[thirdparty/git.git] / xdiff / xprepare.c

/*
 *  LibXDiff by Davide Libenzi ( File Differential Library )
 *  Copyright (C) 2003  Davide Libenzi
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  Davide Libenzi <davidel@xmailserver.org>
 *
 */

#include "xinclude.h"


#define XDL_KPDIS_RUN 4
#define XDL_MAX_EQLIMIT 1024
#define XDL_SIMSCAN_WINDOW 100


typedef struct s_xdlclass {
	struct s_xdlclass *next;
	unsigned long ha;
	char const *line;
	long size;
	long idx;
} xdlclass_t;

typedef struct s_xdlclassifier {
	unsigned int hbits;
	long hsize;
	xdlclass_t **rchash;
	chastore_t ncha;
	long count;
	long flags;
} xdlclassifier_t;


static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags);
static void xdl_free_classifier(xdlclassifier_t *cf);
static int xdl_classify_record(xdlclassifier_t *cf, xrecord_t **rhash, unsigned int hbits,
			       xrecord_t *rec);
static int xdl_prepare_ctx(mmfile_t *mf, long narec, xpparam_t const *xpp,
			   xdlclassifier_t *cf, xdfile_t *xdf);
static void xdl_free_ctx(xdfile_t *xdf);
static int xdl_clean_mmatch(char const *dis, long i, long s, long e);
static int xdl_cleanup_records(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_optimize_ctxs(xdfile_t *xdf1, xdfile_t *xdf2);


static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {
	cf->flags = flags;

	cf->hbits = xdl_hashbits((unsigned int) size);
	cf->hsize = 1 << cf->hbits;

	if (xdl_cha_init(&cf->ncha, sizeof(xdlclass_t), size / 4 + 1) < 0) {

		return -1;
	}
	if (!(cf->rchash = (xdlclass_t **) xdl_malloc(cf->hsize * sizeof(xdlclass_t *)))) {

		xdl_cha_free(&cf->ncha);
		return -1;
	}
	memset(cf->rchash, 0, cf->hsize * sizeof(xdlclass_t *));

	cf->count = 0;

	return 0;
}


static void xdl_free_classifier(xdlclassifier_t *cf) {

	xdl_free(cf->rchash);
	xdl_cha_free(&cf->ncha);
}


static int xdl_classify_record(xdlclassifier_t *cf, xrecord_t **rhash, unsigned int hbits,
			       xrecord_t *rec) {
	long hi;
	char const *line;
	xdlclass_t *rcrec;

	line = rec->ptr;
	hi = (long) XDL_HASHLONG(rec->ha, cf->hbits);
	for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)
		if (rcrec->ha == rec->ha &&
				xdl_recmatch(rcrec->line, rcrec->size,
					rec->ptr, rec->size, cf->flags))
			break;

	if (!rcrec) {
		if (!(rcrec = xdl_cha_alloc(&cf->ncha))) {

			return -1;
		}
		rcrec->idx = cf->count++;
		rcrec->line = line;
		rcrec->size = rec->size;
		rcrec->ha = rec->ha;
		rcrec->next = cf->rchash[hi];
		cf->rchash[hi] = rcrec;
	}

	rec->ha = (unsigned long) rcrec->idx;

	hi = (long) XDL_HASHLONG(rec->ha, hbits);
	rec->next = rhash[hi];
	rhash[hi] = rec;

	return 0;
}


static int xdl_prepare_ctx(mmfile_t *mf, long narec, xpparam_t const *xpp,
			   xdlclassifier_t *cf, xdfile_t *xdf) {
	unsigned int hbits;
	long nrec, hsize, bsize;
	unsigned long hav;
	char const *blk, *cur, *top, *prev;
	xrecord_t *crec;
	xrecord_t **recs, **rrecs;
	xrecord_t **rhash;
	unsigned long *ha;
	char *rchg;
	long *rindex;

	ha = NULL;
	rindex = NULL;
	rchg = NULL;
	rhash = NULL;
	recs = NULL;

	if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0)
		goto abort;
	if (!(recs = (xrecord_t **) xdl_malloc(narec * sizeof(xrecord_t *))))
		goto abort;

	if (xpp->flags & XDF_HISTOGRAM_DIFF)
		hbits = hsize = 0;
	else {
		hbits = xdl_hashbits((unsigned int) narec);
		hsize = 1 << hbits;
		if (!(rhash = (xrecord_t **) xdl_malloc(hsize * sizeof(xrecord_t *))))
			goto abort;
		memset(rhash, 0, hsize * sizeof(xrecord_t *));
	}

	nrec = 0;
	if ((cur = blk = xdl_mmfile_first(mf, &bsize)) != NULL) {
		for (top = blk + bsize;;) {
			if (cur >= top) {
				if (!(cur = blk = xdl_mmfile_next(mf, &bsize)))
					break;
				top = blk + bsize;
			}
			prev = cur;
			hav = xdl_hash_record(&cur, top, xpp->flags);
			if (nrec >= narec) {
				narec *= 2;
				if (!(rrecs = (xrecord_t **) xdl_realloc(recs, narec * sizeof(xrecord_t *))))
					goto abort;
				recs = rrecs;
			}
			if (!(crec = xdl_cha_alloc(&xdf->rcha)))
				goto abort;
			crec->ptr = prev;
			crec->size = (long) (cur - prev);
			crec->ha = hav;
			recs[nrec++] = crec;

			if (!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
				xdl_classify_record(cf, rhash, hbits, crec) < 0)
				goto abort;
		}
	}

	if (!(rchg = (char *) xdl_malloc((nrec + 2) * sizeof(char))))
		goto abort;
	memset(rchg, 0, (nrec + 2) * sizeof(char));

	if (!(rindex = (long *) xdl_malloc((nrec + 1) * sizeof(long))))
		goto abort;
	if (!(ha = (unsigned long *) xdl_malloc((nrec + 1) * sizeof(unsigned long))))
		goto abort;

	xdf->nrec = nrec;
	xdf->recs = recs;
	xdf->hbits = hbits;
	xdf->rhash = rhash;
	xdf->rchg = rchg + 1;
	xdf->rindex = rindex;
	xdf->nreff = 0;
	xdf->ha = ha;
	xdf->dstart = 0;
	xdf->dend = nrec - 1;

	return 0;

abort:
	xdl_free(ha);
	xdl_free(rindex);
	xdl_free(rchg);
	xdl_free(rhash);
	xdl_free(recs);
	xdl_cha_free(&xdf->rcha);
	return -1;
}


static void xdl_free_ctx(xdfile_t *xdf) {

	xdl_free(xdf->rhash);
	xdl_free(xdf->rindex);
	xdl_free(xdf->rchg - 1);
	xdl_free(xdf->ha);
	xdl_free(xdf->recs);
	xdl_cha_free(&xdf->rcha);
}


int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
		    xdfenv_t *xe) {
	long enl1, enl2;
	xdlclassifier_t cf;

	enl1 = xdl_guess_lines(mf1) + 1;
	enl2 = xdl_guess_lines(mf2) + 1;

	if (!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
		xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0) {

		return -1;
	}

	if (xdl_prepare_ctx(mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {

		xdl_free_classifier(&cf);
		return -1;
	}
	if (xdl_prepare_ctx(mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {

		xdl_free_ctx(&xe->xdf1);
		xdl_free_classifier(&cf);
		return -1;
	}

	if (!(xpp->flags & XDF_HISTOGRAM_DIFF))
		xdl_free_classifier(&cf);

	if (!(xpp->flags & XDF_PATIENCE_DIFF) &&
			!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
			xdl_optimize_ctxs(&xe->xdf1, &xe->xdf2) < 0) {

		xdl_free_ctx(&xe->xdf2);
		xdl_free_ctx(&xe->xdf1);
		return -1;
	}

	return 0;
}


void xdl_free_env(xdfenv_t *xe) {

	xdl_free_ctx(&xe->xdf2);
	xdl_free_ctx(&xe->xdf1);
}


static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
	long r, rdis0, rpdis0, rdis1, rpdis1;

	/*
	 * Limits the window the is examined during the similar-lines
	 * scan. The loops below stops when dis[i - r] == 1 (line that
	 * has no match), but there are corner cases where the loop
	 * proceed all the way to the extremities by causing huge
	 * performance penalties in case of big files.
	 */
	if (i - s > XDL_SIMSCAN_WINDOW)
		s = i - XDL_SIMSCAN_WINDOW;
	if (e - i > XDL_SIMSCAN_WINDOW)
		e = i + XDL_SIMSCAN_WINDOW;

	/*
	 * Scans the lines before 'i' to find a run of lines that either
	 * have no match (dis[j] == 0) or have multiple matches (dis[j] > 1).
	 * Note that we always call this function with dis[i] > 1, so the
	 * current line (i) is already a multimatch line.
	 */
	for (r = 1, rdis0 = 0, rpdis0 = 1; (i - r) >= s; r++) {
		if (!dis[i - r])
			rdis0++;
		else if (dis[i - r] == 2)
			rpdis0++;
		else
			break;
	}
	/*
	 * If the run before the line 'i' found only multimatch lines, we
	 * return 0 and hence we don't make the current line (i) discarded.
	 * We want to discard multimatch lines only when they appear in the
	 * middle of runs with nomatch lines (dis[j] == 0).
	 */
	if (rdis0 == 0)
		return 0;
	for (r = 1, rdis1 = 0, rpdis1 = 1; (i + r) <= e; r++) {
		if (!dis[i + r])
			rdis1++;
		else if (dis[i + r] == 2)
			rpdis1++;
		else
			break;
	}
	/*
	 * If the run after the line 'i' found only multimatch lines, we
	 * return 0 and hence we don't make the current line (i) discarded.
	 */
	if (rdis1 == 0)
		return 0;
	rdis1 += rdis0;
	rpdis1 += rpdis0;

	return rpdis1 * XDL_KPDIS_RUN < (rpdis1 + rdis1);
}


/*
 * Try to reduce the problem complexity, discard records that have no
 * matches on the other file. Also, lines that have multiple matches
 * might be potentially discarded if they happear in a run of discardable.
 */
static int xdl_cleanup_records(xdfile_t *xdf1, xdfile_t *xdf2) {
	long i, nm, rhi, nreff, mlim;
	unsigned long hav;
	xrecord_t **recs;
	xrecord_t *rec;
	char *dis, *dis1, *dis2;

	if (!(dis = (char *) xdl_malloc(xdf1->nrec + xdf2->nrec + 2))) {

		return -1;
	}
	memset(dis, 0, xdf1->nrec + xdf2->nrec + 2);
	dis1 = dis;
	dis2 = dis1 + xdf1->nrec + 1;

	if ((mlim = xdl_bogosqrt(xdf1->nrec)) > XDL_MAX_EQLIMIT)
		mlim = XDL_MAX_EQLIMIT;
	for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {
		hav = (*recs)->ha;
		rhi = (long) XDL_HASHLONG(hav, xdf2->hbits);
		for (nm = 0, rec = xdf2->rhash[rhi]; rec; rec = rec->next)
			if (rec->ha == hav && ++nm == mlim)
				break;
		dis1[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;
	}

	if ((mlim = xdl_bogosqrt(xdf2->nrec)) > XDL_MAX_EQLIMIT)
		mlim = XDL_MAX_EQLIMIT;
	for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {
		hav = (*recs)->ha;
		rhi = (long) XDL_HASHLONG(hav, xdf1->hbits);
		for (nm = 0, rec = xdf1->rhash[rhi]; rec; rec = rec->next)
			if (rec->ha == hav && ++nm == mlim)
				break;
		dis2[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;
	}

	for (nreff = 0, i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart];
	     i <= xdf1->dend; i++, recs++) {
		if (dis1[i] == 1 ||
		    (dis1[i] == 2 && !xdl_clean_mmatch(dis1, i, xdf1->dstart, xdf1->dend))) {
			xdf1->rindex[nreff] = i;
			xdf1->ha[nreff] = (*recs)->ha;
			nreff++;
		} else
			xdf1->rchg[i] = 1;
	}
	xdf1->nreff = nreff;

	for (nreff = 0, i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart];
	     i <= xdf2->dend; i++, recs++) {
		if (dis2[i] == 1 ||
		    (dis2[i] == 2 && !xdl_clean_mmatch(dis2, i, xdf2->dstart, xdf2->dend))) {
			xdf2->rindex[nreff] = i;
			xdf2->ha[nreff] = (*recs)->ha;
			nreff++;
		} else
			xdf2->rchg[i] = 1;
	}
	xdf2->nreff = nreff;

	xdl_free(dis);

	return 0;
}


/*
 * Early trim initial and terminal matching records.
 */
static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {
	long i, lim;
	xrecord_t **recs1, **recs2;

	recs1 = xdf1->recs;
	recs2 = xdf2->recs;
	for (i = 0, lim = XDL_MIN(xdf1->nrec, xdf2->nrec); i < lim;
	     i++, recs1++, recs2++)
		if ((*recs1)->ha != (*recs2)->ha)
			break;

	xdf1->dstart = xdf2->dstart = i;

	recs1 = xdf1->recs + xdf1->nrec - 1;
	recs2 = xdf2->recs + xdf2->nrec - 1;
	for (lim -= i, i = 0; i < lim; i++, recs1--, recs2--)
		if ((*recs1)->ha != (*recs2)->ha)
			break;

	xdf1->dend = xdf1->nrec - i - 1;
	xdf2->dend = xdf2->nrec - i - 1;

	return 0;
}


static int xdl_optimize_ctxs(xdfile_t *xdf1, xdfile_t *xdf2) {

	if (xdl_trim_ends(xdf1, xdf2) < 0 ||
	    xdl_cleanup_records(xdf1, xdf2) < 0) {

		return -1;
	}

	return 0;
}
Commit	Line	Data
3443546f LT	1	/*
	2	* LibXDiff by Davide Libenzi ( File Differential Library )
	3	* Copyright (C) 2003 Davide Libenzi
	4	*
	5	* This library is free software; you can redistribute it and/or
	6	* modify it under the terms of the GNU Lesser General Public
	7	* License as published by the Free Software Foundation; either
	8	* version 2.1 of the License, or (at your option) any later version.
	9	*
	10	* This library is distributed in the hope that it will be useful,
	11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	* Lesser General Public License for more details.
	14	*
	15	* You should have received a copy of the GNU Lesser General Public
	16	* License along with this library; if not, write to the Free Software
	17	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	18	*
	19	* Davide Libenzi <davidel@xmailserver.org>
	20	*
	21	*/
	22
	23	#include "xinclude.h"
	24
	25
3443546f	26	#define XDL_KPDIS_RUN 4
ca557aff	27	#define XDL_MAX_EQLIMIT 1024
9b28d554	28	#define XDL_SIMSCAN_WINDOW 100
3443546f LT	29
	30
	31	typedef struct s_xdlclass {
	32	struct s_xdlclass *next;
	33	unsigned long ha;
	34	char const *line;
	35	long size;
	36	long idx;
	37	} xdlclass_t;
	38
	39	typedef struct s_xdlclassifier {
	40	unsigned int hbits;
	41	long hsize;
	42	xdlclass_t **rchash;
	43	chastore_t ncha;
	44	long count;
0d21efa5	45	long flags;
3443546f LT	46	} xdlclassifier_t;
	47
	48
	49
	50
0d21efa5	51	static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags);
3443546f LT	52	static void xdl_free_classifier(xdlclassifier_t *cf);
	53	static int xdl_classify_record(xdlclassifier_t cf, xrecord_t *rhash, unsigned int hbits,
	54	xrecord_t *rec);
	55	static int xdl_prepare_ctx(mmfile_t mf, long narec, xpparam_t const xpp,
	56	xdlclassifier_t cf, xdfile_t xdf);
	57	static void xdl_free_ctx(xdfile_t *xdf);
	58	static int xdl_clean_mmatch(char const *dis, long i, long s, long e);
	59	static int xdl_cleanup_records(xdfile_t xdf1, xdfile_t xdf2);
	60	static int xdl_trim_ends(xdfile_t xdf1, xdfile_t xdf2);
	61	static int xdl_optimize_ctxs(xdfile_t xdf1, xdfile_t xdf2);
	62
	63
	64
	65
0d21efa5	66	static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {
0d21efa5 JS	67	cf->flags = flags;
0d21efa5 JS	68
3443546f LT	69	cf->hbits = xdl_hashbits((unsigned int) size);
	70	cf->hsize = 1 << cf->hbits;
	71
	72	if (xdl_cha_init(&cf->ncha, sizeof(xdlclass_t), size / 4 + 1) < 0) {
	73
	74	return -1;
	75	}
	76	if (!(cf->rchash = (xdlclass_t *) xdl_malloc(cf->hsize sizeof(xdlclass_t *)))) {
	77
	78	xdl_cha_free(&cf->ncha);
	79	return -1;
	80	}
452f4fa5	81	memset(cf->rchash, 0, cf->hsize * sizeof(xdlclass_t *));
3443546f LT	82
	83	cf->count = 0;
	84
	85	return 0;
	86	}
	87
	88
	89	static void xdl_free_classifier(xdlclassifier_t *cf) {
	90
	91	xdl_free(cf->rchash);
	92	xdl_cha_free(&cf->ncha);
	93	}
	94
	95
	96	static int xdl_classify_record(xdlclassifier_t cf, xrecord_t *rhash, unsigned int hbits,
	97	xrecord_t *rec) {
	98	long hi;
	99	char const *line;
	100	xdlclass_t *rcrec;
	101
	102	line = rec->ptr;
	103	hi = (long) XDL_HASHLONG(rec->ha, cf->hbits);
	104	for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)
0d21efa5 JS	105	if (rcrec->ha == rec->ha &&
	106	xdl_recmatch(rcrec->line, rcrec->size,
	107	rec->ptr, rec->size, cf->flags))
3443546f LT	108	break;
	109
	110	if (!rcrec) {
	111	if (!(rcrec = xdl_cha_alloc(&cf->ncha))) {
	112
	113	return -1;
	114	}
	115	rcrec->idx = cf->count++;
	116	rcrec->line = line;
	117	rcrec->size = rec->size;
	118	rcrec->ha = rec->ha;
	119	rcrec->next = cf->rchash[hi];
	120	cf->rchash[hi] = rcrec;
	121	}
	122
	123	rec->ha = (unsigned long) rcrec->idx;
	124
	125	hi = (long) XDL_HASHLONG(rec->ha, hbits);
	126	rec->next = rhash[hi];
	127	rhash[hi] = rec;
	128
	129	return 0;
	130	}
	131
	132
	133	static int xdl_prepare_ctx(mmfile_t mf, long narec, xpparam_t const xpp,
	134	xdlclassifier_t cf, xdfile_t xdf) {
	135	unsigned int hbits;
452f4fa5	136	long nrec, hsize, bsize;
3443546f LT	137	unsigned long hav;
	138	char const blk, cur, top, prev;
	139	xrecord_t *crec;
	140	xrecord_t recs, rrecs;
	141	xrecord_t **rhash;
	142	unsigned long *ha;
	143	char *rchg;
	144	long *rindex;
	145
159607a8 TRC	146	ha = NULL;
	147	rindex = NULL;
	148	rchg = NULL;
	149	rhash = NULL;
	150	recs = NULL;
3443546f	151
159607a8 TRC	152	if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0)
	153	goto abort;
	154	if (!(recs = (xrecord_t *) xdl_malloc(narec sizeof(xrecord_t *))))
	155	goto abort;
3443546f	156
9f37c275 TRC	157	if (xpp->flags & XDF_HISTOGRAM_DIFF)
	158	hbits = hsize = 0;
	159	else {
	160	hbits = xdl_hashbits((unsigned int) narec);
	161	hsize = 1 << hbits;
	162	if (!(rhash = (xrecord_t *) xdl_malloc(hsize sizeof(xrecord_t *))))
	163	goto abort;
	164	memset(rhash, 0, hsize * sizeof(xrecord_t *));
	165	}
3443546f LT	166
	167	nrec = 0;
	168	if ((cur = blk = xdl_mmfile_first(mf, &bsize)) != NULL) {
	169	for (top = blk + bsize;;) {
	170	if (cur >= top) {
	171	if (!(cur = blk = xdl_mmfile_next(mf, &bsize)))
	172	break;
	173	top = blk + bsize;
	174	}
	175	prev = cur;
0d21efa5	176	hav = xdl_hash_record(&cur, top, xpp->flags);
3443546f LT	177	if (nrec >= narec) {
3443546f LT	178	narec *= 2;
159607a8 TRC	179	if (!(rrecs = (xrecord_t *) xdl_realloc(recs, narec sizeof(xrecord_t *))))
159607a8 TRC	180	goto abort;
3443546f LT	181	recs = rrecs;
3443546f LT	182	}
159607a8 TRC	183	if (!(crec = xdl_cha_alloc(&xdf->rcha)))
159607a8 TRC	184	goto abort;
3443546f LT	185	crec->ptr = prev;
	186	crec->size = (long) (cur - prev);
	187	crec->ha = hav;
	188	recs[nrec++] = crec;
	189
9f37c275 TRC	190	if (!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
9f37c275 TRC	191	xdl_classify_record(cf, rhash, hbits, crec) < 0)
159607a8	192	goto abort;
3443546f LT	193	}
	194	}
	195
159607a8 TRC	196	if (!(rchg = (char ) xdl_malloc((nrec + 2) sizeof(char))))
159607a8 TRC	197	goto abort;
3443546f LT	198	memset(rchg, 0, (nrec + 2) * sizeof(char));
3443546f LT	199
159607a8 TRC	200	if (!(rindex = (long ) xdl_malloc((nrec + 1) sizeof(long))))
	201	goto abort;
	202	if (!(ha = (unsigned long ) xdl_malloc((nrec + 1) sizeof(unsigned long))))
	203	goto abort;
3443546f LT	204
	205	xdf->nrec = nrec;
	206	xdf->recs = recs;
	207	xdf->hbits = hbits;
	208	xdf->rhash = rhash;
	209	xdf->rchg = rchg + 1;
	210	xdf->rindex = rindex;
	211	xdf->nreff = 0;
	212	xdf->ha = ha;
	213	xdf->dstart = 0;
	214	xdf->dend = nrec - 1;
	215
	216	return 0;
159607a8 TRC	217
	218	abort:
	219	xdl_free(ha);
	220	xdl_free(rindex);
	221	xdl_free(rchg);
	222	xdl_free(rhash);
	223	xdl_free(recs);
	224	xdl_cha_free(&xdf->rcha);
	225	return -1;
3443546f LT	226	}
	227
	228
	229	static void xdl_free_ctx(xdfile_t *xdf) {
	230
	231	xdl_free(xdf->rhash);
	232	xdl_free(xdf->rindex);
	233	xdl_free(xdf->rchg - 1);
	234	xdl_free(xdf->ha);
	235	xdl_free(xdf->recs);
	236	xdl_cha_free(&xdf->rcha);
	237	}
	238
	239
	240	int xdl_prepare_env(mmfile_t mf1, mmfile_t mf2, xpparam_t const *xpp,
	241	xdfenv_t *xe) {
	242	long enl1, enl2;
	243	xdlclassifier_t cf;
	244
	245	enl1 = xdl_guess_lines(mf1) + 1;
	246	enl2 = xdl_guess_lines(mf2) + 1;
	247
9f37c275 TRC	248	if (!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
9f37c275 TRC	249	xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0) {
3443546f LT	250
	251	return -1;
	252	}
	253
	254	if (xdl_prepare_ctx(mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
	255
	256	xdl_free_classifier(&cf);
	257	return -1;
	258	}
	259	if (xdl_prepare_ctx(mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {
	260
	261	xdl_free_ctx(&xe->xdf1);
	262	xdl_free_classifier(&cf);
	263	return -1;
	264	}
	265
9f37c275 TRC	266	if (!(xpp->flags & XDF_HISTOGRAM_DIFF))
9f37c275 TRC	267	xdl_free_classifier(&cf);
3443546f	268
92b7de93	269	if (!(xpp->flags & XDF_PATIENCE_DIFF) &&
9f37c275	270	!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
92b7de93	271	xdl_optimize_ctxs(&xe->xdf1, &xe->xdf2) < 0) {
3443546f LT	272
	273	xdl_free_ctx(&xe->xdf2);
	274	xdl_free_ctx(&xe->xdf1);
	275	return -1;
	276	}
	277
	278	return 0;
	279	}
	280
	281
	282	void xdl_free_env(xdfenv_t *xe) {
	283
	284	xdl_free_ctx(&xe->xdf2);
	285	xdl_free_ctx(&xe->xdf1);
	286	}
	287
	288
	289	static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
ca557aff DL	290	long r, rdis0, rpdis0, rdis1, rpdis1;
ca557aff DL	291
9b28d554 DL	292	/*
	293	* Limits the window the is examined during the similar-lines
	294	* scan. The loops below stops when dis[i - r] == 1 (line that
	295	* has no match), but there are corner cases where the loop
	296	* proceed all the way to the extremities by causing huge
	297	* performance penalties in case of big files.
	298	*/
	299	if (i - s > XDL_SIMSCAN_WINDOW)
	300	s = i - XDL_SIMSCAN_WINDOW;
	301	if (e - i > XDL_SIMSCAN_WINDOW)
	302	e = i + XDL_SIMSCAN_WINDOW;
	303
ca557aff DL	304	/*
	305	* Scans the lines before 'i' to find a run of lines that either
	306	* have no match (dis[j] == 0) or have multiple matches (dis[j] > 1).
	307	* Note that we always call this function with dis[i] > 1, so the
	308	* current line (i) is already a multimatch line.
	309	*/
	310	for (r = 1, rdis0 = 0, rpdis0 = 1; (i - r) >= s; r++) {
3443546f	311	if (!dis[i - r])
ca557aff	312	rdis0++;
3443546f	313	else if (dis[i - r] == 2)
ca557aff	314	rpdis0++;
3443546f LT	315	else
	316	break;
	317	}
ca557aff DL	318	/*
	319	* If the run before the line 'i' found only multimatch lines, we
	320	* return 0 and hence we don't make the current line (i) discarded.
	321	* We want to discard multimatch lines only when they appear in the
	322	* middle of runs with nomatch lines (dis[j] == 0).
	323	*/
	324	if (rdis0 == 0)
	325	return 0;
	326	for (r = 1, rdis1 = 0, rpdis1 = 1; (i + r) <= e; r++) {
3443546f	327	if (!dis[i + r])
ca557aff	328	rdis1++;
3443546f	329	else if (dis[i + r] == 2)
ca557aff	330	rpdis1++;
3443546f LT	331	else
	332	break;
	333	}
ca557aff DL	334	/*
	335	* If the run after the line 'i' found only multimatch lines, we
	336	* return 0 and hence we don't make the current line (i) discarded.
	337	*/
	338	if (rdis1 == 0)
	339	return 0;
	340	rdis1 += rdis0;
	341	rpdis1 += rpdis0;
	342
	343	return rpdis1 * XDL_KPDIS_RUN < (rpdis1 + rdis1);
3443546f LT	344	}
	345
	346
	347	/*
	348	* Try to reduce the problem complexity, discard records that have no
	349	* matches on the other file. Also, lines that have multiple matches
	350	* might be potentially discarded if they happear in a run of discardable.
	351	*/
	352	static int xdl_cleanup_records(xdfile_t xdf1, xdfile_t xdf2) {
ca557aff	353	long i, nm, rhi, nreff, mlim;
3443546f LT	354	unsigned long hav;
	355	xrecord_t **recs;
	356	xrecord_t *rec;
	357	char dis, dis1, *dis2;
	358
ca557aff	359	if (!(dis = (char *) xdl_malloc(xdf1->nrec + xdf2->nrec + 2))) {
3443546f LT	360
	361	return -1;
	362	}
ca557aff	363	memset(dis, 0, xdf1->nrec + xdf2->nrec + 2);
3443546f LT	364	dis1 = dis;
	365	dis2 = dis1 + xdf1->nrec + 1;
	366
ca557aff DL	367	if ((mlim = xdl_bogosqrt(xdf1->nrec)) > XDL_MAX_EQLIMIT)
ca557aff DL	368	mlim = XDL_MAX_EQLIMIT;
3443546f LT	369	for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {
	370	hav = (*recs)->ha;
	371	rhi = (long) XDL_HASHLONG(hav, xdf2->hbits);
ca557aff DL	372	for (nm = 0, rec = xdf2->rhash[rhi]; rec; rec = rec->next)
ca557aff DL	373	if (rec->ha == hav && ++nm == mlim)
3443546f	374	break;
ca557aff	375	dis1[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;
3443546f LT	376	}
3443546f LT	377
ca557aff DL	378	if ((mlim = xdl_bogosqrt(xdf2->nrec)) > XDL_MAX_EQLIMIT)
ca557aff DL	379	mlim = XDL_MAX_EQLIMIT;
3443546f LT	380	for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {
	381	hav = (*recs)->ha;
	382	rhi = (long) XDL_HASHLONG(hav, xdf1->hbits);
ca557aff DL	383	for (nm = 0, rec = xdf1->rhash[rhi]; rec; rec = rec->next)
ca557aff DL	384	if (rec->ha == hav && ++nm == mlim)
3443546f	385	break;
ca557aff	386	dis2[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;
3443546f LT	387	}
	388
	389	for (nreff = 0, i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart];
	390	i <= xdf1->dend; i++, recs++) {
	391	if (dis1[i] == 1 \|\|
	392	(dis1[i] == 2 && !xdl_clean_mmatch(dis1, i, xdf1->dstart, xdf1->dend))) {
	393	xdf1->rindex[nreff] = i;
	394	xdf1->ha[nreff] = (*recs)->ha;
	395	nreff++;
	396	} else
	397	xdf1->rchg[i] = 1;
	398	}
	399	xdf1->nreff = nreff;
	400
	401	for (nreff = 0, i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart];
	402	i <= xdf2->dend; i++, recs++) {
	403	if (dis2[i] == 1 \|\|
	404	(dis2[i] == 2 && !xdl_clean_mmatch(dis2, i, xdf2->dstart, xdf2->dend))) {
	405	xdf2->rindex[nreff] = i;
	406	xdf2->ha[nreff] = (*recs)->ha;
	407	nreff++;
	408	} else
	409	xdf2->rchg[i] = 1;
	410	}
	411	xdf2->nreff = nreff;
	412
	413	xdl_free(dis);
	414
	415	return 0;
	416	}
	417
	418
	419	/*
	420	* Early trim initial and terminal matching records.
	421	*/
	422	static int xdl_trim_ends(xdfile_t xdf1, xdfile_t xdf2) {
	423	long i, lim;
	424	xrecord_t recs1, recs2;
	425
	426	recs1 = xdf1->recs;
	427	recs2 = xdf2->recs;
	428	for (i = 0, lim = XDL_MIN(xdf1->nrec, xdf2->nrec); i < lim;
	429	i++, recs1++, recs2++)
	430	if ((recs1)->ha != (recs2)->ha)
	431	break;
	432
	433	xdf1->dstart = xdf2->dstart = i;
	434
	435	recs1 = xdf1->recs + xdf1->nrec - 1;
	436	recs2 = xdf2->recs + xdf2->nrec - 1;
	437	for (lim -= i, i = 0; i < lim; i++, recs1--, recs2--)
	438	if ((recs1)->ha != (recs2)->ha)
	439	break;
	440
	441	xdf1->dend = xdf1->nrec - i - 1;
	442	xdf2->dend = xdf2->nrec - i - 1;
	443
	444	return 0;
	445	}
	446
	447
	448	static int xdl_optimize_ctxs(xdfile_t xdf1, xdfile_t xdf2) {
	449
	450	if (xdl_trim_ends(xdf1, xdf2) < 0 \|\|
451	xdl_cleanup_records(xdf1, xdf2) < 0) {
452
453	return -1;
454	}
455
456	return 0;
457	}