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 overflow pOut[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; else cout<<"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; } else cout<<"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。