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Diffstat (limited to 'third_party/git/xdiff/xdiffi.c')
| -rw-r--r-- | third_party/git/xdiff/xdiffi.c | 1054 |
1 files changed, 1054 insertions, 0 deletions
diff --git a/third_party/git/xdiff/xdiffi.c b/third_party/git/xdiff/xdiffi.c new file mode 100644 index 000000000000..bd035139f954 --- /dev/null +++ b/third_party/git/xdiff/xdiffi.c @@ -0,0 +1,1054 @@ +/* + * 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, see + * <http://www.gnu.org/licenses/>. + * + * 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; + +/* + * 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 encounter expensive edge cases + * using this algorithm, 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 extend 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 in the 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 extend 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 in the 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 them 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" (divide & conquer). 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; +} + + +static int recs_match(xrecord_t *rec1, xrecord_t *rec2, long flags) +{ + return (rec1->ha == rec2->ha && + xdl_recmatch(rec1->ptr, rec1->size, + rec2->ptr, rec2->size, + flags)); +} + +/* + * If a line is indented more than this, get_indent() just returns this value. + * This avoids having to do absurd amounts of work for data that are not + * human-readable text, and also ensures that the output of get_indent fits + * within an int. + */ +#define MAX_INDENT 200 + +/* + * Return the amount of indentation of the specified line, treating TAB as 8 + * columns. Return -1 if line is empty or contains only whitespace. Clamp the + * output value at MAX_INDENT. + */ +static int get_indent(xrecord_t *rec) +{ + long i; + int ret = 0; + + for (i = 0; i < rec->size; i++) { + char c = rec->ptr[i]; + + if (!XDL_ISSPACE(c)) + return ret; + else if (c == ' ') + ret += 1; + else if (c == '\t') + ret += 8 - ret % 8; + /* ignore other whitespace characters */ + + if (ret >= MAX_INDENT) + return MAX_INDENT; + } + + /* The line contains only whitespace. */ + return -1; +} + +/* + * If more than this number of consecutive blank rows are found, just return + * this value. This avoids requiring O(N^2) work for pathological cases, and + * also ensures that the output of score_split fits in an int. + */ +#define MAX_BLANKS 20 + +/* Characteristics measured about a hypothetical split position. */ +struct split_measurement { + /* + * Is the split at the end of the file (aside from any blank lines)? + */ + int end_of_file; + + /* + * How much is the line immediately following the split indented (or -1 + * if the line is blank): + */ + int indent; + + /* + * How many consecutive lines above the split are blank? + */ + int pre_blank; + + /* + * How much is the nearest non-blank line above the split indented (or + * -1 if there is no such line)? + */ + int pre_indent; + + /* + * How many lines after the line following the split are blank? + */ + int post_blank; + + /* + * How much is the nearest non-blank line after the line following the + * split indented (or -1 if there is no such line)? + */ + int post_indent; +}; + +struct split_score { + /* The effective indent of this split (smaller is preferred). */ + int effective_indent; + + /* Penalty for this split (smaller is preferred). */ + int penalty; +}; + +/* + * Fill m with information about a hypothetical split of xdf above line split. + */ +static void measure_split(const xdfile_t *xdf, long split, + struct split_measurement *m) +{ + long i; + + if (split >= xdf->nrec) { + m->end_of_file = 1; + m->indent = -1; + } else { + m->end_of_file = 0; + m->indent = get_indent(xdf->recs[split]); + } + + m->pre_blank = 0; + m->pre_indent = -1; + for (i = split - 1; i >= 0; i--) { + m->pre_indent = get_indent(xdf->recs[i]); + if (m->pre_indent != -1) + break; + m->pre_blank += 1; + if (m->pre_blank == MAX_BLANKS) { + m->pre_indent = 0; + break; + } + } + + m->post_blank = 0; + m->post_indent = -1; + for (i = split + 1; i < xdf->nrec; i++) { + m->post_indent = get_indent(xdf->recs[i]); + if (m->post_indent != -1) + break; + m->post_blank += 1; + if (m->post_blank == MAX_BLANKS) { + m->post_indent = 0; + break; + } + } +} + +/* + * The empirically-determined weight factors used by score_split() below. + * Larger values means that the position is a less favorable place to split. + * + * Note that scores are only ever compared against each other, so multiplying + * all of these weight/penalty values by the same factor wouldn't change the + * heuristic's behavior. Still, we need to set that arbitrary scale *somehow*. + * In practice, these numbers are chosen to be large enough that they can be + * adjusted relative to each other with sufficient precision despite using + * integer math. + */ + +/* Penalty if there are no non-blank lines before the split */ +#define START_OF_FILE_PENALTY 1 + +/* Penalty if there are no non-blank lines after the split */ +#define END_OF_FILE_PENALTY 21 + +/* Multiplier for the number of blank lines around the split */ +#define TOTAL_BLANK_WEIGHT (-30) + +/* Multiplier for the number of blank lines after the split */ +#define POST_BLANK_WEIGHT 6 + +/* + * Penalties applied if the line is indented more than its predecessor + */ +#define RELATIVE_INDENT_PENALTY (-4) +#define RELATIVE_INDENT_WITH_BLANK_PENALTY 10 + +/* + * Penalties applied if the line is indented less than both its predecessor and + * its successor + */ +#define RELATIVE_OUTDENT_PENALTY 24 +#define RELATIVE_OUTDENT_WITH_BLANK_PENALTY 17 + +/* + * Penalties applied if the line is indented less than its predecessor but not + * less than its successor + */ +#define RELATIVE_DEDENT_PENALTY 23 +#define RELATIVE_DEDENT_WITH_BLANK_PENALTY 17 + +/* + * We only consider whether the sum of the effective indents for splits are + * less than (-1), equal to (0), or greater than (+1) each other. The resulting + * value is multiplied by the following weight and combined with the penalty to + * determine the better of two scores. + */ +#define INDENT_WEIGHT 60 + +/* + * How far do we slide a hunk at most? + */ +#define INDENT_HEURISTIC_MAX_SLIDING 100 + +/* + * Compute a badness score for the hypothetical split whose measurements are + * stored in m. The weight factors were determined empirically using the tools + * and corpus described in + * + * https://github.com/mhagger/diff-slider-tools + * + * Also see that project if you want to improve the weights based on, for + * example, a larger or more diverse corpus. + */ +static void score_add_split(const struct split_measurement *m, struct split_score *s) +{ + /* + * A place to accumulate penalty factors (positive makes this index more + * favored): + */ + int post_blank, total_blank, indent, any_blanks; + + if (m->pre_indent == -1 && m->pre_blank == 0) + s->penalty += START_OF_FILE_PENALTY; + + if (m->end_of_file) + s->penalty += END_OF_FILE_PENALTY; + + /* + * Set post_blank to the number of blank lines following the split, + * including the line immediately after the split: + */ + post_blank = (m->indent == -1) ? 1 + m->post_blank : 0; + total_blank = m->pre_blank + post_blank; + + /* Penalties based on nearby blank lines: */ + s->penalty += TOTAL_BLANK_WEIGHT * total_blank; + s->penalty += POST_BLANK_WEIGHT * post_blank; + + if (m->indent != -1) + indent = m->indent; + else + indent = m->post_indent; + + any_blanks = (total_blank != 0); + + /* Note that the effective indent is -1 at the end of the file: */ + s->effective_indent += indent; + + if (indent == -1) { + /* No additional adjustments needed. */ + } else if (m->pre_indent == -1) { + /* No additional adjustments needed. */ + } else if (indent > m->pre_indent) { + /* + * The line is indented more than its predecessor. + */ + s->penalty += any_blanks ? + RELATIVE_INDENT_WITH_BLANK_PENALTY : + RELATIVE_INDENT_PENALTY; + } else if (indent == m->pre_indent) { + /* + * The line has the same indentation level as its predecessor. + * No additional adjustments needed. + */ + } else { + /* + * The line is indented less than its predecessor. It could be + * the block terminator of the previous block, but it could + * also be the start of a new block (e.g., an "else" block, or + * maybe the previous block didn't have a block terminator). + * Try to distinguish those cases based on what comes next: + */ + if (m->post_indent != -1 && m->post_indent > indent) { + /* + * The following line is indented more. So it is likely + * that this line is the start of a block. + */ + s->penalty += any_blanks ? + RELATIVE_OUTDENT_WITH_BLANK_PENALTY : + RELATIVE_OUTDENT_PENALTY; + } else { + /* + * That was probably the end of a block. + */ + s->penalty += any_blanks ? + RELATIVE_DEDENT_WITH_BLANK_PENALTY : + RELATIVE_DEDENT_PENALTY; + } + } +} + +static int score_cmp(struct split_score *s1, struct split_score *s2) +{ + /* -1 if s1.effective_indent < s2->effective_indent, etc. */ + int cmp_indents = ((s1->effective_indent > s2->effective_indent) - + (s1->effective_indent < s2->effective_indent)); + + return INDENT_WEIGHT * cmp_indents + (s1->penalty - s2->penalty); +} + +/* + * Represent a group of changed lines in an xdfile_t (i.e., a contiguous group + * of lines that was inserted or deleted from the corresponding version of the + * file). We consider there to be such a group at the beginning of the file, at + * the end of the file, and between any two unchanged lines, though most such + * groups will usually be empty. + * + * If the first line in a group is equal to the line following the group, then + * the group can be slid down. Similarly, if the last line in a group is equal + * to the line preceding the group, then the group can be slid up. See + * group_slide_down() and group_slide_up(). + * + * Note that loops that are testing for changed lines in xdf->rchg do not need + * index bounding since the array is prepared with a zero at position -1 and N. + */ +struct xdlgroup { + /* + * The index of the first changed line in the group, or the index of + * the unchanged line above which the (empty) group is located. + */ + long start; + + /* + * The index of the first unchanged line after the group. For an empty + * group, end is equal to start. + */ + long end; +}; + +/* + * Initialize g to point at the first group in xdf. + */ +static void group_init(xdfile_t *xdf, struct xdlgroup *g) +{ + g->start = g->end = 0; + while (xdf->rchg[g->end]) + g->end++; +} + +/* + * Move g to describe the next (possibly empty) group in xdf and return 0. If g + * is already at the end of the file, do nothing and return -1. + */ +static inline int group_next(xdfile_t *xdf, struct xdlgroup *g) +{ + if (g->end == xdf->nrec) + return -1; + + g->start = g->end + 1; + for (g->end = g->start; xdf->rchg[g->end]; g->end++) + ; + + return 0; +} + +/* + * Move g to describe the previous (possibly empty) group in xdf and return 0. + * If g is already at the beginning of the file, do nothing and return -1. + */ +static inline int group_previous(xdfile_t *xdf, struct xdlgroup *g) +{ + if (g->start == 0) + return -1; + + g->end = g->start - 1; + for (g->start = g->end; xdf->rchg[g->start - 1]; g->start--) + ; + + return 0; +} + +/* + * If g can be slid toward the end of the file, do so, and if it bumps into a + * following group, expand this group to include it. Return 0 on success or -1 + * if g cannot be slid down. + */ +static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g, long flags) +{ + if (g->end < xdf->nrec && + recs_match(xdf->recs[g->start], xdf->recs[g->end], flags)) { + xdf->rchg[g->start++] = 0; + xdf->rchg[g->end++] = 1; + + while (xdf->rchg[g->end]) + g->end++; + + return 0; + } else { + return -1; + } +} + +/* + * If g can be slid toward the beginning of the file, do so, and if it bumps + * into a previous group, expand this group to include it. Return 0 on success + * or -1 if g cannot be slid up. + */ +static int group_slide_up(xdfile_t *xdf, struct xdlgroup *g, long flags) +{ + if (g->start > 0 && + recs_match(xdf->recs[g->start - 1], xdf->recs[g->end - 1], flags)) { + xdf->rchg[--g->start] = 1; + xdf->rchg[--g->end] = 0; + + while (xdf->rchg[g->start - 1]) + g->start--; + + return 0; + } else { + return -1; + } +} + +static void xdl_bug(const char *msg) +{ + fprintf(stderr, "BUG: %s\n", msg); + exit(1); +} + +/* + * Move back and forward change groups for a consistent and pretty diff output. + * This also helps in finding joinable change groups and reducing the diff + * size. + */ +int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) { + struct xdlgroup g, go; + long earliest_end, end_matching_other; + long groupsize; + + group_init(xdf, &g); + group_init(xdfo, &go); + + while (1) { + /* + * If the group is empty in the to-be-compacted file, skip it: + */ + if (g.end == g.start) + goto next; + + /* + * Now shift the change up and then down as far as possible in + * each direction. If it bumps into any other changes, merge + * them. + */ + do { + groupsize = g.end - g.start; + + /* + * Keep track of the last "end" index that causes this + * group to align with a group of changed lines in the + * other file. -1 indicates that we haven't found such + * a match yet: + */ + end_matching_other = -1; + + /* Shift the group backward as much as possible: */ + while (!group_slide_up(xdf, &g, flags)) + if (group_previous(xdfo, &go)) + xdl_bug("group sync broken sliding up"); + + /* + * This is this highest that this group can be shifted. + * Record its end index: + */ + earliest_end = g.end; + + if (go.end > go.start) + end_matching_other = g.end; + + /* Now shift the group forward as far as possible: */ + while (1) { + if (group_slide_down(xdf, &g, flags)) + break; + if (group_next(xdfo, &go)) + xdl_bug("group sync broken sliding down"); + + if (go.end > go.start) + end_matching_other = g.end; + } + } while (groupsize != g.end - g.start); + + /* + * If the group can be shifted, then we can possibly use this + * freedom to produce a more intuitive diff. + * + * The group is currently shifted as far down as possible, so + * the heuristics below only have to handle upwards shifts. + */ + + if (g.end == earliest_end) { + /* no shifting was possible */ + } else if (end_matching_other != -1) { + /* + * Move the possibly merged group of changes back to + * line up with the last group of changes from the + * other file that it can align with. + */ + while (go.end == go.start) { + if (group_slide_up(xdf, &g, flags)) + xdl_bug("match disappeared"); + if (group_previous(xdfo, &go)) + xdl_bug("group sync broken sliding to match"); + } + } else if (flags & XDF_INDENT_HEURISTIC) { + /* + * Indent heuristic: a group of pure add/delete lines + * implies two splits, one between the end of the + * "before" context and the start of the group, and + * another between the end of the group and the + * beginning of the "after" context. Some splits are + * aesthetically better and some are worse. We compute + * a badness "score" for each split, and add the scores + * for the two splits to define a "score" for each + * position that the group can be shifted to. Then we + * pick the shift with the lowest score. + */ + long shift, best_shift = -1; + struct split_score best_score; + + shift = earliest_end; + if (g.end - groupsize - 1 > shift) + shift = g.end - groupsize - 1; + if (g.end - INDENT_HEURISTIC_MAX_SLIDING > shift) + shift = g.end - INDENT_HEURISTIC_MAX_SLIDING; + for (; shift <= g.end; shift++) { + struct split_measurement m; + struct split_score score = {0, 0}; + + measure_split(xdf, shift, &m); + score_add_split(&m, &score); + measure_split(xdf, shift - groupsize, &m); + score_add_split(&m, &score); + if (best_shift == -1 || + score_cmp(&score, &best_score) <= 0) { + best_score.effective_indent = score.effective_indent; + best_score.penalty = score.penalty; + best_shift = shift; + } + } + + while (g.end > best_shift) { + if (group_slide_up(xdf, &g, flags)) + xdl_bug("best shift unreached"); + if (group_previous(xdfo, &go)) + xdl_bug("group sync broken sliding to blank line"); + } + } + + next: + /* Move past the just-processed group: */ + if (group_next(xdf, &g)) + break; + if (group_next(xdfo, &go)) + xdl_bug("group sync broken moving to next group"); + } + + if (!group_next(xdfo, &go)) + xdl_bug("group sync broken at end of file"); + + 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; +} |