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Re: lseek()/read() to physical drive returning wrong data.


On Sat, Feb 03, 2001 at 07:19:15PM +0100, Corinna Vinschen wrote:
>On Sat, Feb 03, 2001 at 12:47:49PM -0500, Robin T. Miller wrote:
>> Hi All,
>> 	I have a Unix test program named 'dt' which runs with Cygwin.
>> This program tests a variety of devices as well as file systems.  The
>> tests which use lseek() to raw mounted disks, are failing with data
>> compare errors.  It appears either lseek() is positioning incorrectly
>> or read() is returning the wrong data after lseek'ing.
>> 
>> 	This random I/O sequence seems to work correctly to a regular
>> file, so maybe the raw device buffering is messing up?  I'm not sure.
>
>Lseek on raw devices isn't yet fully implemented. The underlying
>*cough* operating system *cough* isn't able to do a bytewise access
>to the raw device but only in steps of 512 bytes. A full lseek
>implementation would need to do it's own buffering to simulate
>bytewise buffering. This is still missing.
>
>> 	The only other program restrictions is 32-bit file offsets.
>> 
>> 	BTW: Are there any plans to release 64-bit file support?
>
>Not in the near future.

Not in the non-near future, either.  :-)

cgf

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