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-rw-r--r--src/xdiff/xpatience.c393
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diff --git a/src/xdiff/xpatience.c b/src/xdiff/xpatience.c
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-/*
- * LibXDiff by Davide Libenzi ( File Differential Library )
- * Copyright (C) 2003-2016 Davide Libenzi, Johannes E. Schindelin
- *
- * 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"
-#include "xtypes.h"
-#include "xdiff.h"
-
-/*
- * The basic idea of patience diff is to find lines that are unique in
- * both files. These are intuitively the ones that we want to see as
- * common lines.
- *
- * The maximal ordered sequence of such line pairs (where ordered means
- * that the order in the sequence agrees with the order of the lines in
- * both files) naturally defines an initial set of common lines.
- *
- * Now, the algorithm tries to extend the set of common lines by growing
- * the line ranges where the files have identical lines.
- *
- * Between those common lines, the patience diff algorithm is applied
- * recursively, until no unique line pairs can be found; these line ranges
- * are handled by the well-known Myers algorithm.
- */
-
-#define NON_UNIQUE ULONG_MAX
-
-/*
- * This is a hash mapping from line hash to line numbers in the first and
- * second file.
- */
-struct hashmap {
- int nr, alloc;
- struct entry {
- unsigned long hash;
- /*
- * 0 = unused entry, 1 = first line, 2 = second, etc.
- * line2 is NON_UNIQUE if the line is not unique
- * in either the first or the second file.
- */
- unsigned long line1, line2;
- /*
- * "next" & "previous" are used for the longest common
- * sequence;
- * initially, "next" reflects only the order in file1.
- */
- struct entry *next, *previous;
-
- /*
- * If 1, this entry can serve as an anchor. See
- * Documentation/diff-options.txt for more information.
- */
- unsigned anchor : 1;
- } *entries, *first, *last;
- /* were common records found? */
- unsigned long has_matches;
- mmfile_t *file1, *file2;
- xdfenv_t *env;
- xpparam_t const *xpp;
-};
-
-static int is_anchor(xpparam_t const *xpp, const char *line)
-{
- unsigned long i;
- for (i = 0; i < xpp->anchors_nr; i++) {
- if (!strncmp(line, xpp->anchors[i], strlen(xpp->anchors[i])))
- return 1;
- }
- return 0;
-}
-
-/* The argument "pass" is 1 for the first file, 2 for the second. */
-static void insert_record(xpparam_t const *xpp, int line, struct hashmap *map,
- int pass)
-{
- xrecord_t **records = pass == 1 ?
- map->env->xdf1.recs : map->env->xdf2.recs;
- xrecord_t *record = records[line - 1], *other;
- /*
- * After xdl_prepare_env() (or more precisely, due to
- * xdl_classify_record()), the "ha" member of the records (AKA lines)
- * is _not_ the hash anymore, but a linearized version of it. In
- * other words, the "ha" member is guaranteed to start with 0 and
- * the second record's ha can only be 0 or 1, etc.
- *
- * So we multiply ha by 2 in the hope that the hashing was
- * "unique enough".
- */
- int index = (int)((record->ha << 1) % map->alloc);
-
- while (map->entries[index].line1) {
- other = map->env->xdf1.recs[map->entries[index].line1 - 1];
- if (map->entries[index].hash != record->ha ||
- !xdl_recmatch(record->ptr, record->size,
- other->ptr, other->size,
- map->xpp->flags)) {
- if (++index >= map->alloc)
- index = 0;
- continue;
- }
- if (pass == 2)
- map->has_matches = 1;
- if (pass == 1 || map->entries[index].line2)
- map->entries[index].line2 = NON_UNIQUE;
- else
- map->entries[index].line2 = line;
- return;
- }
- if (pass == 2)
- return;
- map->entries[index].line1 = line;
- map->entries[index].hash = record->ha;
- map->entries[index].anchor = is_anchor(xpp, map->env->xdf1.recs[line - 1]->ptr);
- if (!map->first)
- map->first = map->entries + index;
- if (map->last) {
- map->last->next = map->entries + index;
- map->entries[index].previous = map->last;
- }
- map->last = map->entries + index;
- map->nr++;
-}
-
-/*
- * This function has to be called for each recursion into the inter-hunk
- * parts, as previously non-unique lines can become unique when being
- * restricted to a smaller part of the files.
- *
- * It is assumed that env has been prepared using xdl_prepare().
- */
-static int fill_hashmap(mmfile_t *file1, mmfile_t *file2,
- xpparam_t const *xpp, xdfenv_t *env,
- struct hashmap *result,
- int line1, int count1, int line2, int count2)
-{
- result->file1 = file1;
- result->file2 = file2;
- result->xpp = xpp;
- result->env = env;
-
- /* We know exactly how large we want the hash map */
- result->alloc = count1 * 2;
- result->entries = (struct entry *)
- xdl_malloc(result->alloc * sizeof(struct entry));
- if (!result->entries)
- return -1;
- memset(result->entries, 0, result->alloc * sizeof(struct entry));
-
- /* First, fill with entries from the first file */
- while (count1--)
- insert_record(xpp, line1++, result, 1);
-
- /* Then search for matches in the second file */
- while (count2--)
- insert_record(xpp, line2++, result, 2);
-
- return 0;
-}
-
-/*
- * Find the longest sequence with a smaller last element (meaning a smaller
- * line2, as we construct the sequence with entries ordered by line1).
- */
-static int binary_search(struct entry **sequence, int longest,
- struct entry *entry)
-{
- int left = -1, right = longest;
-
- while (left + 1 < right) {
- int middle = left + (right - left) / 2;
- /* by construction, no two entries can be equal */
- if (sequence[middle]->line2 > entry->line2)
- right = middle;
- else
- left = middle;
- }
- /* return the index in "sequence", _not_ the sequence length */
- return left;
-}
-
-/*
- * The idea is to start with the list of common unique lines sorted by
- * the order in file1. For each of these pairs, the longest (partial)
- * sequence whose last element's line2 is smaller is determined.
- *
- * For efficiency, the sequences are kept in a list containing exactly one
- * item per sequence length: the sequence with the smallest last
- * element (in terms of line2).
- */
-static struct entry *find_longest_common_sequence(struct hashmap *map)
-{
- struct entry **sequence = xdl_malloc(map->nr * sizeof(struct entry *));
- int longest = 0, i;
- struct entry *entry;
-
- /*
- * If not -1, this entry in sequence must never be overridden.
- * Therefore, overriding entries before this has no effect, so
- * do not do that either.
- */
- int anchor_i = -1;
-
- if (!sequence)
- return NULL;
-
- for (entry = map->first; entry; entry = entry->next) {
- if (!entry->line2 || entry->line2 == NON_UNIQUE)
- continue;
- i = binary_search(sequence, longest, entry);
- entry->previous = i < 0 ? NULL : sequence[i];
- ++i;
- if (i <= anchor_i)
- continue;
- sequence[i] = entry;
- if (entry->anchor) {
- anchor_i = i;
- longest = anchor_i + 1;
- } else if (i == longest) {
- longest++;
- }
- }
-
- /* No common unique lines were found */
- if (!longest) {
- xdl_free(sequence);
- return NULL;
- }
-
- /* Iterate starting at the last element, adjusting the "next" members */
- entry = sequence[longest - 1];
- entry->next = NULL;
- while (entry->previous) {
- entry->previous->next = entry;
- entry = entry->previous;
- }
- xdl_free(sequence);
- return entry;
-}
-
-static int match(struct hashmap *map, int line1, int line2)
-{
- xrecord_t *record1 = map->env->xdf1.recs[line1 - 1];
- xrecord_t *record2 = map->env->xdf2.recs[line2 - 1];
- return xdl_recmatch(record1->ptr, record1->size,
- record2->ptr, record2->size, map->xpp->flags);
-}
-
-static int patience_diff(mmfile_t *file1, mmfile_t *file2,
- xpparam_t const *xpp, xdfenv_t *env,
- int line1, int count1, int line2, int count2);
-
-static int walk_common_sequence(struct hashmap *map, struct entry *first,
- int line1, int count1, int line2, int count2)
-{
- int end1 = line1 + count1, end2 = line2 + count2;
- int next1, next2;
-
- for (;;) {
- /* Try to grow the line ranges of common lines */
- if (first) {
- next1 = first->line1;
- next2 = first->line2;
- while (next1 > line1 && next2 > line2 &&
- match(map, next1 - 1, next2 - 1)) {
- next1--;
- next2--;
- }
- } else {
- next1 = end1;
- next2 = end2;
- }
- while (line1 < next1 && line2 < next2 &&
- match(map, line1, line2)) {
- line1++;
- line2++;
- }
-
- /* Recurse */
- if (next1 > line1 || next2 > line2) {
- struct hashmap submap;
-
- memset(&submap, 0, sizeof(submap));
- if (patience_diff(map->file1, map->file2,
- map->xpp, map->env,
- line1, next1 - line1,
- line2, next2 - line2))
- return -1;
- }
-
- if (!first)
- return 0;
-
- while (first->next &&
- first->next->line1 == first->line1 + 1 &&
- first->next->line2 == first->line2 + 1)
- first = first->next;
-
- line1 = first->line1 + 1;
- line2 = first->line2 + 1;
-
- first = first->next;
- }
-}
-
-static int fall_back_to_classic_diff(struct hashmap *map,
- int line1, int count1, int line2, int count2)
-{
- xpparam_t xpp;
- xpp.flags = map->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
-
- return xdl_fall_back_diff(map->env, &xpp,
- line1, count1, line2, count2);
-}
-
-/*
- * Recursively find the longest common sequence of unique lines,
- * and if none was found, ask xdl_do_diff() to do the job.
- *
- * This function assumes that env was prepared with xdl_prepare_env().
- */
-static int patience_diff(mmfile_t *file1, mmfile_t *file2,
- xpparam_t const *xpp, xdfenv_t *env,
- int line1, int count1, int line2, int count2)
-{
- struct hashmap map;
- struct entry *first;
- int result = 0;
-
- /* trivial case: one side is empty */
- if (!count1) {
- while(count2--)
- env->xdf2.rchg[line2++ - 1] = 1;
- return 0;
- } else if (!count2) {
- while(count1--)
- env->xdf1.rchg[line1++ - 1] = 1;
- return 0;
- }
-
- memset(&map, 0, sizeof(map));
- if (fill_hashmap(file1, file2, xpp, env, &map,
- line1, count1, line2, count2))
- return -1;
-
- /* are there any matching lines at all? */
- if (!map.has_matches) {
- while(count1--)
- env->xdf1.rchg[line1++ - 1] = 1;
- while(count2--)
- env->xdf2.rchg[line2++ - 1] = 1;
- xdl_free(map.entries);
- return 0;
- }
-
- first = find_longest_common_sequence(&map);
- if (first)
- result = walk_common_sequence(&map, first,
- line1, count1, line2, count2);
- else
- result = fall_back_to_classic_diff(&map,
- line1, count1, line2, count2);
-
- xdl_free(map.entries);
- return result;
-}
-
-int xdl_do_patience_diff(mmfile_t *file1, mmfile_t *file2,
- xpparam_t const *xpp, xdfenv_t *env)
-{
- if (xdl_prepare_env(file1, file2, xpp, env) < 0)
- return -1;
-
- /* environment is cleaned up in xdl_diff() */
- return patience_diff(file1, file2, xpp, env,
- 1, env->xdf1.nrec, 1, env->xdf2.nrec);
-}