git-commit-vandalism/diffcore-rename.c
Junio C Hamano f0c6b2a2fd [PATCH] Optimize diff-tree -[CM] --stdin
This attempts to optimize "diff-tree -[CM] --stdin", which
compares successible tree pairs.  This optimization does not
make much sense for other commands in the diff-* brothers.

When reading from --stdin and using rename/copy detection, the
patch makes diff-tree to read the current index file first.
This is done to reuse the optimization used by diff-cache in the
non-cached case.  Similarity estimator can avoid expanding a
blob if the index says what is in the work tree has an exact
copy of that blob already expanded.

Another optimization the patch makes is to check only file sizes
first to terminate similarity estimation early.  In order for
this to work, it needs a way to tell the size of the blob
without expanding it.  Since an obvious way of doing it, which
is to keep all the blobs previously used in the memory, is too
costly, it does so by keeping the filesize for each object it
has already seen in memory.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-29 11:17:44 -07:00

376 lines
10 KiB
C

/*
* Copyright (C) 2005 Junio C Hamano
*/
#include "cache.h"
#include "diff.h"
#include "diffcore.h"
#include "delta.h"
#include "count-delta.h"
/* Table of rename/copy destinations */
static struct diff_rename_dst {
struct diff_filespec *two;
struct diff_filepair *pair;
} *rename_dst;
static int rename_dst_nr, rename_dst_alloc;
static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
int insert_ok)
{
int first, last;
first = 0;
last = rename_dst_nr;
while (last > first) {
int next = (last + first) >> 1;
struct diff_rename_dst *dst = &(rename_dst[next]);
int cmp = strcmp(two->path, dst->two->path);
if (!cmp)
return dst;
if (cmp < 0) {
last = next;
continue;
}
first = next+1;
}
/* not found */
if (!insert_ok)
return NULL;
/* insert to make it at "first" */
if (rename_dst_alloc <= rename_dst_nr) {
rename_dst_alloc = alloc_nr(rename_dst_alloc);
rename_dst = xrealloc(rename_dst,
rename_dst_alloc * sizeof(*rename_dst));
}
rename_dst_nr++;
if (first < rename_dst_nr)
memmove(rename_dst + first + 1, rename_dst + first,
(rename_dst_nr - first - 1) * sizeof(*rename_dst));
rename_dst[first].two = two;
rename_dst[first].pair = NULL;
return &(rename_dst[first]);
}
/* Table of rename/copy src files */
static struct diff_rename_src {
struct diff_filespec *one;
unsigned src_stays : 1;
} *rename_src;
static int rename_src_nr, rename_src_alloc;
static struct diff_rename_src *register_rename_src(struct diff_filespec *one,
int src_stays)
{
int first, last;
first = 0;
last = rename_src_nr;
while (last > first) {
int next = (last + first) >> 1;
struct diff_rename_src *src = &(rename_src[next]);
int cmp = strcmp(one->path, src->one->path);
if (!cmp)
return src;
if (cmp < 0) {
last = next;
continue;
}
first = next+1;
}
/* insert to make it at "first" */
if (rename_src_alloc <= rename_src_nr) {
rename_src_alloc = alloc_nr(rename_src_alloc);
rename_src = xrealloc(rename_src,
rename_src_alloc * sizeof(*rename_src));
}
rename_src_nr++;
if (first < rename_src_nr)
memmove(rename_src + first + 1, rename_src + first,
(rename_src_nr - first - 1) * sizeof(*rename_src));
rename_src[first].one = one;
rename_src[first].src_stays = src_stays;
return &(rename_src[first]);
}
static int is_exact_match(struct diff_filespec *src, struct diff_filespec *dst)
{
if (src->sha1_valid && dst->sha1_valid &&
!memcmp(src->sha1, dst->sha1, 20))
return 1;
if (diff_populate_filespec(src, 1) || diff_populate_filespec(dst, 1))
return 0;
if (src->size != dst->size)
return 0;
if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
return 0;
if (src->size == dst->size &&
!memcmp(src->data, dst->data, src->size))
return 1;
return 0;
}
struct diff_score {
int src; /* index in rename_src */
int dst; /* index in rename_dst */
int score;
};
static int estimate_similarity(struct diff_filespec *src,
struct diff_filespec *dst,
int minimum_score)
{
/* src points at a file that existed in the original tree (or
* optionally a file in the destination tree) and dst points
* at a newly created file. They may be quite similar, in which
* case we want to say src is renamed to dst or src is copied into
* dst, and then some edit has been applied to dst.
*
* Compare them and return how similar they are, representing
* the score as an integer between 0 and MAX_SCORE.
*
* When there is an exact match, it is considered a better
* match than anything else; the destination does not even
* call into this function in that case.
*/
void *delta;
unsigned long delta_size, base_size;
int score;
/* We deal only with regular files. Symlink renames are handled
* only when they are exact matches --- in other words, no edits
* after renaming.
*/
if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
return 0;
delta_size = ((src->size < dst->size) ?
(dst->size - src->size) : (src->size - dst->size));
base_size = ((src->size < dst->size) ? src->size : dst->size);
/* We would not consider edits that change the file size so
* drastically. delta_size must be smaller than
* (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
*
* Note that base_size == 0 case is handled here already
* and the final score computation below would not have a
* divide-by-zero issue.
*/
if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
return 0;
if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
return 0; /* error but caught downstream */
delta = diff_delta(src->data, src->size,
dst->data, dst->size,
&delta_size);
/* A delta that has a lot of literal additions would have
* big delta_size no matter what else it does.
*/
if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
return 0;
/* Estimate the edit size by interpreting delta. */
delta_size = count_delta(delta, delta_size);
free(delta);
if (delta_size == UINT_MAX)
return 0;
/*
* Now we will give some score to it. 100% edit gets 0 points
* and 0% edit gets MAX_SCORE points.
*/
score = MAX_SCORE - (MAX_SCORE * delta_size / base_size);
if (score < 0) return 0;
if (MAX_SCORE < score) return MAX_SCORE;
return score;
}
static void record_rename_pair(struct diff_queue_struct *renq,
int dst_index, int src_index, int score)
{
struct diff_filespec *one, *two, *src, *dst;
struct diff_filepair *dp;
if (rename_dst[dst_index].pair)
die("internal error: dst already matched.");
src = rename_src[src_index].one;
one = alloc_filespec(src->path);
fill_filespec(one, src->sha1, src->mode);
dst = rename_dst[dst_index].two;
two = alloc_filespec(dst->path);
fill_filespec(two, dst->sha1, dst->mode);
dp = diff_queue(renq, one, two);
dp->score = score ? : 1; /* make sure it is at least 1 */
dp->source_stays = rename_src[src_index].src_stays;
rename_dst[dst_index].pair = dp;
}
/*
* We sort the rename similarity matrix with the score, in descending
* order (the most similar first).
*/
static int score_compare(const void *a_, const void *b_)
{
const struct diff_score *a = a_, *b = b_;
return b->score - a->score;
}
int diff_scoreopt_parse(const char *opt)
{
int diglen, num, scale, i;
if (opt[0] != '-' || (opt[1] != 'M' && opt[1] != 'C'))
return -1; /* that is not a -M nor -C option */
diglen = strspn(opt+2, "0123456789");
if (diglen == 0 || strlen(opt+2) != diglen)
return 0; /* use default */
sscanf(opt+2, "%d", &num);
for (i = 0, scale = 1; i < diglen; i++)
scale *= 10;
/* user says num divided by scale and we say internally that
* is MAX_SCORE * num / scale.
*/
return MAX_SCORE * num / scale;
}
void diffcore_rename(int detect_rename, int minimum_score)
{
struct diff_queue_struct *q = &diff_queued_diff;
struct diff_queue_struct renq, outq;
struct diff_score *mx;
int i, j;
int num_create, num_src, dst_cnt;
if (!minimum_score)
minimum_score = DEFAULT_MINIMUM_SCORE;
renq.queue = NULL;
renq.nr = renq.alloc = 0;
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
if (!DIFF_FILE_VALID(p->one))
if (!DIFF_FILE_VALID(p->two))
continue; /* unmerged */
else
locate_rename_dst(p->two, 1);
else if (!DIFF_FILE_VALID(p->two))
register_rename_src(p->one, 0);
else if (detect_rename == DIFF_DETECT_COPY)
register_rename_src(p->one, 1);
}
if (rename_dst_nr == 0)
goto cleanup; /* nothing to do */
/* We really want to cull the candidates list early
* with cheap tests in order to avoid doing deltas.
*/
for (i = 0; i < rename_dst_nr; i++) {
struct diff_filespec *two = rename_dst[i].two;
for (j = 0; j < rename_src_nr; j++) {
struct diff_filespec *one = rename_src[j].one;
if (!is_exact_match(one, two))
continue;
record_rename_pair(&renq, i, j, MAX_SCORE);
break; /* we are done with this entry */
}
}
diff_debug_queue("done detecting exact", &renq);
/* Have we run out the created file pool? If so we can avoid
* doing the delta matrix altogether.
*/
if (renq.nr == rename_dst_nr)
goto cleanup;
num_create = (rename_dst_nr - renq.nr);
num_src = rename_src_nr;
mx = xmalloc(sizeof(*mx) * num_create * num_src);
for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
int base = dst_cnt * num_src;
struct diff_filespec *two = rename_dst[i].two;
if (rename_dst[i].pair)
continue; /* dealt with exact match already. */
for (j = 0; j < rename_src_nr; j++) {
struct diff_filespec *one = rename_src[j].one;
struct diff_score *m = &mx[base+j];
m->src = j;
m->dst = i;
m->score = estimate_similarity(one, two,
minimum_score);
}
dst_cnt++;
}
/* cost matrix sorted by most to least similar pair */
qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
for (i = 0; i < num_create * num_src; i++) {
struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
if (dst->pair)
continue; /* already done, either exact or fuzzy. */
if (mx[i].score < minimum_score)
break; /* there is no more usable pair. */
record_rename_pair(&renq, mx[i].dst, mx[i].src, mx[i].score);
}
free(mx);
diff_debug_queue("done detecting fuzzy", &renq);
cleanup:
/* At this point, we have found some renames and copies and they
* are kept in renq. The original list is still in *q.
*/
outq.queue = NULL;
outq.nr = outq.alloc = 0;
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
struct diff_rename_dst *dst = locate_rename_dst(p->two, 0);
struct diff_filepair *pair_to_free = NULL;
if (dst) {
/* creation */
if (dst->pair) {
/* renq has rename/copy to produce
* this file already, so we do not
* emit the creation record in the
* output.
*/
diff_q(&outq, dst->pair);
pair_to_free = p;
}
else
/* no matching rename/copy source, so record
* this as a creation.
*/
diff_q(&outq, p);
}
else if (!diff_unmodified_pair(p))
/* all the usual ones need to be kept */
diff_q(&outq, p);
else
/* no need to keep unmodified pairs */
pair_to_free = p;
if (pair_to_free)
diff_free_filepair(pair_to_free);
}
diff_debug_queue("done copying original", &outq);
free(renq.queue);
free(q->queue);
*q = outq;
diff_debug_queue("done collapsing", q);
free(rename_dst);
rename_dst = NULL;
rename_dst_nr = rename_dst_alloc = 0;
free(rename_src);
rename_src = NULL;
rename_src_nr = rename_src_alloc = 0;
return;
}