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From: 048321887-0001 AT t-online DOT de
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Adding 64-bit file support to DJGPP
Date: 17 Jan 2006 21:41:56 -0800
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To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

DJ Delorie wrote:

> DJGPP relies on MS-DOS's file api, and MS-DOS doesn't support 64 bit
> operations.

The LFN API in MS-DOS 7.0 and higher already uses 64-bit file
operations in some functions, e.g. 714E/4Fh of Int 21h. Also, DOS is
still evolving, so newer DOS versions provide functions that old
versions lack.

For example, this is the new 64-bit LSEEK function of Enhanced DR-DOS,
which will also eventually be supported by FreeDOS:

--------O-2142-------------------------------
INT 21 - EDR-DOS 7.01.08+ - "Long LSEEK" - SET CURRENT 64-bit FILE
POSITION
	AX = 7142h
	CL = origin of move
	    00h start of file
	    01h current file position
	    02h end of file
	BX = file handle
	DS:DX = pointer to (signed) 64-bit offset from origin of new position
Return: CF clear if successful
	    DS:DX unchanged, new 64-bit position from start of file at ->
DS:DX
	CF set on error
	    AX = error code (01h,06h) (see #01680 at AH=59h/BX=0000h)

For the moment, I would like to put the question of API support in the
OSes aside and concentrate on the implementation of 64-bit file support
in DJGPP itself.

Udo