match.a

一些关于HTTP协议处理的文档,还包括了gzip包(它是用来解压缩HTTP传送的压缩数据)

; match.a -- optional optimized asm version of longest match in deflate.c
; Copyright (C) 1992-1993 Jean-loup Gailly
; This is free software; you can redistribute it and/or modify it under the
; terms of the GNU General Public License, see the file COPYING.
 
; $Id: match.a,v 1.1 1993/03/11 16:05:57 jloup Exp $
;
; Adapted for the Amiga by Carsten Steger <[e-mail]>
; using the code in match.S.
; The major change in this code consists of removing all unaligned
; word accesses, because they cause 68000-based Amigas to crash.
; For maximum speed, UNALIGNED_OK can be defined in Makefile.sasc.
; The program will then only run on 68020-based Amigas, though.
;
; This code will run with registerized parameters too, unless SAS
; changes parameter passing conventions between new releases of SAS/C.


Cur_Match	reg	d0	; Must be in d0!
Best_Len	reg	d1
Loop_Counter	reg	d2
Scan_Start	reg	d3
Scan_End	reg	d4
Limit		reg	d5
Chain_Length	reg	d6
Scan_Test	reg	d7
Scan		reg	a0
Match		reg	a1
Prev_Address	reg	a2
Scan_Ini	reg	a3
Match_Ini	reg	a4

MAX_MATCH	equ	258
MIN_MATCH	equ	3
WSIZE		equ	32768
MAX_DIST	equ	WSIZE-MAX_MATCH-MIN_MATCH-1


	xref	_max_chain_length
	xref	_prev_length
	xref	_prev
	xref	_window
	xref	_strstart
	xref	_good_match
	xref	_match_start
	xref	_nice_match


	section match,code

	xdef	_match_init
	xdef	@match_init
	xdef	_longest_match
	xdef	@longest_match


_match_init:
@match_init:
	rts


_longest_match:
	move.l	4(sp),Cur_Match
@longest_match:
	ifd	UNALIGNED_OK
	movem.l	d2-d6/a2-a4,-(sp)
	else
	movem.l	d2-d7/a2-a4,-(sp)
	endc
	move.l	_max_chain_length,Chain_Length
	move.l	_prev_length,Best_Len
	lea	_prev,Prev_Address
	lea	_window+MIN_MATCH,Match_Ini
	move.l	_strstart,Limit
	move.l	Match_Ini,Scan_Ini
	add.l	Limit,Scan_Ini
	subi.w	#MAX_DIST,Limit
	bhi.b	limit_ok
	moveq	#0,Limit
limit_ok:
	cmp.l	_good_match,Best_Len
	bcs.b	length_ok
	lsr.l	#2,Chain_Length
length_ok:
	subq.l	#1,Chain_Length

	ifd	UNALIGNED_OK

	move.w	-MIN_MATCH(Scan_Ini),Scan_Start
	move.w	-MIN_MATCH-1(Scan_Ini,Best_Len),Scan_End

	else

	move.b	-MIN_MATCH(Scan_Ini),Scan_Start
	lsl.w	#8,Scan_Start
	move.b	-MIN_MATCH+1(Scan_Ini),Scan_Start
	move.b	-MIN_MATCH-1(Scan_Ini,Best_Len),Scan_End
	lsl.w	#8,Scan_End
	move.b	-MIN_MATCH(Scan_Ini,Best_Len),Scan_End

	endc

	bra.b	do_scan

long_loop:

	ifd	UNALIGNED_OK

	move.w	-MIN_MATCH-1(Scan_Ini,Best_Len),Scan_End

	else

	move.b	-MIN_MATCH-1(Scan_Ini,Best_Len),Scan_End
	lsl.w	#8,Scan_End
	move.b	-MIN_MATCH(Scan_Ini,Best_Len),Scan_End

	endc

short_loop:
	lsl.w	#1,Cur_Match
	move.w	0(Prev_Address,Cur_Match),Cur_Match
	cmp.w	Limit,Cur_Match
	dbls	Chain_Length,do_scan
	bra.b	return

do_scan:
	move.l	Match_Ini,Match
	add.l	Cur_Match,Match

	ifd	UNALIGNED_OK

	cmp.w	-MIN_MATCH-1(Match,Best_Len),Scan_End
	bne.b	short_loop
	cmp.w	-MIN_MATCH(Match),Scan_Start
	bne.b	short_loop

	else

	move.b	-MIN_MATCH-1(Match,Best_Len),Scan_Test
	lsl.w	#8,Scan_Test
	move.b	-MIN_MATCH(Match,Best_Len),Scan_Test
	cmp.w	Scan_Test,Scan_End
	bne.b	short_loop
	move.b	-MIN_MATCH(Match),Scan_Test
	lsl.w	#8,Scan_Test
	move.b	-MIN_MATCH+1(Match),Scan_Test
	cmp.w	Scan_Test,Scan_Start
	bne.b	short_loop

	endc

	move.w	#(MAX_MATCH-MIN_MATCH),Loop_Counter
	move.l	Scan_Ini,Scan
scan_loop:
	cmpm.b	(Match)+,(Scan)+
	dbne	Loop_Counter,scan_loop

	sub.l	Scan_Ini,Scan
	addq.l	#(MIN_MATCH-1),Scan
	cmp.l	Best_Len,Scan
	bls.b	short_loop
	move.l	Scan,Best_Len
	move.l	Cur_Match,_match_start
	cmp.l	_nice_match,Best_Len
	bcs.b	long_loop
return:
	move.l	Best_Len,d0
	ifd	UNALIGNED_OK
	movem.l	(sp)+,d2-d6/a2-a4
	else
	movem.l	(sp)+,d2-d7/a2-a4
	endc
	rts

	end