元サイト
http://yano.hatenadiary.jp/entry/20100908/1283945820
消えたら困るのでメモ
base64.hpp
#ifndef BASE64_HPP_20100908_
#define BASE64_HPP_20100908_
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif
#include <string>
#include <vector>
namespace algorithm {
bool encode_base64(const std::vector<unsigned char>& src, std::string& dst);
bool decode_base64(const std::string& src, std::vector<unsigned char>& dst);
}
#endif
base64.cpp
#include "base64.hpp"
// base64 エンコード
bool algorithm::encode_base64(const std::vector<unsigned char>& src, std::string& dst)
{
const std::string table("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
std::string cdst;
for (std::size_t i = 0; i < src.size(); ++i) {
switch (i % 3) {
case 0:
cdst.push_back(table[(src[i] & 0xFC) >> 2]);
if (i + 1 == src.size()) {
cdst.push_back(table[(src[i] & 0x03) << 4]);
cdst.push_back('=');
cdst.push_back('=');
}
break;
case 1:
cdst.push_back(table[((src[i - 1] & 0x03) << 4) | ((src[i + 0] & 0xF0) >> 4)]);
if (i + 1 == src.size()) {
cdst.push_back(table[(src[i] & 0x0F) << 2]);
cdst.push_back('=');
}
break;
case 2:
cdst.push_back(table[((src[i - 1] & 0x0F) << 2) | ((src[i + 0] & 0xC0) >> 6)]);
cdst.push_back(table[src[i] & 0x3F]);
break;
}
}
dst.swap(cdst);
return true;
}
// base64 デコード
bool algorithm::decode_base64(const std::string& src, std::vector<unsigned char>& dst)
{
if (src.size() & 0x00000003) {
return false;
}
else {
const std::string table("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
std::vector<unsigned char> cdst;
for (std::size_t i = 0; i < src.size(); i += 4) {
if (src[i + 0] == '=') {
return false;
}
else if (src[i + 1] == '=') {
return false;
}
else if (src[i + 2] == '=') {
const std::string::size_type s1 = table.find(src[i + 0]);
const std::string::size_type s2 = table.find(src[i + 1]);
if (s1 == std::string::npos || s2 == std::string::npos) {
return false;
}
cdst.push_back(static_cast<unsigned char>(((s1 & 0x3F) << 2) | ((s2 & 0x30) >> 4)));
break;
}
else if (src[i + 3] == '=') {
const std::string::size_type s1 = table.find(src[i + 0]);
const std::string::size_type s2 = table.find(src[i + 1]);
const std::string::size_type s3 = table.find(src[i + 2]);
if (s1 == std::string::npos || s2 == std::string::npos || s3 == std::string::npos) {
return false;
}
cdst.push_back(static_cast<unsigned char>(((s1 & 0x3F) << 2) | ((s2 & 0x30) >> 4)));
cdst.push_back(static_cast<unsigned char>(((s2 & 0x0F) << 4) | ((s3 & 0x3C) >> 2)));
break;
}
else {
const std::string::size_type s1 = table.find(src[i + 0]);
const std::string::size_type s2 = table.find(src[i + 1]);
const std::string::size_type s3 = table.find(src[i + 2]);
const std::string::size_type s4 = table.find(src[i + 3]);
if (s1 == std::string::npos || s2 == std::string::npos || s3 == std::string::npos || s4 == std::string::npos) {
return false;
}
cdst.push_back(static_cast<unsigned char>(((s1 & 0x3F) << 2) | ((s2 & 0x30) >> 4)));
cdst.push_back(static_cast<unsigned char>(((s2 & 0x0F) << 4) | ((s3 & 0x3C) >> 2)));
cdst.push_back(static_cast<unsigned char>(((s3 & 0x03) << 6) | ((s4 & 0x3F) >> 0)));
}
}
dst.swap(cdst);
return true;
}
}
test.cpp
#include <iostream>
#include <iomanip>
#include <vector>
#include "base64.hpp"
int main()
{
std::vector<unsigned char> v1, v2;
v1.push_back(0xde);
v1.push_back(0xad);
v1.push_back(0xbe);
v1.push_back(0xef);
std::string s;
algorithm::encode_base64(v1, s); // base64 エンコード
std::cout << s << std::endl; // 3q2+7w==
algorithm::decode_base64(s, v2); // base64 デコード
for (std::vector<unsigned char>::const_iterator it = v2.begin(); it != v2.end(); ++it) {
std::cout << std::hex << static_cast<int>(*it);
} // deadbeef
return 0;
}