;; Copyright (C) 1990-1993 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,; that it is not sold for profit, and that this copyright notice is retained.;; 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 change its value; below.        .386        name    match_BSS    segment  dword USE32 public 'BSS'        extrn   _match_start  : dword        extrn   _prev_length  : dword        extrn   _good_match   : dword        extrn   _strstart     : dword        extrn   _max_chain_length : dword        extrn   _prev         : word        extrn   _window       : byte_BSS    endsDGROUP  group _BSS_TEXT   segment dword USE32 public 'CODE'        assume  cs: _TEXT, ds: DGROUP, ss: DGROUP        public match_init_        public longest_match_        MIN_MATCH     equ 3        MAX_MATCH     equ 258        WSIZE         equ 32768         ; keep in sync with zip.h !        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        retmatch_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     ebp,_max_chain_length   ; chain_length = max_chain_length        mov     edi,_strstart        mov     edx,edi        sub     edx,MAX_DIST            ; limit = strstart-MAX_DIST        jae     short limit_ok        sub     edx,edx                 ; limit = NILlimit_ok:        add     edi,2+offset _window    ; edi = offset(window + strstart + 2)        mov     ebx,_prev_length        ; best_len = prev_length        mov     ax,[ebx+edi-3]          ; ax = scan[best_len-1..best_len]        mov     cx,[edi-2]              ; cx = scan[0..1]        cmp     ebx,_good_match         ; do we have a good match already?        jb      do_scan        shr     ebp,2                   ; chain_length >>= 2        jmp     short do_scan        align   4                       ; align destination of branchlong_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:        dec     ebp                     ; --chain_length        jz      the_end; 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        mov     si,_prev[esi+esi]       ; cur_match = prev[cur_match]                                        ; top word of esi is still 0        cmp     esi,edx                 ; cur_match <= limit ?        jbe     short the_enddo_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]      ; si = match        mov     eax,edi                 ; ax = scan+2        mov     ecx,(MAX_MATCH-2)/2     ; scan for at most MAX_MATCH bytes        repe    cmpsw                   ; loop until mismatch        je      maxmatch                ; match of length MAX_MATCH?mismatch:        mov     cl,[edi-2]              ; mismatch on first or second byte?        sub     cl,[esi-2]              ; cl = 0 if first bytes equal        xchg    eax,edi                 ; edi = scan+2, eax = end of scan        sub     eax,edi                 ; eax = len        sub     esi,eax                 ; esi = cur_match + 2 + offset(window)        sub     esi,2+offset _window    ; esi = cur_match        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        cmp     eax,MAX_MATCH           ; len >= MAX_MATCH ?        jl      long_loopthe_end:        mov     eax,ebx                 ; result = eax = best_len        pop     ebx        pop     esi        pop     edi        pop     ebp        retmaxmatch:                               ; come here if maximum match        cmpsb                           ; increment esi and edi        jmp     mismatch                ; force match_length = MAX_LENGTHlongest_match_ endp_TEXT   endsend