/* * 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 * */ #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; /* * 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 extenal 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 extenal 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 = -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 = 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; } } return -1; } /* * 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; /* * 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; } static int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo) { 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 joineable 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], recs[ix - 1])) { 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], recs[ix])) { 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) < 0 || xdl_change_compact(&xe.xdf2, &xe.xdf1) < 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; }