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1.1.1.5 ! root 1: ; ! 2: ; Copyright (C) 1990-1992 Mark Adler, Richard B. Wales, and Jean-loup Gailly. ! 3: ; Permission is granted to any individual or institution to use, copy, or ! 4: ; redistribute this software so long as all of the original files are included ! 5: ; unmodified, that it is not sold for profit, and that this copyright notice ! 6: ; is retained. ! 7: ; ! 8: ; match.asm by Jean-loup Gailly. ! 9: ! 10: ; match.asm, optimized version of longest_match() in deflate.c ! 11: ; Must be assembled with masm -ml. To be used only with C large model. ! 12: ; (For compact model, follow the instructions given below.) ! 13: ; This file is only optional. If you don't have masm or tasm, use the ! 14: ; C version (add -DNO_ASM to CFLAGS in makefile.msc and remove match.obj ! 15: ; from OBJI). If you have reduced WSIZE in zip.h, then change its value ! 16: ; below. ! 17: ; ! 18: ; Turbo C 2.0 does not support static allocation of more than 64K bytes per ! 19: ; file, and does not have SS == DS. So TC and BC++ users must use: ! 20: ; tasm -ml -DDYN_ALLOC -DSS_NEQ_DS match; ! 21: ; ! 22: ; To simplify the code, the option -DDYN_ALLOC is supported for OS/2 ! 23: ; only if the arrays are guaranteed to have zero offset (allocated by ! 24: ; halloc). We also require SS==DS. This is satisfied for MSC but not Turbo C. ! 25: ! 26: name match ! 27: ! 28: ; define LCODE as follows: ! 29: ; model: compact large (small and medium not supported here) ! 30: ; LCODE 0 1 ! 31: ! 32: LCODE equ 1 ! 33: ; Better define them on the command line ! 34: ;DYN_ALLOC equ 1 ! 35: ;SS_NEQ_DS equ 1 ! 36: ; For Turbo C, define SS_NEQ_DS as 1, but for MSC you can leave it undefined. ! 37: ; The code is a little better when SS_NEQ_DS is not defined. ! 38: ! 39: ifndef DYN_ALLOC ! 40: extrn _prev : word ! 41: extrn _slide : byte ! 42: prev equ _prev ; offset part ! 43: slide equ _slide ! 44: endif ! 45: ! 46: _DATA segment word public 'DATA' ! 47: extrn _match_start : word ! 48: extrn _prev_length : word ! 49: extrn _good_match : word ! 50: extrn _strstart : word ! 51: extrn _max_chain_length : word ! 52: ifdef DYN_ALLOC ! 53: extrn _prev : word ! 54: extrn _slide : word ! 55: prev equ 0 ; offset forced to zero ! 56: slide equ 0 ! 57: slide_seg equ _slide[2] ! 58: slide_off equ 0 ! 59: else ! 60: wseg dw seg _slide ! 61: slide_seg equ wseg ! 62: slide_off equ offset _slide ! 63: endif ! 64: _DATA ends ! 65: ! 66: DGROUP group _DATA ! 67: ! 68: if LCODE ! 69: extrn _exit : far ! 70: else ! 71: extrn _exit : near ! 72: endif ! 73: ! 74: _TEXT segment word public 'CODE' ! 75: assume cs: _TEXT, ds: DGROUP ! 76: ! 77: public _match_init ! 78: public _longest_match ! 79: ! 80: MIN_MATCH equ 3 ! 81: MAX_MATCH equ 258 ! 82: WSIZE equ 8192 ; keep in sync with zip.h ! ! 83: WMASK equ (WSIZE-1) ! 84: MIN_LOOKAHEAD equ (MAX_MATCH+MIN_MATCH+1) ! 85: MAX_DIST equ (WSIZE-MIN_LOOKAHEAD) ! 86: ! 87: prev_ptr dw seg _prev ; pointer to the prev array ! 88: ifdef SS_NEQ_DS ! 89: match_start dw 0 ; copy of _match_start if SS != DS ! 90: endif ! 91: ! 92: ; initialize or check the variables used in match.asm. ! 93: ! 94: if LCODE ! 95: _match_init proc far ! 96: else ! 97: _match_init proc near ! 98: endif ! 99: ifdef SS_NEQ_DS ! 100: ma_start equ cs:match_start ; does not work on OS/2 ! 101: else ! 102: assume ss: DGROUP ! 103: ma_start equ ss:_match_start ! 104: mov ax,ds ! 105: mov bx,ss ! 106: cmp ax,bx ; SS == DS? ! 107: jne error ! 108: endif ! 109: ifdef DYN_ALLOC ! 110: mov ax,_slide[0] ; force zero offset ! 111: add ax,15 ! 112: mov cx,4 ! 113: shr ax,cl ! 114: add _slide[2],ax ! 115: mov _slide[0],0 ! 116: ! 117: mov ax,_prev[0] ; force zero offset ! 118: add ax,15 ! 119: mov cx,4 ! 120: shr ax,cl ! 121: add _prev[2],ax ! 122: mov _prev[0],0 ! 123: ifdef SS_NEQ_DS ! 124: mov ax,_prev[2] ; segment value ! 125: mov cs:prev_ptr,ax ; ugly write to code, crash on OS/2 ! 126: prev_seg equ cs:prev_ptr ! 127: else ! 128: prev_seg equ ss:_prev[2] ; works on OS/2 if SS == DS ! 129: endif ! 130: else ! 131: prev_seg equ cs:prev_ptr ! 132: endif ! 133: ret ! 134: error: call _exit ! 135: ! 136: _match_init endp ! 137: ! 138: ; ----------------------------------------------------------------------- ! 139: ; Set match_start to the longest match starting at the given string and ! 140: ; return its length. Matches shorter or equal to prev_length are discarded, ! 141: ; in which case the result is equal to prev_length and match_start is ! 142: ; garbage. ! 143: ; IN assertions: cur_match is the head of the hash chain for the current ! 144: ; string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1 ! 145: ! 146: ; int longest_match(cur_match) ! 147: ! 148: if LCODE ! 149: _longest_match proc far ! 150: else ! 151: _longest_match proc near ! 152: endif ! 153: push bp ! 154: mov bp,sp ! 155: push di ! 156: push si ! 157: push ds ! 158: ! 159: if LCODE ! 160: cur_match equ word ptr [bp+6] ! 161: else ! 162: cur_match equ word ptr [bp+4] ! 163: endif ! 164: ; slide equ es:slide (es:0 for DYN_ALLOC) ! 165: ; prev equ ds:prev ! 166: ; match equ es:si ! 167: ; scan equ es:di ! 168: ; chain_length equ bp ! 169: ; best_len equ bx ! 170: ; limit equ dx ! 171: ! 172: mov si,cur_match ; use bp before it is destroyed ! 173: mov bp,_max_chain_length ; chain_length = max_chain_length ! 174: mov di,_strstart ! 175: mov dx,di ! 176: sub dx,MAX_DIST ; limit = strstart-MAX_DIST ! 177: jae limit_ok ! 178: sub dx,dx ; limit = NIL ! 179: limit_ok: ! 180: add di,2+slide_off ; di = offset(slide + strstart + 2) ! 181: mov bx,_prev_length ; best_len = prev_length ! 182: mov es,slide_seg ! 183: mov ax,es:[bx+di-3] ; ax = scan[best_len-1..best_len] ! 184: mov cx,es:[di-2] ; cx = scan[0..1] ! 185: cmp bx,_good_match ; do we have a good match already? ! 186: mov ds,prev_seg ; (does not destroy the flags) ! 187: assume ds: nothing ! 188: jb do_scan ; good match? ! 189: shr bp,1 ; chain_length >>= 2 ! 190: shr bp,1 ! 191: jmp short do_scan ! 192: ! 193: even ; align destination of branch ! 194: long_loop: ! 195: ; at this point, ds:di == scan+2, ds:si == cur_match ! 196: mov ax,[bx+di-3] ; ax = scan[best_len-1..best_len] ! 197: mov cx,[di-2] ; cx = scan[0..1] ! 198: mov ds,prev_seg ; reset ds to address the prev array ! 199: short_loop: ! 200: dec bp ; --chain_length ! 201: jz the_end ! 202: ; at this point, di == scan+2, si = cur_match, ! 203: ; ax = scan[best_len-1..best_len] and cx = scan[0..1] ! 204: if (WSIZE-32768) ! 205: and si,WMASK ! 206: endif ! 207: shl si,1 ; cur_match as word index ! 208: mov si,prev[si] ; cur_match = prev[cur_match] ! 209: cmp si,dx ; cur_match <= limit ? ! 210: jbe the_end ! 211: do_scan: ! 212: cmp ax,word ptr es:slide[bx+si-1] ; check match at best_len-1 ! 213: jne short_loop ! 214: cmp cx,word ptr es:slide[si] ; check min_match_length match ! 215: jne short_loop ! 216: ! 217: lea si,slide[si+2] ; si = match ! 218: mov ax,di ; ax = scan+2 ! 219: mov cx,es ! 220: mov ds,cx ; ds = es = slide ! 221: mov cx,(MAX_MATCH-2)/2 ; scan for at most MAX_MATCH bytes ! 222: repe cmpsw ; loop until mismatch ! 223: je maxmatch ; match of length MAX_MATCH? ! 224: mismatch: ! 225: mov cl,[di-2] ; mismatch on first or second byte? ! 226: sub cl,[si-2] ; cl = 0 if first bytes equal ! 227: xchg ax,di ; di = scan+2, ax = end of scan ! 228: sub ax,di ; ax = len ! 229: sub si,ax ; si = cur_match + 2 + offset(slide) ! 230: sub si,2+slide_off ; si = cur_match ! 231: sub cl,1 ; set carry if cl == 0 (can't use DEC) ! 232: adc ax,0 ; ax = carry ? len+1 : len ! 233: cmp ax,bx ; len > best_len ? ! 234: jle long_loop ! 235: mov ma_start,si ; match_start = cur_match ! 236: mov bx,ax ; bx = best_len = len ! 237: cmp ax,MAX_MATCH ; len >= MAX_MATCH ? ! 238: jl long_loop ! 239: the_end: ! 240: pop ds ! 241: assume ds: DGROUP ! 242: ifdef SS_NEQ_DS ! 243: mov ax,ma_start ; garbage if no match found ! 244: mov ds:_match_start,ax ! 245: endif ! 246: pop si ! 247: pop di ! 248: pop bp ! 249: mov ax,bx ; result = ax = best_len ! 250: ret ! 251: maxmatch: ; come here if maximum match ! 252: cmpsb ; increment si and di ! 253: jmp mismatch ; force match_length = MAX_LENGTH ! 254: ! 255: _longest_match endp ! 256: ! 257: _TEXT ends ! 258: end
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