base64的C++实现

1.  概述
   base64可以将不可显示的编码转换成可显示的编码，以便于存储。
   比如http一般传输的是文本格式的报文，如果要传输图片，那么就要先将图片编码成base64的报文传输，然后在客客户端显示的时候，将base64的报文解密，转换成二进制的图片数据显示。
   下面给出源代码，可以直接在linux,msvc环境下进行编译。
2. 代码
   Base64.h代码如下：
   /*** (C) Copyright 2009, asiainfo* @version v1.0* @author chenli* @brief base64编码和解码** history:* <p>chenli 2009-02-17 1.0 build this moudle</p>*/#ifndef ___BASE64_H___#define ___BASE64_H___#include <string>using namespace std;class CBase64{public:CBase64();~CBase64();/********************************************************** 函数说明：将输入数据进行base64编码* 参数说明：[in]pIn需要进行编码的数据[in]uInLen 输入参数的字节数[out]strOut 输出的进行base64编码之后的字符串* 返回值 ：true处理成功,false失败* 作 者 ：ChenLi* 编写时间：2009-02-17**********************************************************/bool static Encode(const unsigned char *pIn, unsigned long uInLen, string& strOut);/********************************************************** 函数说明：将输入数据进行base64编码* 参数说明：[in]pIn需要进行编码的数据[in]uInLen输入参数的字节数[out]pOut输出的进行base64编码之后的字符串[out]uOutLen输出的进行base64编码之后的字符串长度* 返回值 ：true处理成功,false失败* 作 者 ：ChenLi* 编写时间：2009-02-17**********************************************************/bool static Encode(const unsigned char *pIn, unsigned long uInLen, unsigned char *pOut, unsigned long *uOutLen);/********************************************************** 函数说明：将输入数据进行base64解码* 参数说明：[in]strIn需要进行解码的数据[out]pOut输出解码之后的节数数据[out]uOutLen输出的解码之后的字节数长度* 返回值 ：true处理成功,false失败* 作 者 ：ChenLi* 编写时间：2009-02-17**********************************************************/bool static Decode(const string& strIn, unsigned char *pOut, unsigned long *uOutLen) ;/********************************************************** 函数说明：将输入数据进行base64解码* 参数说明：[in]strIn需要进行解码的数据[out]pOut输出解码之后的节数数据[out]uOutLen输出的解码之后的字节数长度* 返回值 ：true处理成功,false失败* 作 者 ：ChenLi* 编写时间：2009-02-17**********************************************************/bool static Decode(const unsigned char *pIn, unsigned long uInLen, unsigned char *pOut, unsigned long *uOutLen) ;};#endif // ___BASE64_H___
   Base64.cpp代码如下：
   /* * *Base64? * * **/#include "Base64.h"static const char *g_pCodes ="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";static const unsigned char g_pMap[256] ={255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255,255, 254, 255, 255, 255, 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, 255, 255, 255, 255, 255,255, 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, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,255, 255, 255, 255};CBase64::CBase64(){}CBase64::~CBase64(){}bool CBase64::Encode(const unsigned char *pIn, unsigned long uInLen, unsigned char *pOut, unsigned long *uOutLen){unsigned long i, len2, leven;unsigned char *p;if(pOut == NULL || *uOutLen == 0)return false;//ASSERT((pIn != NULL) && (uInLen != 0) && (pOut != NULL) && (uOutLen != NULL));len2 = ((uInLen + 2) / 3) << 2;if((*uOutLen) < (len2 + 1)) return false;p = pOut;leven = 3 * (uInLen / 3);for(i = 0; i < leven; i += 3){*p++ = g_pCodes[pIn[0] >> 2];*p++ = g_pCodes[((pIn[0] & 3) << 4) + (pIn[1] >> 4)];*p++ = g_pCodes[((pIn[1] & 0xf) << 2) + (pIn[2] >> 6)];*p++ = g_pCodes[pIn[2] & 0x3f];pIn += 3;}if (i < uInLen){unsigned char a = pIn[0];unsigned char b = ((i + 1) < uInLen) ? pIn[1] : 0;unsigned char c = 0;*p++ = g_pCodes[a >> 2];*p++ = g_pCodes[((a & 3) << 4) + (b >> 4)];*p++ = ((i + 1) < uInLen) ? g_pCodes[((b & 0xf) << 2) + (c >> 6)] : '=';*p++ = '=';}*p = 0; // Append NULL byte*uOutLen = p - pOut;return true;}bool CBase64::Encode(const unsigned char *pIn, unsigned long uInLen, string& strOut) {unsigned long i, len2, leven;strOut = "";//ASSERT((pIn != NULL) && (uInLen != 0) && (pOut != NULL) && (uOutLen != NULL));len2 = ((uInLen + 2) / 3) << 2;//if((*uOutLen) < (len2 + 1)) return false;//p = pOut;leven = 3 * (uInLen / 3);for(i = 0; i < leven; i += 3){strOut += g_pCodes[pIn[0] >> 2];strOut += g_pCodes[((pIn[0] & 3) << 4) + (pIn[1] >> 4)];strOut += g_pCodes[((pIn[1] & 0xf) << 2) + (pIn[2] >> 6)];strOut += g_pCodes[pIn[2] & 0x3f];pIn += 3;}if (i < uInLen){unsigned char a = pIn[0];unsigned char b = ((i + 1) < uInLen) ? pIn[1] : 0;unsigned char c = 0;strOut += g_pCodes[a >> 2];strOut += g_pCodes[((a & 3) << 4) + (b >> 4)];strOut += ((i + 1) < uInLen) ? g_pCodes[((b & 0xf) << 2) + (c >> 6)] : '=';strOut += '=';}//*p = 0; // Append NULL byte//*uOutLen = p - pOut;return true;}bool CBase64::Decode(const string& strIn, unsigned char *pOut, unsigned long *uOutLen) {unsigned long t, x, y, z;unsigned char c;unsigned long g = 3;//ASSERT((pIn != NULL) && (uInLen != 0) && (pOut != NULL) && (uOutLen != NULL));for(x = y = z = t = 0; x < strIn.length(); x++){c = g_pMap[strIn[x]];if(c == 255) continue;if(c == 254) { c = 0; g--; }t = (t << 6) | c;if(++y == 4){if((z + g) > *uOutLen) { return false; } // Buffer overflowpOut[z++] = (unsigned char)((t>>16)&255);if(g > 1) pOut[z++] = (unsigned char)((t>>8)&255);if(g > 2) pOut[z++] = (unsigned char)(t&255);y = t = 0;}}*uOutLen = z;return true;}
   
   上面有了base64的算法，下面写个程序进行测试。
   main.cpp文件内容如下：
   #include "Base64.h"#include <iostream>using namespace std;int main(){unsigned long len = 10;unsigned char pIn[100];unsigned char pOut[100];memcpy(pIn,"你好",5);string strout;cout<<(char*)pIn<<endl;if(CBase64::Encode(pIn, 4, strout))cout<<strout<<endl;elsecout<<"加密失败"<<endl;string stroIn = strout;cout<<stroIn<<endl;memset(pOut,0,sizeof(pOut));if(CBase64::Decode(stroIn, pOut, &len)){cout<<(char *)pOut<<endl;cout<<"len="<<strlen((char *)pOut)<<endl;}elsecout<<"解密失败"<<endl;cout<<len<<endl;return 0;}
   
   上面的代码直接编译就可以运行了。