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Date: Tue, 14 Sep 2004 14:25:19 -0400
From: Christopher Faylor <cgf-no-personal-reply-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: BUG: Bad call to GetFileSze in ext2fsprogs lib/ext2fs/getsize.c
Message-ID: <20040914182519.GD5258@trixie.casa.cgf.cx>
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References: <414532D7 DOT 8050506 AT agilent DOT com> <41472B3F DOT 8030800 AT agilent DOT com>
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On Tue, Sep 14, 2004 at 10:32:47AM -0700, Earl Chew wrote:
>Earl Chew wrote:
>>The call to GetFileSize() doesn't match the Microsoft documentation,
>>and invariably mis-sizes the disk image as zero.
>
>A couple of comments regarding your recent changes:
>
>a. GetFileSize() returns the bits 32-63 of the file size in
>   the 2nd parameter. I think code like this is more better:
>
>	DWORD high_filesize;
>	filesize = GetFileSize(dev, &high_filesize);
>	if (filesize != INVALID_FILE_SIZE || GetLastError() != NO_ERROR)
>		*retblocks (((unsigned long long) high_filesize << 32)
>                            + filesize) / blocksize;
>
>b. Use of CreateFile() causes problems because win32 doesn't know
>   about the cygwin mount points. Code like this is more flexible:
>
>	fd = open(file, O_RDONLY | O_BINARY);
>	if (fd == -1)
>	    return EBADF;
>	dev = (HANDLE) get_osfhandle(fd);
>
>	...
>	close(fd);
>
>c. Similarly, code in unix_io.c needs to force binary mode to
>   avoid getting incorrect results when cygwin decides the image
>   is text!
>
>	open_flags = (flags & IO_FLAG_RW) ? O_RDWR : O_RDONLY;
>	#ifdef O_BINARY
>	open_flags |= O_BINARY;
>	#endif

Let me again point out that a cygwin program shouldn't be doing *ANY OF
THIS*.

It shouldn't be calling GetFileSize and it shouldn't be calling
CreateFile.

cgf

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