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; gvmat32.asm -- Asm portion of the optimized longest_match for 32 bits x86

; Copyright (C) 1995-1996 Jean-loup Gailly and Gilles Vollant.

; File written by Gilles Vollant, by modifiying the longest_match

;  from Jean-loup Gailly in deflate.c

;

;         http://www.zlib.net

;         http://www.winimage.com/zLibDll

;         http://www.muppetlabs.com/~breadbox/software/assembly.html

;

; For Visual C++ 4.x and higher and ML 6.x and higher

;   ml.exe is in directory \MASM611C of Win95 DDK

;   ml.exe is also distributed in http://www.masm32.com/masmdl.htm

;    and in VC++2003 toolkit at http://msdn.microsoft.com/visualc/vctoolkit2003/

;

; this file contain two implementation of longest_match

;

;  longest_match_7fff : written 1996 by Gilles Vollant optimized for

;            first Pentium. Assume s->w_mask == 0x7fff

;  longest_match_686 : written by Brian raiter (1998), optimized for Pentium Pro

;

;  for using an seembly version of longest_match, you need define ASMV in project

;  There is two way in using gvmat32.asm

;

;  A) Suggested method

;    if you want include both longest_match_7fff and longest_match_686

;    compile the asm file running

;           ml /coff /Zi /Flgvmat32.lst /c gvmat32.asm

;    and include gvmat32c.c in your project

;    if you have an old cpu (386,486 or first Pentium) and s->w_mask==0x7fff,

;        longest_match_7fff will be used

;    if you have a more modern CPU (Pentium Pro, II and higher)

;        longest_match_686 will be used

;    on old cpu with s->w_mask!=0x7fff, longest_match_686 will be used,

;        but this is not a sitation you'll find often

;

;  B) Alternative

;    if you are not interresed in old cpu performance and want the smaller

;       binaries possible

;

;    compile the asm file running

;           ml /coff /Zi /c /Flgvmat32.lst /DNOOLDPENTIUMCODE gvmat32.asm

;    and do not include gvmat32c.c in your project (ou define also

;              NOOLDPENTIUMCODE)

;

; note : as I known, longest_match_686 is very faster than longest_match_7fff

;        on pentium Pro/II/III, faster (but less) in P4, but it seem

;        longest_match_7fff can be faster (very very litte) on AMD Athlon64/K8

;

; see below : zlib1222add must be adjuster if you use a zlib version < 1.2.2.2

;uInt longest_match_7fff(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)

    .386p

    name    gvmatch

    .MODEL  FLAT

;  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 1.2.2.1, use "zlib1222add equ 0").

;  if you compile with zlib 1.2.2.2 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

IFDEF NOUNDERLINE

   IFDEF NOOLDPENTIUMCODE

            public  longest_match

            public  match_init

   ELSE

            public  longest_match_7fff

            public  cpudetect32

            public  longest_match_686

   ENDIF

ELSE

   IFDEF NOOLDPENTIUMCODE

            public  _longest_match

            public  _match_init

   ELSE

            public  _longest_match_7fff

            public  _cpudetect32

            public  _longest_match_686

   ENDIF

ENDIF

    MAX_MATCH           equ     258

    MIN_MATCH           equ     3

    MIN_LOOKAHEAD       equ     (MAX_MATCH+MIN_MATCH+1)

IFNDEF NOOLDPENTIUMCODE

IFDEF NOUNDERLINE

longest_match_7fff   proc near

ELSE

_longest_match_7fff  proc near

ENDIF

    mov     edx,[esp+4]

    push    ebp

    push    edi

    push    esi

    push    ebx

    sub     esp,NbStackAdd

; initialize or check the variables used in match.asm.

    mov     ebp,edx

; chain_length = s->max_chain_length

; if (prev_length>=good_match) chain_length >>= 2

    mov     edx,[ebp+dep_chain_length]

    mov     ebx,[ebp+dep_prev_length]

    cmp     [ebp+dep_good_match],ebx

    ja      noshr

    shr     edx,2

noshr:

; we increment chain_length because in the asm, the --chain_lenght is in the beginning of the loop

    inc     edx

    mov     edi,[ebp+dep_nice_match]

    mov     chain_length,edx

    mov     eax,[ebp+dep_lookahead]

    cmp     eax,edi

; if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead;

    jae     nolookaheadnicematch

    mov     edi,eax

nolookaheadnicematch:

; best_len = s->prev_length

    mov     best_len,ebx

; window = s->window

    mov     esi,[ebp+dep_window]

    mov     ecx,[ebp+dep_strstart]

    mov     window,esi

    mov     nice_match,edi

; scan = window + strstart

    add     esi,ecx

    mov     scan,esi

; dx = *window

    mov     dx,word ptr [esi]

; bx = *(window+best_len-1)

    mov     bx,word ptr [esi+ebx-1]

    add     esi,MAX_MATCH-1

; scan_start = *scan

    mov     scan_start,dx

; strend = scan + MAX_MATCH-1

    mov     strend,esi

; bx = scan_end = *(window+best_len-1)

;    IPos limit = s->strstart > (IPos)MAX_DIST(s) ?

;        s->strstart - (IPos)MAX_DIST(s) : NIL;

    mov     esi,[ebp+dep_w_size]

    sub     esi,MIN_LOOKAHEAD

; here esi = MAX_DIST(s)

    sub     ecx,esi

    ja      nodist

    xor     ecx,ecx

nodist:

    mov     limit,ecx

; prev = s->prev

    mov     edx,[ebp+dep_prev]

    mov     prev,edx

;

    mov     edx,dword ptr [ebp+dep_match_start]

    mov     bp,scan_start

    mov     eax,cur_match

    mov     match_start,edx

    mov     edx,window

    mov     edi,edx

    add     edi,best_len

    mov     esi,prev

    dec     edi

; windowlen = window + best_len -1

    mov     windowlen,edi

    jmp     beginloop2

    align   4

; here, in the loop

;       eax = ax = cur_match

;       ecx = limit

;        bx = scan_end

;        bp = scan_start

;       edi = windowlen (window + best_len -1)

;       esi = prev

;// here; chain_length <=16

normalbeg0add16:

    add     chain_length,16

    jz      exitloop

normalbeg0:

    cmp     word ptr[edi+eax],bx

    je      normalbeg2noroll

rcontlabnoroll:

; cur_match = prev[cur_match & wmask]

    and     eax,7fffh

    mov     ax,word ptr[esi+eax*2]

; if cur_match > limit, go to exitloop

    cmp     ecx,eax

    jnb     exitloop

; if --chain_length != 0, go to exitloop

    dec     chain_length

    jnz     normalbeg0

    jmp     exitloop

normalbeg2noroll:

; if (scan_start==*(cur_match+window)) goto normalbeg2

    cmp     bp,word ptr[edx+eax]

    jne     rcontlabnoroll

    jmp     normalbeg2

contloop3:

    mov     edi,windowlen

; cur_match = prev[cur_match & wmask]

    and     eax,7fffh

    mov     ax,word ptr[esi+eax*2]

; if cur_match > limit, go to exitloop

    cmp     ecx,eax

jnbexitloopshort1:

    jnb     exitloop

; if --chain_length != 0, go to exitloop

; begin the main loop

beginloop2:

    sub     chain_length,16+1

; if chain_length <=16, don't use the unrolled loop

    jna     normalbeg0add16

do16:

    cmp     word ptr[edi+eax],bx

    je      normalbeg2dc0

maccn   MACRO   lab

    and     eax,7fffh

    mov     ax,word ptr[esi+eax*2]

    cmp     ecx,eax

    jnb     exitloop

    cmp     word ptr[edi+eax],bx

    je      lab

    ENDM

rcontloop0:

    maccn   normalbeg2dc1

rcontloop1:

    maccn   normalbeg2dc2

rcontloop2:

    maccn   normalbeg2dc3

rcontloop3:

    maccn   normalbeg2dc4

rcontloop4:

    maccn   normalbeg2dc5

rcontloop5:

    maccn   normalbeg2dc6

rcontloop6:

    maccn   normalbeg2dc7

rcontloop7:

    maccn   normalbeg2dc8

rcontloop8:

    maccn   normalbeg2dc9

rcontloop9:

    maccn   normalbeg2dc10

rcontloop10:

    maccn   short normalbeg2dc11

rcontloop11:

    maccn   short normalbeg2dc12

rcontloop12:

    maccn   short normalbeg2dc13

rcontloop13:

    maccn   short normalbeg2dc14

rcontloop14:

    maccn   short normalbeg2dc15

rcontloop15:

    and     eax,7fffh

    mov     ax,word ptr[esi+eax*2]

    cmp     ecx,eax

    jnb     exitloop

    sub     chain_length,16

    ja      do16

    jmp     normalbeg0add16

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

normbeg MACRO   rcontlab,valsub

; if we are here, we know that *(match+best_len-1) == scan_end

    cmp     bp,word ptr[edx+eax]

; if (match != scan_start) goto rcontlab

    jne     rcontlab

; calculate the good chain_length, and we'll compare scan and match string

    add     chain_length,16-valsub

    jmp     iseq

    ENDM

normalbeg2dc11:

    normbeg rcontloop11,11

normalbeg2dc12:

    normbeg short rcontloop12,12

normalbeg2dc13:

    normbeg short rcontloop13,13

normalbeg2dc14:

    normbeg short rcontloop14,14

normalbeg2dc15:

    normbeg short rcontloop15,15

normalbeg2dc10:

    normbeg rcontloop10,10

normalbeg2dc9:

    normbeg rcontloop9,9

normalbeg2dc8:

    normbeg rcontloop8,8

normalbeg2dc7:

    normbeg rcontloop7,7

normalbeg2dc6:

    normbeg rcontloop6,6

normalbeg2dc5:

    normbeg rcontloop5,5

normalbeg2dc4:

    normbeg rcontloop4,4

normalbeg2dc3:

    normbeg rcontloop3,3

normalbeg2dc2:

    normbeg rcontloop2,2

normalbeg2dc1:

    normbeg rcontloop1,1

normalbeg2dc0:

    normbeg rcontloop0,0

; we go in normalbeg2 because *(ushf*)(match+best_len-1) == scan_end

normalbeg2:

    mov     edi,window

    cmp     bp,word ptr[edi+eax]

    jne     contloop3                   ; if *(ushf*)match != scan_start, continue

iseq:

; if we are here, we know that *(match+best_len-1) == scan_end

; and (match == scan_start)

    mov     edi,edx

    mov     esi,scan                    ; esi = scan

    add     edi,eax                     ; edi = window + cur_match = match

    mov     edx,[esi+3]                 ; compare manually dword at match+3

    xor     edx,[edi+3]                 ; and scan +3

    jz      begincompare                ; if equal, go to long compare

; we will determine the unmatch byte and calculate len (in esi)

    or      dl,dl

    je      eq1rr

    mov     esi,3

    jmp     trfinval

eq1rr:

    or      dx,dx

    je      eq1

    mov     esi,4

    jmp     trfinval

eq1:

    and     edx,0ffffffh

    jz      eq11

    mov     esi,5

    jmp     trfinval

eq11:

    mov     esi,6

    jmp     trfinval

begincompare:

    ; here we now scan and match begin same

    add     edi,6

    add     esi,6

    mov     ecx,(MAX_MATCH-(2+4))/4     ; scan for at most MAX_MATCH bytes

    repe    cmpsd                       ; loop until mismatch

    je      trfin                       ; go to trfin if not unmatch

; we determine the unmatch byte

    sub     esi,4

    mov     edx,[edi-4]

    xor     edx,[esi]

    or      dl,dl

    jnz     trfin

    inc     esi

    or      dx,dx

    jnz     trfin

    inc     esi

    and     edx,0ffffffh

    jnz     trfin

    inc     esi

trfin:

    sub     esi,scan          ; esi = len

trfinval:

; here we have finised compare, and esi contain len of equal string

    cmp     esi,best_len        ; if len > best_len, go newbestlen

    ja      short newbestlen

; now we restore edx, ecx and esi, for the big loop

    mov     esi,prev

    mov     ecx,limit

    mov     edx,window

    jmp     contloop3

newbestlen:

    mov     best_len,esi        ; len become best_len

    mov     match_start,eax     ; save new position as match_start

    cmp     esi,nice_match      ; if best_len >= nice_match, exit

    jae     exitloop

    mov     ecx,scan

    mov     edx,window          ; restore edx=window

    add     ecx,esi

    add     esi,edx

    dec     esi

    mov     windowlen,esi       ; windowlen = window + best_len-1

    mov     bx,[ecx-1]          ; bx = *(scan+best_len-1) = scan_end

; now we restore ecx and esi, for the big loop :

    mov     esi,prev

    mov     ecx,limit

    jmp     contloop3

exitloop:

; exit : s->match_start=match_start

    mov     ebx,match_start

    mov     ebp,str_s

    mov     ecx,best_len

    mov     dword ptr [ebp+dep_match_start],ebx

    mov     eax,dword ptr [ebp+dep_lookahead]

    cmp     ecx,eax

    ja      minexlo

    mov     eax,ecx

minexlo:

; return min(best_len,s->lookahead)

; restore stack and register ebx,esi,edi,ebp

    add     esp,NbStackAdd

    pop     ebx

    pop     esi

    pop     edi

    pop     ebp

    ret

InfoAuthor:

; please don't remove this string !

; Your are free use gvmat32 in any fre or commercial apps if you don't remove the string in the binary!

    db     0dh,0ah,"GVMat32 optimised assembly code written 1996-98 by Gilles Vollant",0dh,0ah

IFDEF NOUNDERLINE

longest_match_7fff   endp

ELSE

_longest_match_7fff  endp

ENDIF

IFDEF NOUNDERLINE

cpudetect32     proc near

ELSE

_cpudetect32    proc near

ENDIF

    push    ebx

    pushfd                  ; push original EFLAGS

    pop     eax             ; get original EFLAGS

    mov     ecx, eax        ; save original EFLAGS

    xor     eax, 40000h     ; flip AC bit in EFLAGS

    push    eax             ; save new EFLAGS value on stack

    popfd                   ; replace current EFLAGS value

    pushfd                  ; get new EFLAGS

    pop     eax             ; store new EFLAGS in EAX

    xor     eax, ecx        ; can’t toggle AC bit, processor=80386

    jz      end_cpu_is_386  ; jump if 80386 processor

    push    ecx

    popfd                   ; restore AC bit in EFLAGS first

    pushfd

    pushfd

    pop     ecx

    mov     eax, ecx        ; get original EFLAGS

    xor     eax, 200000h    ; flip ID bit in EFLAGS

    push    eax             ; save new EFLAGS value on stack

    popfd                   ; replace current EFLAGS value

    pushfd                  ; get new EFLAGS

    pop     eax             ; store new EFLAGS in EAX

    popfd                   ; restore original EFLAGS

    xor     eax, ecx        ; can’t toggle ID bit,

    je      is_old_486      ; processor=old

    mov     eax,1

    db      0fh,0a2h        ;CPUID

exitcpudetect:

    pop ebx

    ret

end_cpu_is_386:

    mov     eax,0300h

    jmp     exitcpudetect

is_old_486:

    mov     eax,0400h

    jmp     exitcpudetect

IFDEF NOUNDERLINE

cpudetect32     endp

ELSE

_cpudetect32    endp

ENDIF

ENDIF

MAX_MATCH       equ     258

MIN_MATCH       equ     3

MIN_LOOKAHEAD   equ     (MAX_MATCH + MIN_MATCH + 1)

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

;;; match.asm -- Pentium-Pro-optimized version of longest_match()

;;; Written for zlib 1.1.2

;;; Copyright (C) 1998 Brian Raiter 

;;; You can look at http://www.muppetlabs.com/~breadbox/software/assembly.html

;;;

;;; This is free software; you can redistribute it and/or modify it

;;; under the terms of the GNU General Public License.

;GLOBAL _longest_match, _match_init

;SECTION    .text

;;; uInt longest_match(deflate_state *deflatestate, IPos curmatch)

;_longest_match:

IFDEF NOOLDPENTIUMCODE

    IFDEF NOUNDERLINE

    longest_match       proc near

    ELSE

    _longest_match      proc near

    ENDIF

ELSE

    IFDEF NOUNDERLINE

    longest_match_686   proc near

    ELSE

    _longest_match_686  proc near

    ENDIF

ENDIF

;;; 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

LastMatchGood:

;;; 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 eax, MIN_LOOKAHEAD

        sub ebp, eax

        jg  LimitPositive

        xor ebp, ebp

LimitPositive:

;;; 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

LookupLoop:

        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.

LoopCmps:

        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;

LeaveNow:

        mov edx, [deflatestate]

        mov ebx, [bestlen]

        mov eax, [edx + dsLookahead]

        cmp ebx, eax

        jg  LookaheadRet

        mov eax, ebx

LookaheadRet:

;;; Restore the stack and return from whence we came.

        add esp, LocalVarsSize

        pop ebx

        pop esi

        pop edi

        pop ebp