1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
|
;===========================================================================
; Copyright (c) 1990-2005 Info-ZIP. All rights reserved.
;
; See the accompanying file LICENSE, version 2005-Feb-10 or later
; (the contents of which are also included in zip.h) for terms of use.
; If, for some reason, all these files are missing, the Info-ZIP license
; also may be found at: ftp://ftp.info-zip.org/pub/infozip/license.html
;===========================================================================
;
; match32.asm by Jean-loup Gailly.
; match32.asm, optimized version of longest_match() in deflate.c
; To be used only with 32 bit flat model. To simplify the code, the option
; -DDYN_ALLOC is not supported.
; This file is only optional. If you don't have an assembler, use 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 make sure this is
; assembled with an equivalent -DWSIZE=<whatever>.
;
; Win32 (Windows NT) version - 1994/04/13 by Steve Salisbury
; * works with Microsoft MASM 6.1X and Microsoft Visual C++ / 32-bit edition
;
; Adapted to work with Borland Turbo Assembler 5.0 by Cosmin Truta, 1997
;
; Adapted to work with OpenWatcom WASM by Chr. Spieler, 2005
; (Define the symbol WATCOM_DSEG to activate the specific Watcom C
; data segment naming convention.)
;
;==============================================================================
;
; Do NOT assemble this source if external crc32 routine from zlib gets used.
;
IFNDEF USE_ZLIB
;
.386p
ifdef ASM_NEW
.MODEL FLAT
endif
name match
ifdef ASM_NEW
_BSS segment public use32
else
_BSS segment public use32 'DATA'
endif
extrn _match_start : dword
extrn _prev_length : dword
extrn _good_match : dword
ifndef FULL_SEARCH
extrn _nice_match : dword
endif
extrn _strstart : dword
extrn _max_chain_length : dword
extrn _prev : word
extrn _window : byte
_BSS ends
ifdef WATCOM_DSEG
DGROUP group _BSS
endif
ifdef ASM_NEW
_TEXT segment public use32
else
_TEXT segment para public use32 'CODE'
endif
assume CS: _TEXT
assume DS: _BSS, ES: _BSS, FS: _BSS
public _match_init
public _longest_match
ifndef WSIZE
WSIZE equ 32768 ; keep in sync with zip.h !
endif
MIN_MATCH equ 3
MAX_MATCH equ 258
MIN_LOOKAHEAD equ (MAX_MATCH+MIN_MATCH+1)
MAX_DIST equ (WSIZE-MIN_LOOKAHEAD)
; initialize or check the variables used in match.asm.
_match_init proc near
ret
_match_init endp
; -----------------------------------------------------------------------
; 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
; int longest_match(cur_match)
_longest_match proc near
cur_match equ dword ptr [esp+20]
; 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 esi,cur_match
mov edx,_strstart
mov ebp,_max_chain_length ; chain_length = max_chain_length
mov edi,edx
sub edx,MAX_DIST ; limit = strstart-MAX_DIST
cld ; string ops increment esi and edi
jae short limit_ok
sub edx,edx ; limit = NIL
limit_ok:
add edi,2+offset _window ; edi = offset(window + strstart + 2)
mov ebx,_prev_length ; best_len = prev_length
mov cx,[edi-2] ; cx = scan[0..1]
mov ax,[ebx+edi-3] ; ax = scan[best_len-1..best_len]
cmp ebx,_good_match ; do we have a good match already?
jb short do_scan
shr ebp,2 ; chain_length >>= 2
jmp short do_scan
align 4 ; align destination of branch
long_loop:
; at this point, edi == scan+2, esi == cur_match
mov ax,[ebx+edi-3] ; ax = scan[best_len-1..best_len]
mov cx,[edi-2] ; cx = scan[0..1]
short_loop:
; at this point, edi == scan+2, esi == cur_match,
; ax = scan[best_len-1..best_len] and cx = scan[0..1]
and esi,WSIZE-1
dec ebp ; --chain_length
mov si,_prev[esi+esi] ; cur_match = prev[cur_match]
; top word of esi is still 0
jz short the_end
cmp esi,edx ; cur_match <= limit ?
jbe short the_end
do_scan:
cmp ax,word ptr _window[ebx+esi-1] ; check match at best_len-1
jne short_loop
cmp cx,word ptr _window[esi] ; check min_match_length match
jne short_loop
lea esi,_window[esi+2] ; esi = match
mov ecx,(MAX_MATCH-2)/2 ; scan for at most MAX_MATCH bytes
mov eax,edi ; eax = scan+2
repe cmpsw ; loop until mismatch
je short maxmatch ; match of length MAX_MATCH?
mismatch:
mov cl,[edi-2] ; mismatch on first or second byte?
xchg eax,edi ; edi = scan+2, eax = end of scan
sub cl,[esi-2] ; cl = 0 if first bytes equal
sub eax,edi ; eax = len
sub esi,2+offset _window ; esi = match - (2 + offset(window))
sub esi,eax ; esi = cur_match (= match - len)
sub cl,1 ; set carry if cl == 0 (can't use DEC)
adc eax,0 ; eax = carry ? len+1 : len
cmp eax,ebx ; len > best_len ?
jle long_loop
mov _match_start,esi ; match_start = cur_match
mov ebx,eax ; ebx = best_len = len
ifdef FULL_SEARCH
cmp eax,MAX_MATCH ; len >= MAX_MATCH ?
else
cmp eax,_nice_match ; len >= nice_match ?
endif
jl long_loop
the_end:
mov eax,ebx ; result = eax = best_len
pop ebx
pop esi
pop edi
pop ebp
ret
maxmatch: ; come here if maximum match
cmpsb ; increment esi and edi
jmp mismatch ; force match_length = MAX_LENGTH
_longest_match endp
_TEXT ends
;
ENDIF ; !USE_ZLIB
;
end
|
