转自链接：http://hi.baidu.com/luckwxx623/blog/item/e4e04c3d7e54450dbaa167da.html

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下面的代码实现了一个用于C++中转码的类strCoding。里面有UTF8、UNICODE、GB2312编码的互相转换。

.H文件：

#pragma once
#include <iostream>
#include <string>
#include <windows.h>
using namespace std;
class strCoding
public:
    strCoding(void);
    ~strCoding(void);
    void UTF_8ToGB2312(string &pOut, char *pText, int pLen);//utf_8转为gb2312
    void GB2312ToUTF_8(string& pOut,char *pText, int pLen); //gb2312 转utf_8
    string UrlGB2312(char * str);                           //urlgb2312编码
    string UrlUTF8(char * str);                             //urlutf8 编码
    string UrlUTF8Decode(string str);                  //urlutf8解码
    string UrlGB2312Decode(string str);                //urlgb2312解码
private:
    void Gb2312ToUnicode(WCHAR* pOut,char *gbBuffer);
    void UTF_8ToUnicode(WCHAR* pOut,char *pText);
    void UnicodeToUTF_8(char* pOut,WCHAR* pText);
    void UnicodeToGB2312(char* pOut,WCHAR uData);
    char CharToInt(char ch);
    char StrToBin(char *str);
.cpp文件： 
#include "StdAfx.h"
#include ".\urlcodeing.h"
//这是个类strCoding (strCoding.cpp文件)
strCoding::strCoding(void)
strCoding::~strCoding(void)
void strCoding::Gb2312ToUnicode(WCHAR* pOut,char *gbBuffer)
    ::MultiByteToWideChar(CP_ACP,MB_PRECOMPOSED,gbBuffer,2,pOut,1);
    return;
void strCoding::UTF_8ToUnicode(WCHAR* pOut,char *pText)
    char* uchar = (char *)pOut;
    uchar[1] = ((pText[0] & 0x0F) << 4) + ((pText[1] >> 2) & 0x0F);
    uchar[0] = ((pText[1] & 0x03) << 6) + (pText[2] & 0x3F);
    return;
void strCoding::UnicodeToUTF_8(char* pOut,WCHAR* pText)
    // 注意 WCHAR高低字的顺序,低字节在前，高字节在后
    char* pchar = (char *)pText;
    pOut[0] = (0xE0 | ((pchar[1] & 0xF0) >> 4));
    pOut[1] = (0x80 | ((pchar[1] & 0x0F) << 2)) + ((pchar[0] & 0xC0) >> 6);
    pOut[2] = (0x80 | (pchar[0] & 0x3F));
    return;
void strCoding::UnicodeToGB2312(char* pOut,WCHAR uData)
    WideCharToMultiByte(CP_ACP,NULL,&uData,1,pOut,sizeof(WCHAR),NULL,NULL);
    return;
//做为解Url使用
char strCoding:: CharToInt(char ch){
        if(ch>='0' && ch<='9')return (char)(ch-'0');
        if(ch>='a' && ch<='f')return (char)(ch-'a'+10);
        if(ch>='A' && ch<='F')return (char)(ch-'A'+10);
        return -1;
char strCoding::StrToBin(char *str){
        char tempWord[2];
        char chn;
        tempWord[0] = CharToInt(str[0]);                         //make the B to 11 -- 00001011
        tempWord[1] = CharToInt(str[1]);                         //make the 0 to 0 -- 00000000
        chn = (tempWord[0] << 4) | tempWord[1];                //to change the BO to 10110000
        return chn;
//UTF_8 转gb2312
void strCoding::UTF_8ToGB2312(string &pOut, char *pText, int pLen)
     char buf[4];
     char* rst = new char[pLen + (pLen >> 2) + 2];
    memset(buf,0,4);
    memset(rst,0,pLen + (pLen >> 2) + 2);
    int i =0;
    int j = 0;
    while(i < pLen)
        if(*(pText + i) >= 0)
            rst[j++] = pText[i++];
            WCHAR Wtemp;
            UTF_8ToUnicode(&Wtemp,pText + i);
            UnicodeToGB2312(buf,Wtemp);
            unsigned short int tmp = 0;
            tmp = rst[j] = buf[0];
            tmp = rst[j+1] = buf[1];
            tmp = rst[j+2] = buf[2];
            //newBuf[j] = Ctemp[0];
            //newBuf[j + 1] = Ctemp[1];
            i += 3;   
            j += 2;  
    rst[j]='\0';
   pOut = rst;
    delete []rst;
//GB2312 转为 UTF-8
void strCoding::GB2312ToUTF_8(string& pOut,char *pText, int pLen)
    char buf[4];
    memset(buf,0,4);
    pOut.clear();
    int i = 0;
    while(i < pLen)
        //如果是英文直接复制就可以
        if( pText[i] >= 0)
            char asciistr[2]={0};
            asciistr[0] = (pText[i++]);
            pOut.append(asciistr);
            WCHAR pbuffer;
            Gb2312ToUnicode(&pbuffer,pText+i);
            UnicodeToUTF_8(buf,&pbuffer);
            pOut.append(buf);
            i += 2;
    return;
//把str编码为网页中的 GB2312 url encode ,英文不变，汉字双字节 如%3D%AE%88
string strCoding::UrlGB2312(char * str)
    string dd;
    size_t len = strlen(str);
    for (size_t i=0;i<len;i++)
        if(isalnum((BYTE)str[i]))
            char tempbuff[2];
            sprintf(tempbuff,"%c",str[i]);
            dd.append(tempbuff);
        else if (isspace((BYTE)str[i]))
            dd.append("+");
            char tempbuff[4];
            sprintf(tempbuff,"%%%X%X",((BYTE*)str)[i] >>4,((BYTE*)str)[i] %16);
            dd.append(tempbuff);
    return dd;
//把str编码为网页中的 UTF-8 url encode ,英文不变，汉字三字节 如%3D%AE%88
string strCoding::UrlUTF8(char * str)
    string tt;
    string dd;
    GB2312ToUTF_8(tt,str,(int)strlen(str));
    size_t len=tt.length();
    for (size_t i=0;i<len;i++)
        if(isalnum((BYTE)tt.at(i)))
            char tempbuff[2]={0};
            sprintf(tempbuff,"%c",(BYTE)tt.at(i));
            dd.append(tempbuff);
        else if (isspace((BYTE)tt.at(i)))
            dd.append("+");
            char tempbuff[4];
            sprintf(tempbuff,"%%%X%X",((BYTE)tt.at(i)) >>4,((BYTE)tt.at(i)) %16);
            dd.append(tempbuff);
    return dd;
//把url GB2312解码
string strCoding::UrlGB2312Decode(string str)
   string output="";
        char tmp[2];
        int i=0,idx=0,ndx,len=str.length();
        while(i<len){
                if(str[i]=='%'){
                        tmp[0]=str[i+1];
                        tmp[1]=str[i+2];
                        output += StrToBin(tmp);
                        i=i+3;
                else if(str[i]=='+'){
                        output+=' ';
                        i++;
                else{
                        output+=str[i];
                        i++;
        return output;
//把url utf8解码
string strCoding::UrlUTF8Decode(string str)
     string output="";
    string temp =UrlGB2312Decode(str);//
    UTF_8ToGB2312(output,(char *)temp.data(),strlen(temp.data()));
    return output;