/*
 * Copyright (C) 1990-1992 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
 * unmodified, that it is not sold for profit, and that this copyright notice
 * is retained.
 *
 * match.s by Jean-loup Gailly. Translated to 32 bit code by Kai Uwe Rommel.
 
 * match.s, optimized version of longest_match() in deflate.c
 * This version is for 386 Unix or OS/2 in 32 bit mode.
 * Warning: it uses the AT&T syntax: mov source,dest
 * This file is only optional. If you want to force 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.
 * This version assumes static allocation of the arrays (-DDYN_ALLOC not used).
 */

	.file   "match.s"

#ifdef SYSV
#  define _prev             prev
#  define _window           window
#  define _match_start	    match_start
#  define _prev_length	    prev_length
#  define _good_match	    good_match
#  define _strstart	    strstart
#  define _max_chain_length max_chain_length

#  define _match_init       match_init
#  define _longest_match    longest_match
#endif

#define MAX_MATCH 	258
#define MAX_MATCH2      128     /* MAX_MATCH/2-1 */
#define MIN_MATCH	3
#define WSIZE 		32768
#define MAX_DIST 	WSIZE - MAX_MATCH - MIN_MATCH - 1

	.globl	_match_init
	.globl  _longest_match

	.text

_match_init:
	ret

/*-----------------------------------------------------------------------
 * 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
 */

_longest_match:	/* int longest_match(cur_match) */

#define cur_match   20(%esp)
     /* 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 	cur_match,%esi
        mov 	_max_chain_length,%ebp /* chain_length = max_chain_length */
	mov 	_strstart,%edi
	mov 	%edi,%edx
	sub	$ MAX_DIST,%edx        /* limit = strstart-MAX_DIST */
	jae	limit_ok
	sub	%edx,%edx              /* limit = NIL */
limit_ok:
        add	$_window+2,%edi        /* edi = offset(window + strstart + 2) */
        mov	_prev_length,%ebx      /* best_len = prev_length */
        movw 	-3(%ebx,%edi),%ax      /* ax = scan[best_len-1..best_len] */
        movw 	-2(%edi),%cx           /* cx = scan[0..1] */
	cmp	_good_match,%ebx       /* do we have a good match already? */
        jb      do_scan
	shr 	$2,%ebp                /* chain_length >>= 2 */
        jmp     do_scan

        .align  4
long_loop:
/* at this point, edi == scan+2, esi == cur_match */
        movw	-3(%ebx,%edi),%ax       /* ax = scan[best_len-1..best_len] */
        movw     -2(%edi),%cx           /* cx = scan[0..1] */
short_loop:
        dec     %ebp                    /* --chain_length */
        jz      the_end
/*
 * at this point, di == scan+2, si == cur_match,
 * ax = scan[best_len-1..best_len] and cx = scan[0..1]
 */
        and     $ WSIZE-1, %esi
        movw     _prev(%esi,%esi),%si   /* cur_match = prev[cur_match] */
                                        /* top word of esi is still 0 */
        cmp     %edx,%esi		/* cur_match <= limit ? */
        jbe     the_end
do_scan:
        cmpw    _window-1(%ebx,%esi),%ax /* check match at best_len-1 */
        jne     short_loop
        cmpw    _window(%esi),%cx       /* check min_match_length match */
        jne     short_loop

        lea     _window+2(%esi),%esi    /* si = match */
        mov     %edi,%eax               /* ax = scan+2 */
        mov 	$ MAX_MATCH2,%ecx       /* scan for at most MAX_MATCH bytes */
#ifdef SYSV
        repz;   cmpsw                   /* loop until mismatch */
#else
        repe;   cmpsw
#endif
        je      maxmatch                /* match of length MAX_MATCH? */
mismatch:
        movb    -2(%edi),%cl        /* mismatch on first or second byte? */
        subb    -2(%esi),%cl        /* cl = 0 if first bytes equal */
        xchg    %edi,%eax           /* edi = scan+2, eax = end of scan */
        sub     %edi,%eax           /* eax = len */
	sub	%eax,%esi           /* esi = cur_match + 2 + offset(window) */
	sub	$_window+2,%esi     /* esi = cur_match */
        subb    $1,%cl              /* set carry if cl == 0 (cannot use DEC) */
        adc     $0,%eax             /* eax = carry ? len+1 : len */
        cmp     %ebx,%eax           /* len > best_len ? */
        jle     long_loop
        mov     %esi,_match_start       /* match_start = cur_match */
        mov     %eax,%ebx               /* ebx = best_len = len */
        cmp     $ MAX_MATCH,%eax        /* len >= MAX_MATCH ? */
        jl      long_loop
the_end:
        mov     %ebx,%eax               /* result = eax = best_len */
	pop     %ebx
        pop     %esi
        pop     %edi
        pop     %ebp
        ret
maxmatch:
        cmpsb
        jmp     mismatch
