', '7', '8', '9', '+', '/'
};

/*
  Base64-encode LENGTH bytes of DATA in *CODE, which will be a newly
  malloced area.  *CODE will be a null-terminated string.

  Return -1 on failure, or number of bytes of base64 code on success.
 */

ssize_t
encode_base64 (const void *data, size_t length, char **code)
{
  const unsigned char *s, *end;
  unsigned char *buf;
  unsigned int x;
  ssize_t n;
  int i, j;

  if (length == 0)
    return 0;

  end = (char *)data + length - 3;

  buf = malloc (4 * ((length + 2) / 3) + 1);
  if (buf == NULL)
    return -1;

  n = 0;

  for (s = data; s < end;)
    {
      x = *s++ << 24;
      x |= *s++ << 16;
      x |= *s++ << 8;

      *buf++ = encode[x >> 26];
      x <<= 6;
      *buf++ = encode[x >> 26];
      x <<= 6;
      *buf++ = encode[x >> 26];
      x <<= 6;
      *buf++ = encode[x >> 26];
      n += 4;
    }

  end += 3;

  x = 0;
  for (i = 0; s < end; i++)
    x |= *s++ << (24 - 8 * i);

  for (j = 0; j < 4; j++)
    {
      if (8 * i >= 6 * j)
	{
	  *buf++ = encode [x >> 26];
	  x <<= 6;
	  n++;
	}
      else
	{
	  *buf++ = '=';
	  n++;
	}
    }

  *buf = 0;

  *code = buf - n;
  return n;
}