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d8febde370
Convert the loop in score_trees() to tree_entry(). The code becomes shorter and simpler because the calls to update_tree_entry() are not needed any more. Another benefit is that we need less variables to track the current tree entries; as a side-effect of that the compiler has an easier job figuring out the control flow and thus can avoid false warnings about uninitialized variables. Using struct name_entry also allows the use of tree_entry_len() for finding the path length instead of strlen(), which may be slightly more efficient. Also unify the handling of missing entries in one of the two trees (i.e. added or removed files): Just set cmp appropriately first, no matter if we ran off the end of a tree or if we actually have two entries to compare, and check its value a bit later without duplicating the handler code. Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx> Signed-off-by: Junio C Hamano <gitster@pobox.com>
359 lines
8.5 KiB
C
359 lines
8.5 KiB
C
#include "cache.h"
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#include "tree.h"
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#include "tree-walk.h"
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static int score_missing(unsigned mode, const char *path)
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{
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int score;
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if (S_ISDIR(mode))
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score = -1000;
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else if (S_ISLNK(mode))
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score = -500;
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else
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score = -50;
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return score;
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}
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static int score_differs(unsigned mode1, unsigned mode2, const char *path)
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{
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int score;
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if (S_ISDIR(mode1) != S_ISDIR(mode2))
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score = -100;
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else if (S_ISLNK(mode1) != S_ISLNK(mode2))
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score = -50;
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else
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score = -5;
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return score;
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}
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static int score_matches(unsigned mode1, unsigned mode2, const char *path)
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{
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int score;
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/* Heh, we found SHA-1 collisions between different kind of objects */
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if (S_ISDIR(mode1) != S_ISDIR(mode2))
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score = -100;
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else if (S_ISLNK(mode1) != S_ISLNK(mode2))
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score = -50;
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else if (S_ISDIR(mode1))
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score = 1000;
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else if (S_ISLNK(mode1))
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score = 500;
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else
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score = 250;
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return score;
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}
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static int base_name_entries_compare(const struct name_entry *a,
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const struct name_entry *b)
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{
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return base_name_compare(a->path, tree_entry_len(a), a->mode,
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b->path, tree_entry_len(b), b->mode);
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}
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/*
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* Inspect two trees, and give a score that tells how similar they are.
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*/
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static int score_trees(const unsigned char *hash1, const unsigned char *hash2)
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{
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struct tree_desc one;
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struct tree_desc two;
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void *one_buf, *two_buf;
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int score = 0;
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enum object_type type;
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unsigned long size;
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one_buf = read_sha1_file(hash1, &type, &size);
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if (!one_buf)
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die("unable to read tree (%s)", sha1_to_hex(hash1));
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if (type != OBJ_TREE)
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die("%s is not a tree", sha1_to_hex(hash1));
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init_tree_desc(&one, one_buf, size);
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two_buf = read_sha1_file(hash2, &type, &size);
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if (!two_buf)
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die("unable to read tree (%s)", sha1_to_hex(hash2));
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if (type != OBJ_TREE)
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die("%s is not a tree", sha1_to_hex(hash2));
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init_tree_desc(&two, two_buf, size);
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for (;;) {
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struct name_entry e1, e2;
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int got_entry_from_one = tree_entry(&one, &e1);
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int got_entry_from_two = tree_entry(&two, &e2);
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int cmp;
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if (got_entry_from_one && got_entry_from_two)
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cmp = base_name_entries_compare(&e1, &e2);
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else if (got_entry_from_one)
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/* two lacks this entry */
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cmp = -1;
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else if (got_entry_from_two)
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/* two has more entries */
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cmp = 1;
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else
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break;
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if (cmp < 0)
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/* path1 does not appear in two */
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score += score_missing(e1.mode, e1.path);
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else if (cmp > 0)
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/* path2 does not appear in one */
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score += score_missing(e2.mode, e2.path);
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else if (hashcmp(e1.sha1, e2.sha1))
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/* they are different */
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score += score_differs(e1.mode, e2.mode, e1.path);
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else
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/* same subtree or blob */
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score += score_matches(e1.mode, e2.mode, e1.path);
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}
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free(one_buf);
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free(two_buf);
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return score;
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}
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/*
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* Match one itself and its subtrees with two and pick the best match.
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*/
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static void match_trees(const unsigned char *hash1,
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const unsigned char *hash2,
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int *best_score,
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char **best_match,
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const char *base,
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int recurse_limit)
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{
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struct tree_desc one;
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void *one_buf;
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enum object_type type;
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unsigned long size;
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one_buf = read_sha1_file(hash1, &type, &size);
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if (!one_buf)
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die("unable to read tree (%s)", sha1_to_hex(hash1));
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if (type != OBJ_TREE)
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die("%s is not a tree", sha1_to_hex(hash1));
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init_tree_desc(&one, one_buf, size);
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while (one.size) {
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const char *path;
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const unsigned char *elem;
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unsigned mode;
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int score;
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elem = tree_entry_extract(&one, &path, &mode);
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if (!S_ISDIR(mode))
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goto next;
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score = score_trees(elem, hash2);
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if (*best_score < score) {
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char *newpath;
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newpath = xmalloc(strlen(base) + strlen(path) + 1);
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sprintf(newpath, "%s%s", base, path);
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free(*best_match);
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*best_match = newpath;
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*best_score = score;
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}
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if (recurse_limit) {
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char *newbase;
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newbase = xmalloc(strlen(base) + strlen(path) + 2);
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sprintf(newbase, "%s%s/", base, path);
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match_trees(elem, hash2, best_score, best_match,
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newbase, recurse_limit - 1);
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free(newbase);
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}
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next:
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update_tree_entry(&one);
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}
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free(one_buf);
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}
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/*
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* A tree "hash1" has a subdirectory at "prefix". Come up with a
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* tree object by replacing it with another tree "hash2".
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*/
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static int splice_tree(const unsigned char *hash1,
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const char *prefix,
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const unsigned char *hash2,
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unsigned char *result)
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{
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char *subpath;
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int toplen;
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char *buf;
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unsigned long sz;
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struct tree_desc desc;
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unsigned char *rewrite_here;
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const unsigned char *rewrite_with;
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unsigned char subtree[20];
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enum object_type type;
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int status;
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subpath = strchr(prefix, '/');
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if (!subpath)
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toplen = strlen(prefix);
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else {
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toplen = subpath - prefix;
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subpath++;
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}
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buf = read_sha1_file(hash1, &type, &sz);
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if (!buf)
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die("cannot read tree %s", sha1_to_hex(hash1));
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init_tree_desc(&desc, buf, sz);
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rewrite_here = NULL;
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while (desc.size) {
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const char *name;
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unsigned mode;
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const unsigned char *sha1;
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sha1 = tree_entry_extract(&desc, &name, &mode);
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if (strlen(name) == toplen &&
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!memcmp(name, prefix, toplen)) {
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if (!S_ISDIR(mode))
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die("entry %s in tree %s is not a tree",
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name, sha1_to_hex(hash1));
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rewrite_here = (unsigned char *) sha1;
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break;
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}
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update_tree_entry(&desc);
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}
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if (!rewrite_here)
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die("entry %.*s not found in tree %s",
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toplen, prefix, sha1_to_hex(hash1));
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if (subpath) {
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status = splice_tree(rewrite_here, subpath, hash2, subtree);
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if (status)
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return status;
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rewrite_with = subtree;
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}
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else
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rewrite_with = hash2;
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hashcpy(rewrite_here, rewrite_with);
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status = write_sha1_file(buf, sz, tree_type, result);
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free(buf);
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return status;
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}
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/*
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* We are trying to come up with a merge between one and two that
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* results in a tree shape similar to one. The tree two might
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* correspond to a subtree of one, in which case it needs to be
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* shifted down by prefixing otherwise empty directories. On the
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* other hand, it could cover tree one and we might need to pick a
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* subtree of it.
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*/
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void shift_tree(const unsigned char *hash1,
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const unsigned char *hash2,
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unsigned char *shifted,
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int depth_limit)
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{
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char *add_prefix;
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char *del_prefix;
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int add_score, del_score;
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/*
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* NEEDSWORK: this limits the recursion depth to hardcoded
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* value '2' to avoid excessive overhead.
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*/
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if (!depth_limit)
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depth_limit = 2;
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add_score = del_score = score_trees(hash1, hash2);
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add_prefix = xcalloc(1, 1);
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del_prefix = xcalloc(1, 1);
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/*
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* See if one's subtree resembles two; if so we need to prefix
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* two with a few fake trees to match the prefix.
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*/
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match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
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/*
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* See if two's subtree resembles one; if so we need to
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* pick only subtree of two.
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*/
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match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
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/* Assume we do not have to do any shifting */
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hashcpy(shifted, hash2);
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if (add_score < del_score) {
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/* We need to pick a subtree of two */
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unsigned mode;
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if (!*del_prefix)
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return;
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if (get_tree_entry(hash2, del_prefix, shifted, &mode))
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die("cannot find path %s in tree %s",
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del_prefix, sha1_to_hex(hash2));
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return;
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}
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if (!*add_prefix)
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return;
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splice_tree(hash1, add_prefix, hash2, shifted);
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}
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/*
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* The user says the trees will be shifted by this much.
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* Unfortunately we cannot fundamentally tell which one to
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* be prefixed, as recursive merge can work in either direction.
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*/
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void shift_tree_by(const unsigned char *hash1,
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const unsigned char *hash2,
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unsigned char *shifted,
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const char *shift_prefix)
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{
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unsigned char sub1[20], sub2[20];
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unsigned mode1, mode2;
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unsigned candidate = 0;
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/* Can hash2 be a tree at shift_prefix in tree hash1? */
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if (!get_tree_entry(hash1, shift_prefix, sub1, &mode1) &&
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S_ISDIR(mode1))
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candidate |= 1;
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/* Can hash1 be a tree at shift_prefix in tree hash2? */
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if (!get_tree_entry(hash2, shift_prefix, sub2, &mode2) &&
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S_ISDIR(mode2))
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candidate |= 2;
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if (candidate == 3) {
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/* Both are plausible -- we need to evaluate the score */
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int best_score = score_trees(hash1, hash2);
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int score;
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candidate = 0;
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score = score_trees(sub1, hash2);
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if (score > best_score) {
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candidate = 1;
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best_score = score;
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}
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score = score_trees(sub2, hash1);
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if (score > best_score)
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candidate = 2;
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}
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if (!candidate) {
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/* Neither is plausible -- do not shift */
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hashcpy(shifted, hash2);
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return;
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}
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if (candidate == 1)
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/*
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* shift tree2 down by adding shift_prefix above it
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* to match tree1.
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*/
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splice_tree(hash1, shift_prefix, hash2, shifted);
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else
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/*
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* shift tree2 up by removing shift_prefix from it
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* to match tree1.
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*/
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hashcpy(shifted, sub2);
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}
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