Base64编解码(C++版)

.h文件：

#pragma once
#include <string>
using namespace std;

class ZBase64
{
  
public:
	/*编码
	DataByte
	[in]输入的数据长度,以字节为单位
	*/
	string Encode(const unsigned char* Data, int DataByte);
	/*解码
	DataByte
	[in]输入的数据长度,以字节为单位
	OutByte
	[out]输出的数据长度,以字节为单位,请不要通过返回值计算
	输出数据的长度
	*/
	string Decode(const char* Data, int DataByte, int& OutByte);
};

.cpp文件：

#include"stdafx.h"
#include "ZBase64.h"
string ZBase64::Encode(const unsigned char* Data, int DataByte)
{
  
	//编码表
	const char EncodeTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	//返回值
	string strEncode;
	unsigned char Tmp[4] = {
   0 };
	int LineLength = 0;
	for (int i = 0; i<(int)(DataByte / 3); i++)
	{
  
		Tmp[1] = *Data++;
		Tmp[2] = *Data++;
		Tmp[3] = *Data++;
		strEncode += EncodeTable[Tmp[1] >> 2];
		strEncode += EncodeTable[((Tmp[1] << 4) | (Tmp[2] >> 4)) & 0x3F];
		strEncode += EncodeTable[((Tmp[2] << 2) | (Tmp[3] >> 6)) & 0x3F];
		strEncode += EncodeTable[Tmp[3] & 0x3F];
		if (LineLength += 4, LineLength == 76) {
   strEncode += "\r\n"; LineLength = 0; }
	}
	//对剩余数据进行编码
	int Mod = DataByte % 3;
	if (Mod == 1)
	{
  
		Tmp[1] = *Data++;
		strEncode += EncodeTable[(Tmp[1] & 0xFC) >> 2];
		strEncode += EncodeTable[((Tmp[1] & 0x03) << 4)];
		strEncode += "==";
	}
	else if (Mod == 2)
	{
  
		Tmp[1] = *Data++;
		Tmp[2] = *Data++;
		strEncode += EncodeTable[(Tmp[1] & 0xFC) >> 2];
		strEncode += EncodeTable[((Tmp[1] & 0x03) << 4) | ((Tmp[2] & 0xF0) >> 4)];
		strEncode += EncodeTable[((Tmp[2] & 0x0F) << 2)];
		strEncode += "=";
	}

	return strEncode;
}

string ZBase64::Decode(const char* Data, int DataByte, int& OutByte)
{
  
	//解码表
	const char DecodeTable[] =
	{
  
		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		62, // '+'
		0, 0, 0,
		63, // '/'
		52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // '0'-'9'
		0, 0, 0, 0, 0, 0, 0,
		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
		13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // 'A'-'Z'
		0, 0, 0, 0, 0, 0,
		26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
		39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // 'a'-'z'
	};
	//返回值
	string strDecode;
	int nValue;
	int i = 0;
	while (i < DataByte)
	{
  
		if (*Data != '\r' && *Data != '\n')
		{
  
			nValue = DecodeTable[*Data++] << 18;
			nValue += DecodeTable[*Data++] << 12;
			strDecode += (nValue & 0x00FF0000) >> 16;
			OutByte++;
			if (*Data != '=')
			{
  
				nValue += DecodeTable[*Data++] << 6;
				strDecode += (nValue & 0x0000FF00) >> 8;
				OutByte++;
				if (*Data != '=')
				{
  
					nValue += DecodeTable[*Data++];
					strDecode += nValue & 0x000000FF;
					OutByte++;
				}
			}
			i += 4;
		}
		else// 回车换行,跳过
		{
  
			Data++;
			i++;
		}
	}
	return strDecode;
}

调用示例：

int main()
{
  
	ZBase64 base64;
	int datalen(0);
	const unsigned char Data[] = "Hello ZBase64";
	string imgbase64 = base64.Encode(Data,sizeof(Data));

	cout << "imgbase64: " << imgbase64 << endl;

	string strcode = base64.Decode(imgbase64.c_str(), imgbase64.size(), datalen);

	cout << "strcode: " << strcode << endl;
	return 0;
}

结果输出：

imgbase64: SGVsbG8gWkJhc2U2NAA=
strcode: Hello ZBase64