c++base64編解碼應用示例

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
static const char b64_table[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const char reverse_table[128] =
{
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63,
    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64,
    64,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 64, 64, 64, 64, 64,
    64, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 64, 64, 64, 64, 64
};

unsigned char *base64_encode(unsigned char *bindata,size_t inlen,unsigned char **out,size_t *outlen)
{
    size_t _outlen = *outlen;
    unsigned char *_out = NULL;
    size_t out_pos = 0;

    if(NULL == *out)
    {
        _outlen = (inlen / 3 + (inlen%3 != 0)) * 4 + 1;
        _out = malloc(_outlen);
    }
    else
    {
        _outlen = *outlen;
        _out = *out;
    }

    memset(_out,'=',_outlen);
    _out[_outlen-1] = 0;

    unsigned int bits_collected = 0;
    unsigned int accumulator = 0;
    for(int i = 0; i < inlen; i++)
    {
        accumulator = (accumulator << 8) | (bindata[i] & 0xffu);
        bits_collected += 8;
        while (bits_collected >= 6)
        {
            bits_collected -= 6;
            _out[out_pos++] = b64_table[(accumulator >> bits_collected) & 0x3fu];
        }
    }

    if(bits_collected >= 6)
    {
        if(NULL == *out)
        {
            free(_out);
        }
        return NULL;
    }

    if (bits_collected > 0)
    {
        // Any trailing bits that are missing.
        accumulator <<= 6 - bits_collected;
        _out[out_pos++] = b64_table[accumulator & 0x3fu];
    }

    *outlen = _outlen;
    *out = _out;
    return _out;
}

unsigned char *base64_decode(unsigned char *bindata,size_t inlen,unsigned char **out,size_t *outlen)
{
    size_t _outlen = *outlen;
    unsigned char *_out = NULL;
    int bits_collected = 0;
    unsigned int accumulator = 0;
    size_t out_pos = 0;

    if(NULL == *out)
    {
        _outlen = inlen;
        _out = malloc(_outlen);
    }
    else
    {
        _outlen = *outlen;
        _out = *out;
    }

    int c = 0;
    for(int i = 0; i < inlen; i++)
    {
        c = bindata[i];
        if (isspace(c) || c == '=')
        {
            // Skip whitespace and padding. Be liberal in what you accept.
            continue;
        }
        if ((c > 127) || (c < 0) || (reverse_table[c] > 63))
        {
            return NULL;
        }
        accumulator = (accumulator << 6) | reverse_table[c];
        bits_collected += 6;
        if (bits_collected >= 8)
        {
            bits_collected -= 8;
            _out[out_pos++] = (char)((accumulator >> bits_collected) & 0xffu);
        }
    }

    *outlen = _outlen;
    *out = _out;
    return _out;
}

int main(int argc,char *argv[])
{
    unsigned char *str = argv[1];
    unsigned char *out = 0;
    size_t len = 0;
    printf("%s\n",base64_encode(str,strlen(str),&out,&len));
    unsigned char *_out = 0;
    size_t _len = 0;
    printf("%s\n",base64_decode(out,strlen(out),&_out,&_len));
    return 0;
}