view mercurial/thirdparty/xdiff/xprepare.c @ 46335:25be21ec6c65

share: rework config options to be much clearer and easier

Recently I implemented various boolean configs which control how to behave when
there is a share-safe mismatch between source and share repository. Mismatch
means that source supports share-safe where as share does not or vice versa.

However, while discussion and documentation we realized that it's too
complicated and there are some combinations of values which makes no sense.

We decided to introduce a config option with 4 possible values which
makes controlling and understanding things easier.

The config option `share.safe-mismatch.source-{not-}safe` can have
following 4 values:

* abort (default): error out if there is mismatch
* allow: allow to work with respecting share source configuration
* {up|down}grade-abort: try to {up|down}grade, if it fails, abort
* {up|down}grade-allow: try to {up|down}grade, if it fails, continue in allow
mode


I am not sure if I can explain 3 config options which I deleted right now in
just 5 lines which is a sign of how complex they became.

No test changes demonstrate that functionality is same, only names have changed.

Differential Revision: https://phab.mercurial-scm.org/D9785

/*
 *  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, see
 *  <http://www.gnu.org/licenses/>.
 *
 *  Davide Libenzi <[e-mail]>
 *
 */

#include "xinclude.h"


#define XDL_KPDIS_RUN 4
#define XDL_MAX_EQLIMIT 1024
#define XDL_SIMSCAN_WINDOW 100
#define XDL_GUESS_NLINES1 256


typedef struct s_xdlclass {
	struct s_xdlclass *next;
	uint64_t ha;
	char const *line;
	int64_t size;
	int64_t idx;
	int64_t len1, len2;
} xdlclass_t;

typedef struct s_xdlclassifier {
	unsigned int hbits;
	int64_t hsize;
	xdlclass_t **rchash;
	chastore_t ncha;
	xdlclass_t **rcrecs;
	int64_t alloc;
	int64_t count;
	int64_t flags;
} xdlclassifier_t;




static int xdl_init_classifier(xdlclassifier_t *cf, int64_t size, int64_t flags);
static void xdl_free_classifier(xdlclassifier_t *cf);
static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t **rhash,
			       unsigned int hbits, xrecord_t *rec);
static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, int64_t narec,
			   xdlclassifier_t *cf, xdfile_t *xdf);
static void xdl_free_ctx(xdfile_t *xdf);
static int xdl_clean_mmatch(char const *dis, int64_t i, int64_t s, int64_t e);
static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2);




static int xdl_init_classifier(xdlclassifier_t *cf, int64_t size, int64_t flags) {
	cf->flags = flags;

	cf->hbits = xdl_hashbits(size);
	cf->hsize = ((uint64_t)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->alloc = size;
	if (!(cf->rcrecs = (xdlclass_t **) xdl_malloc(cf->alloc * sizeof(xdlclass_t *)))) {

		xdl_free(cf->rchash);
		xdl_cha_free(&cf->ncha);
		return -1;
	}

	cf->count = 0;

	return 0;
}


static void xdl_free_classifier(xdlclassifier_t *cf) {

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


static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t **rhash,
			       unsigned int hbits, xrecord_t *rec) {
	int64_t hi;
	char const *line;
	xdlclass_t *rcrec;
	xdlclass_t **rcrecs;

	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))
			break;

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

			return -1;
		}
		rcrec->idx = cf->count++;
		if (cf->count > cf->alloc) {
			cf->alloc *= 2;
			if (!(rcrecs = (xdlclass_t **) xdl_realloc(cf->rcrecs, cf->alloc * sizeof(xdlclass_t *)))) {

				return -1;
			}
			cf->rcrecs = rcrecs;
		}
		cf->rcrecs[rcrec->idx] = rcrec;
		rcrec->line = line;
		rcrec->size = rec->size;
		rcrec->ha = rec->ha;
		rcrec->len1 = rcrec->len2 = 0;
		rcrec->next = cf->rchash[hi];
		cf->rchash[hi] = rcrec;
	}

	(pass == 1) ? rcrec->len1++ : rcrec->len2++;

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

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

	return 0;
}


/*
 * Trim common prefix from files.
 *
 * Note: trimming could affect hunk shifting. But the performance benefit
 * outweighs the shift change. A diff result with suboptimal shifting is still
 * valid.
 */
static void xdl_trim_files(mmfile_t *mf1, mmfile_t *mf2, int64_t reserved,
		xdfenv_t *xe, mmfile_t *out_mf1, mmfile_t *out_mf2) {
	mmfile_t msmall, mlarge;
	/* prefix lines, prefix bytes, suffix lines, suffix bytes */
	int64_t plines = 0, pbytes = 0, slines = 0, sbytes = 0, i;
	/* prefix char pointer for msmall and mlarge */
	const char *pp1, *pp2;
	/* suffix char pointer for msmall and mlarge */
	const char *ps1, *ps2;

	/* reserved must >= 0 for the line boundary adjustment to work */
	if (reserved < 0)
		reserved = 0;

	if (mf1->size < mf2->size) {
		memcpy(&msmall, mf1, sizeof(mmfile_t));
		memcpy(&mlarge, mf2, sizeof(mmfile_t));
	} else {
		memcpy(&msmall, mf2, sizeof(mmfile_t));
		memcpy(&mlarge, mf1, sizeof(mmfile_t));
	}

	pp1 = msmall.ptr, pp2 = mlarge.ptr;
	for (i = 0; i < msmall.size && *pp1 == *pp2; ++i) {
		plines += (*pp1 == '\n');
		pp1++, pp2++;
	}

	ps1 = msmall.ptr + msmall.size - 1, ps2 = mlarge.ptr + mlarge.size - 1;
	while (ps1 > pp1 && *ps1 == *ps2) {
		slines += (*ps1 == '\n');
		ps1--, ps2--;
	}

	/* Retract common prefix and suffix boundaries for reserved lines */
	if (plines <= reserved + 1) {
		plines = 0;
	} else {
		i = 0;
		while (i <= reserved) {
			pp1--;
			i += (*pp1 == '\n');
		}
		/* The new mmfile starts at the next char just after '\n' */
		pbytes = pp1 - msmall.ptr + 1;
		plines -= reserved;
	}

	if (slines <= reserved + 1) {
		slines = 0;
	} else {
		/* Note: with compiler SIMD support (ex. -O3 -mavx2), this
		 * might perform better than memchr. */
		i = 0;
		while (i <= reserved) {
			ps1++;
			i += (*ps1 == '\n');
		}
		/* The new mmfile includes this '\n' */
		sbytes = msmall.ptr + msmall.size - ps1 - 1;
		slines -= reserved;
		if (msmall.ptr[msmall.size - 1] == '\n')
			slines -= 1;
	}

	xe->nprefix = plines;
	xe->nsuffix = slines;
	out_mf1->ptr = mf1->ptr + pbytes;
	out_mf1->size = mf1->size - pbytes - sbytes;
	out_mf2->ptr = mf2->ptr + pbytes;
	out_mf2->size = mf2->size - pbytes - sbytes;
}


static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, int64_t narec,
			   xdlclassifier_t *cf, xdfile_t *xdf) {
	unsigned int hbits;
	int64_t nrec, hsize, bsize;
	uint64_t hav;
	char const *blk, *cur, *top, *prev;
	xrecord_t *crec;
	xrecord_t **recs, **rrecs;
	xrecord_t **rhash;
	uint64_t *ha;
	char *rchg;
	int64_t *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;

	{
		hbits = xdl_hashbits(narec);
		hsize = ((uint64_t)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; cur < top; ) {
			prev = cur;
			hav = xdl_hash_record(&cur, top);
			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 (xdl_classify_record(pass, 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 = (int64_t *) xdl_malloc((nrec + 1) * sizeof(int64_t))))
		goto abort;
	if (!(ha = (uint64_t *) xdl_malloc((nrec + 1) * sizeof(uint64_t))))
		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);
}

/* Reserved lines for trimming, to leave room for shifting */
#define TRIM_RESERVED_LINES 100

int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
		    xdfenv_t *xe) {
	int64_t enl1, enl2, sample;
	mmfile_t tmf1, tmf2;
	xdlclassifier_t cf;

	memset(&cf, 0, sizeof(cf));

	sample = XDL_GUESS_NLINES1;

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

	if (xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
		return -1;

	xdl_trim_files(mf1, mf2, TRIM_RESERVED_LINES, xe, &tmf1, &tmf2);

	if (xdl_prepare_ctx(1, &tmf1, enl1, &cf, &xe->xdf1) < 0) {

		xdl_free_classifier(&cf);
		return -1;
	}
	if (xdl_prepare_ctx(2, &tmf2, enl2, &cf, &xe->xdf2) < 0) {

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

	if (xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {
		xdl_free_ctx(&xe->xdf2);
		xdl_free_ctx(&xe->xdf1);
		xdl_free_classifier(&cf);
		return -1;
	}

	xdl_free_classifier(&cf);

	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, int64_t i, int64_t s, int64_t e) {
	int64_t 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(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {
	int64_t i, nm, nreff, mlim;
	xrecord_t **recs;
	xdlclass_t *rcrec;
	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++) {
		rcrec = cf->rcrecs[(*recs)->ha];
		nm = rcrec ? rcrec->len2 : 0;
		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++) {
		rcrec = cf->rcrecs[(*recs)->ha];
		nm = rcrec ? rcrec->len1 : 0;
		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) {
	int64_t 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(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {

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

		return -1;
	}

	return 0;
}