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Re: BUG: Bad call to GetFileSze in ext2fsprogs lib/ext2fs/getsize.c
- From: Christopher Faylor <cgf-no-personal-reply-please at cygwin dot com>
- To: cygwin at cygwin dot com
- Date: Tue, 14 Sep 2004 14:25:19 -0400
- Subject: Re: BUG: Bad call to GetFileSze in ext2fsprogs lib/ext2fs/getsize.c
- References: <414532D7.8050506@agilent.com> <41472B3F.8030800@agilent.com>
- Reply-to: cygwin at cygwin dot com
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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