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![Junio C Hamano](/assets/img/avatar_default.png)
The second round similarity estimator simply used the size of the xdelta itself to estimate the extent of damage. This patch keeps that logic to detect big insertions to terminate the check early, but otherwise looks at the generated delta in order to estimate the extent of edit more accurately. Signed-off-by: Junio C Hamano <junkio@cox.net> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
386 lines
10 KiB
C
386 lines
10 KiB
C
/*
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* Copyright (C) 2005 Junio C Hamano
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*/
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#include "cache.h"
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#include "diff.h"
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#include "diffcore.h"
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#include "delta.h"
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#include "count-delta.h"
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/* Table of rename/copy destinations */
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static struct diff_rename_dst {
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struct diff_filespec *two;
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struct diff_filepair *pair;
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} *rename_dst;
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static int rename_dst_nr, rename_dst_alloc;
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static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
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int insert_ok)
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{
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int first, last;
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first = 0;
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last = rename_dst_nr;
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while (last > first) {
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int next = (last + first) >> 1;
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struct diff_rename_dst *dst = &(rename_dst[next]);
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int cmp = strcmp(two->path, dst->two->path);
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if (!cmp)
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return dst;
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if (cmp < 0) {
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last = next;
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continue;
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}
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first = next+1;
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}
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/* not found */
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if (!insert_ok)
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return NULL;
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/* insert to make it at "first" */
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if (rename_dst_alloc <= rename_dst_nr) {
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rename_dst_alloc = alloc_nr(rename_dst_alloc);
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rename_dst = xrealloc(rename_dst,
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rename_dst_alloc * sizeof(*rename_dst));
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}
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rename_dst_nr++;
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if (first < rename_dst_nr)
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memmove(rename_dst + first + 1, rename_dst + first,
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(rename_dst_nr - first - 1) * sizeof(*rename_dst));
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rename_dst[first].two = two;
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rename_dst[first].pair = NULL;
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return &(rename_dst[first]);
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}
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static struct diff_rename_src {
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struct diff_filespec *one;
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unsigned src_used : 1;
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} *rename_src;
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static int rename_src_nr, rename_src_alloc;
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static struct diff_rename_src *locate_rename_src(struct diff_filespec *one,
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int insert_ok)
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{
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int first, last;
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first = 0;
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last = rename_src_nr;
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while (last > first) {
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int next = (last + first) >> 1;
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struct diff_rename_src *src = &(rename_src[next]);
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int cmp = strcmp(one->path, src->one->path);
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if (!cmp)
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return src;
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if (cmp < 0) {
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last = next;
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continue;
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}
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first = next+1;
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}
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/* not found */
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if (!insert_ok)
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return NULL;
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/* insert to make it at "first" */
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if (rename_src_alloc <= rename_src_nr) {
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rename_src_alloc = alloc_nr(rename_src_alloc);
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rename_src = xrealloc(rename_src,
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rename_src_alloc * sizeof(*rename_src));
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}
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rename_src_nr++;
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if (first < rename_src_nr)
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memmove(rename_src + first + 1, rename_src + first,
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(rename_src_nr - first - 1) * sizeof(*rename_src));
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rename_src[first].one = one;
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rename_src[first].src_used = 0;
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return &(rename_src[first]);
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}
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static int is_exact_match(struct diff_filespec *src, struct diff_filespec *dst)
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{
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if (src->sha1_valid && dst->sha1_valid &&
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!memcmp(src->sha1, dst->sha1, 20))
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return 1;
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if (diff_populate_filespec(src) || diff_populate_filespec(dst))
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/* this is an error but will be caught downstream */
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return 0;
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if (src->size == dst->size &&
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!memcmp(src->data, dst->data, src->size))
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return 1;
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return 0;
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}
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struct diff_score {
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int src; /* index in rename_src */
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int dst; /* index in rename_dst */
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int score;
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int rank;
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};
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static int estimate_similarity(struct diff_filespec *src,
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struct diff_filespec *dst,
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int minimum_score)
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{
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/* src points at a file that existed in the original tree (or
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* optionally a file in the destination tree) and dst points
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* at a newly created file. They may be quite similar, in which
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* case we want to say src is renamed to dst or src is copied into
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* dst, and then some edit has been applied to dst.
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*
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* Compare them and return how similar they are, representing
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* the score as an integer between 0 and 10000, except
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* where they match exactly it is considered better than anything
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* else.
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*/
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void *delta;
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unsigned long delta_size, base_size;
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int score;
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/* We deal only with regular files. Symlink renames are handled
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* only when they are exact matches --- in other words, no edits
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* after renaming.
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*/
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if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
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return 0;
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delta_size = ((src->size < dst->size) ?
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(dst->size - src->size) : (src->size - dst->size));
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base_size = ((src->size < dst->size) ? src->size : dst->size);
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/* We would not consider edits that change the file size so
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* drastically. delta_size must be smaller than
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* (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
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* Note that base_size == 0 case is handled here already
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* and the final score computation below would not have a
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* divide-by-zero issue.
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*/
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if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
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return 0;
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delta = diff_delta(src->data, src->size,
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dst->data, dst->size,
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&delta_size);
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/* A delta that has a lot of literal additions would have
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* big delta_size no matter what else it does.
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*/
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if (minimum_score < MAX_SCORE * delta_size / base_size)
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return 0;
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/* Estimate the edit size by interpreting delta. */
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delta_size = count_delta(delta, delta_size);
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free(delta);
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if (delta_size == UINT_MAX)
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return 0;
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/*
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* Now we will give some score to it. 100% edit gets 0 points
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* and 0% edit gets MAX_SCORE points.
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*/
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score = MAX_SCORE - (MAX_SCORE * delta_size / base_size);
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if (score < 0) return 0;
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if (MAX_SCORE < score) return MAX_SCORE;
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return score;
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}
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static void record_rename_pair(struct diff_queue_struct *renq,
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int dst_index, int src_index, int score)
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{
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struct diff_filespec *one, *two, *src, *dst;
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struct diff_filepair *dp;
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if (rename_dst[dst_index].pair)
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die("internal error: dst already matched.");
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src = rename_src[src_index].one;
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one = alloc_filespec(src->path);
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fill_filespec(one, src->sha1, src->mode);
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dst = rename_dst[dst_index].two;
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two = alloc_filespec(dst->path);
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fill_filespec(two, dst->sha1, dst->mode);
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dp = diff_queue(renq, one, two);
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dp->score = score;
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rename_src[src_index].src_used = 1;
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rename_dst[dst_index].pair = dp;
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}
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/*
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* We sort the rename similarity matrix with the score, in descending
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* order (more similar first).
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*/
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static int score_compare(const void *a_, const void *b_)
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{
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const struct diff_score *a = a_, *b = b_;
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return b->score - a->score;
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}
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int diff_scoreopt_parse(const char *opt)
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{
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int diglen, num, scale, i;
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if (opt[0] != '-' || (opt[1] != 'M' && opt[1] != 'C'))
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return -1; /* that is not a -M nor -C option */
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diglen = strspn(opt+2, "0123456789");
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if (diglen == 0 || strlen(opt+2) != diglen)
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return 0; /* use default */
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sscanf(opt+2, "%d", &num);
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for (i = 0, scale = 1; i < diglen; i++)
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scale *= 10;
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/* user says num divided by scale and we say internally that
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* is MAX_SCORE * num / scale.
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*/
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return MAX_SCORE * num / scale;
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}
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void diffcore_rename(int detect_rename, int minimum_score)
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{
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struct diff_queue_struct *q = &diff_queued_diff;
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struct diff_queue_struct renq, outq;
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struct diff_score *mx;
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int i, j;
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int num_create, num_src, dst_cnt;
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if (!minimum_score)
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minimum_score = DEFAULT_MINIMUM_SCORE;
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renq.queue = NULL;
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renq.nr = renq.alloc = 0;
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for (i = 0; i < q->nr; i++) {
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struct diff_filepair *p = q->queue[i];
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if (!DIFF_FILE_VALID(p->one))
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if (!DIFF_FILE_VALID(p->two))
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continue; /* unmerged */
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else
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locate_rename_dst(p->two, 1);
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else if (!DIFF_FILE_VALID(p->two))
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locate_rename_src(p->one, 1);
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else if (1 < detect_rename) /* find copy, too */
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locate_rename_src(p->one, 1);
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}
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if (rename_dst_nr == 0)
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goto cleanup; /* nothing to do */
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/* We really want to cull the candidates list early
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* with cheap tests in order to avoid doing deltas.
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*/
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for (i = 0; i < rename_dst_nr; i++) {
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struct diff_filespec *two = rename_dst[i].two;
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for (j = 0; j < rename_src_nr; j++) {
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struct diff_filespec *one = rename_src[j].one;
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if (!is_exact_match(one, two))
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continue;
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record_rename_pair(&renq, i, j, MAX_SCORE);
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break; /* we are done with this entry */
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}
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}
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diff_debug_queue("done detecting exact", &renq);
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/* Have we run out the created file pool? If so we can avoid
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* doing the delta matrix altogether.
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*/
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if (renq.nr == rename_dst_nr)
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goto flush_rest;
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num_create = (rename_dst_nr - renq.nr);
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num_src = rename_src_nr;
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mx = xmalloc(sizeof(*mx) * num_create * num_src);
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for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
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int base = dst_cnt * num_src;
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struct diff_filespec *two = rename_dst[i].two;
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if (rename_dst[i].pair)
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continue; /* dealt with exact match already. */
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for (j = 0; j < rename_src_nr; j++) {
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struct diff_filespec *one = rename_src[j].one;
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struct diff_score *m = &mx[base+j];
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m->src = j;
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m->dst = i;
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m->score = estimate_similarity(one, two,
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minimum_score);
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}
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dst_cnt++;
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}
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/* cost matrix sorted by most to least similar pair */
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qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
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for (i = 0; i < num_create * num_src; i++) {
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struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
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if (dst->pair)
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continue; /* already done, either exact or fuzzy. */
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if (mx[i].score < minimum_score)
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break; /* there is not any more diffs applicable. */
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record_rename_pair(&renq, mx[i].dst, mx[i].src, mx[i].score);
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}
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free(mx);
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diff_debug_queue("done detecting fuzzy", &renq);
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flush_rest:
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/* At this point, we have found some renames and copies and they
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* are kept in renq. The original list is still in *q.
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*
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* Scan the original list and move them into the outq; we will sort
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* outq and swap it into the queue supplied to pass that to
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* downstream, so we assign the sort keys in this loop.
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*
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* See comments at the top of record_rename_pair for numbers used
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* to assign rename_rank.
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*/
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outq.queue = NULL;
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outq.nr = outq.alloc = 0;
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for (i = 0; i < q->nr; i++) {
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struct diff_filepair *p = q->queue[i];
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struct diff_rename_src *src = locate_rename_src(p->one, 0);
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struct diff_rename_dst *dst = locate_rename_dst(p->two, 0);
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struct diff_filepair *pair_to_free = NULL;
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if (dst) {
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/* creation */
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if (dst->pair) {
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/* renq has rename/copy already to produce
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* this file, so we do not emit the creation
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* record in the output.
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*/
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diff_q(&outq, dst->pair);
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pair_to_free = p;
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}
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else
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/* no matching rename/copy source, so record
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* this as a creation.
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*/
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diff_q(&outq, p);
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}
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else if (!diff_unmodified_pair(p))
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/* all the other cases need to be recorded as is */
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diff_q(&outq, p);
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else {
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/* unmodified pair needs to be recorded only if
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* it is used as the source of rename/copy
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*/
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if (src && src->src_used)
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diff_q(&outq, p);
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else
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pair_to_free = p;
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}
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if (pair_to_free) {
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diff_free_filespec_data(pair_to_free->one);
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diff_free_filespec_data(pair_to_free->two);
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free(pair_to_free);
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}
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}
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diff_debug_queue("done copying original", &outq);
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free(renq.queue);
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free(q->queue);
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*q = outq;
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diff_debug_queue("done collapsing", q);
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cleanup:
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free(rename_dst);
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rename_dst = NULL;
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rename_dst_nr = rename_dst_alloc = 0;
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free(rename_src);
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rename_src = NULL;
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rename_src_nr = rename_src_alloc = 0;
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return;
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}
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