thodg/libgit2/src/xdiff/xprepare.c

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• Hash : 3a5ad90a
  Author :
  Date : 2012-01-24T12:23:20
  

  Import xdiff library from git This is the initial import of the xdiff code (LGPL) from core git as of rev f349b562086e2b7595d8a977d2734ab2ef9e71ef

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• src/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
  #define XDL_GUESS_NLINES1 256
  #define XDL_GUESS_NLINES2 20
  
  
  typedef struct s_xdlclass {
  	struct s_xdlclass *next;
  	unsigned long ha;
  	char const *line;
  	long size;
  	long idx;
  	long len1, len2;
  } xdlclass_t;
  
  typedef struct s_xdlclassifier {
  	unsigned int hbits;
  	long hsize;
  	xdlclass_t **rchash;
  	chastore_t ncha;
  	xdlclass_t **rcrecs;
  	long alloc;
  	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(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, 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(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, 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->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) {
  	long 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, cf->flags))
  			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;
  }
  
  
  static int xdl_prepare_ctx(unsigned int pass, 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; cur < top; ) {
  			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(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 = (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, sample;
  	xdlclassifier_t cf;
  
  	memset(&cf, 0, sizeof(cf));
  
  	/*
  	 * For histogram diff, we can afford a smaller sample size and
  	 * thus a poorer estimate of the number of lines, as the hash
  	 * table (rhash) won't be filled up/grown. The number of lines
  	 * (nrecs) will be updated correctly anyway by
  	 * xdl_prepare_ctx().
  	 */
  	sample = xpp->flags & XDF_HISTOGRAM_DIFF ? XDL_GUESS_NLINES2 : XDL_GUESS_NLINES1;
  
  	enl1 = xdl_guess_lines(mf1, sample) + 1;
  	enl2 = xdl_guess_lines(mf2, sample) + 1;
  
  	if (!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
  		xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0) {
  
  		return -1;
  	}
  
  	if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
  
  		xdl_free_classifier(&cf);
  		return -1;
  	}
  	if (xdl_prepare_ctx(2, mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {
  
  		xdl_free_ctx(&xe->xdf1);
  		xdl_free_classifier(&cf);
  		return -1;
  	}
  
  	if (!(xpp->flags & XDF_PATIENCE_DIFF) &&
  			!(xpp->flags & XDF_HISTOGRAM_DIFF) &&
  			xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {
  
  		xdl_free_ctx(&xe->xdf2);
  		xdl_free_ctx(&xe->xdf1);
  		return -1;
  	}
  
  	if (!(xpp->flags & XDF_HISTOGRAM_DIFF))
  		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, 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(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {
  	long 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) {
  	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(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;
  }
  

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