공간사랑

base64 Encode

http://www.opinionatedgeek.com/dotnet/tools/Base64Encode/Default.aspx

http://www.faqs.org/rfcs/rfc3548.html

/*** coreutils 소스에서 일부분만 발취 BASE64 ENCODE ***/

#define BASE64_LENGTH(inlen) ((((inlen) + 2) / 3) * 4);

/***************************************************/

static unsigned char to_uchar (char ch)
{
  return ch;
}

void base64_encode (const char *in, size_t inlen, char *out, size_t outlen)
{

  static const char b64str[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

  while (inlen && outlen) {

    *out++ = b64str[(to_uchar (in[0]) >> 2) & 0x3f];

    if (!--outlen) {
      break;
    }

    *out++ = b64str[((to_uchar (in[0]) << 4) + (--inlen ? to_uchar (in[1]) >> 4 : 0)) & 0x3f];

    if (!--outlen) {
      break;
    }

    *out++ = (inlen ? b64str[((to_uchar (in[1]) << 2) + (--inlen ? to_uchar (in[2]) >> 6 : 0)) & 0x3f] : '=');

    if (!--outlen) {
      break;
    }

    *out++ = inlen ? b64str[to_uchar (in[2]) & 0x3f] : '=';

    if (!--outlen) {
      break;
    }

    if (inlen) {
      inlen--;
    }

    if (inlen) {
      in += 3;
    }

  }

  if (outlen) {
    *out = '\0';
  }

}

size_t base64_encode_alloc (const char *in, size_t inlen, char **out)
{
  size_t outlen = 1 + BASE64_LENGTH (inlen);

  if (inlen > outlen) {
      *out = NULL;
      return 0;
  }

  *out = malloc (outlen);

  if (!*out) {
    return outlen;
  }

  base64_encode (in, inlen, *out, outlen);

  return outlen - 1;
}

그외 다른 소스

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

/*------ Base64 Encoding Table ------*/
static const char MimeBase64[] = {
    '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 Decoding Table ------*/
static int DecodeMimeBase64[256] = {
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,  /* 00-0F */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,  /* 10-1F */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,62,-1,-1,-1,63,  /* 20-2F */
    52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-1,-1,-1,  /* 30-3F */
    -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,  /* 40-4F */
    15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,  /* 50-5F */
    -1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,  /* 60-6F */
    41,42,43,44,45,46,47,48,49,50,51,-1,-1,-1,-1,-1,  /* 70-7F */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,  /* 80-8F */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,  /* 90-9F */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,  /* A0-AF */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,  /* B0-BF */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,  /* C0-CF */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,  /* D0-DF */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,  /* E0-EF */
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1   /* F0-FF */
};

int base64_decode(char *text, unsigned char *dst, int numBytes )
{
    const char* cp;
    int space_idx = 0, phase;
    int d, prev_d = 0;
    unsigned char c;

    space_idx = 0;
    phase = 0;

    for ( cp = text; *cp != '\0'; ++cp ) {

        d = DecodeMimeBase64[(int) *cp];

        if ( d != -1 ) {

            switch ( phase ) {

                case 0:
                    ++phase;
                    break;
                case 1:
                    c = ( ( prev_d << 2 ) | ( ( d & 0x30 ) >> 4 ) );
                    if ( space_idx < numBytes )
                        dst[space_idx++] = c;
                    ++phase;
                    break;
                case 2:
                    c = ( ( ( prev_d & 0xf ) << 4 ) | ( ( d & 0x3c ) >> 2 ) );
                    if ( space_idx < numBytes )
                        dst[space_idx++] = c;
                    ++phase;
                    break;
                case 3:
                    c = ( ( ( prev_d & 0x03 ) << 6 ) | d );
                    if ( space_idx < numBytes )
                        dst[space_idx++] = c;
                    phase = 0;
                    break;

            }

            prev_d = d;

        }

    }

    return space_idx;

}

int base64_encode(char *text, int numBytes, char **encodedText)
{
    unsigned char input[3]  = {0,0,0};
    unsigned char output[4] = {0,0,0,0};
    int   index, i, j, size;
    char *p, *plen;

    plen           = text + numBytes - 1;

    size           = (4 * (numBytes / 3)) + (numBytes % 3? 4 : 0) + 1;

    (*encodedText) = (char*)malloc(size);

    j              = 0;

    for  (i = 0, p = text;p <= plen; i++, p++) {

        index = i % 3;
        input[index] = *p;

        if (index == 2 || p == plen) {

            output[0] = ((input[0] & 0xFC) >> 2);
            output[1] = ((input[0] & 0x3) << 4) | ((input[1] & 0xF0) >> 4);
            output[2] = ((input[1] & 0xF) << 2) | ((input[2] & 0xC0) >> 6);
            output[3] = (input[2] & 0x3F);

            (*encodedText)[j++] = MimeBase64[output[0]];
            (*encodedText)[j++] = MimeBase64[output[1]];
            (*encodedText)[j++] = index == 0? '=' : MimeBase64[output[2]];
            (*encodedText)[j++] = index <  2? '=' : MimeBase64[output[3]];

            input[0] = input[1] = input[2] = 0;
        }

    }

    (*encodedText)[j] = '\0';

    return size;

}