base64编解码的两个函数(安全版本)

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void base64_encode_s(const unsigned char *str, long inlen, std::string& outstr, long* lpBufLen)
{
long len;
long str_len;
//unsigned char *res;
//std::shared_ptr<std::string> res;
int i,j;
//定义base64编码表
const unsigned char *base64_table = (const unsigned char *)("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
//计算经过base64编码后的字符串长度
str_len= inlen;
if(str_len % 3 == 0)
len=str_len/3*4;
else
len=(str_len/3+1)*4;
if (NULL != lpBufLen) {
*lpBufLen = len;
}
//std::shared_ptr<std::string> res(new std::string(sizeof(unsigned char)*len+1)); //(unsigned char *)malloc(sizeof(unsigned char)*len+1);
outstr.resize(sizeof(unsigned char)*len+1);
outstr[len] = '\0';
//以3个8位字符为一组进行编码
for(i=0,j=0;i<len-2;j+=3,i+=4)
{
outstr[i] = base64_table[str[j]>>2]; //取出第一个字符的前6位并找出对应的结果字符
outstr[i+1] = base64_table[(str[j]&0x3)<<4 | (str[j+1]>>4)]; //将第一个字符的后位与第二个字符的前4位进行组合并找到对应的结果字符
outstr[i+2] = base64_table[(str[j+1]&0xf)<<2 | (str[j+2]>>6)]; //将第二个字符的后4位与第三个字符的前2位组合并找出对应的结果字符
outstr[i+3] = base64_table[str[j+2]&0x3f]; //取出第三个字符的后6位并找出结果字符
}
switch(str_len % 3)
{
case 1:
outstr[i-2]='=';
outstr[i-1]='=';
break;
case 2:
outstr[i-1]='=';
break;
}
return;
}
void base64_decode_s(const unsigned char *code, std::string& outstr, long* lpBufLen)
{
//根据base64表,以字符找到对应的十进制数据
int table[]={0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,62,0,0,0,
63,52,53,54,55,56,57,58,
59,60,61,0,0,0,0,0,0,0,0,
1,2,3,4,5,6,7,8,9,10,11,12,
13,14,15,16,17,18,19,20,21,
22,23,24,25,0,0,0,0,0,0,26,
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
};
long len;
long str_len;
//unsigned char *res = NULL;
int i,j;
//计算解码后的字符串长度
len = strlen((const char*)code);
//判断编码后的字符串后是否有=
if(strstr((const char*)code,"=="))
str_len=len/4*3-2;
else if(strstr((const char*)code,"="))
str_len=len/4*3-1;
else
str_len=len/4*3;
if (NULL != lpBufLen) {
*lpBufLen = str_len;
}
//res = (unsigned char*)malloc(sizeof(unsigned char)*str_len+1);
outstr.resize(sizeof(unsigned char)*len+1);
//memset(outstr.,0, str_len+1);
//res[str_len]='\0';
//以4个字符为一位进行解码
for(i=0,j=0;i < len-2;j+=3,i+=4)
{
outstr[j]=((unsigned char)table[code[i]])<<2 | (((unsigned char)table[code[i+1]])>>4); //取出第一个字符对应base64表的十进制数的前6位与第二个字符对应base64表的十进制数的后2位进行组合
outstr[j+1]=(((unsigned char)table[code[i+1]])<<4) | (((unsigned char)table[code[i+2]])>>2); //取出第二个字符对应base64表的十进制数的后4位与第三个字符对应bas464表的十进制数的后4位进行组合
outstr[j+2]=(((unsigned char)table[code[i+2]])<<6) | ((unsigned char)table[code[i+3]]); //取出第三个字符对应base64表的十进制数的后2位与第4个字符进行组合
}
return;
}
posted @   日月王  阅读(618)  评论(0编辑  收藏  举报
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