【C++】base64加密解密_c++如何base64加密-优快云博客

本文链接：https://blog.youkuaiyun.com/m0_62692681/article/details/134788290

博客涉及C++和密码学相关内容，虽未给出具体内容，但可知围绕C++在密码学领域的应用或密码学相关知识借助C++来呈现等方面。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

#include <iostream>

static const std::string base64_chars =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "abcdefghijklmnopqrstuvwxyz"
    "0123456789+/";

static inline bool is_base64(unsigned char c) {
    return (isalnum(c) || (c == '+') || (c == '/'));
}

// base64 编码
std::string base64_encode(char const* bytes_to_encode, int in_len) {
    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 += base64_chars[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 += base64_chars[char_array_4[j]];

        while ((i++ < 3)) ret += '=';
    }

    return ret;
}

// base64 解码
std::string base64_decode(std::string& 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_] != '=') &&
           is_base64(encoded_string[in_])) {
        char_array_4[i++] = encoded_string[in_];
        in_++;
        if (i == 4) {
            for (i = 0; i < 4; i++)
                char_array_4[i] = base64_chars.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] = base64_chars.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;
}

int main()
{
    std::string text = "abcdefg";
    std::string base64Text = base64_encode(text.c_str(),text.length());
    std::cout<<"base64_encode:"<<base64Text;
    text = base64_decode(base64Text);
    std::cout<<"base64_decode:"<<text;
    return 0;
}