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Diffstat (limited to 'os2/match32.asm')
| -rw-r--r-- | os2/match32.asm | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/os2/match32.asm b/os2/match32.asm new file mode 100644 index 0000000..4797a73 --- /dev/null +++ b/os2/match32.asm @@ -0,0 +1,175 @@ +;=========================================================================== +; 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>. + +; Caution: this module works for IBM's C/C++ compiler versions 2 and 3 +; and for Watcom's 32-bit C/C++ compiler. Both pass the first (and only) +; argument for longest_match in the EAX register, not on the stack, with +; the default calling conventions (_System would use the stack). +; +;============================================================================== +; +; Do NOT assemble this source if external crc32 routine from zlib gets used. +; + IFNDEF USE_ZLIB +; + .386 + + name match + +BSS32 segment dword USE32 public 'BSS' + extrn window : byte + extrn prev : word + extrn prev_length : dword + extrn strstart : dword + extrn match_start : dword + extrn max_chain_length : dword + extrn good_match : dword + extrn nice_match : dword +BSS32 ends + +CODE32 segment dword USE32 public 'CODE' + assume cs:CODE32, ds:FLAT, ss:FLAT + + 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 + + ; return address ; esp+16 + push ebp ; esp+12 + push edi ; esp+8 + push esi ; esp+4 + + lea ebx,window + add ebx,2 + window_off equ dword ptr [esp] + push ebx ; esp + +; match equ esi +; scan equ edi +; chain_length equ ebp +; best_len equ ebx +; limit equ edx + + mov esi,eax ; 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,window_off ; 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 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 ; not needed if WSIZE=32768 + dec ebp ; --chain_length + shl esi,1 ; cur_match as word index + mov si,prev[esi] ; cur_match = prev[cur_match] + ; top word of esi is still 0 + jz 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 + + add esi,window_off ; 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 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,window_off ; 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 + +CODE32 ends +; + ENDIF ; !USE_ZLIB +; + end |