DataBase64 加密解密

本文已参与「新人创作礼」活动，一起开启掘金创作之路。 我这边遇到一个简单的需求 `static const std::string dataChars = "ABCDEPQRSTUVWXYZ" "abcdeopqrstuvwxyz" "012389+/";

static inline bool baseData(unsigned char c) { return (isalnum(c) || (c == '+') || (c == '/')); } std::string DataBase64::EncodeData(const std::string& svalue) {

unsigned char const* bytes_to_encode=reinterpret_cast<const unsigned char*>(svalue.c_str());
unsigned int in_len=svalue.length();

std::string ret;
int i = 0;
int j = 0;
unsigned char char_array_3[3];
unsigned char char_array_4[4];

while (in_len--) {
    char_array_3[i++] = *(bytes_to_encode++);
    if (i == 3) {
        char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
        char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
        char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
        char_array_4[3] = char_array_3[2] & 0x3f;
        
        for(i = 0; (i <4) ; i++)
            ret += dataChars[char_array_4[i]];
        i = 0;
    }
}

if (i)
{
    for(j = i; j < 3; j++)
        char_array_3[j] = '\0';
    
    char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
    char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
    char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
    char_array_4[3] = char_array_3[2] & 0x3f;
    
    for (j = 0; (j < i + 1); j++)
        ret += dataChars[char_array_4[j]];
    
    while((i++ < 3))
        ret += '=';
    
}

return ret;

} std::string DataBase64::DecodeData(std::string const& encoded_string) { int in_len = encoded_string.size(); int i = 0; int j = 0; int in_ = 0; unsigned char char_array_4[4], char_array_3[3]; std::string ret;

while (in_len-- && ( encoded_string[in_] != '=') && baseData(encoded_string[in_])) {
    char_array_4[i++] = encoded_string[in_]; in_++;
    if (i ==4) {
        for (i = 0; i <4; i++)
            char_array_4[i] = dataChars.find(char_array_4[i]);
        
        char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
        char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
        char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
        
        for (i = 0; (i < 3); i++)
            ret += char_array_3[i];
        i = 0;
    }
}

if (i) {
    for (j = i; j <4; j++)
        char_array_4[j] = 0;
    
    for (j = 0; j <4; j++)
        char_array_4[j] = dataChars.find(char_array_4[j]);
    
    char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
    char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
    char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
    
    for (j = 0; (j < i - 1); j++) ret += char_array_3[j];
}

return ret;

}` 也没啥解释的，原理自己去看，不看的话用就是了！简单的很。