标签：style class blog c code ext
Base64要求把每三个8Bit的字节转换为四个6Bit的字节（3*8 = 4*6 = 24），然后把6Bit再添两位高位0，组成四个8Bit的字节。Base64编码表
| 码值 | 字符 | 码值 | 字符 | 码值 | 字符 | 码值 | 字符 | |||
|---|---|---|---|---|---|---|---|---|---|---|
| 0 | A | 16 | Q | 32 | g | 48 | w | |||
| 1 | B | 17 | R | 33 | h | 49 | x | |||
| 2 | C | 18 | S | 34 | i | 50 | y | |||
| 3 | D | 19 | T | 35 | j | 51 | z | |||
| 4 | E | 20 | U | 36 | k | 52 | 0 | |||
| 5 | F | 21 | V | 37 | l | 53 | 1 | |||
| 6 | G | 22 | W | 38 | m | 54 | 2 | |||
| 7 | H | 23 | X | 39 | n | 55 | 3 | |||
| 8 | I | 24 | Y | 40 | o | 56 | 4 | |||
| 9 | J | 25 | Z | 41 | p | 57 | 5 | |||
| 10 | K | 26 | a | 42 | q | 58 | 6 | |||
| 11 | L | 27 | b | 43 | r | 59 | 7 | |||
| 12 | M | 28 | c | 44 | s | 60 | 8 | |||
| 13 | N | 29 | d | 45 | t | 61 | 9 | |||
| 14 | O | 30 | e | 46 | u | 62 | + | |||
| 15 | P | 31 | f | 47 | v | 63 | / |
static const char s_acBase64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
/*
* 函数名称: Base64Encode
* 函数功能: base64编码
* 参 数:
* pucIN - 编码前数据
* ulINLen - 编码前数据长度
* pucOUT - 编码后数据
* pucOUTLen - 编码后数据长度
* 返 回 值: 成功返回R__OK,否则返回相应错误码
*/
unsigned int Base64Encode(const unsigned char *pucIN, unsigned long ulINLen, unsigned char *pucOUT, unsigned long *pulOUTLen)
{
if (NULL == pucIN || NULL == pucOUT || NULL == pulOUTLen)
{
return -1;
}
unsigned long i, len2, leven;
unsigned char *p;
len2 = 4 * ((ulINLen + 2) / 3);
if (*pulOUTLen < len2 + 1)
{
*pulOUTLen = len2 + 1;
return -2;
}
p = pucOUT;
leven = 3*(ulINLen / 3);
for (i = 0; i < leven; i += 3)
{
*pucOUT++ = s_acBase64[(pucIN[0] >> 2) & 0x3F];
*pucOUT++ = s_acBase64[(((pucIN[0] & 3) << 4) + (pucIN[1] >> 4)) & 0x3F];
*pucOUT++ = s_acBase64[(((pucIN[1] & 0xf) << 2) + (pucIN[2] >> 6)) & 0x3F];
*pucOUT++ = s_acBase64[pucIN[2] & 0x3F];
pucIN += 3;
}
if (i < ulINLen)
{
unsigned a = pucIN[0];
unsigned b = (i+1 < ulINLen) ? pucIN[1] : 0;
*pucOUT++ = s_acBase64[(a >> 2) & 0x3F];
*pucOUT++ = s_acBase64[(((a & 3) << 4) + (b >> 4)) & 0x3F];
*pucOUT++ = (i+1 < ulINLen) ? s_acBase64[(((b & 0xf) << 2)) & 0x3F] : '=';
*pucOUT++ = '=';
}
*pucOUT = '\0';
*pulOUTLen = pucOUT - p;
return 0;
}
标签：style class blog c code ext
原文地址：http://blog.csdn.net/wenwei19861106/article/details/26678033
