字符串： 怎样在ANSI 和 UNICODE间做转换

问题: 怎样在ANSI 和 UNICODE间做转换？

答案:

这个答案启发自 Yves M贴出的一张回复（reply）

ANSI 到 UNICODE:

这个转换用函数MultiByteToWideChar()完成

代码:
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  char *ansistr = "Hello";
  int a = lstrlenA(ansistr)+1;
  BSTR unicodestr = SysAllocStringLen(NULL, 2*a);
  MultiByteToWideChar(CP_ACP, 0, ansistr, a, unicodestr, a);
  AfxMessageBox(CString(unicodestr), MB_OK, 0); //displays "Hello"
  //... when done, free the BSTR
  SysfreeString(unicodestr);
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UNICODE 到 ANSI:

UNICODE大多数情况下被OLE函数返回， 像这个

代码:
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HRESULT SomeOLEFunction(BSTR &bstr)
{
  bstr = ::SysAllocString(L"Hello");
  return S_OK;
}
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这个转换用WideCharToMultiByte()函数完成

代码:
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  BSTR unicodestr;
  SomeOLEFunction(unicodestr);
  int a = SysStringLen(unicodestr)+1;
  char *ansistr = new char[a];
  WideCharToMultiByte(CP_ACP,
  0,
  unicodestr,
  -1,
  ansistr,
  a,
  NULL,
  NULL);
  AfxMessageBox(ansistr, MB_OK, 0); // will display "Hello"
  //...use the strings, then free their memory:
  delete[] ansistr;
  SysFreeString(unicodestr);
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