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/*
* 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 = alloc_filespec(two->path);
fill_filespec(rename_dst[first].two, two->sha1, two->mode);
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_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)
{
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_path_left = src_path_left;
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, src_copied, literal_added;
unsigned long delta_limit;
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_limit = base_size * (MAX_SCORE-minimum_score) / MAX_SCORE;
delta = diff_delta(src->data, src->size,
dst->data, dst->size,
&delta_size, delta_limit);
if (!delta)
/* If delta_limit is exceeded, we have too much differences */
return 0;

/* 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. */
if (count_delta(delta, delta_size, &src_copied, &literal_added)) {
free(delta);
return 0;
}
free(delta);

/* Extent of damage */
if (src->size + literal_added < src_copied)
delta_size = 0;
else
delta_size = (src->size - src_copied) + literal_added;

/*
* 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(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(NULL, one, two);
dp->score = score;
dp->source_stays = rename_src[src_index].src_path_left;
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;
}

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;
}

void diffcore_rename(struct diff_options *options)
{
int detect_rename = options->detect_rename;
int minimum_score = options->rename_score;
int rename_limit = options->rename_limit;
struct diff_queue_struct *q = &diff_queued_diff;
struct diff_queue_struct outq;
struct diff_score *mx;
int i, j, rename_count;
int num_create, num_src, dst_cnt;

if (!minimum_score)
minimum_score = DEFAULT_RENAME_SCORE;
rename_count = 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)) {
/* If the source is a broken "delete", and
* they did not really want to get broken,
* that means the source actually stays.
*/
int stays = (p->broken_pair && !p->score);
register_rename_src(p->one, stays);
}
else if (detect_rename == DIFF_DETECT_COPY)
register_rename_src(p->one, 1);
}
if (rename_dst_nr == 0 ||
(0 <= rename_limit && rename_limit < rename_dst_nr))
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(i, j, MAX_SCORE);
rename_count++;
break; /* we are done with this entry */
}
}

/* Have we run out the created file pool? If so we can avoid
* doing the delta matrix altogether.
*/
if (rename_count == rename_dst_nr)
goto cleanup;

num_create = (rename_dst_nr - rename_count);
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(mx[i].dst, mx[i].src, mx[i].score);
rename_count++;
}
free(mx);

 cleanup:
/* At this point, we have found some renames and copies and they
* are recorded in rename_dst. 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_filepair *pair_to_free = NULL;

if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
/*
* Creation
*
* We would output this create record if it has
* not been turned into a rename/copy already.
*/
struct diff_rename_dst *dst =
locate_rename_dst(p->two, 0);
if (dst && dst->pair) {
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_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
/*
* Deletion
*
* We would output this delete record if:
*
* (1) this is a broken delete and the counterpart
* broken create remains in the output; or
* (2) this is not a broken delete, and rename_dst
* does not have a rename/copy to move p->one->path
* out of existence.
*
* Otherwise, the counterpart broken create
* has been turned into a rename-edit; or
* delete did not have a matching create to
* begin with.
*/
if (DIFF_PAIR_BROKEN(p)) {
/* broken delete */
struct diff_rename_dst *dst =
locate_rename_dst(p->one, 0);
if (dst && dst->pair)
/* counterpart is now rename/copy */
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)
/* this path remains */
pair_to_free = p;
}

if (pair_to_free)
;
else
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(q->queue);
*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++) {
diff_free_filespec_data(rename_dst[i].two);
free(rename_dst[i].two);
}

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;
}
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