1 files changed, 507 insertions, 0 deletions
diff --git a/third_party/git/delta-islands.c b/third_party/git/delta-islands.c
new file mode 100644
index 000000000000..09dbd3cf72ba
--- /dev/null
+++ b/third_party/git/delta-islands.c
@@ -0,0 +1,507 @@
+#include "cache.h"
+#include "attr.h"
+#include "object.h"
+#include "blob.h"
+#include "commit.h"
+#include "tag.h"
+#include "tree.h"
+#include "delta.h"
+#include "pack.h"
+#include "tree-walk.h"
+#include "diff.h"
+#include "revision.h"
+#include "list-objects.h"
+#include "progress.h"
+#include "refs.h"
+#include "khash.h"
+#include "pack-bitmap.h"
+#include "pack-objects.h"
+#include "delta-islands.h"
+#include "sha1-array.h"
+#include "config.h"
+
+KHASH_INIT(str, const char *, void *, 1, kh_str_hash_func, kh_str_hash_equal)
+
+static kh_oid_map_t *island_marks;
+static unsigned island_counter;
+static unsigned island_counter_core;
+
+static kh_str_t *remote_islands;
+
+struct remote_island {
+	uint64_t hash;
+	struct oid_array oids;
+};
+
+struct island_bitmap {
+	uint32_t refcount;
+	uint32_t bits[FLEX_ARRAY];
+};
+
+static uint32_t island_bitmap_size;
+
+/*
+ * Allocate a new bitmap; if "old" is not NULL, the new bitmap will be a copy
+ * of "old". Otherwise, the new bitmap is empty.
+ */
+static struct island_bitmap *island_bitmap_new(const struct island_bitmap *old)
+{
+	size_t size = sizeof(struct island_bitmap) + (island_bitmap_size * 4);
+	struct island_bitmap *b = xcalloc(1, size);
+
+	if (old)
+		memcpy(b, old, size);
+
+	b->refcount = 1;
+	return b;
+}
+
+static void island_bitmap_or(struct island_bitmap *a, const struct island_bitmap *b)
+{
+	uint32_t i;
+
+	for (i = 0; i < island_bitmap_size; ++i)
+		a->bits[i] |= b->bits[i];
+}
+
+static int island_bitmap_is_subset(struct island_bitmap *self,
+		struct island_bitmap *super)
+{
+	uint32_t i;
+
+	if (self == super)
+		return 1;
+
+	for (i = 0; i < island_bitmap_size; ++i) {
+		if ((self->bits[i] & super->bits[i]) != self->bits[i])
+			return 0;
+	}
+
+	return 1;
+}
+
+#define ISLAND_BITMAP_BLOCK(x) (x / 32)
+#define ISLAND_BITMAP_MASK(x) (1 << (x % 32))
+
+static void island_bitmap_set(struct island_bitmap *self, uint32_t i)
+{
+	self->bits[ISLAND_BITMAP_BLOCK(i)] |= ISLAND_BITMAP_MASK(i);
+}
+
+static int island_bitmap_get(struct island_bitmap *self, uint32_t i)
+{
+	return (self->bits[ISLAND_BITMAP_BLOCK(i)] & ISLAND_BITMAP_MASK(i)) != 0;
+}
+
+int in_same_island(const struct object_id *trg_oid, const struct object_id *src_oid)
+{
+	khiter_t trg_pos, src_pos;
+
+	/* If we aren't using islands, assume everything goes together. */
+	if (!island_marks)
+		return 1;
+
+	/*
+	 * If we don't have a bitmap for the target, we can delta it
+	 * against anything -- it's not an important object
+	 */
+	trg_pos = kh_get_oid_map(island_marks, *trg_oid);
+	if (trg_pos >= kh_end(island_marks))
+		return 1;
+
+	/*
+	 * if the source (our delta base) doesn't have a bitmap,
+	 * we don't want to base any deltas on it!
+	 */
+	src_pos = kh_get_oid_map(island_marks, *src_oid);
+	if (src_pos >= kh_end(island_marks))
+		return 0;
+
+	return island_bitmap_is_subset(kh_value(island_marks, trg_pos),
+				kh_value(island_marks, src_pos));
+}
+
+int island_delta_cmp(const struct object_id *a, const struct object_id *b)
+{
+	khiter_t a_pos, b_pos;
+	struct island_bitmap *a_bitmap = NULL, *b_bitmap = NULL;
+
+	if (!island_marks)
+		return 0;
+
+	a_pos = kh_get_oid_map(island_marks, *a);
+	if (a_pos < kh_end(island_marks))
+		a_bitmap = kh_value(island_marks, a_pos);
+
+	b_pos = kh_get_oid_map(island_marks, *b);
+	if (b_pos < kh_end(island_marks))
+		b_bitmap = kh_value(island_marks, b_pos);
+
+	if (a_bitmap) {
+		if (!b_bitmap || !island_bitmap_is_subset(a_bitmap, b_bitmap))
+			return -1;
+	}
+	if (b_bitmap) {
+		if (!a_bitmap || !island_bitmap_is_subset(b_bitmap, a_bitmap))
+			return 1;
+	}
+
+	return 0;
+}
+
+static struct island_bitmap *create_or_get_island_marks(struct object *obj)
+{
+	khiter_t pos;
+	int hash_ret;
+
+	pos = kh_put_oid_map(island_marks, obj->oid, &hash_ret);
+	if (hash_ret)
+		kh_value(island_marks, pos) = island_bitmap_new(NULL);
+
+	return kh_value(island_marks, pos);
+}
+
+static void set_island_marks(struct object *obj, struct island_bitmap *marks)
+{
+	struct island_bitmap *b;
+	khiter_t pos;
+	int hash_ret;
+
+	pos = kh_put_oid_map(island_marks, obj->oid, &hash_ret);
+	if (hash_ret) {
+		/*
+		 * We don't have one yet; make a copy-on-write of the
+		 * parent.
+		 */
+		marks->refcount++;
+		kh_value(island_marks, pos) = marks;
+		return;
+	}
+
+	/*
+	 * We do have it. Make sure we split any copy-on-write before
+	 * updating.
+	 */
+	b = kh_value(island_marks, pos);
+	if (b->refcount > 1) {
+		b->refcount--;
+		b = kh_value(island_marks, pos) = island_bitmap_new(b);
+	}
+	island_bitmap_or(b, marks);
+}
+
+static void mark_remote_island_1(struct repository *r,
+				 struct remote_island *rl,
+				 int is_core_island)
+{
+	uint32_t i;
+
+	for (i = 0; i < rl->oids.nr; ++i) {
+		struct island_bitmap *marks;
+		struct object *obj = parse_object(r, &rl->oids.oid[i]);
+
+		if (!obj)
+			continue;
+
+		marks = create_or_get_island_marks(obj);
+		island_bitmap_set(marks, island_counter);
+
+		if (is_core_island && obj->type == OBJ_COMMIT)
+			obj->flags |= NEEDS_BITMAP;
+
+		/* If it was a tag, also make sure we hit the underlying object. */
+		while (obj && obj->type == OBJ_TAG) {
+			obj = ((struct tag *)obj)->tagged;
+			if (obj) {
+				parse_object(r, &obj->oid);
+				marks = create_or_get_island_marks(obj);
+				island_bitmap_set(marks, island_counter);
+			}
+		}
+	}
+
+	if (is_core_island)
+		island_counter_core = island_counter;
+
+	island_counter++;
+}
+
+struct tree_islands_todo {
+	struct object_entry *entry;
+	unsigned int depth;
+};
+
+static int tree_depth_compare(const void *a, const void *b)
+{
+	const struct tree_islands_todo *todo_a = a;
+	const struct tree_islands_todo *todo_b = b;
+
+	return todo_a->depth - todo_b->depth;
+}
+
+void resolve_tree_islands(struct repository *r,
+			  int progress,
+			  struct packing_data *to_pack)
+{
+	struct progress *progress_state = NULL;
+	struct tree_islands_todo *todo;
+	int nr = 0;
+	int i;
+
+	if (!island_marks)
+		return;
+
+	/*
+	 * We process only trees, as commits and tags have already been handled
+	 * (and passed their marks on to root trees, as well. We must make sure
+	 * to process them in descending tree-depth order so that marks
+	 * propagate down the tree properly, even if a sub-tree is found in
+	 * multiple parent trees.
+	 */
+	ALLOC_ARRAY(todo, to_pack->nr_objects);
+	for (i = 0; i < to_pack->nr_objects; i++) {
+		if (oe_type(&to_pack->objects[i]) == OBJ_TREE) {
+			todo[nr].entry = &to_pack->objects[i];
+			todo[nr].depth = oe_tree_depth(to_pack, &to_pack->objects[i]);
+			nr++;
+		}
+	}
+	QSORT(todo, nr, tree_depth_compare);
+
+	if (progress)
+		progress_state = start_progress(_("Propagating island marks"), nr);
+
+	for (i = 0; i < nr; i++) {
+		struct object_entry *ent = todo[i].entry;
+		struct island_bitmap *root_marks;
+		struct tree *tree;
+		struct tree_desc desc;
+		struct name_entry entry;
+		khiter_t pos;
+
+		pos = kh_get_oid_map(island_marks, ent->idx.oid);
+		if (pos >= kh_end(island_marks))
+			continue;
+
+		root_marks = kh_value(island_marks, pos);
+
+		tree = lookup_tree(r, &ent->idx.oid);
+		if (!tree || parse_tree(tree) < 0)
+			die(_("bad tree object %s"), oid_to_hex(&ent->idx.oid));
+
+		init_tree_desc(&desc, tree->buffer, tree->size);
+		while (tree_entry(&desc, &entry)) {
+			struct object *obj;
+
+			if (S_ISGITLINK(entry.mode))
+				continue;
+
+			obj = lookup_object(r, &entry.oid);
+			if (!obj)
+				continue;
+
+			set_island_marks(obj, root_marks);
+		}
+
+		free_tree_buffer(tree);
+
+		display_progress(progress_state, i+1);
+	}
+
+	stop_progress(&progress_state);
+	free(todo);
+}
+
+static regex_t *island_regexes;
+static unsigned int island_regexes_alloc, island_regexes_nr;
+static const char *core_island_name;
+
+static int island_config_callback(const char *k, const char *v, void *cb)
+{
+	if (!strcmp(k, "pack.island")) {
+		struct strbuf re = STRBUF_INIT;
+
+		if (!v)
+			return config_error_nonbool(k);
+
+		ALLOC_GROW(island_regexes, island_regexes_nr + 1, island_regexes_alloc);
+
+		if (*v != '^')
+			strbuf_addch(&re, '^');
+		strbuf_addstr(&re, v);
+
+		if (regcomp(&island_regexes[island_regexes_nr], re.buf, REG_EXTENDED))
+			die(_("failed to load island regex for '%s': %s"), k, re.buf);
+
+		strbuf_release(&re);
+		island_regexes_nr++;
+		return 0;
+	}
+
+	if (!strcmp(k, "pack.islandcore"))
+		return git_config_string(&core_island_name, k, v);
+
+	return 0;
+}
+
+static void add_ref_to_island(const char *island_name, const struct object_id *oid)
+{
+	uint64_t sha_core;
+	struct remote_island *rl = NULL;
+
+	int hash_ret;
+	khiter_t pos = kh_put_str(remote_islands, island_name, &hash_ret);
+
+	if (hash_ret) {
+		kh_key(remote_islands, pos) = xstrdup(island_name);
+		kh_value(remote_islands, pos) = xcalloc(1, sizeof(struct remote_island));
+	}
+
+	rl = kh_value(remote_islands, pos);
+	oid_array_append(&rl->oids, oid);
+
+	memcpy(&sha_core, oid->hash, sizeof(uint64_t));
+	rl->hash += sha_core;
+}
+
+static int find_island_for_ref(const char *refname, const struct object_id *oid,
+			       int flags, void *data)
+{
+	/*
+	 * We should advertise 'ARRAY_SIZE(matches) - 2' as the max,
+	 * so we can diagnose below a config with more capture groups
+	 * than we support.
+	 */
+	regmatch_t matches[16];
+	int i, m;
+	struct strbuf island_name = STRBUF_INIT;
+
+	/* walk backwards to get last-one-wins ordering */
+	for (i = island_regexes_nr - 1; i >= 0; i--) {
+		if (!regexec(&island_regexes[i], refname,
+			     ARRAY_SIZE(matches), matches, 0))
+			break;
+	}
+
+	if (i < 0)
+		return 0;
+
+	if (matches[ARRAY_SIZE(matches) - 1].rm_so != -1)
+		warning(_("island regex from config has "
+			  "too many capture groups (max=%d)"),
+			(int)ARRAY_SIZE(matches) - 2);
+
+	for (m = 1; m < ARRAY_SIZE(matches); m++) {
+		regmatch_t *match = &matches[m];
+
+		if (match->rm_so == -1)
+			continue;
+
+		if (island_name.len)
+			strbuf_addch(&island_name, '-');
+
+		strbuf_add(&island_name, refname + match->rm_so, match->rm_eo - match->rm_so);
+	}
+
+	add_ref_to_island(island_name.buf, oid);
+	strbuf_release(&island_name);
+	return 0;
+}
+
+static struct remote_island *get_core_island(void)
+{
+	if (core_island_name) {
+		khiter_t pos = kh_get_str(remote_islands, core_island_name);
+		if (pos < kh_end(remote_islands))
+			return kh_value(remote_islands, pos);
+	}
+
+	return NULL;
+}
+
+static void deduplicate_islands(struct repository *r)
+{
+	struct remote_island *island, *core = NULL, **list;
+	unsigned int island_count, dst, src, ref, i = 0;
+
+	island_count = kh_size(remote_islands);
+	ALLOC_ARRAY(list, island_count);
+
+	kh_foreach_value(remote_islands, island, {
+		list[i++] = island;
+	});
+
+	for (ref = 0; ref + 1 < island_count; ref++) {
+		for (src = ref + 1, dst = src; src < island_count; src++) {
+			if (list[ref]->hash == list[src]->hash)
+				continue;
+
+			if (src != dst)
+				list[dst] = list[src];
+
+			dst++;
+		}
+		island_count = dst;
+	}
+
+	island_bitmap_size = (island_count / 32) + 1;
+	core = get_core_island();
+
+	for (i = 0; i < island_count; ++i) {
+		mark_remote_island_1(r, list[i], core && list[i]->hash == core->hash);
+	}
+
+	free(list);
+}
+
+void load_delta_islands(struct repository *r, int progress)
+{
+	island_marks = kh_init_oid_map();
+	remote_islands = kh_init_str();
+
+	git_config(island_config_callback, NULL);
+	for_each_ref(find_island_for_ref, NULL);
+	deduplicate_islands(r);
+
+	if (progress)
+		fprintf(stderr, _("Marked %d islands, done.\n"), island_counter);
+}
+
+void propagate_island_marks(struct commit *commit)
+{
+	khiter_t pos = kh_get_oid_map(island_marks, commit->object.oid);
+
+	if (pos < kh_end(island_marks)) {
+		struct commit_list *p;
+		struct island_bitmap *root_marks = kh_value(island_marks, pos);
+
+		parse_commit(commit);
+		set_island_marks(&get_commit_tree(commit)->object, root_marks);
+		for (p = commit->parents; p; p = p->next)
+			set_island_marks(&p->item->object, root_marks);
+	}
+}
+
+int compute_pack_layers(struct packing_data *to_pack)
+{
+	uint32_t i;
+
+	if (!core_island_name || !island_marks)
+		return 1;
+
+	for (i = 0; i < to_pack->nr_objects; ++i) {
+		struct object_entry *entry = &to_pack->objects[i];
+		khiter_t pos = kh_get_oid_map(island_marks, entry->idx.oid);
+
+		oe_set_layer(to_pack, entry, 1);
+
+		if (pos < kh_end(island_marks)) {
+			struct island_bitmap *bitmap = kh_value(island_marks, pos);
+
+			if (island_bitmap_get(bitmap, island_counter_core))
+				oe_set_layer(to_pack, entry, 0);
+		}
+	}
+
+	return 2;
+}