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ZIP191SR.ZIP
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match.s
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1993-09-04
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6KB
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148 lines
/* */
/* Copyright (C) 1990-1992 Mark Adler, Richard B. Wales, Jean-loup Gailly, */
/* Kai Uwe Rommel and Igor Mandrichenko. */
/* Permission is granted to any individual or institution to use, copy, or */
/* redistribute this software so long as all of the original files are included */
/* unmodified, that it is not sold for profit, and that this copyright notice */
/* is retained. */
/* */
/* match.s by Jean-loup Gailly. Translated to 32 bit code by Kai Uwe Rommel. */
/* syntax changed for gas 2.1.1 by DJ Delorie dj@ctron.com */
/* match.s, optimized version of longest_match() in deflate.c */
/* This version is for 386 Unix or OS/2 in 32 bit mode. */
/* Warning: it uses the AT&T syntax: mov source,dest */
/* This file is only optional. If you want to force the C version, */
/* add -DNO_ASM to CFLAGS in makefile and remove match.o from OBJI). */
/* If you have reduced WSIZE in zip.h, then change its value below. */
/* This version assumes static allocation of the arrays (-DDYN_ALLOC not used). */
.file "match.s"
#if defined(__GO32__) && defined(unix)
# undef unix
#endif
#ifdef unix
# define _prev prev
# define _window window
# define _match_start match_start
# define _prev_length prev_length
# define _good_match good_match
# define _strstart strstart
# define _max_chain_length max_chain_length
# define _match_init match_init
# define _longest_match longest_match
#endif
#define MAX_MATCH 258
#define MAX_MATCH2 128 /* MAX_MATCH/2-1 */
#define MIN_MATCH 3
#define WSIZE 32768
#define MAX_DIST WSIZE - MAX_MATCH - MIN_MATCH - 1
.globl _match_init
.globl _longest_match
.text
_match_init:
ret
/* ----------------------------------------------------------------------- */
/* Set match_start to the longest match starting at the given string and */
/* return its length. Matches shorter or equal to prev_length are discarded, */
/* in which case the result is equal to prev_length and match_start is */
/* garbage. */
/* IN assertions: cur_match is the head of the hash chain for the current */
/* string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1 */
_longest_match: /* int longest_match(cur_match) */
#define cur_match 20(%esp)
/* return address / esp+16 */
push %ebp /* esp+12 */
push %edi /* esp+8 */
push %esi /* esp+4 */
push %ebx /* esp */
/* match equ esi */
/* scan equ edi */
/* chain_length equ ebp */
/* best_len equ ebx */
/* limit equ edx */
mov cur_match,%esi
mov _max_chain_length,%ebp /* chain_length = max_chain_length */
mov _strstart,%edi
mov %edi,%edx
sub $(MAX_DIST),%edx /* limit = strstart-MAX_DIST */
jae limit_ok
sub %edx,%edx /* limit = NIL */
limit_ok:
add $_window+2,%edi /* edi = offset(window + strstart + 2) */
mov _prev_length,%ebx /* best_len = prev_length */
movw -3(%ebx,%edi),%ax /* ax = scan[best_len-1..best_len] */
movw -2(%edi),%cx /* cx = scan[0..1] */
cmp _good_match,%ebx /* do we have a good match already? */
jb do_scan
shr $2,%ebp /* chain_length >>= 2 */
jmp do_scan
.align 4
long_loop:
/* at this point, edi == scan+2, esi == cur_match */
movw -3(%ebx,%edi),%ax /* ax = scan[best_len-1..best_len] */
movw -2(%edi),%cx /* cx = scan[0..1] */
short_loop:
dec %ebp /* --chain_length */
jz the_end
/* at this point, di == scan+2, si == cur_match, */
/* ax = scan[best_len-1..best_len] and cx = scan[0..1] */
and $(WSIZE-1), %esi
movw _prev(%esi,%esi),%si /* cur_match = prev[cur_match] */
/* top word of esi is still 0 */
cmp %edx,%esi /* cur_match <= limit ? */
jbe the_end
do_scan:
cmpw _window-1(%ebx,%esi),%ax /* check match at best_len-1 */
jne short_loop
cmpw _window(%esi),%cx /* check min_match_length match */
jne short_loop
lea _window+2(%esi),%esi /* si = match */
mov %edi,%eax /* ax = scan+2 */
mov $(MAX_MATCH2),%ecx /* scan for at most MAX_MATCH bytes */
#ifdef unix
repz; cmpsw /* loop until mismatch */
#else
repe; cmpsw
#endif
je maxmatch /* match of length MAX_MATCH? */
mismatch:
movb -2(%edi),%cl /* mismatch on first or second byte? */
subb -2(%esi),%cl /* cl = 0 if first bytes equal */
xchg %edi,%eax /* edi = scan+2, eax = end of scan */
sub %edi,%eax /* eax = len */
sub %eax,%esi /* esi = cur_match + 2 + offset(window) */
sub $_window+2,%esi /* esi = cur_match */
subb $1,%cl /* set carry if cl == 0 (cannot use DEC) */
adc $0,%eax /* eax = carry ? len+1 : len */
cmp %ebx,%eax /* len > best_len ? */
jle long_loop
mov %esi,_match_start /* match_start = cur_match */
mov %eax,%ebx /* ebx = best_len = len */
cmp $(MAX_MATCH),%eax /* len >= MAX_MATCH ? */
jl long_loop
the_end:
mov %ebx,%eax /* result = eax = best_len */
pop %ebx
pop %esi
pop %edi
pop %ebp
ret
maxmatch:
cmpsb
jmp mismatch