base64.c

可以在linux下使用的ddns的测试程式

#include <ctype.h>


static const char base64digits[] =
   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

#define BAD     -1
static const char base64val[] = {
    BAD,BAD,BAD,BAD, BAD,BAD,BAD,BAD, BAD,BAD,BAD,BAD, BAD,BAD,BAD,BAD,
    BAD,BAD,BAD,BAD, BAD,BAD,BAD,BAD, BAD,BAD,BAD,BAD, BAD,BAD,BAD,BAD,
    BAD,BAD,BAD,BAD, BAD,BAD,BAD,BAD, BAD,BAD,BAD, 62, BAD,BAD,BAD, 63,
     52, 53, 54, 55,  56, 57, 58, 59,  60, 61,BAD,BAD, BAD,BAD,BAD,BAD,
    BAD,  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,BAD, BAD,BAD,BAD,BAD,
    BAD, 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,BAD, BAD,BAD,BAD,BAD
};
#define DECODE64(c)  (isascii(c) ? base64val[c] : BAD)

void to64frombits(unsigned char *out, const unsigned char *in, int inlen)
{
        for (; inlen >= 3; inlen -= 3)
        {
                *out++ = base64digits[in[0] >> 2];
                *out++ = base64digits[((in[0] << 4) & 0x30) | (in[1] >> 4)];
                *out++ = base64digits[((in[1] << 2) & 0x3c) | (in[2] >> 6)];
                *out++ = base64digits[in[2] & 0x3f];
                in += 3;
        }

        if (inlen > 0)
        {
                unsigned char fragment;

                *out++ = base64digits[in[0] >> 2];
                fragment = (in[0] << 4) & 0x30;

                if (inlen > 1)
                        fragment |= in[1] >> 4;

                *out++ = base64digits[fragment];
                *out++ = (inlen < 2) ? '=' : base64digits[(in[1] << 2) & 0x3c];
                *out++ = '=';
        }
        
        *out = '\0';
}

int from64tobits(char *out, const char *in)
{
        int len = 0;
        register unsigned char digit1, digit2, digit3, digit4;

        if (in[0] == '+' && in[1] == ' ')
                in += 2;
        if (*in == '\r')
                return(0);

        do {
                digit1 = in[0];
                if (DECODE64(digit1) == BAD)
                        return(-1);
                digit2 = in[1];
                if (DECODE64(digit2) == BAD)
                        return(-1);
                digit3 = in[2];
                if (digit3 != '=' && DECODE64(digit3) == BAD)
                        return(-1);
                digit4 = in[3];
                if (digit4 != '=' && DECODE64(digit4) == BAD)
                        return(-1);
                in += 4;
                *out++ = (DECODE64(digit1) << 2) | (DECODE64(digit2) >> 4);
                ++len;
                if (digit3 != '=')
                {
                        *out++ = ((DECODE64(digit2) << 4) & 0xf0) | (DECODE64(digit3) >> 2);
                        ++len;
                        if (digit4 != '=')
                        {
                                *out++ = ((DECODE64(digit3) << 6) & 0xc0) | DECODE64(digit4);
                                ++len;
                        }
                }
        } while (*in && *in != '\r' && digit4 != '=');

        return (len);
}