base64

Base64编码解码实现

最新推荐文章于 2025-07-02 20:33:18 发布

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#ifndef _BASE64_H_
#define _BASE64_H_
#include <string>
std::string base64_encode(unsigned char const* , unsigned int len);
std::string base64_decode(std::string const& s);
#endif

// base64.cpp
#include "stdafx.h"
#include "base64.h"

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


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

std::string base64_encode(unsigned char const* bytes_to_encode, unsigned 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;

}

std::string base64_decode(std::string const& encoded_string) {
    size_t in_len = encoded_string.size();
    size_t i = 0;
    size_t 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] = static_cast<unsigned char>(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] = static_cast<unsigned char>(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;
}