Add "named object array" concept

We've had this notion of a "object_list" for a long time, which eventually
grew a "name" member because some users (notably git-rev-list) wanted to
name each object as it is generated.

That object_list is great for some things, but it isn't all that wonderful
for others, and the "name" member is generally not used by everybody.

This patch splits the users of the object_list array up into two: the
traditional list users, who want the list-like format, and who don't
actually use or want the name. And another class of users that really used
the list as an extensible array, and generally wanted to name the objects.

The patch is fairly straightforward, but it's also biggish. Most of it
really just cleans things up: switching the revision parsing and listing
over to the array makes things like the builtin-diff usage much simpler
(we now see exactly how many members the array has, and we don't get the
objects reversed from the order they were on the command line).

One of the main reasons for doing this at all is that the malloc overhead
of the simple object list was actually pretty high, and the array is just
a lot denser. So this patch brings down memory usage by git-rev-list by
just under 3% (on top of all the other memory use optimizations) on the
mozilla archive.

It does add more lines than it removes, and more importantly, it adds a
whole new infrastructure for maintaining lists of objects, but on the
other hand, the new dynamic array code is pretty obvious. The change to
builtin-diff-tree.c shows a fairly good example of why an array interface
is sometimes more natural, and just much simpler for everybody.

Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

builtin-diff-files.c

@@ -41,7 +41,7 @@ int cmd_diff_files(int argc, const char **argv, char **envp)
 	 * rev.max_count is reasonable (0 <= n <= 3),
 	 * there is no other revision filtering parameters.
 	 */
-	if (rev.pending_objects ||
+	if (rev.pending.nr ||
 	    rev.min_age != -1 || rev.max_age != -1)
 		usage(diff_files_usage);
 	/*

builtin-diff-index.c

@@ -32,7 +32,7 @@ int cmd_diff_index(int argc, const char **argv, char **envp)
 	 * Make sure there is one revision (i.e. pending object),
 	 * and there is no revision filtering parameters.
 	 */
-	if (!rev.pending_objects || rev.pending_objects->next ||
+	if (rev.pending.nr != 1 ||
 	    rev.max_count != -1 || rev.min_age != -1 || rev.max_age != -1)
 		usage(diff_cache_usage);
 	return run_diff_index(&rev, cached);

builtin-diff-tree.c

@@ -65,7 +65,6 @@ int cmd_diff_tree(int argc, const char **argv, char **envp)
 	char line[1000];
 	struct object *tree1, *tree2;
 	static struct rev_info *opt = &log_tree_opt;
-	struct object_list *list;
 	int read_stdin = 0;
 
 	git_config(git_diff_config);
@@ -86,45 +85,28 @@ int cmd_diff_tree(int argc, const char **argv, char **envp)
 	}
 
 	/*
-	 * NOTE! "setup_revisions()" will have inserted the revisions
-	 * it parsed in reverse order. So if you do
-	 *
-	 *	git-diff-tree a b
-	 *
-	 * the commit list will be "b" -> "a" -> NULL, so we reverse
-	 * the order of the objects if the first one is not marked
-	 * UNINTERESTING.
+	 * NOTE! We expect "a ^b" to be equal to "a..b", so we
+	 * reverse the order of the objects if the second one
+	 * is marked UNINTERESTING.
 	 */
-	nr_sha1 = 0;
-	list = opt->pending_objects;
-	if (list) {
-		nr_sha1++;
-		tree1 = list->item;
-		list = list->next;
-		if (list) {
-			nr_sha1++;
-			tree2 = tree1;
-			tree1 = list->item;
-			if (list->next)
-				usage(diff_tree_usage);
-			/* Switch them around if the second one was uninteresting.. */
-			if (tree2->flags & UNINTERESTING) {
-				struct object *tmp = tree2;
-				tree2 = tree1;
-				tree1 = tmp;
-			}
-		}
-	}
-
+	nr_sha1 = opt->pending.nr;
 	switch (nr_sha1) {
 	case 0:
 		if (!read_stdin)
 			usage(diff_tree_usage);
 		break;
 	case 1:
+		tree1 = opt->pending.objects[0].item;
 		diff_tree_commit_sha1(tree1->sha1);
 		break;
 	case 2:
+		tree1 = opt->pending.objects[0].item;
+		tree2 = opt->pending.objects[1].item;
+		if (tree2->flags & UNINTERESTING) {
+			struct object *tmp = tree2;
+			tree2 = tree1;
+			tree1 = tmp;
+		}
 		diff_tree_sha1(tree1->sha1,
 			       tree2->sha1,
 			       "", &opt->diffopt);

builtin-diff.c

@@ -50,7 +50,7 @@ static int builtin_diff_files(struct rev_info *revs,
 	 * specified rev.max_count is reasonable (0 <= n <= 3), and
 	 * there is no other revision filtering parameter.
 	 */
-	if (revs->pending_objects ||
+	if (revs->pending.nr ||
 	    revs->min_age != -1 ||
 	    revs->max_age != -1 ||
 	    3 < revs->max_count)
@@ -172,7 +172,7 @@ static int builtin_diff_index(struct rev_info *revs,
 	 * Make sure there is one revision (i.e. pending object),
 	 * and there is no revision filtering parameters.
 	 */
-	if (!revs->pending_objects || revs->pending_objects->next ||
+	if (revs->pending.nr != 1 ||
 	    revs->max_count != -1 || revs->min_age != -1 ||
 	    revs->max_age != -1)
 		usage(builtin_diff_usage);
@@ -181,10 +181,10 @@ static int builtin_diff_index(struct rev_info *revs,
 
 static int builtin_diff_tree(struct rev_info *revs,
 			     int argc, const char **argv,
-			     struct object_list *ent)
+			     struct object_array_entry *ent)
 {
 	const unsigned char *(sha1[2]);
-	int swap = 1;
+	int swap = 0;
 	while (1 < argc) {
 		const char *arg = argv[1];
 		if (!strcmp(arg, "--raw"))
@@ -195,10 +195,10 @@ static int builtin_diff_tree(struct rev_info *revs,
 	}
 
 	/* We saw two trees, ent[0] and ent[1].
-	 * unless ent[0] is unintesting, they are swapped
+	 * if ent[1] is unintesting, they are swapped
 	 */
-	if (ent[0].item->flags & UNINTERESTING)
-		swap = 0;
+	if (ent[1].item->flags & UNINTERESTING)
+		swap = 1;
 	sha1[swap] = ent[0].item->sha1;
 	sha1[1-swap] = ent[1].item->sha1;
 	diff_tree_sha1(sha1[0], sha1[1], "", &revs->diffopt);
@@ -208,7 +208,7 @@ static int builtin_diff_tree(struct rev_info *revs,
 
 static int builtin_diff_combined(struct rev_info *revs,
 				 int argc, const char **argv,
-				 struct object_list *ent,
+				 struct object_array_entry *ent,
 				 int ents)
 {
 	const unsigned char (*parent)[20];
@@ -242,13 +242,14 @@ void add_head(struct rev_info *revs)
 	obj = parse_object(sha1);
 	if (!obj)
 		return;
-	add_object(obj, &revs->pending_objects, NULL, "HEAD");
+	add_pending_object(revs, obj, "HEAD");
 }
 
 int cmd_diff(int argc, const char **argv, char **envp)
 {
+	int i;
 	struct rev_info rev;
-	struct object_list *list, ent[100];
+	struct object_array_entry ent[100];
 	int ents = 0, blobs = 0, paths = 0;
 	const char *path = NULL;
 	struct blobinfo blob[2];
@@ -281,7 +282,7 @@ int cmd_diff(int argc, const char **argv, char **envp)
 	/* Do we have --cached and not have a pending object, then
 	 * default to HEAD by hand.  Eek.
 	 */
-	if (!rev.pending_objects) {
+	if (!rev.pending.nr) {
 		int i;
 		for (i = 1; i < argc; i++) {
 			const char *arg = argv[i];
@@ -294,7 +295,8 @@ int cmd_diff(int argc, const char **argv, char **envp)
 		}
 	}
 
-	for (list = rev.pending_objects; list; list = list->next) {
+	for (i = 0; i < rev.pending.nr; i++) {
+		struct object_array_entry *list = rev.pending.objects+i;
 		struct object *obj = list->item;
 		const char *name = list->name;
 		int flags = (obj->flags & UNINTERESTING);

builtin-grep.c

@@ -657,7 +657,7 @@ int cmd_grep(int argc, const char **argv, char **envp)
 	int cached = 0;
 	int seen_dashdash = 0;
 	struct grep_opt opt;
-	struct object_list *list, **tail, *object_list = NULL;
+	struct object_array list = { 0, 0, NULL };
 	const char *prefix = setup_git_directory();
 	const char **paths = NULL;
 	int i;
@@ -677,7 +677,6 @@ int cmd_grep(int argc, const char **argv, char **envp)
 	 * that continues up to the -- (if exists), and then paths.
 	 */
 
-	tail = &object_list;
 	while (1 < argc) {
 		const char *arg = argv[1];
 		argc--; argv++;
@@ -851,12 +850,9 @@ int cmd_grep(int argc, const char **argv, char **envp)
 		/* Is it a rev? */
 		if (!get_sha1(arg, sha1)) {
 			struct object *object = parse_object(sha1);
-			struct object_list *elem;
 			if (!object)
 				die("bad object %s", arg);
-			elem = object_list_insert(object, tail);
-			elem->name = arg;
-			tail = &elem->next;
+			add_object_array(object, arg, &list);
 			continue;
 		}
 		if (!strcmp(arg, "--")) {
@@ -881,16 +877,16 @@ int cmd_grep(int argc, const char **argv, char **envp)
 		paths[1] = NULL;
 	}
 
-	if (!object_list)
+	if (!list.nr)
 		return !grep_cache(&opt, paths, cached);
 
 	if (cached)
 		die("both --cached and trees are given.");
 
-	for (list = object_list; list; list = list->next) {
+	for (i = 0; i < list.nr; i++) {
 		struct object *real_obj;
-		real_obj = deref_tag(list->item, NULL, 0);
-		if (grep_object(&opt, paths, real_obj, list->name))
+		real_obj = deref_tag(list.objects[i].item, NULL, 0);
+		if (grep_object(&opt, paths, real_obj, list.objects[i].name))
 			hit = 1;
 	}
 	return !hit;

builtin-log.c

@@ -257,8 +257,8 @@ int cmd_format_patch(int argc, const char **argv, char **envp)
 			    output_directory);
 	}
 
-	if (rev.pending_objects && rev.pending_objects->next == NULL) {
-		rev.pending_objects->item->flags |= UNINTERESTING;
+	if (rev.pending.nr == 1) {
+		rev.pending.objects[0].item->flags |= UNINTERESTING;
 		add_head(&rev);
 	}
 

builtin-rev-list.c

@@ -99,41 +99,41 @@ static void show_commit(struct commit *commit)
 	}
 }
 
-static struct object_list **process_blob(struct blob *blob,
-					 struct object_list **p,
-					 struct name_path *path,
-					 const char *name)
+static void process_blob(struct blob *blob,
+			 struct object_array *p,
+			 struct name_path *path,
+			 const char *name)
 {
 	struct object *obj = &blob->object;
 
 	if (!revs.blob_objects)
-		return p;
+		return;
 	if (obj->flags & (UNINTERESTING | SEEN))
-		return p;
+		return;
 	obj->flags |= SEEN;
 	name = strdup(name);
-	return add_object(obj, p, path, name);
+	add_object(obj, p, path, name);
 }
 
-static struct object_list **process_tree(struct tree *tree,
-					 struct object_list **p,
-					 struct name_path *path,
-					 const char *name)
+static void process_tree(struct tree *tree,
+			 struct object_array *p,
+			 struct name_path *path,
+			 const char *name)
 {
 	struct object *obj = &tree->object;
 	struct tree_desc desc;
 	struct name_entry entry;
 	struct name_path me;
 
 	if (!revs.tree_objects)
-		return p;
+		return;
 	if (obj->flags & (UNINTERESTING | SEEN))
-		return p;
+		return;
 	if (parse_tree(tree) < 0)
 		die("bad tree object %s", sha1_to_hex(obj->sha1));
 	obj->flags |= SEEN;
 	name = strdup(name);
-	p = add_object(obj, p, path, name);
+	add_object(obj, p, path, name);
 	me.up = path;
 	me.elem = name;
 	me.elem_len = strlen(name);
@@ -143,57 +143,59 @@ static struct object_list **process_tree(struct tree *tree,
 
 	while (tree_entry(&desc, &entry)) {
 		if (S_ISDIR(entry.mode))
-			p = process_tree(lookup_tree(entry.sha1), p, &me, entry.path);
+			process_tree(lookup_tree(entry.sha1), p, &me, entry.path);
 		else
-			p = process_blob(lookup_blob(entry.sha1), p, &me, entry.path);
+			process_blob(lookup_blob(entry.sha1), p, &me, entry.path);
 	}
 	free(tree->buffer);
 	tree->buffer = NULL;
-	return p;
 }
 
 static void show_commit_list(struct rev_info *revs)
 {
+	int i;
 	struct commit *commit;
-	struct object_list *objects = NULL, **p = &objects, *pending;
+	struct object_array objects = { 0, 0, NULL };
 
 	while ((commit = get_revision(revs)) != NULL) {
-		p = process_tree(commit->tree, p, NULL, "");
+		process_tree(commit->tree, &objects, NULL, "");
 		show_commit(commit);
 	}
-	for (pending = revs->pending_objects; pending; pending = pending->next) {
+	for (i = 0; i < revs->pending.nr; i++) {
+		struct object_array_entry *pending = revs->pending.objects + i;
 		struct object *obj = pending->item;
 		const char *name = pending->name;
 		if (obj->flags & (UNINTERESTING | SEEN))
 			continue;
 		if (obj->type == TYPE_TAG) {
 			obj->flags |= SEEN;
-			p = add_object(obj, p, NULL, name);
+			add_object_array(obj, name, &objects);
 			continue;
 		}
 		if (obj->type == TYPE_TREE) {
-			p = process_tree((struct tree *)obj, p, NULL, name);
+			process_tree((struct tree *)obj, &objects, NULL, name);
 			continue;
 		}
 		if (obj->type == TYPE_BLOB) {
-			p = process_blob((struct blob *)obj, p, NULL, name);
+			process_blob((struct blob *)obj, &objects, NULL, name);
 			continue;
 		}
 		die("unknown pending object %s (%s)", sha1_to_hex(obj->sha1), name);
 	}
-	while (objects) {
+	for (i = 0; i < objects.nr; i++) {
+		struct object_array_entry *p = objects.objects + i;
+
 		/* An object with name "foo\n0000000..." can be used to
 		 * confuse downstream git-pack-objects very badly.
 		 */
-		const char *ep = strchr(objects->name, '\n');
+		const char *ep = strchr(p->name, '\n');
 		if (ep) {
-			printf("%s %.*s\n", sha1_to_hex(objects->item->sha1),
-			       (int) (ep - objects->name),
-			       objects->name);
+			printf("%s %.*s\n", sha1_to_hex(p->item->sha1),
+			       (int) (ep - p->name),
+			       p->name);
 		}
 		else
-			printf("%s %s\n", sha1_to_hex(objects->item->sha1), objects->name);
-		objects = objects->next;
+			printf("%s %s\n", sha1_to_hex(p->item->sha1), p->name);
 	}
 }
 
@@ -348,7 +350,7 @@ int cmd_rev_list(int argc, const char **argv, char **envp)
 
 	if ((!list &&
 	     (!(revs.tag_objects||revs.tree_objects||revs.blob_objects) &&
-	      !revs.pending_objects)) ||
+	      !revs.pending.nr)) ||
 	    revs.diff)
 		usage(rev_list_usage);
 

diff-lib.c

@@ -329,8 +329,8 @@ int run_diff_index(struct rev_info *revs, int cached)
 	}
 	mark_merge_entries();
 
-	ent = revs->pending_objects->item;
-	tree_name = revs->pending_objects->name;
+	ent = revs->pending.objects[0].item;
+	tree_name = revs->pending.objects[0].name;
 	tree = parse_tree_indirect(ent->sha1);
 	if (!tree)
 		return error("bad tree object %s", tree_name);