text: /*
   *  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_MAX_COST_MIN 256
  #define XDL_HEUR_MIN_COST 256
  #define XDL_LINE_MAX (long)((1UL << (CHAR_BIT * sizeof(long) - 1)) - 1)
  #define XDL_SNAKE_CNT 20
  #define XDL_K_HEUR 4
  
  
  
  typedef struct s_xdpsplit {
  	long i1, i2;
  	int min_lo, min_hi;
  } xdpsplit_t;
  
  
  
  
  static long xdl_split(unsigned long const *ha1, long off1, long lim1,
  		      unsigned long const *ha2, long off2, long lim2,
  		      long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
  		      xdalgoenv_t *xenv);
  static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2);
  
  
  
  
  
  /*
   * See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers.
   * Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
   * the forward diagonal starting from (off1, off2) and the backward diagonal
   * starting from (lim1, lim2). If the K values on the same diagonal crosses
   * returns the furthest point of reach. We might end up having to expensive
   * cases using this algorithm is full, so a little bit of heuristic is needed
   * to cut the search and to return a suboptimal point.
   */
  static long xdl_split(unsigned long const *ha1, long off1, long lim1,
  		      unsigned long const *ha2, long off2, long lim2,
  		      long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
  		      xdalgoenv_t *xenv) {
  	long dmin = off1 - lim2, dmax = lim1 - off2;
  	long fmid = off1 - off2, bmid = lim1 - lim2;
  	long odd = (fmid - bmid) & 1;
  	long fmin = fmid, fmax = fmid;
  	long bmin = bmid, bmax = bmid;
  	long ec, d, i1, i2, prev1, best, dd, v, k;
  
  	/*
  	 * Set initial diagonal values for both forward and backward path.
  	 */
  	kvdf[fmid] = off1;
  	kvdb[bmid] = lim1;
  
  	for (ec = 1;; ec++) {
  		int got_snake = 0;
  
  		/*
  		 * We need to extent the diagonal "domain" by one. If the next
  		 * values exits the box boundaries we need to change it in the
  		 * opposite direction because (max - min) must be a power of two.
  		 * Also we initialize the external K value to -1 so that we can
  		 * avoid extra conditions check inside the core loop.
  		 */
  		if (fmin > dmin)
  			kvdf[--fmin - 1] = -1;
  		else
  			++fmin;
  		if (fmax < dmax)
  			kvdf[++fmax + 1] = -1;
  		else
  			--fmax;
  
  		for (d = fmax; d >= fmin; d -= 2) {
  			if (kvdf[d - 1] >= kvdf[d + 1])
  				i1 = kvdf[d - 1] + 1;
  			else
  				i1 = kvdf[d + 1];
  			prev1 = i1;
  			i2 = i1 - d;
  			for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++);
  			if (i1 - prev1 > xenv->snake_cnt)
  				got_snake = 1;
  			kvdf[d] = i1;
  			if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) {
  				spl->i1 = i1;
  				spl->i2 = i2;
  				spl->min_lo = spl->min_hi = 1;
  				return ec;
  			}
  		}
  
  		/*
  		 * We need to extent the diagonal "domain" by one. If the next
  		 * values exits the box boundaries we need to change it in the
  		 * opposite direction because (max - min) must be a power of two.
  		 * Also we initialize the external K value to -1 so that we can
  		 * avoid extra conditions check inside the core loop.
  		 */
  		if (bmin > dmin)
  			kvdb[--bmin - 1] = XDL_LINE_MAX;
  		else
  			++bmin;
  		if (bmax < dmax)
  			kvdb[++bmax + 1] = XDL_LINE_MAX;
  		else
  			--bmax;
  
  		for (d = bmax; d >= bmin; d -= 2) {
  			if (kvdb[d - 1] < kvdb[d + 1])
  				i1 = kvdb[d - 1];
  			else
  				i1 = kvdb[d + 1] - 1;
  			prev1 = i1;
  			i2 = i1 - d;
  			for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--);
  			if (prev1 - i1 > xenv->snake_cnt)
  				got_snake = 1;
  			kvdb[d] = i1;
  			if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) {
  				spl->i1 = i1;
  				spl->i2 = i2;
  				spl->min_lo = spl->min_hi = 1;
  				return ec;
  			}
  		}
  
  		if (need_min)
  			continue;
  
  		/*
  		 * If the edit cost is above the heuristic trigger and if
  		 * we got a good snake, we sample current diagonals to see
  		 * if some of the, have reached an "interesting" path. Our
  		 * measure is a function of the distance from the diagonal
  		 * corner (i1 + i2) penalized with the distance from the
  		 * mid diagonal itself. If this value is above the current
  		 * edit cost times a magic factor (XDL_K_HEUR) we consider
  		 * it interesting.
  		 */
  		if (got_snake && ec > xenv->heur_min) {
  			for (best = 0, d = fmax; d >= fmin; d -= 2) {
  				dd = d > fmid ? d - fmid: fmid - d;
  				i1 = kvdf[d];
  				i2 = i1 - d;
  				v = (i1 - off1) + (i2 - off2) - dd;
  
  				if (v > XDL_K_HEUR * ec && v > best &&
  				    off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&
  				    off2 + xenv->snake_cnt <= i2 && i2 < lim2) {
  					for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++)
  						if (k == xenv->snake_cnt) {
  							best = v;
  							spl->i1 = i1;
  							spl->i2 = i2;
  							break;
  						}
  				}
  			}
  			if (best > 0) {
  				spl->min_lo = 1;
  				spl->min_hi = 0;
  				return ec;
  			}
  
  			for (best = 0, d = bmax; d >= bmin; d -= 2) {
  				dd = d > bmid ? d - bmid: bmid - d;
  				i1 = kvdb[d];
  				i2 = i1 - d;
  				v = (lim1 - i1) + (lim2 - i2) - dd;
  
  				if (v > XDL_K_HEUR * ec && v > best &&
  				    off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&
  				    off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {
  					for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++)
  						if (k == xenv->snake_cnt - 1) {
  							best = v;
  							spl->i1 = i1;
  							spl->i2 = i2;
  							break;
  						}
  				}
  			}
  			if (best > 0) {
  				spl->min_lo = 0;
  				spl->min_hi = 1;
  				return ec;
  			}
  		}
  
  		/*
  		 * Enough is enough. We spent too much time here and now we collect
  		 * the furthest reaching path using the (i1 + i2) measure.
  		 */
  		if (ec >= xenv->mxcost) {
  			long fbest, fbest1, bbest, bbest1;
  
  			fbest = fbest1 = -1;
  			for (d = fmax; d >= fmin; d -= 2) {
  				i1 = XDL_MIN(kvdf[d], lim1);
  				i2 = i1 - d;
  				if (lim2 < i2)
  					i1 = lim2 + d, i2 = lim2;
  				if (fbest < i1 + i2) {
  					fbest = i1 + i2;
  					fbest1 = i1;
  				}
  			}
  
  			bbest = bbest1 = XDL_LINE_MAX;
  			for (d = bmax; d >= bmin; d -= 2) {
  				i1 = XDL_MAX(off1, kvdb[d]);
  				i2 = i1 - d;
  				if (i2 < off2)
  					i1 = off2 + d, i2 = off2;
  				if (i1 + i2 < bbest) {
  					bbest = i1 + i2;
  					bbest1 = i1;
  				}
  			}
  
  			if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) {
  				spl->i1 = fbest1;
  				spl->i2 = fbest - fbest1;
  				spl->min_lo = 1;
  				spl->min_hi = 0;
  			} else {
  				spl->i1 = bbest1;
  				spl->i2 = bbest - bbest1;
  				spl->min_lo = 0;
  				spl->min_hi = 1;
  			}
  			return ec;
  		}
  	}
  }
  
  
  /*
   * Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling
   * the box splitting function. Note that the real job (marking changed lines)
   * is done in the two boundary reaching checks.
   */
  int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
  		 diffdata_t *dd2, long off2, long lim2,
  		 long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {
  	unsigned long const *ha1 = dd1->ha, *ha2 = dd2->ha;
  
  	/*
  	 * Shrink the box by walking through each diagonal snake (SW and NE).
  	 */
  	for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++);
  	for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--);
  
  	/*
  	 * If one dimension is empty, then all records on the other one must
  	 * be obviously changed.
  	 */
  	if (off1 == lim1) {
  		char *rchg2 = dd2->rchg;
  		long *rindex2 = dd2->rindex;
  
  		for (; off2 < lim2; off2++)
  			rchg2[rindex2[off2]] = 1;
  	} else if (off2 == lim2) {
  		char *rchg1 = dd1->rchg;
  		long *rindex1 = dd1->rindex;
  
  		for (; off1 < lim1; off1++)
  			rchg1[rindex1[off1]] = 1;
  	} else {
  		xdpsplit_t spl;
  		spl.i1 = spl.i2 = 0;
  
  		/*
  		 * Divide ...
  		 */
  		if (xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,
  			      need_min, &spl, xenv) < 0) {
  
  			return -1;
  		}
  
  		/*
  		 * ... et Impera.
  		 */
  		if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,
  				 kvdf, kvdb, spl.min_lo, xenv) < 0 ||
  		    xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,
  				 kvdf, kvdb, spl.min_hi, xenv) < 0) {
  
  			return -1;
  		}
  	}
  
  	return 0;
  }
  
  
  int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
  		xdfenv_t *xe) {
  	long ndiags;
  	long *kvd, *kvdf, *kvdb;
  	xdalgoenv_t xenv;
  	diffdata_t dd1, dd2;
  
  	if (XDF_DIFF_ALG(xpp->flags) == XDF_PATIENCE_DIFF)
  		return xdl_do_patience_diff(mf1, mf2, xpp, xe);
  
  	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)
  		return xdl_do_histogram_diff(mf1, mf2, xpp, xe);
  
  	if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
  
  		return -1;
  	}
  
  	/*
  	 * Allocate and setup K vectors to be used by the differential algorithm.
  	 * One is to store the forward path and one to store the backward path.
  	 */
  	ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
  	if (!(kvd = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {
  
  		xdl_free_env(xe);
  		return -1;
  	}
  	kvdf = kvd;
  	kvdb = kvdf + ndiags;
  	kvdf += xe->xdf2.nreff + 1;
  	kvdb += xe->xdf2.nreff + 1;
  
  	xenv.mxcost = xdl_bogosqrt(ndiags);
  	if (xenv.mxcost < XDL_MAX_COST_MIN)
  		xenv.mxcost = XDL_MAX_COST_MIN;
  	xenv.snake_cnt = XDL_SNAKE_CNT;
  	xenv.heur_min = XDL_HEUR_MIN_COST;
  
  	dd1.nrec = xe->xdf1.nreff;
  	dd1.ha = xe->xdf1.ha;
  	dd1.rchg = xe->xdf1.rchg;
  	dd1.rindex = xe->xdf1.rindex;
  	dd2.nrec = xe->xdf2.nreff;
  	dd2.ha = xe->xdf2.ha;
  	dd2.rchg = xe->xdf2.rchg;
  	dd2.rindex = xe->xdf2.rindex;
  
  	if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
  			 kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {
  
  		xdl_free(kvd);
  		xdl_free_env(xe);
  		return -1;
  	}
  
  	xdl_free(kvd);
  
  	return 0;
  }
  
  
  static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) {
  	xdchange_t *xch;
  
  	if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
  		return NULL;
  
  	xch->next = xscr;
  	xch->i1 = i1;
  	xch->i2 = i2;
  	xch->chg1 = chg1;
  	xch->chg2 = chg2;
  	xch->ignore = 0;
  
  	return xch;
  }
  
  
  int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
  	long ix, ixo, ixs, ixref, grpsiz, nrec = xdf->nrec;
  	char *rchg = xdf->rchg, *rchgo = xdfo->rchg;
  	xrecord_t **recs = xdf->recs;
  
  	/*
  	 * This is the same of what GNU diff does. Move back and forward
  	 * change groups for a consistent and pretty diff output. This also
  	 * helps in finding joinable change groups and reduce the diff size.
  	 */
  	for (ix = ixo = 0;;) {
  		/*
  		 * Find the first changed line in the to-be-compacted file.
  		 * We need to keep track of both indexes, so if we find a
  		 * changed lines group on the other file, while scanning the
  		 * to-be-compacted file, we need to skip it properly. Note
  		 * that loops that are testing for changed lines on rchg* do
  		 * not need index bounding since the array is prepared with
  		 * a zero at position -1 and N.
  		 */
  		for (; ix < nrec && !rchg[ix]; ix++)
  			while (rchgo[ixo++]);
  		if (ix == nrec)
  			break;
  
  		/*
  		 * Record the start of a changed-group in the to-be-compacted file
  		 * and find the end of it, on both to-be-compacted and other file
  		 * indexes (ix and ixo).
  		 */
  		ixs = ix;
  		for (ix++; rchg[ix]; ix++);
  		for (; rchgo[ixo]; ixo++);
  
  		do {
  			grpsiz = ix - ixs;
  
  			/*
  			 * If the line before the current change group, is equal to
  			 * the last line of the current change group, shift backward
  			 * the group.
  			 */
  			while (ixs > 0 && recs[ixs - 1]->ha == recs[ix - 1]->ha &&
  			       xdl_recmatch(recs[ixs - 1]->ptr, recs[ixs - 1]->size, recs[ix - 1]->ptr, recs[ix - 1]->size, flags)) {
  				rchg[--ixs] = 1;
  				rchg[--ix] = 0;
  
  				/*
  				 * This change might have joined two change groups,
  				 * so we try to take this scenario in account by moving
  				 * the start index accordingly (and so the other-file
  				 * end-of-group index).
  				 */
  				for (; rchg[ixs - 1]; ixs--);
  				while (rchgo[--ixo]);
  			}
  
  			/*
  			 * Record the end-of-group position in case we are matched
  			 * with a group of changes in the other file (that is, the
  			 * change record before the end-of-group index in the other
  			 * file is set).
  			 */
  			ixref = rchgo[ixo - 1] ? ix: nrec;
  
  			/*
  			 * If the first line of the current change group, is equal to
  			 * the line next of the current change group, shift forward
  			 * the group.
  			 */
  			while (ix < nrec && recs[ixs]->ha == recs[ix]->ha &&
  			       xdl_recmatch(recs[ixs]->ptr, recs[ixs]->size, recs[ix]->ptr, recs[ix]->size, flags)) {
  				rchg[ixs++] = 0;
  				rchg[ix++] = 1;
  
  				/*
  				 * This change might have joined two change groups,
  				 * so we try to take this scenario in account by moving
  				 * the start index accordingly (and so the other-file
  				 * end-of-group index). Keep tracking the reference
  				 * index in case we are shifting together with a
  				 * corresponding group of changes in the other file.
  				 */
  				for (; rchg[ix]; ix++);
  				while (rchgo[++ixo])
  					ixref = ix;
  			}
  		} while (grpsiz != ix - ixs);
  
  		/*
  		 * Try to move back the possibly merged group of changes, to match
  		 * the recorded position in the other file.
  		 */
  		while (ixref < ix) {
  			rchg[--ixs] = 1;
  			rchg[--ix] = 0;
  			while (rchgo[--ixo]);
  		}
  	}
  
  	return 0;
  }
  
  
  int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
  	xdchange_t *cscr = NULL, *xch;
  	char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
  	long i1, i2, l1, l2;
  
  	/*
  	 * Trivial. Collects "groups" of changes and creates an edit script.
  	 */
  	for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--)
  		if (rchg1[i1 - 1] || rchg2[i2 - 1]) {
  			for (l1 = i1; rchg1[i1 - 1]; i1--);
  			for (l2 = i2; rchg2[i2 - 1]; i2--);
  
  			if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
  				xdl_free_script(cscr);
  				return -1;
  			}
  			cscr = xch;
  		}
  
  	*xscr = cscr;
  
  	return 0;
  }
  
  
  void xdl_free_script(xdchange_t *xscr) {
  	xdchange_t *xch;
  
  	while ((xch = xscr) != NULL) {
  		xscr = xscr->next;
  		xdl_free(xch);
  	}
  }
  
  static int xdl_call_hunk_func(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
  			      xdemitconf_t const *xecfg)
  {
  	xdchange_t *xch, *xche;
  
  	(void)xe;
  
  	for (xch = xscr; xch; xch = xche->next) {
  		xche = xdl_get_hunk(&xch, xecfg);
  		if (!xch)
  			break;
  		if (xecfg->hunk_func(xch->i1, xche->i1 + xche->chg1 - xch->i1,
  				     xch->i2, xche->i2 + xche->chg2 - xch->i2,
  				     ecb->priv) < 0)
  			return -1;
  	}
  	return 0;
  }
  
  static void xdl_mark_ignorable(xdchange_t *xscr, xdfenv_t *xe, long flags)
  {
  	xdchange_t *xch;
  
  	for (xch = xscr; xch; xch = xch->next) {
  		int ignore = 1;
  		xrecord_t **rec;
  		long i;
  
  		rec = &xe->xdf1.recs[xch->i1];
  		for (i = 0; i < xch->chg1 && ignore; i++)
  			ignore = xdl_blankline(rec[i]->ptr, rec[i]->size, flags);
  
  		rec = &xe->xdf2.recs[xch->i2];
  		for (i = 0; i < xch->chg2 && ignore; i++)
  			ignore = xdl_blankline(rec[i]->ptr, rec[i]->size, flags);
  
  		xch->ignore = ignore;
  	}
  }
  
  int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
  	     xdemitconf_t const *xecfg, xdemitcb_t *ecb) {
  	xdchange_t *xscr;
  	xdfenv_t xe;
  	emit_func_t ef = xecfg->hunk_func ? xdl_call_hunk_func : xdl_emit_diff;
  
  	if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
  
  		return -1;
  	}
  	if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
  	    xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
  	    xdl_build_script(&xe, &xscr) < 0) {
  
  		xdl_free_env(&xe);
  		return -1;
  	}
  	if (xscr) {
  		if (xpp->flags & XDF_IGNORE_BLANK_LINES)
  			xdl_mark_ignorable(xscr, &xe, xpp->flags);
  
  		if (ef(&xe, xscr, ecb, xecfg) < 0) {
  
  			xdl_free_script(xscr);
  			xdl_free_env(&xe);
  			return -1;
  		}
  		xdl_free_script(xscr);
  	}
  	xdl_free_env(&xe);
  
  	return 0;
  }
  