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#include "pub.h"
static const char base64[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const char index_64[128] =
{
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
-1, 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, -1, -1, -1, -1, -1,
-1, 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, -1, -1, -1, -1, -1,
};
int base64_encode(char *dst, int dstlen, const char *src, int srclen)
{
char *to = dst;
const unsigned char *from;
unsigned char c1, c2;
int dst_needed;
// 参数检测
if (dst == NULL || dstlen <= 0 || src == NULL || srclen <= 0)
{
return MS_ERROR;
}
/* dst 缓冲区的空间不足。
* Base64 编码是每 3 个原始字符编码成 4 个字符，
* 如果原始字符串长度不能被 3 整除，使用 0 来补充原始字符串。*/
dst_needed = (srclen + 2) / 3;
dst_needed *= 4;
if (dstlen < dst_needed + 1)
{
return MS_ERROR;
}
from = (unsigned char *)src;
while (srclen > 0)
{
c1 = *from++;
srclen--;
*to++ = base64[c1 >> 2];
c1 = (c1 & 0x03) << 4;
if (srclen <= 0)
{
*to++ = base64[c1];
*to++ = '=';
*to++ = '=';
break;
}
c2 = *from++;
srclen--;
c1 |= (c2 >> 4) & 0x0f;
*to++ = base64[c1];
c1 = (c2 & 0x0f) << 2;
if (srclen <= 0)
{
*to++ = base64[c1];
*to++ = '=';
break;
}
c2 = *from++;
srclen--;
c1 |= (c2 >> 6) & 0x03;
*to++ = base64[c1];
*to++ = base64[c2 & 0x3f];
}
*to = '\0';
return to - dst;
}
int base64_decode(char *dst, int dstlen, const char *src, int srclen)
{
const unsigned char *p, *q;
unsigned char *t;
int c1, c2;
// 参数检测
if (dst == NULL || dstlen <= 0 || src == NULL || srclen <= 0)
{
return MS_ERROR;
}
// 移除首尾的空白字符
for (p = (const unsigned char *) src; srclen > 0 && isspace(*p); p++, srclen--)
{
/* void */ ;
}
for (q = p + srclen - 1; q >= p && isspace(*q); q--, srclen--)
{
/* void */ ;
}
// 长度必须为 4 的倍数
if (srclen % 4 != 0)
{
return MS_ERROR;
}
// 目标缓冲区必须足够长
if (srclen / 4 * 3 + 1 > dstlen)
{
return MS_ERROR;
}
t = (unsigned char *)dst;
while (srclen > 0)
{
srclen -= 4;
if (*p >= 128 || (c1 = index_64[*p++]) == -1)
{
return MS_ERROR;
}
if (*p >= 128 || (c2 = index_64[*p++]) == -1)
{
return MS_ERROR;
}
*t++ = (c1 << 2) | ((c2 & 0x30) >> 4);
if (p[0] == '=' && p[1] == '=')
{
break;
}
if (*p >= 128 || (c1 = index_64[*p++]) == -1)
{
return MS_ERROR;
}
*t++ = ((c2 & 0x0f) << 4) | ((c1 & 0x3c) >> 2);
if (p[0] == '=')
{
break;
}
if (*p >= 128 || (c2 = index_64[*p++]) == -1)
{
return MS_ERROR;
}
*t++ = ((c1 & 0x03) << 6) | c2;
}
return t - (unsigned char *) dst;
}
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