Add libxdiff library

xdiff/xdiffi.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_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;
+
+        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;
+}