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Date: Fri, 17 Sep 2004 17:15:30 -0500 (CDT)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: "Ross A. Finlayson" <raf@tiki-lounge.com>
Subject: RE: [Tiff] BigTIFF Tag Value Count issue
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On Fri, 17 Sep 2004, Ross A. Finlayson wrote:
>
> I agree with Fernando, et al., that "Baseline" BigTIFF or so only require
> 63 of 64 bits in offset with file size support to 2^63-1.  Any software is
> obviously free to support 64 bits in the 64 bit offset, but actually as
> some system file APIs such as UNIX do use signed offsets, those that don't
> should still offer relatively uncomplicated standard conformance.

This is a reasonable argument.

For Solaris 9, when large files are supported these are the basic 
types:

size_t  unsigned 64 bits - size of something in bytes
ssize_t   signed 64 bits - size of something in bytes or -1
off_t     signed 64 bits - offsets within files

The ftruncate() and lseek() functions accept off_t arguments and 
lseek() returns off_t.  Therefore the useable file size is indeed 
currently constrained to 63 bits.

Just as we are getting used to 64 bit file offsets, Solaris 10 is 
introducing a file system (zfs) which supports 128 bit offsets. :-)

Bob
======================================
Bob Friesenhahn
bfriesen@simple.dallas.tx.us
http://www.simplesystems.org/users/bfriesen
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