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From: "Bill C. Riemers" <cygwin AT docbill DOT net>
To: <cygwin AT cygwin DOT com>
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Subject: Re: ftruncate64() question?
Date: Sat, 22 May 2004 16:24:22 -0400
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> What's wrong with ftruncate?

ftruncate fails with files larger >= 2GB because off_t gets interpreted as
32 bit signed integer...

I can find some archived cygwin messages referencing bug fixes to
ftruncate64 in the cygwin.dll.  However, using ftruncate64 results in an
unresolved symbol.

In fact based on those messages, I inserted the following code in my program
as a workaround for a truncate64() function:

#if defined(__CYGWIN__)||defined(__GW32__)
__int64 truncate64(const char *filename,__int64 newFileSize)
{
  DWORD dw;
  HANDLE h=CreateFile(filename,GENERIC_WRITE,0,NULL,OPEN_ALWAYS,0,NULL);
  DeviceIoControl(h,FSCTL_SET_SPARSE,NULL,0,NULL,0,&dw,NULL);
  SetFilePointerEx(h,(LARGE_INTEGER)newFileSize,NULL,FILE_BEGIN);
  SetEndOfFile(h);
  CloseHandle(h);
  return newFileSize;
}
#endif

This seems to work up to file sizes of 16TeraBytes, which for my purposes is
more than adiquate.

                                                      Bill





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