【转载】Windows 字符串编码转换实现

来源：UTF-8与多字节字符串转化_utf8转多字节_H Journey的博客-CSDN博客 

// 宽字符字符串转多字节字符串
inline std::string _W2A_(const wchar_t* pwszText)
{
  if (pwszText == NULL || wcslen(pwszText) == 0)
  {
    return std::string();
  }
  int iSizeInBytes = WideCharToMultiByte(CP_ACP, 0, pwszText, -1, NULL, 0, NULL, NULL);
  char* pMultiByte = new(std::nothrow) char[iSizeInBytes];
  if (pMultiByte == NULL)
  {
    return std::string();
  }

  memset(pMultiByte, 0, iSizeInBytes);
  WideCharToMultiByte(CP_ACP, 0, pwszText, -1, pMultiByte, iSizeInBytes, NULL, NULL);

  std::string strResult = std::string(pMultiByte);
  
  delete[] pMultiByte;
  pMultiByte = NULL;
  return strResult;
}

// UTF-8字符串转宽字符字符串
inline std::wstring _U82W_(const char* pszText)
{
  if (pszText == NULL || strlen(pszText) == 0)
  {
    return std::wstring();
  }
  int iSizeInChars = MultiByteToWideChar(CP_UTF8, 0, pszText, -1, NULL, 0);
  wchar_t* pWideChar = new(std::nothrow) wchar_t[iSizeInChars];
  if (pWideChar == NULL)
  {
    return std::wstring();
  }

  wmemset(pWideChar, 0, iSizeInChars);
  MultiByteToWideChar(CP_UTF8, 0, pszText, -1, pWideChar, iSizeInChars);

  std::wstring strResult = std::wstring(pWideChar);
  delete[] pWideChar;
  pWideChar = NULL;
  return strResult;
}

// UTF-8字符串转多字节字符串
inline std::string _U82A_(const char* pszText)
{
  return _W2A_(_U82W_(pszText).c_str());
}

// 多字节字符串转宽字符字符串
inline std::wstring _A2W_(const char* pszText)
{
  if (pszText == NULL || strlen(pszText) == 0)
  {
    return std::wstring();
  }
  int iSizeInChars = MultiByteToWideChar(CP_ACP, 0, pszText, -1, NULL, 0);
  wchar_t* pWideChar = new(std::nothrow) wchar_t[iSizeInChars];
  if (pWideChar == NULL)
  {
    return std::wstring();
  }

  wmemset(pWideChar, 0, iSizeInChars);
  MultiByteToWideChar(CP_ACP, 0, pszText, -1, pWideChar, iSizeInChars);

  std::wstring strResult = std::wstring(pWideChar);
  delete[] pWideChar;
  pWideChar = NULL;
  return strResult;
}

// 宽字符字符串转UTF-8字符串
inline std::string _W2U8_(const wchar_t* pwszText)
{
  if (pwszText == NULL || wcslen(pwszText) == 0)
  {
    return std::string();
  }
  int iSizeInBytes = WideCharToMultiByte(CP_UTF8, 0, pwszText, -1, NULL, 0, NULL, NULL);
  char* pUTF8 = new(std::nothrow) char[iSizeInBytes];
  if (pUTF8 == NULL)
  {
    return std::string();
  }

  memset(pUTF8, 0, iSizeInBytes);
  WideCharToMultiByte(CP_UTF8, 0, pwszText, -1, pUTF8, iSizeInBytes, NULL, NULL);

  std::string strResult = std::string(pUTF8);
  delete[] pUTF8;
  pUTF8 = NULL;
  return strResult;
}

// 多字节字符串转UTF-8字符串
inline std::string _A2U8_(const char* pszText)
{
  return _W2U8_(_A2W_(pszText).c_str());
}

#define _U82A(lpu8Text) (const_cast(_U82A_(static_cast(lpu8Text)).c_str()))
#define _A2U8(lpszText) (const_cast(_A2U8_(static_cast(lpszText)).c_str()))