下面貼個寫的很簡潔高效的類

CharacterEncoding.h

#pragma once
#include <string>
#include <Windows.h>
using namespace  std;
class CharacterEncoding
{
public:
	CharacterEncoding(void);
	~CharacterEncoding(void);

	void  unicodeToUTF8( const  wstring  & src,  string &  result);
void  unicodeToGB2312( const  wstring &  wstr ,  string &  result);
void  utf8ToUnicode( const   string &  src, wstring &  result);
void  gb2312ToUnicode( const   string &  src, wstring &  result);
string gb2312ToUTF8(const string src);
string utf8ToGB2312(const string src);

};
 

CharacterEncoding.cpp

#include "CharacterEncoding.h"

CharacterEncoding::CharacterEncoding(void)
{
}

CharacterEncoding::~CharacterEncoding(void)
{
}

void CharacterEncoding::unicodeToUTF8( const wstring & src, string & result )
{
	int  n  =  WideCharToMultiByte( CP_UTF8,  0 , src.c_str(),  - 1 ,  0 ,  0 ,  0 ,  0  );
	result.resize(n);
	::WideCharToMultiByte( CP_UTF8,  0 , src.c_str(),  - 1 , ( char * )result.c_str(), result.length(),  0 ,  0  );
}

void CharacterEncoding::unicodeToGB2312( const wstring & wstr , string & result )
{
	int  n  =  WideCharToMultiByte( CP_ACP,  0 , wstr.c_str(),  - 1 ,  0 ,  0 ,  0 ,  0  );
	result.resize(n);
	::WideCharToMultiByte(CP_ACP,  0 , wstr.c_str(),  - 1 , ( char * )result.c_str(), n,  0 ,  0  );
}

void CharacterEncoding::utf8ToUnicode( const string & src, wstring & result )
{
	int  n  =  MultiByteToWideChar( CP_UTF8,  0 , src.c_str(),  - 1 , NULL,  0  );
	result.resize(n);
	::MultiByteToWideChar( CP_UTF8,  0 , src.c_str(),  - 1 , (LPWSTR)result.c_str(), result.length());
}

void CharacterEncoding::gb2312ToUnicode( const string & src, wstring & result )
{
	int  n  =  MultiByteToWideChar( CP_ACP,  0 , src.c_str(),  - 1 , NULL,  0  );
	result.resize(n);
	::MultiByteToWideChar( CP_ACP,  0 , src.c_str(),  - 1 , (LPWSTR)result.c_str(), result.length());
}

std::string CharacterEncoding::gb2312ToUTF8( const string src )
{
   wstring temp;
   gb2312ToUnicode(src,temp);
	string ret;
	unicodeToUTF8(temp,ret);
	return ret;
}

std::string CharacterEncoding::utf8ToGB2312( const string src )
{
	wstring temp;
	utf8ToUnicode(src,temp);
	string ret;
	unicodeToGB2312(temp,ret);
	return ret;
}