如何判断文本是不是UNICODE，书本上有错了，你们都看看

怎么判断文本是不是UNICODE，书本上有错了，你们都看看
BOOL PopFileRead (HWND hwndEdit, PTSTR pstrFileName)
{
  BYTE bySwap ;
  DWORD dwBytesRead ;
  HANDLE hFile ;
  int i, iFileLength, iUniTest ;
  PBYTE pBuffer, pText, pConv ;

  // Open the file.

  if (INVALID_HANDLE_VALUE == 
  (hFile = CreateFile (pstrFileName, GENERIC_READ, FILE_SHARE_READ,
  NULL, OPEN_EXISTING, 0, NULL)))
  return FALSE ;

  // Get file size in bytes and allocate memory for read.
  // Add an extra two bytes for zero termination.
   
  iFileLength = GetFileSize (hFile, NULL) ; 
  pBuffer = malloc (iFileLength + 2) ;

  // Read file and put terminating zeros at end.
   
  ReadFile (hFile, pBuffer, iFileLength, &dwBytesRead, NULL) ;
  CloseHandle (hFile) ;
  pBuffer[iFileLength] = '\0' ;
  pBuffer[iFileLength + 1] = '\0' ;

  // Test to see if the text is Unicode

  iUniTest = IS_TEXT_UNICODE_SIGNATURE | IS_TEXT_UNICODE_REVERSE_SIGNATURE ;
   
  if (IsTextUnicode (pBuffer, iFileLength, &iUniTest))
  {
  pText = pBuffer + 2 ;
  iFileLength -= 2 ;

  if (iUniTest & IS_TEXT_UNICODE_REVERSE_SIGNATURE)
  {
  for (i = 0 ; i < iFileLength / 2 ; i++)
  {
  bySwap = ((BYTE *) pText) [2 * i] ;
  ((BYTE *) pText) [2 * i] = ((BYTE *) pText) [2 * i + 1] ;
  ((BYTE *) pText) [2 * i + 1] = bySwap ;
  }
  }

  // Allocate memory for possibly converted string

  pConv = malloc (iFileLength + 2) ;

  // If the edit control is not Unicode, convert Unicode text to 
  // non-Unicode (ie, in general, wide character).

#ifndef UNICODE
  WideCharToMultiByte (CP_ACP, 0, (PWSTR) pText, -1, pConv, 
  iFileLength + 2, NULL, NULL) ;

  // If the edit control is Unicode, just copy the string
#else
  lstrcpy ((PTSTR) pConv, (PTSTR) pText) ;
#endif

  }
  else // the file is not Unicode
  {
  pText = pBuffer ;

  // Allocate memory for possibly converted string.

  pConv = malloc (2 * iFileLength + 2) ;

  // If the edit control is Unicode, convert ASCII text.

#ifdef UNICODE
  MultiByteToWideChar (CP_ACP, 0, pText, -1, (PTSTR) pConv, 
  iFileLength + 1) ;

  // If not, just copy buffer
#else
  lstrcpy ((PTSTR) pConv, (PTSTR) pText) ;
#endif
  }
   
  SetWindowText (hwndEdit, (PTSTR) pConv) ;
  free (pBuffer) ;
  free (pConv) ;
   
  return TRUE ;
}
这个的读取文件的代码，就是首先要判断这个文本是不是UNICODE文本，我就有个疑问，就是要是这个文本是UNICODE就执行第一个IF里的语言，否则就执行IF的else 语言，你们看，要是我选择的文本是UNICODE文本，就直接执行if (IsTextUnicode (pBuffer, iFileLength, &iUniTest))
  {
  pText = pBuffer + 2 ;
  iFileLength -= 2 ;

  if (iUniTest & IS_TEXT_UNICODE_REVERSE_SIGNATURE)
  {
  for (i = 0 ; i < iFileLength / 2 ; i++)
  {