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-rw-r--r--third_party/git/xdiff/xpatience.c388
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diff --git a/third_party/git/xdiff/xpatience.c b/third_party/git/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"
-
-/*
- * 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)
-{
-	int 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;
-
-	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);
-}