mergecopies: invoke _computenonoverlap for both base and tca during merges
The algorithm of _checkcopies can only walk backwards in the DAG, never
forward. Because of this, the two _checkcopies patches need to run from
their respective endpoints to the TCA to cover the entire subgraph where
the merge is being performed. However, detection of files new in both
endpoints, as well as directory rename detection, need to run with respect
to the merge base, so we need lists of new files both from the TCA's and
the merge base's viewpoint to correctly detect renames in a graft-like
merge scenario.
(Series reworked by Pierre-Yves David)
/*
bdiff.c - efficient binary diff extension for Mercurial
Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
This software may be used and distributed according to the terms of
the GNU General Public License, incorporated herein by reference.
Based roughly on Python difflib
*/
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include "compat.h"
#include "bitmanipulation.h"
#include "bdiff.h"
struct pos {
int pos, len;
};
int bdiff_splitlines(const char *a, ssize_t len, struct bdiff_line **lr)
{
unsigned hash;
int i;
const char *p, *b = a;
const char * const plast = a + len - 1;
struct bdiff_line *l;
/* count the lines */
i = 1; /* extra line for sentinel */
for (p = a; p < a + len; p++)
if (*p == '\n' || p == plast)
i++;
*lr = l = (struct bdiff_line *)malloc(sizeof(struct bdiff_line) * i);
if (!l)
return -1;
/* build the line array and calculate hashes */
hash = 0;
for (p = a; p < a + len; p++) {
/* Leonid Yuriev's hash */
hash = (hash * 1664525) + (unsigned char)*p + 1013904223;
if (*p == '\n' || p == plast) {
l->hash = hash;
hash = 0;
l->len = p - b + 1;
l->l = b;
l->n = INT_MAX;
l++;
b = p + 1;
}
}
/* set up a sentinel */
l->hash = 0;
l->len = 0;
l->l = a + len;
return i - 1;
}
static inline int cmp(struct bdiff_line *a, struct bdiff_line *b)
{
return a->hash != b->hash || a->len != b->len || memcmp(a->l, b->l, a->len);
}
static int equatelines(struct bdiff_line *a, int an, struct bdiff_line *b,
int bn)
{
int i, j, buckets = 1, t, scale;
struct pos *h = NULL;
/* build a hash table of the next highest power of 2 */
while (buckets < bn + 1)
buckets *= 2;
/* try to allocate a large hash table to avoid collisions */
for (scale = 4; scale; scale /= 2) {
h = (struct pos *)malloc(scale * buckets * sizeof(struct pos));
if (h)
break;
}
if (!h)
return 0;
buckets = buckets * scale - 1;
/* clear the hash table */
for (i = 0; i <= buckets; i++) {
h[i].pos = -1;
h[i].len = 0;
}
/* add lines to the hash table chains */
for (i = 0; i < bn; i++) {
/* find the equivalence class */
for (j = b[i].hash & buckets; h[j].pos != -1;
j = (j + 1) & buckets)
if (!cmp(b + i, b + h[j].pos))
break;
/* add to the head of the equivalence class */
b[i].n = h[j].pos;
b[i].e = j;
h[j].pos = i;
h[j].len++; /* keep track of popularity */
}
/* compute popularity threshold */
t = (bn >= 31000) ? bn / 1000 : 1000000 / (bn + 1);
/* match items in a to their equivalence class in b */
for (i = 0; i < an; i++) {
/* find the equivalence class */
for (j = a[i].hash & buckets; h[j].pos != -1;
j = (j + 1) & buckets)
if (!cmp(a + i, b + h[j].pos))
break;
a[i].e = j; /* use equivalence class for quick compare */
if (h[j].len <= t)
a[i].n = h[j].pos; /* point to head of match list */
else
a[i].n = -1; /* too popular */
}
/* discard hash tables */
free(h);
return 1;
}
static int longest_match(struct bdiff_line *a, struct bdiff_line *b,
struct pos *pos,
int a1, int a2, int b1, int b2, int *omi, int *omj)
{
int mi = a1, mj = b1, mk = 0, i, j, k, half;
/* window our search on large regions to better bound
worst-case performance. by choosing a window at the end, we
reduce skipping overhead on the b chains. */
if (a2 - a1 > 30000)
a1 = a2 - 30000;
half = (a1 + a2) / 2;
for (i = a1; i < a2; i++) {
/* skip all lines in b after the current block */
for (j = a[i].n; j >= b2; j = b[j].n)
;
/* loop through all lines match a[i] in b */
for (; j >= b1; j = b[j].n) {
/* does this extend an earlier match? */
for (k = 1; j - k >= b1 && i - k >= a1; k++) {
/* reached an earlier match? */
if (pos[j - k].pos == i - k) {
k += pos[j - k].len;
break;
}
/* previous line mismatch? */
if (a[i - k].e != b[j - k].e)
break;
}
pos[j].pos = i;
pos[j].len = k;
/* best match so far? we prefer matches closer
to the middle to balance recursion */
if (k > mk || (k == mk && (i <= mi || i < half))) {
mi = i;
mj = j;
mk = k;
}
}
}
if (mk) {
mi = mi - mk + 1;
mj = mj - mk + 1;
}
/* expand match to include subsequent popular lines */
while (mi + mk < a2 && mj + mk < b2 &&
a[mi + mk].e == b[mj + mk].e)
mk++;
*omi = mi;
*omj = mj;
return mk;
}
static struct bdiff_hunk *recurse(struct bdiff_line *a, struct bdiff_line *b,
struct pos *pos,
int a1, int a2, int b1, int b2, struct bdiff_hunk *l)
{
int i, j, k;
while (1) {
/* find the longest match in this chunk */
k = longest_match(a, b, pos, a1, a2, b1, b2, &i, &j);
if (!k)
return l;
/* and recurse on the remaining chunks on either side */
l = recurse(a, b, pos, a1, i, b1, j, l);
if (!l)
return NULL;
l->next = (struct bdiff_hunk *)malloc(sizeof(struct bdiff_hunk));
if (!l->next)
return NULL;
l = l->next;
l->a1 = i;
l->a2 = i + k;
l->b1 = j;
l->b2 = j + k;
l->next = NULL;
/* tail-recursion didn't happen, so do equivalent iteration */
a1 = i + k;
b1 = j + k;
}
}
int bdiff_diff(struct bdiff_line *a, int an, struct bdiff_line *b,
int bn, struct bdiff_hunk *base)
{
struct bdiff_hunk *curr;
struct pos *pos;
int t, count = 0;
/* allocate and fill arrays */
t = equatelines(a, an, b, bn);
pos = (struct pos *)calloc(bn ? bn : 1, sizeof(struct pos));
if (pos && t) {
/* generate the matching block list */
curr = recurse(a, b, pos, 0, an, 0, bn, base);
if (!curr)
return -1;
/* sentinel end hunk */
curr->next = (struct bdiff_hunk *)malloc(sizeof(struct bdiff_hunk));
if (!curr->next)
return -1;
curr = curr->next;
curr->a1 = curr->a2 = an;
curr->b1 = curr->b2 = bn;
curr->next = NULL;
}
free(pos);
/* normalize the hunk list, try to push each hunk towards the end */
for (curr = base->next; curr; curr = curr->next) {
struct bdiff_hunk *next = curr->next;
if (!next)
break;
if (curr->a2 == next->a1 || curr->b2 == next->b1)
while (curr->a2 < an && curr->b2 < bn
&& next->a1 < next->a2
&& next->b1 < next->b2
&& !cmp(a + curr->a2, b + curr->b2)) {
curr->a2++;
next->a1++;
curr->b2++;
next->b1++;
}
}
for (curr = base->next; curr; curr = curr->next)
count++;
return count;
}
void bdiff_freehunks(struct bdiff_hunk *l)
{
struct bdiff_hunk *n;
for (; l; l = n) {
n = l->next;
free(l);
}
}