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Diffstat (limited to 'win32/match32.asm')
| -rw-r--r-- | win32/match32.asm | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/win32/match32.asm b/win32/match32.asm new file mode 100644 index 0000000..81db41f --- /dev/null +++ b/win32/match32.asm @@ -0,0 +1,192 @@ +;=========================================================================== +; 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 |