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+;===========================================================================
+; Copyright (c) 1990-1999 Info-ZIP. All rights reserved.
+;
+; See the accompanying file LICENSE, version 1999-Oct-05 or later
+; (the contents of which are also included in zip.h) for terms of use.
+; If, for some reason, both of these files are missing, the Info-ZIP license
+; also may be found at: ftp://ftp.cdrom.com/pub/infozip/license.html
+;===========================================================================
+; This is a 68000 assembly language version of the Zip function
+; longest_match(). It is written for any 680x0 based computer, but at this
+; time the feature for runtime testing of CPU type is only supported for the
+; Amiga. Hopefully a similar test for the Macintosh is possible, and for any
+; other system that supports both 68000 and 68020+ CPUs. This is written by
+; Paul Kienitz, partially derived from a simpler version by Carsten Steger,
+; derived in turn from a 386 assembly function by Jean-loup Gailly and Kai Uwe
+; Rommel... but also based directly on the C original.
+;
+; The main difference of this from other longest_match() implementations is
+; that it includes both byte based and word based versions of the function,
+; and various symbols can be defined to select whether to use one routine or
+; the other, or to do a platform-specific test at runtime. The symbols that
+; can be used to select behavior are as follows:
+;
+; CPU020 if defined, use 68020 instructions always
+; CPUTEST if defined, check at runtime for CPU type. Another symbol
+; specifying the platform-specific test must be used with this.
+; If neither of these is defined, use 68000 instructions only.
+; AMIGA use Amiga-specific test for 68020, if CPUTEST defined. Also
+; tells it to let a0/a1/d1 be clobbered by functions.
+; ATSIGN define entry symbols in @foo form as well as _foo, with
+; @longest_match taking its parm in d0 instead of on the stack.
+; WSIZE if defined, determines the sliding window size for deflate;
+; the default is 32K. If you have reduced WSIZE for the C code,
+; make sure that this module is assembled with an equivalent
+; "-dWSIZE=<whatever>" (or "-e...") switch.
+;
+; NOTE: no provision is made for 16 bit ints. All external int variables are
+; treated as 32 bit values. This also assumes that longest_match's result is
+; returned in D0.
+
+ IFND CPU020
+ IFND CPUTEST
+CPU000 equ 1
+ ENDC
+ ENDC
+
+; global variables:
+ xref _max_chain_length ; unsigned int
+ xref _prev_length ; unsigned int
+ xref _match_start ; unsigned int
+ xref _strstart ; unsigned int
+ xref _good_match ; signed int
+ xref _nice_match ; signed int
+ xref _window ; array of unsigned char
+ xref _prev ; array of unsigned short
+
+; our entry points:
+ xdef _match_init ; void match_init(void);
+ xdef _longest_match ; int longest_match(unsigned cur_match);
+ IFD ATSIGN
+ xdef @match_init ; for SAS assembler
+ xdef @longest_match ; ditto
+ ENDC
+
+; flag variable for remembering CPU type:
+ IFD CPUTEST
+ section cpuflag,data
+is020: ds.w 1
+ ENDC
+
+
+ section match,code
+_match_init:
+ IFD ATSIGN
+@match_init:
+ ENDC
+
+ IFD CPUTEST ; now check for platform type
+ IFD AMIGA ; Amiga specific test for '020 CPU:
+
+ xref _SysBase
+
+ NOLIST
+ INCLUDE 'exec/execbase.i'
+ LIST
+
+ clr.w is020 ; default value is 68000
+ move.l _SysBase,a0
+ btst #AFB_68020,AttnFlags+1(a0)
+ beq.s cheap
+ move.w #1,is020
+
+cheap:
+ ELSE ; !AMIGA
+
+ !! Write an '020-detector for your system here!
+
+ ENDC ; AMIGA
+ ENDC ; CPUTEST
+ rts ; match_init consists only of rts if CPUTEST unset
+
+
+ IFD AMIGA
+SAVEREGS reg d3-d7/a2/a3/a5 ; don't protect d0/d1/a0/a1
+ ELSE
+SAVEREGS reg d1/d3-d7/a0-a3/a5 ; protect all but d0 return val
+ ENDC
+
+Cur_Match equr d0 ; Must be in d0!
+Best_Len equr d1
+Scan_Start equr d3
+Scan_End equr d4
+Limit equr d5
+Chain_Length equr d6
+Scan_Test equr d7
+Scan equr a0
+Match equr a1
+Prev_Address equr a2
+Scan_Ini equr a3
+Match_Ini equr a5
+
+
+MAX_MATCH equ 258
+MIN_MATCH equ 3
+ IFND WSIZE
+WSIZE equ 32768
+ ENDC
+MAX_DIST equ WSIZE-MAX_MATCH-MIN_MATCH-1
+
+_longest_match:
+ move.l 4(sp),Cur_Match ; stack arg to register
+ IFD ATSIGN
+@longest_match:
+ ENDC
+ movem.l SAVEREGS,-(sp)
+
+; setup steps common to byte and word versions:
+ move.l _max_chain_length,Chain_Length
+ move.l _prev_length,Best_Len
+ lea _prev,Prev_Address
+ lea _window,Match_Ini
+ move.l _strstart,Limit
+ move.l Match_Ini,Scan_Ini
+ addq #MIN_MATCH,Match_Ini
+ add.l Limit,Scan_Ini
+ subi.w #MAX_DIST,Limit
+ bhi.s limit_ok
+ moveq #0,Limit
+limit_ok:
+ cmp.l _good_match,Best_Len
+ bcs.s length_ok
+ lsr.l #2,Chain_Length
+length_ok:
+ subq.l #1,Chain_Length
+
+ IFD CPUTEST
+ tst.w is020 ; can we use '020 stuff today?
+ bne WORD_match
+ ENDC
+
+ IFND CPU020
+
+; for 68000 or 68010, use byte operations:
+ moveq #0,Scan_Start ; clear 2nd and 4th bytes, use 1st & 3rd
+ moveq #0,Scan_End
+ moveq #0,Scan_Test
+ move.b (Scan_Ini),Scan_Start
+ swap Scan_Start
+ move.b 1(Scan_Ini),Scan_Start
+ move.b -1(Scan_Ini,Best_Len),Scan_End
+ swap Scan_End
+ move.b 0(Scan_Ini,Best_Len),Scan_End
+ bra.s bdo_scan
+
+blong_loop:
+ move.b -1(Scan_Ini,Best_Len),Scan_End
+ swap Scan_End
+ move.b 0(Scan_Ini,Best_Len),Scan_End
+
+bshort_loop:
+ add.w Cur_Match,Cur_Match
+ move.w 0(Prev_Address,Cur_Match.l),Cur_Match
+ cmp.l Limit,Cur_Match
+ dbls Chain_Length,bdo_scan
+ bra return
+
+bdo_scan:
+ move.l Match_Ini,Match
+ add.l Cur_Match,Match
+ move.b -MIN_MATCH-1(Match,Best_Len),Scan_Test
+ swap Scan_Test
+ move.b -MIN_MATCH(Match,Best_Len),Scan_Test
+ cmp.l Scan_Test,Scan_End
+ bne.s bshort_loop
+ move.b -MIN_MATCH(Match),Scan_Test
+ swap Scan_Test
+ move.b -MIN_MATCH+1(Match),Scan_Test
+ cmp.l Scan_Test,Scan_Start
+ bne.s bshort_loop
+ move.w #(MAX_MATCH-MIN_MATCH),Scan_Test
+ lea MIN_MATCH(Scan_Ini),Scan
+
+bscan_loop:
+ cmpm.b (Match)+,(Scan)+
+ dbne Scan_Test,bscan_loop
+ subq #1,Scan
+
+ sub.l Scan_Ini,Scan
+ cmp.l Best_Len,Scan
+ bls.s bshort_loop
+ move.l Scan,Best_Len
+ move.l Cur_Match,_match_start
+ cmp.l _nice_match,Best_Len
+ bcs.s blong_loop
+ IFD CPUTEST
+ bra return
+ ENDC
+
+ ENDC ; !CPU020
+
+ IFND CPU000
+
+; for 68020 or higher, use word operations even on odd addresses:
+WORD_match:
+ move.w (Scan_Ini),Scan_Start
+ move.w -1(Scan_Ini,Best_Len),Scan_End
+ bra.s wdo_scan
+
+wlong_loop:
+ move.w -1(Scan_Ini,Best_Len),Scan_End
+
+wshort_loop:
+ add.w Cur_Match,Cur_Match
+ move.w (Prev_Address,Cur_Match.l),Cur_Match
+ cmp.l Limit,Cur_Match
+ dbls Chain_Length,wdo_scan
+ bra.s return
+
+wdo_scan:
+ move.l Match_Ini,Match
+ add.l Cur_Match,Match
+ cmp.w -MIN_MATCH-1(Match,Best_Len),Scan_End
+ bne.s wshort_loop
+ cmp.w -MIN_MATCH(Match),Scan_Start
+ bne.s wshort_loop
+ moveq #((MAX_MATCH-MIN_MATCH)/2),Scan_Test ; value = 127
+ lea MIN_MATCH(Scan_Ini),Scan
+
+wscan_loop:
+ cmpm.w (Match)+,(Scan)+
+ dbne Scan_Test,wscan_loop
+ subq #2,Scan
+ move.b -MIN_MATCH+1(Match),Scan_Test
+ cmp.b (Scan),Scan_Test
+ bne steven
+ addq #1,Scan
+steven:
+ sub.l Scan_Ini,Scan
+ cmp.l Best_Len,Scan
+ bls.s wshort_loop
+ move.l Scan,Best_Len
+ move.l Cur_Match,_match_start
+ cmp.l _nice_match,Best_Len
+ bcs.s wlong_loop
+
+ ENDC ; !CPU000
+
+return:
+ move.l Best_Len,d0 ; function return value
+ movem.l (sp)+,SAVEREGS
+ rts
+
+ end
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-24 13:31:31 +0000