在WIN32開發過程中經常需要在不同的字符集之間進行轉換，這可以通過WIN32 API函數WideCharToMultiByte和MultiByteToWideChar來完成，但轉換過程涉及空間的分配與回收問題，直接調用API稍顯麻煩，故在此將字符集轉換功能封裝到一個模板類中，以簡化轉換過程。該類代碼如下：

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?/**************************************************************************
*?? Copyright (C) 2009 by Linmei,Jiang??????????????????????????????????? *
*?? clough@hqu.edu.cn???????????????????????????????????????????????????? *
*???????????????????????????????????????????????????????????????????????? *
*?? This program is free software; you can redistribute it and/or modify? *
*?? it under the terms of the GNU General Public License as published by? *
*?? the Free Software Foundation; either version 2 of the License, or???? *
*?? (at your option) any later version.?????????????????????????????????? *
*???????????????????????????????????????????????????????????????????????? *
*?? This program is distributed in the hope that it will be useful,?????? *
*?? but WITHOUT ANY WARRANTY; without even the implied warranty of??????? *
*?? MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.? See the???????? *
*?? GNU General Public License for more details.????????????????????????? *
*???????????????????????????????????????????????????????????????????????? *
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***************************************************************************/

#ifndef _C_TRANS_CODE_
#define _C_TRANS_CODE_

template <typename T = LPCTSTR>
class CTransCode
{
public:
??? enum ECode {EN_NULL, EN_ANSI, EN_UNICODE, EN_UTF8};
public:
??? CTransCode(T pSrcStr, ECode enSrcCode = EN_NULL)
??????? : m_pSrcStr(pSrcStr), m_enSrcCode(enSrcCode),
??????? m_pAnsi(NULL), m_pUtf8(NULL), m_pMulti(NULL)
??? {
#ifdef _UNICODE
??????? if (m_enSrcCode == EN_NULL)
??????? {
??????????? m_enSrcCode = EN_UNICODE;
??????? }
#else
??????? if (m_enSrcCode == EN_NULL)
??????? {
??????????? m_enSrcCode = EN_ANSI;
??????? }
#endif
??? }
??? ~CTransCode(void)
??? {
??????? Release();
??? }
public:
??? const wchar_t* ToUnicode();
??? const char* ToAnsi();
??? const char* ToUtf8();
??? // You can manually release the buffer or wait for the destructor to do it.
??? void Release()
??? {
??????? if (m_pAnsi)
??????? {
??????????? delete[] m_pAnsi;
??????????? m_pAnsi = NULL;
??????? }
??????? if (m_pUtf8)
??????? {
??????????? delete[] m_pUtf8;
??????????? m_pUtf8 = NULL;
??????? }
??????? if (m_pMulti)
??????? {
??????????? delete[] m_pMulti;
??????????? m_pMulti = NULL;
??????? }
??? }
private:
??? T?????????? m_pSrcStr;
??? ECode?????? m_enSrcCode;
??? char*?????? m_pAnsi;
??? char*?????? m_pUtf8;
??? wchar_t*??? m_pMulti;
};

//
template <typename T>
const wchar_t* CTransCode<T>::ToUnicode()
{
??? //ASSERT(m_enSrcCode == EN_ANSI || m_enSrcCode == EN_UTF8);
??? if (m_enSrcCode == EN_UNICODE) return (const wchar_t*)m_pSrcStr;
??? if (m_pMulti) return m_pMulti;

??? UINT uCodePage = m_enSrcCode == EN_UTF8 ? CP_UTF8 : CP_ACP;
??? int iLen = MultiByteToWideChar(uCodePage, 0, (LPCSTR)m_pSrcStr, -1, NULL, 0);
??? m_pMulti = new wchar_t[iLen + 1];
??? memset(m_pMulti, 0, (iLen + 1) * sizeof(wchar_t));
??? MultiByteToWideChar(uCodePage, 0, (LPCSTR)m_pSrcStr, -1, m_pMulti, iLen);

??? return m_pMulti;
}

template <typename T>
const char* CTransCode<T>::ToAnsi()
{
??? //ASSERT(m_enSrcCode == EN_UNICODE || m_enSrcCode == EN_UTF8);
??? if (m_enSrcCode == EN_ANSI) return (const char*)m_pSrcStr;
??? if (m_pAnsi) return m_pAnsi;

??? if (m_enSrcCode == EN_UTF8)
??? {
??????? ToUnicode();
??? }
??? const wchar_t* pMulti = m_enSrcCode == EN_UTF8 ? m_pMulti : (const wchar_t*)m_pSrcStr;
???
??? int iLen = WideCharToMultiByte(CP_ACP, 0, (LPCWSTR)pMulti, -1, NULL, 0, NULL, NULL);
??? m_pAnsi = new char[iLen + 1];
??? memset(m_pAnsi, 0, (iLen + 1) * sizeof(char));
??? WideCharToMultiByte(CP_ACP, 0, (LPCWSTR)pMulti, -1, m_pAnsi, iLen, NULL, NULL);

??? return m_pAnsi;
}

template <typename T>
const char* CTransCode<T>::ToUtf8()
{
??? //ASSERT(m_enSrcCode == EN_ANSI || m_enSrcCode == EN_UNICODE);
??? if (m_enSrcCode == EN_UTF8) return (const char*)m_pSrcStr;
??? if (m_pUtf8) return m_pUtf8;

??? if (m_enSrcCode == EN_ANSI)
??? {
??????? ToUnicode();
??? }
??? const wchar_t* pMulti = m_enSrcCode == EN_ANSI ? m_pMulti : (const wchar_t*)m_pSrcStr;

??? int iLen = WideCharToMultiByte(CP_UTF8, 0, (LPCWSTR)pMulti, -1, NULL, 0, NULL, NULL);
??? m_pUtf8 = new char[iLen + 1];
??? memset(m_pUtf8, 0, (iLen + 1) * sizeof(char));
??? WideCharToMultiByte(CP_UTF8, 0, (LPCWSTR)pMulti, -1, m_pUtf8, iLen, NULL, NULL);

??? return m_pUtf8;
}

#endif

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使用方式如下：

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CTransCode<> tc(_T("字符集轉換"));

// 或顯示指定源串的類型和字符集，如：

// CTransCode<LPCWSTR> tc(_T("字符集轉換"), CTransCode<LPCWSTR>::EN_ANSI);

char *? pAnsi = tc.ToAnsi(); // 返回一個ansi串

wchar_t * pUnicode = tc.ToUnicode(); // 返回一個unicode串

char* pUtf8 = tc.ToUtf8(); // 返回一個utf8串

// 使用完后，可以顯式調用 Release() 方法釋放資源如下：

tc.Release();

// 也可以不調用 Release() 方法，析構函數中會自動調用。

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