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+/*
+ * 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 << (8 * 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 {
+ long ec;
+ xdpsplit_t spl;
+ spl.i1 = spl.i2 = 0;
+
+ /*
+ * Divide ...
+ */
+ if ((ec = 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 (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;
+
+ 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 enf-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 postion 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);
+ }
+}
+
+
+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;
+
+ 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 (xdl_emit_diff(&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;
+}
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