base64编解码的两个函数（安全版本）

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 %  == )
        len=str_len/*;
    else
        len=(str_len/+)*;

    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+);
    outstr[len] = '\0';  

    //以3个8位字符为一组进行编码
    for(i=,j=;i<len-;j+=,i+=)
    {
        outstr[i] = base64_table[str[j]>>]; //取出第一个字符的前6位并找出对应的结果字符
        outstr[i+] = base64_table[(str[j]&0x3)<< | (str[j+]>>)]; //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+] = base64_table[(str[j+]&0xf)<< | (str[j+]>>)]; //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+] = base64_table[str[j+]&0x3f]; //取出第三个字符的后6位并找出结果字符
    }  

    switch(str_len % )
    {
        case :
            outstr[i-]='=';
            outstr[i-]='=';
            break;
        case :
            outstr[i-]='=';
            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[]={,,,,,,,,,,,,
             ,,,,,,,,,,,,
             ,,,,,,,,,,,,
             ,,,,,,,,,,,
             ,,,,,,,,
             ,,,,,,,,,,,
             ,,,,,,,,,,,,
             ,,,,,,,,,
             ,,,,,,,,,,,
             ,,,,,,,,,
             ,,,,,,,,,
             ,,,,,,
               };
    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/*-;
    else if(strstr((const char*)code,"="))
        str_len=len/*-;
    else
        str_len=len/*;  

    if (NULL != lpBufLen) {
        *lpBufLen = str_len;
    }

    //res = (unsigned char*)malloc(sizeof(unsigned char)*str_len+1);
    outstr.resize(sizeof(unsigned char)*len+);
    //memset(outstr.,0, str_len+1);
    //res[str_len]='\0';

    //以4个字符为一位进行解码
    for(i=,j=;i < len-;j+=,i+=)
    {
        outstr[j]=((unsigned char)table[code[i]])<< | (((unsigned char)table[code[i+]])>>); //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+]=(((unsigned char)table[code[i+]])<<) | (((unsigned char)table[code[i+]])>>); //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+]=(((unsigned char)table[code[i+]])<<) | ((unsigned char)table[code[i+]]); //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;
}