C++ base64

百科：https://baike.baidu.com/item/base64/8545775?fr=aladdin

1.自己写的解析方法：

class UTILS_API CBase64
	{
	public:
		static std::string base64_encode(unsigned const char*, unsigned int len);
		static std::string base64_decode(const std::string&s);
	};

 

//base64编解码
	static const std::string base64_chars =
		"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
		"abcdefghijklmnopqrstuvwxyz"
		"0123456789+/";

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

	std::string CBase64::base64_encode(unsigned const char* 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 (int j = 0; j < 4; j++)
				{
					ret += base64_chars[char_array_4[j]];
				}
				i = 0;
			}
		}
		//如果字符串不是3的整数倍，则会有剩余1个字节或2个字节的情况
		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 CBase64::base64_decode(const 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] = 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;
	}

2.使用ATL库：

// ConsoleApplication1.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <strsafe.h>
#include <atlenc.h>
#include <string>
#include <iostream>
int main()
{
	std::wstring strMsg = L"1&13661901285&123456&WdpqZOLXJg3WZ0cEVhi687CQyAw722UuH4CRZXHQS91WVe9K48p08B2-pJ0Zl_M_gMs&&0&&2019-04-03 09:53:35&&";
	size_t nLen = (strMsg.length() + 1) * 2;
	wchar_t* lpszValue = (wchar_t*)_alloca(nLen);//在栈上分配内存，使用完毕，立即释放。
	memcpy_s(lpszValue, nLen, strMsg.c_str(), nLen);
	
	int nDstLen = nLen * 2 + 1;
	char* pDstValue = new char[nDstLen];
	memset(pDstValue, 0, nDstLen);
	ATL::Base64Encode((const BYTE*)lpszValue, nLen, pDstValue, &nDstLen, ATL_BASE64_FLAG_NOCRLF);//编码
	

	int nDstLen2 = 0;
	BYTE* pDstValueDecode = NULL;
	if (FALSE == ATL::Base64Decode(pDstValue, nDstLen, NULL, &nDstLen2))//获取目标字符串的长度
	{
		pDstValueDecode = new BYTE[nDstLen2 + 1];
		memset(pDstValueDecode, 0, nDstLen2 + 1);
		ATL::Base64Decode(pDstValue, nDstLen, pDstValueDecode, &nDstLen2);//解码
	}
	std::wstring ret = (wchar_t*)pDstValueDecode;
	USES_CONVERSION;
	std::string ret2 = W2A(ret.c_str());
	delete[]pDstValue;
	delete[]pDstValueDecode;
    return 0;
}