copy vs rename detection: avoid unnecessary O(n*m) loops

The core rename detection had some rather stupid code to check if a
pathname was used by a later modification or rename, which basically
walked the whole pathname space for all renames for each rename, in
order to tell whether it was a pure rename (no remaining users) or
should be considered a copy (other users of the source file remaining).

That's really silly, since we can just keep a count of users around, and
replace all those complex and expensive loops with just testing that
simple counter (but this all depends on the previous commit that shared
the diff_filespec data structure by using a separate reference count).

Note that the reference count is not the same as the rename count: they
behave otherwise rather similarly, but the reference count is tied to
the allocation (and decremented at de-allocation, so that when it turns
zero we can get rid of the memory), while the rename count is tied to
the renames and is decremented when we find a rename (so that when it
turns zero we know that it was a rename, not a copy).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Linus Torvalds 2007-10-25 11:20:56 -07:00 коммит произвёл Junio C Hamano
Родитель 9fb88419ba
Коммит 644797119d
3 изменённых файлов: 35 добавлений и 75 удалений

40
diff.c
Просмотреть файл

@ -2597,9 +2597,9 @@ void diff_debug_filepair(const struct diff_filepair *p, int i)
{
diff_debug_filespec(p->one, i, "one");
diff_debug_filespec(p->two, i, "two");
fprintf(stderr, "score %d, status %c stays %d broken %d\n",
fprintf(stderr, "score %d, status %c rename_used %d broken %d\n",
p->score, p->status ? p->status : '?',
p->source_stays, p->broken_pair);
p->one->rename_used, p->broken_pair);
}
void diff_debug_queue(const char *msg, struct diff_queue_struct *q)
@ -2617,8 +2617,8 @@ void diff_debug_queue(const char *msg, struct diff_queue_struct *q)
static void diff_resolve_rename_copy(void)
{
int i, j;
struct diff_filepair *p, *pp;
int i;
struct diff_filepair *p;
struct diff_queue_struct *q = &diff_queued_diff;
diff_debug_queue("resolve-rename-copy", q);
@ -2640,27 +2640,21 @@ static void diff_resolve_rename_copy(void)
* either in-place edit or rename/copy edit.
*/
else if (DIFF_PAIR_RENAME(p)) {
if (p->source_stays) {
p->status = DIFF_STATUS_COPIED;
continue;
}
/* See if there is some other filepair that
* copies from the same source as us. If so
* we are a copy. Otherwise we are either a
* copy if the path stays, or a rename if it
* does not, but we already handled "stays" case.
/*
* A rename might have re-connected a broken
* pair up, causing the pathnames to be the
* same again. If so, that's not a rename at
* all, just a modification..
*
* Otherwise, see if this source was used for
* multiple renames, in which case we decrement
* the count, and call it a copy.
*/
for (j = i + 1; j < q->nr; j++) {
pp = q->queue[j];
if (strcmp(pp->one->path, p->one->path))
continue; /* not us */
if (!DIFF_PAIR_RENAME(pp))
continue; /* not a rename/copy */
/* pp is a rename/copy from the same source */
if (!strcmp(p->one->path, p->two->path))
p->status = DIFF_STATUS_MODIFIED;
else if (--p->one->rename_used > 0)
p->status = DIFF_STATUS_COPIED;
break;
}
if (!p->status)
else
p->status = DIFF_STATUS_RENAMED;
}
else if (hashcmp(p->one->sha1, p->two->sha1) ||

Просмотреть файл

@ -55,12 +55,10 @@ static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
static struct diff_rename_src {
struct diff_filespec *one;
unsigned short score; /* to remember the break score */
unsigned src_path_left : 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_path_left,
unsigned short score)
{
int first, last;
@ -92,7 +90,6 @@ static struct diff_rename_src *register_rename_src(struct diff_filespec *one,
(rename_src_nr - first - 1) * sizeof(*rename_src));
rename_src[first].one = one;
rename_src[first].score = score;
rename_src[first].src_path_left = src_path_left;
return &(rename_src[first]);
}
@ -216,6 +213,7 @@ static void record_rename_pair(int dst_index, int src_index, int score)
die("internal error: dst already matched.");
src = rename_src[src_index].one;
src->rename_used++;
src->count++;
dst = rename_dst[dst_index].two;
@ -227,7 +225,6 @@ static void record_rename_pair(int dst_index, int src_index, int score)
dp->score = rename_src[src_index].score;
else
dp->score = score;
dp->source_stays = rename_src[src_index].src_path_left;
rename_dst[dst_index].pair = dp;
}
@ -245,21 +242,6 @@ static int score_compare(const void *a_, const void *b_)
return b->score - a->score;
}
static int compute_stays(struct diff_queue_struct *q,
struct diff_filespec *one)
{
int i;
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
if (strcmp(one->path, p->two->path))
continue;
if (DIFF_PAIR_RENAME(p)) {
return 0; /* something else is renamed into this */
}
}
return 1;
}
/*
* Find exact renames first.
*
@ -338,15 +320,25 @@ void diffcore_rename(struct diff_options *options)
locate_rename_dst(p->two, 1);
}
else if (!DIFF_FILE_VALID(p->two)) {
/* If the source is a broken "delete", and
/*
* If the source is a broken "delete", and
* they did not really want to get broken,
* that means the source actually stays.
* So we increment the "rename_used" score
* by one, to indicate ourselves as a user
*/
int stays = (p->broken_pair && !p->score);
register_rename_src(p->one, stays, p->score);
if (p->broken_pair && !p->score)
p->one->rename_used++;
register_rename_src(p->one, p->score);
}
else if (detect_rename == DIFF_DETECT_COPY) {
/*
* Increment the "rename_used" score by
* one, to indicate ourselves as a user.
*/
p->one->rename_used++;
register_rename_src(p->one, p->score);
}
else if (detect_rename == DIFF_DETECT_COPY)
register_rename_src(p->one, 1, p->score);
}
if (rename_dst_nr == 0 || rename_src_nr == 0)
goto cleanup; /* nothing to do */
@ -472,16 +464,7 @@ void diffcore_rename(struct diff_options *options)
pair_to_free = p;
}
else {
for (j = 0; j < rename_dst_nr; j++) {
if (!rename_dst[j].pair)
continue;
if (strcmp(rename_dst[j].pair->
one->path,
p->one->path))
continue;
break;
}
if (j < rename_dst_nr)
if (p->one->rename_used)
/* this path remains */
pair_to_free = p;
}
@ -507,23 +490,6 @@ void diffcore_rename(struct diff_options *options)
*q = outq;
diff_debug_queue("done collapsing", q);
/* We need to see which rename source really stays here;
* earlier we only checked if the path is left in the result,
* but even if a path remains in the result, if that is coming
* from copying something else on top of it, then the original
* source is lost and does not stay.
*/
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
if (DIFF_PAIR_RENAME(p) && p->source_stays) {
/* If one appears as the target of a rename-copy,
* then mark p->source_stays = 0; otherwise
* leave it as is.
*/
p->source_stays = compute_stays(q, p->one);
}
}
for (i = 0; i < rename_dst_nr; i++)
free_filespec(rename_dst[i].two);

Просмотреть файл

@ -31,6 +31,7 @@ struct diff_filespec {
unsigned long size;
int count; /* Reference count */
int xfrm_flags; /* for use by the xfrm */
int rename_used; /* Count of rename users */
unsigned short mode; /* file mode */
unsigned sha1_valid : 1; /* if true, use sha1 and trust mode;
* if false, use the name and read from
@ -58,7 +59,6 @@ struct diff_filepair {
struct diff_filespec *two;
unsigned short int score;
char status; /* M C R N D U (see Documentation/diff-format.txt) */
unsigned source_stays : 1; /* all of R/C are copies */
unsigned broken_pair : 1;
unsigned renamed_pair : 1;
unsigned is_unmerged : 1;