C / C++ / MFC

// WIN32 CODE

BOOL File_Read(
  HANDLE hFile,                // handle to file
  LPVOID lpBuffer,             // data buffer
  DWORD nNumberOfBytesToRead,  // number of bytes to read
  LPDWORD lpNumberOfBytesRead, // number of bytes read
  LPOVERLAPPED lpOverlapped    // overlapped buffer
)
{
  if( !ReadFile(hFile,lpBuffer,nNumberOfBytesToRead,lpNumberOfBytesRead,NULL) )
  {
    TCHAR szError[512];
    // Format error message
    DWORD dwLen = FormatMessage(
            FORMAT_MESSAGE_FROM_SYSTEM
            | FORMAT_MESSAGE_IGNORE_INSERTS, NULL,
            GetLastError(),
            MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // User default language
            szError, sizeof(szError)/sizeof(TCHAR), NULL);
    if( dwLen )
        Vsl_MessageBox(ghwnd,szError,gszAppName,MB_OK|MB_ICONSTOP);
    return FALSE;
  }
  return TRUE;
}

// CODE THAT DOES NOT FAIL BUT NO DATA IS READ INTO THE BUFFER.
// CONTAINS ALL 0x00 BEFORE AND AFTER READING (RELEASE ONLY)

// Allocate binary font storage space
lpBinFont = (LPBIN_FONT)GlobalAllocPtr(GPTR,(DWORD)sizeof(BIN_FONT)+dwFLen);
if( !lpBinFont )
	return(NULL);

.....

// 0x800 = smallest font file size ?
DWORD nNumberOfBytesToRead = 0x0800L;
SetFilePointer(hFontFile,0,NULL,FILE_BEGIN);
dwRead = 0;
for( dwOffset=0;dwOffset<dwFLen;dwOffset+=dwRead )
{
  if( nNumberOfBytesToRead > (dwFLen-dwOffset) )
    nNumberOfBytesToRead = dwFLen - dwOffset;

  if( !File_Read(hFontFile,(LPVOID)((lpBinFont->DataBits)+dwOffset),
    nNumberOfBytesToRead,&dwRead,NULL) )
  {
    break;
  }

  if( dwRead < nNumberOfBytesToRead )
  {
    dwOffset += dwRead;
    break;
  }
}

/********************************************************************/

// WIN16
// CODE THAT DOES NOT FAIL BUT NO DATA IS READ INTO THE BUFFER.
// CONTAINS ALL 0x00 BEFORE AND AFTER READING (RELEASE ONLY)

// Allocate binary font storage space
lpBinFont = (LPBIN_FONT)GlobalAllocPtr(GPTR,(DWORD)sizeof(BIN_FONT)+dwFLen);
if( !lpBinFont )
  return(NULL);

.....

_llseek(hFontFile,0,0);
for( dwOffset=0;dwOffset<dwFLen;dwOffset+=uRet )
{
  // 0x800 = smallest font file size ?
  uRet = _lread(hFontFile,(lpBinFont->DataBits)+dwOffset,0x0800U);
  if( uRet == HFILE_ERROR )
    break;

  if( uRet < 0x0800U )
  {
    dwOffset += uRet;
    break;
  }
}