--- /dev/null
+/*
+ * LibXDiff by Davide Libenzi ( File Differential Library )
+ * Copyright (C) 2003-2009 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, 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"
+#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;
+ } *entries, *first, *last;
+ /* were common records found? */
+ unsigned long has_matches;
+ mmfile_t *file1, *file2;
+ xdfenv_t *env;
+ xpparam_t const *xpp;
+};
+
+/* The argument "pass" is 1 for the first file, 2 for the second. */
+static void insert_record(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;
+ 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(line1++, result, 1);
+
+ /* Then search for matches in the second file */
+ while (count2--)
+ insert_record(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) / 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;
+
+ 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];
+ sequence[++i] = entry;
+ 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)
+{
+ /*
+ * This probably does not work outside Git, since
+ * we have a very simple mmfile structure.
+ *
+ * Note: ideally, we would reuse the prepared environment, but
+ * the libxdiff interface does not (yet) allow for diffing only
+ * ranges of lines instead of the whole files.
+ */
+ mmfile_t subfile1, subfile2;
+ xpparam_t xpp;
+ xdfenv_t env;
+
+ subfile1.ptr = (char *)map->env->xdf1.recs[line1 - 1]->ptr;
+ subfile1.size = map->env->xdf1.recs[line1 + count1 - 2]->ptr +
+ map->env->xdf1.recs[line1 + count1 - 2]->size - subfile1.ptr;
+ subfile2.ptr = (char *)map->env->xdf2.recs[line2 - 1]->ptr;
+ subfile2.size = map->env->xdf2.recs[line2 + count2 - 2]->ptr +
+ map->env->xdf2.recs[line2 + count2 - 2]->size - subfile2.ptr;
+ xpp.flags = map->xpp->flags & ~XDF_PATIENCE_DIFF;
+ if (xdl_do_diff(&subfile1, &subfile2, &xpp, &env) < 0)
+ return -1;
+
+ memcpy(map->env->xdf1.rchg + line1 - 1, env.xdf1.rchg, count1);
+ memcpy(map->env->xdf2.rchg + line2 - 1, env.xdf2.rchg, count2);
+
+ xdl_free_env(&env);
+
+ return 0;
+}
+
+/*
+ * 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);
+}