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; match686.asm -- Asm portion of the optimized longest_match for 32 bits x86
; Copyright (C) 1995-1996 Jean-loup Gailly, Brian Raiter and Gilles Vollant.
; File written by Gilles Vollant, by converting match686.S from Brian Raiter
; for MASM. This is as assembly version of longest_match
; from Jean-loup Gailly in deflate.c
; For Visual C++ 4.x and higher and ML 6.x and higher
; ml.exe is distributed in
; this file contain two implementation of longest_match
; this longest_match was written by Brian raiter (1998), optimized for Pentium Pro
; (and the faster known version of match_init on modern Core 2 Duo and AMD Phenom)
; for using an assembly version of longest_match, you need define ASMV in project
; compile the asm file running
; ml /coff /Zi /c /Flmatch686.lst match686.asm
; and do not include match686.obj in your project
; note: contrib of zLib 1.2.3 and earlier contained both a deprecated version for
; Pentium (prior Pentium Pro) and this version for Pentium Pro and modern processor
; with autoselect (with cpu detection code)
; if you want support the old pentium optimization, you can still use these version
; this file is not optimized for old pentium, but it compatible with all x86 32 bits
; processor (starting 80386)
; see below : zlib1222add must be adjuster if you use a zlib version <
;uInt longest_match(s, cur_match)
; deflate_state *s;
; IPos cur_match; /* current match */
NbStack equ 76
cur_match equ dword ptr[esp+NbStack-0]
str_s equ dword ptr[esp+NbStack-4]
; 5 dword on top (ret,ebp,esi,edi,ebx)
adrret equ dword ptr[esp+NbStack-8]
pushebp equ dword ptr[esp+NbStack-12]
pushedi equ dword ptr[esp+NbStack-16]
pushesi equ dword ptr[esp+NbStack-20]
pushebx equ dword ptr[esp+NbStack-24]
chain_length equ dword ptr [esp+NbStack-28]
limit equ dword ptr [esp+NbStack-32]
best_len equ dword ptr [esp+NbStack-36]
window equ dword ptr [esp+NbStack-40]
prev equ dword ptr [esp+NbStack-44]
scan_start equ word ptr [esp+NbStack-48]
wmask equ dword ptr [esp+NbStack-52]
match_start_ptr equ dword ptr [esp+NbStack-56]
nice_match equ dword ptr [esp+NbStack-60]
scan equ dword ptr [esp+NbStack-64]
windowlen equ dword ptr [esp+NbStack-68]
match_start equ dword ptr [esp+NbStack-72]
strend equ dword ptr [esp+NbStack-76]
NbStackAdd equ (NbStack-24)
name gvmatch
; all the +zlib1222add offsets are due to the addition of fields
; in zlib in the deflate_state structure since the asm code was first written
; (if you compile with zlib 1.0.4 or older, use "zlib1222add equ (-4)").
; (if you compile with zlib between 1.0.5 and, use "zlib1222add equ 0").
; if you compile with zlib or later , use "zlib1222add equ 8").
zlib1222add equ 8
; Note : these value are good with a 8 bytes boundary pack structure
dep_chain_length equ 74h+zlib1222add
dep_window equ 30h+zlib1222add
dep_strstart equ 64h+zlib1222add
dep_prev_length equ 70h+zlib1222add
dep_nice_match equ 88h+zlib1222add
dep_w_size equ 24h+zlib1222add
dep_prev equ 38h+zlib1222add
dep_w_mask equ 2ch+zlib1222add
dep_good_match equ 84h+zlib1222add
dep_match_start equ 68h+zlib1222add
dep_lookahead equ 6ch+zlib1222add
_TEXT segment
public longest_match
public match_init
public _longest_match
public _match_init
MAX_MATCH equ 258
MAX_MATCH equ 258
MAX_MATCH_8_ equ ((MAX_MATCH + 7) AND 0FFF0h)
;;; stack frame offsets
chainlenwmask equ esp + 0 ; high word: current chain len
; low word: s->wmask
window equ esp + 4 ; local copy of s->window
windowbestlen equ esp + 8 ; s->window + bestlen
scanstart equ esp + 16 ; first two bytes of string
scanend equ esp + 12 ; last two bytes of string
scanalign equ esp + 20 ; dword-misalignment of string
nicematch equ esp + 24 ; a good enough match size
bestlen equ esp + 28 ; size of best match so far
scan equ esp + 32 ; ptr to string wanting match
LocalVarsSize equ 36
; saved ebx byte esp + 36
; saved edi byte esp + 40
; saved esi byte esp + 44
; saved ebp byte esp + 48
; return address byte esp + 52
deflatestate equ esp + 56 ; the function arguments
curmatch equ esp + 60
;;; Offsets for fields in the deflate_state structure. These numbers
;;; are calculated from the definition of deflate_state, with the
;;; assumption that the compiler will dword-align the fields. (Thus,
;;; changing the definition of deflate_state could easily cause this
;;; program to crash horribly, without so much as a warning at
;;; compile time. Sigh.)
dsWSize equ 36+zlib1222add
dsWMask equ 44+zlib1222add
dsWindow equ 48+zlib1222add
dsPrev equ 56+zlib1222add
dsMatchLen equ 88+zlib1222add
dsPrevMatch equ 92+zlib1222add
dsStrStart equ 100+zlib1222add
dsMatchStart equ 104+zlib1222add
dsLookahead equ 108+zlib1222add
dsPrevLen equ 112+zlib1222add
dsMaxChainLen equ 116+zlib1222add
dsGoodMatch equ 132+zlib1222add
dsNiceMatch equ 136+zlib1222add
;;; match686.asm -- Pentium-Pro-optimized version of longest_match()
;;; Written for zlib 1.1.2
;;; Copyright (C) 1998 Brian Raiter <>
;;; You can look at
;; This software is provided 'as-is', without any express or implied
;; warranty. In no event will the authors be held liable for any damages
;; arising from the use of this software.
;; Permission is granted to anyone to use this software for any purpose,
;; including commercial applications, and to alter it and redistribute it
;; freely, subject to the following restrictions:
;; 1. The origin of this software must not be misrepresented; you must not
;; claim that you wrote the original software. If you use this software
;; in a product, an acknowledgment in the product documentation would be
;; appreciated but is not required.
;; 2. Altered source versions must be plainly marked as such, and must not be
;; misrepresented as being the original software
;; 3. This notice may not be removed or altered from any source distribution.
;GLOBAL _longest_match, _match_init
;SECTION .text
;;; uInt longest_match(deflate_state *deflatestate, IPos curmatch)
longest_match proc near
_longest_match proc near
.FPO (9, 4, 0, 0, 1, 0)
;;; Save registers that the compiler may be using, and adjust esp to
;;; make room for our stack frame.
push ebp
push edi
push esi
push ebx
sub esp, LocalVarsSize
;;; Retrieve the function arguments. ecx will hold cur_match
;;; throughout the entire function. edx will hold the pointer to the
;;; deflate_state structure during the function's setup (before
;;; entering the main loop.
mov edx, [deflatestate]
mov ecx, [curmatch]
;;; uInt wmask = s->w_mask;
;;; unsigned chain_length = s->max_chain_length;
;;; if (s->prev_length >= s->good_match) {
;;; chain_length >>= 2;
;;; }
mov eax, [edx + dsPrevLen]
mov ebx, [edx + dsGoodMatch]
cmp eax, ebx
mov eax, [edx + dsWMask]
mov ebx, [edx + dsMaxChainLen]
jl LastMatchGood
shr ebx, 2
;;; chainlen is decremented once beforehand so that the function can
;;; use the sign flag instead of the zero flag for the exit test.
;;; It is then shifted into the high word, to make room for the wmask
;;; value, which it will always accompany.
dec ebx
shl ebx, 16
or ebx, eax
mov [chainlenwmask], ebx
;;; if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;
mov eax, [edx + dsNiceMatch]
mov ebx, [edx + dsLookahead]
cmp ebx, eax
jl LookaheadLess
mov ebx, eax
LookaheadLess: mov [nicematch], ebx
;;; register Bytef *scan = s->window + s->strstart;
mov esi, [edx + dsWindow]
mov [window], esi
mov ebp, [edx + dsStrStart]
lea edi, [esi + ebp]
mov [scan], edi
;;; Determine how many bytes the scan ptr is off from being
;;; dword-aligned.
mov eax, edi
neg eax
and eax, 3
mov [scanalign], eax
;;; IPos limit = s->strstart > (IPos)MAX_DIST(s) ?
;;; s->strstart - (IPos)MAX_DIST(s) : NIL;
mov eax, [edx + dsWSize]
sub ebp, eax
jg LimitPositive
xor ebp, ebp
;;; int best_len = s->prev_length;
mov eax, [edx + dsPrevLen]
mov [bestlen], eax
;;; Store the sum of s->window + best_len in esi locally, and in esi.
add esi, eax
mov [windowbestlen], esi
;;; register ush scan_start = *(ushf*)scan;
;;; register ush scan_end = *(ushf*)(scan+best_len-1);
;;; Posf *prev = s->prev;
movzx ebx, word ptr [edi]
mov [scanstart], ebx
movzx ebx, word ptr [edi + eax - 1]
mov [scanend], ebx
mov edi, [edx + dsPrev]
;;; Jump into the main loop.
mov edx, [chainlenwmask]
jmp short LoopEntry
align 4
;;; do {
;;; match = s->window + cur_match;
;;; if (*(ushf*)(match+best_len-1) != scan_end ||
;;; *(ushf*)match != scan_start) continue;
;;; [...]
;;; } while ((cur_match = prev[cur_match & wmask]) > limit
;;; && --chain_length != 0);
;;; Here is the inner loop of the function. The function will spend the
;;; majority of its time in this loop, and majority of that time will
;;; be spent in the first ten instructions.
;;; Within this loop:
;;; ebx = scanend
;;; ecx = curmatch
;;; edx = chainlenwmask - i.e., ((chainlen << 16) | wmask)
;;; esi = windowbestlen - i.e., (window + bestlen)
;;; edi = prev
;;; ebp = limit
and ecx, edx
movzx ecx, word ptr [edi + ecx*2]
cmp ecx, ebp
jbe LeaveNow
sub edx, 00010000h
js LeaveNow
LoopEntry: movzx eax, word ptr [esi + ecx - 1]
cmp eax, ebx
jnz LookupLoop
mov eax, [window]
movzx eax, word ptr [eax + ecx]
cmp eax, [scanstart]
jnz LookupLoop
;;; Store the current value of chainlen.
mov [chainlenwmask], edx
;;; Point edi to the string under scrutiny, and esi to the string we
;;; are hoping to match it up with. In actuality, esi and edi are
;;; both pointed (MAX_MATCH_8 - scanalign) bytes ahead, and edx is
;;; initialized to -(MAX_MATCH_8 - scanalign).
mov esi, [window]
mov edi, [scan]
add esi, ecx
mov eax, [scanalign]
mov edx, 0fffffef8h; -(MAX_MATCH_8)
lea edi, [edi + eax + 0108h] ;MAX_MATCH_8]
lea esi, [esi + eax + 0108h] ;MAX_MATCH_8]
;;; Test the strings for equality, 8 bytes at a time. At the end,
;;; adjust edx so that it is offset to the exact byte that mismatched.
;;; We already know at this point that the first three bytes of the
;;; strings match each other, and they can be safely passed over before
;;; starting the compare loop. So what this code does is skip over 0-3
;;; bytes, as much as necessary in order to dword-align the edi
;;; pointer. (esi will still be misaligned three times out of four.)
;;; It should be confessed that this loop usually does not represent
;;; much of the total running time. Replacing it with a more
;;; straightforward "rep cmpsb" would not drastically degrade
;;; performance.
mov eax, [esi + edx]
xor eax, [edi + edx]
jnz LeaveLoopCmps
mov eax, [esi + edx + 4]
xor eax, [edi + edx + 4]
jnz LeaveLoopCmps4
add edx, 8
jnz LoopCmps
jmp short LenMaximum
LeaveLoopCmps4: add edx, 4
LeaveLoopCmps: test eax, 0000FFFFh
jnz LenLower
add edx, 2
shr eax, 16
LenLower: sub al, 1
adc edx, 0
;;; Calculate the length of the match. If it is longer than MAX_MATCH,
;;; then automatically accept it as the best possible match and leave.
lea eax, [edi + edx]
mov edi, [scan]
sub eax, edi
cmp eax, MAX_MATCH
jge LenMaximum
;;; If the length of the match is not longer than the best match we
;;; have so far, then forget it and return to the lookup loop.
mov edx, [deflatestate]
mov ebx, [bestlen]
cmp eax, ebx
jg LongerMatch
mov esi, [windowbestlen]
mov edi, [edx + dsPrev]
mov ebx, [scanend]
mov edx, [chainlenwmask]
jmp LookupLoop
;;; s->match_start = cur_match;
;;; best_len = len;
;;; if (len >= nice_match) break;
;;; scan_end = *(ushf*)(scan+best_len-1);
LongerMatch: mov ebx, [nicematch]
mov [bestlen], eax
mov [edx + dsMatchStart], ecx
cmp eax, ebx
jge LeaveNow
mov esi, [window]
add esi, eax
mov [windowbestlen], esi
movzx ebx, word ptr [edi + eax - 1]
mov edi, [edx + dsPrev]
mov [scanend], ebx
mov edx, [chainlenwmask]
jmp LookupLoop
;;; Accept the current string, with the maximum possible length.
LenMaximum: mov edx, [deflatestate]
mov dword ptr [bestlen], MAX_MATCH
mov [edx + dsMatchStart], ecx
;;; if ((uInt)best_len <= s->lookahead) return (uInt)best_len;
;;; return s->lookahead;
mov edx, [deflatestate]
mov ebx, [bestlen]
mov eax, [edx + dsLookahead]
cmp ebx, eax
jg LookaheadRet
mov eax, ebx
;;; Restore the stack and return from whence we came.
add esp, LocalVarsSize
pop ebx
pop esi
pop edi
pop ebp
; please don't remove this string !
; Your can freely use match686 in any free or commercial app if you don't remove the string in the binary!
db 0dh,0ah,"asm686 with masm, optimised assembly code from Brian Raiter, written 1998",0dh,0ah
longest_match endp
_longest_match endp
match_init proc near
match_init endp
_match_init proc near
_match_init endp
_TEXT ends