From 1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5 Mon Sep 17 00:00:00 2001
From: Vincent Ambo <Vincent Ambo>
Date: Sat, 11 Jan 2020 23:36:56 +0000
Subject: Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7
---
 pack-bitmap.c | 1135 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1135 insertions(+)
 create mode 100644 pack-bitmap.c

(limited to 'pack-bitmap.c')

diff --git a/pack-bitmap.c b/pack-bitmap.c
new file mode 100644
index 000000000000..ed2befaac653
--- /dev/null
+++ b/pack-bitmap.c
@@ -0,0 +1,1135 @@
+#include "cache.h"
+#include "commit.h"
+#include "tag.h"
+#include "diff.h"
+#include "revision.h"
+#include "progress.h"
+#include "list-objects.h"
+#include "pack.h"
+#include "pack-bitmap.h"
+#include "pack-revindex.h"
+#include "pack-objects.h"
+#include "packfile.h"
+#include "repository.h"
+#include "object-store.h"
+
+/*
+ * An entry on the bitmap index, representing the bitmap for a given
+ * commit.
+ */
+struct stored_bitmap {
+	struct object_id oid;
+	struct ewah_bitmap *root;
+	struct stored_bitmap *xor;
+	int flags;
+};
+
+/*
+ * The active bitmap index for a repository. By design, repositories only have
+ * a single bitmap index available (the index for the biggest packfile in
+ * the repository), since bitmap indexes need full closure.
+ *
+ * If there is more than one bitmap index available (e.g. because of alternates),
+ * the active bitmap index is the largest one.
+ */
+struct bitmap_index {
+	/* Packfile to which this bitmap index belongs to */
+	struct packed_git *pack;
+
+	/*
+	 * Mark the first `reuse_objects` in the packfile as reused:
+	 * they will be sent as-is without using them for repacking
+	 * calculations
+	 */
+	uint32_t reuse_objects;
+
+	/* mmapped buffer of the whole bitmap index */
+	unsigned char *map;
+	size_t map_size; /* size of the mmaped buffer */
+	size_t map_pos; /* current position when loading the index */
+
+	/*
+	 * Type indexes.
+	 *
+	 * Each bitmap marks which objects in the packfile  are of the given
+	 * type. This provides type information when yielding the objects from
+	 * the packfile during a walk, which allows for better delta bases.
+	 */
+	struct ewah_bitmap *commits;
+	struct ewah_bitmap *trees;
+	struct ewah_bitmap *blobs;
+	struct ewah_bitmap *tags;
+
+	/* Map from object ID -> `stored_bitmap` for all the bitmapped commits */
+	kh_oid_map_t *bitmaps;
+
+	/* Number of bitmapped commits */
+	uint32_t entry_count;
+
+	/* If not NULL, this is a name-hash cache pointing into map. */
+	uint32_t *hashes;
+
+	/*
+	 * Extended index.
+	 *
+	 * When trying to perform bitmap operations with objects that are not
+	 * packed in `pack`, these objects are added to this "fake index" and
+	 * are assumed to appear at the end of the packfile for all operations
+	 */
+	struct eindex {
+		struct object **objects;
+		uint32_t *hashes;
+		uint32_t count, alloc;
+		kh_oid_pos_t *positions;
+	} ext_index;
+
+	/* Bitmap result of the last performed walk */
+	struct bitmap *result;
+
+	/* "have" bitmap from the last performed walk */
+	struct bitmap *haves;
+
+	/* Version of the bitmap index */
+	unsigned int version;
+};
+
+static struct ewah_bitmap *lookup_stored_bitmap(struct stored_bitmap *st)
+{
+	struct ewah_bitmap *parent;
+	struct ewah_bitmap *composed;
+
+	if (st->xor == NULL)
+		return st->root;
+
+	composed = ewah_pool_new();
+	parent = lookup_stored_bitmap(st->xor);
+	ewah_xor(st->root, parent, composed);
+
+	ewah_pool_free(st->root);
+	st->root = composed;
+	st->xor = NULL;
+
+	return composed;
+}
+
+/*
+ * Read a bitmap from the current read position on the mmaped
+ * index, and increase the read position accordingly
+ */
+static struct ewah_bitmap *read_bitmap_1(struct bitmap_index *index)
+{
+	struct ewah_bitmap *b = ewah_pool_new();
+
+	ssize_t bitmap_size = ewah_read_mmap(b,
+		index->map + index->map_pos,
+		index->map_size - index->map_pos);
+
+	if (bitmap_size < 0) {
+		error("Failed to load bitmap index (corrupted?)");
+		ewah_pool_free(b);
+		return NULL;
+	}
+
+	index->map_pos += bitmap_size;
+	return b;
+}
+
+static int load_bitmap_header(struct bitmap_index *index)
+{
+	struct bitmap_disk_header *header = (void *)index->map;
+
+	if (index->map_size < sizeof(*header) + the_hash_algo->rawsz)
+		return error("Corrupted bitmap index (missing header data)");
+
+	if (memcmp(header->magic, BITMAP_IDX_SIGNATURE, sizeof(BITMAP_IDX_SIGNATURE)) != 0)
+		return error("Corrupted bitmap index file (wrong header)");
+
+	index->version = ntohs(header->version);
+	if (index->version != 1)
+		return error("Unsupported version for bitmap index file (%d)", index->version);
+
+	/* Parse known bitmap format options */
+	{
+		uint32_t flags = ntohs(header->options);
+
+		if ((flags & BITMAP_OPT_FULL_DAG) == 0)
+			return error("Unsupported options for bitmap index file "
+				"(Git requires BITMAP_OPT_FULL_DAG)");
+
+		if (flags & BITMAP_OPT_HASH_CACHE) {
+			unsigned char *end = index->map + index->map_size - the_hash_algo->rawsz;
+			index->hashes = ((uint32_t *)end) - index->pack->num_objects;
+		}
+	}
+
+	index->entry_count = ntohl(header->entry_count);
+	index->map_pos += sizeof(*header) - GIT_MAX_RAWSZ + the_hash_algo->rawsz;
+	return 0;
+}
+
+static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
+					  struct ewah_bitmap *root,
+					  const unsigned char *hash,
+					  struct stored_bitmap *xor_with,
+					  int flags)
+{
+	struct stored_bitmap *stored;
+	khiter_t hash_pos;
+	int ret;
+
+	stored = xmalloc(sizeof(struct stored_bitmap));
+	stored->root = root;
+	stored->xor = xor_with;
+	stored->flags = flags;
+	oidread(&stored->oid, hash);
+
+	hash_pos = kh_put_oid_map(index->bitmaps, stored->oid, &ret);
+
+	/* a 0 return code means the insertion succeeded with no changes,
+	 * because the SHA1 already existed on the map. this is bad, there
+	 * shouldn't be duplicated commits in the index */
+	if (ret == 0) {
+		error("Duplicate entry in bitmap index: %s", hash_to_hex(hash));
+		return NULL;
+	}
+
+	kh_value(index->bitmaps, hash_pos) = stored;
+	return stored;
+}
+
+static inline uint32_t read_be32(const unsigned char *buffer, size_t *pos)
+{
+	uint32_t result = get_be32(buffer + *pos);
+	(*pos) += sizeof(result);
+	return result;
+}
+
+static inline uint8_t read_u8(const unsigned char *buffer, size_t *pos)
+{
+	return buffer[(*pos)++];
+}
+
+#define MAX_XOR_OFFSET 160
+
+static int load_bitmap_entries_v1(struct bitmap_index *index)
+{
+	uint32_t i;
+	struct stored_bitmap *recent_bitmaps[MAX_XOR_OFFSET] = { NULL };
+
+	for (i = 0; i < index->entry_count; ++i) {
+		int xor_offset, flags;
+		struct ewah_bitmap *bitmap = NULL;
+		struct stored_bitmap *xor_bitmap = NULL;
+		uint32_t commit_idx_pos;
+		const unsigned char *sha1;
+
+		commit_idx_pos = read_be32(index->map, &index->map_pos);
+		xor_offset = read_u8(index->map, &index->map_pos);
+		flags = read_u8(index->map, &index->map_pos);
+
+		sha1 = nth_packed_object_sha1(index->pack, commit_idx_pos);
+
+		bitmap = read_bitmap_1(index);
+		if (!bitmap)
+			return -1;
+
+		if (xor_offset > MAX_XOR_OFFSET || xor_offset > i)
+			return error("Corrupted bitmap pack index");
+
+		if (xor_offset > 0) {
+			xor_bitmap = recent_bitmaps[(i - xor_offset) % MAX_XOR_OFFSET];
+
+			if (xor_bitmap == NULL)
+				return error("Invalid XOR offset in bitmap pack index");
+		}
+
+		recent_bitmaps[i % MAX_XOR_OFFSET] = store_bitmap(
+			index, bitmap, sha1, xor_bitmap, flags);
+	}
+
+	return 0;
+}
+
+static char *pack_bitmap_filename(struct packed_git *p)
+{
+	size_t len;
+
+	if (!strip_suffix(p->pack_name, ".pack", &len))
+		BUG("pack_name does not end in .pack");
+	return xstrfmt("%.*s.bitmap", (int)len, p->pack_name);
+}
+
+static int open_pack_bitmap_1(struct bitmap_index *bitmap_git, struct packed_git *packfile)
+{
+	int fd;
+	struct stat st;
+	char *idx_name;
+
+	if (open_pack_index(packfile))
+		return -1;
+
+	idx_name = pack_bitmap_filename(packfile);
+	fd = git_open(idx_name);
+	free(idx_name);
+
+	if (fd < 0)
+		return -1;
+
+	if (fstat(fd, &st)) {
+		close(fd);
+		return -1;
+	}
+
+	if (bitmap_git->pack) {
+		warning("ignoring extra bitmap file: %s", packfile->pack_name);
+		close(fd);
+		return -1;
+	}
+
+	bitmap_git->pack = packfile;
+	bitmap_git->map_size = xsize_t(st.st_size);
+	bitmap_git->map = xmmap(NULL, bitmap_git->map_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	bitmap_git->map_pos = 0;
+	close(fd);
+
+	if (load_bitmap_header(bitmap_git) < 0) {
+		munmap(bitmap_git->map, bitmap_git->map_size);
+		bitmap_git->map = NULL;
+		bitmap_git->map_size = 0;
+		return -1;
+	}
+
+	return 0;
+}
+
+static int load_pack_bitmap(struct bitmap_index *bitmap_git)
+{
+	assert(bitmap_git->map);
+
+	bitmap_git->bitmaps = kh_init_oid_map();
+	bitmap_git->ext_index.positions = kh_init_oid_pos();
+	if (load_pack_revindex(bitmap_git->pack))
+		goto failed;
+
+	if (!(bitmap_git->commits = read_bitmap_1(bitmap_git)) ||
+		!(bitmap_git->trees = read_bitmap_1(bitmap_git)) ||
+		!(bitmap_git->blobs = read_bitmap_1(bitmap_git)) ||
+		!(bitmap_git->tags = read_bitmap_1(bitmap_git)))
+		goto failed;
+
+	if (load_bitmap_entries_v1(bitmap_git) < 0)
+		goto failed;
+
+	return 0;
+
+failed:
+	munmap(bitmap_git->map, bitmap_git->map_size);
+	bitmap_git->map = NULL;
+	bitmap_git->map_size = 0;
+	return -1;
+}
+
+static int open_pack_bitmap(struct repository *r,
+			    struct bitmap_index *bitmap_git)
+{
+	struct packed_git *p;
+	int ret = -1;
+
+	assert(!bitmap_git->map);
+
+	for (p = get_all_packs(r); p; p = p->next) {
+		if (open_pack_bitmap_1(bitmap_git, p) == 0)
+			ret = 0;
+	}
+
+	return ret;
+}
+
+struct bitmap_index *prepare_bitmap_git(struct repository *r)
+{
+	struct bitmap_index *bitmap_git = xcalloc(1, sizeof(*bitmap_git));
+
+	if (!open_pack_bitmap(r, bitmap_git) && !load_pack_bitmap(bitmap_git))
+		return bitmap_git;
+
+	free_bitmap_index(bitmap_git);
+	return NULL;
+}
+
+struct include_data {
+	struct bitmap_index *bitmap_git;
+	struct bitmap *base;
+	struct bitmap *seen;
+};
+
+static inline int bitmap_position_extended(struct bitmap_index *bitmap_git,
+					   const struct object_id *oid)
+{
+	kh_oid_pos_t *positions = bitmap_git->ext_index.positions;
+	khiter_t pos = kh_get_oid_pos(positions, *oid);
+
+	if (pos < kh_end(positions)) {
+		int bitmap_pos = kh_value(positions, pos);
+		return bitmap_pos + bitmap_git->pack->num_objects;
+	}
+
+	return -1;
+}
+
+static inline int bitmap_position_packfile(struct bitmap_index *bitmap_git,
+					   const struct object_id *oid)
+{
+	off_t offset = find_pack_entry_one(oid->hash, bitmap_git->pack);
+	if (!offset)
+		return -1;
+
+	return find_revindex_position(bitmap_git->pack, offset);
+}
+
+static int bitmap_position(struct bitmap_index *bitmap_git,
+			   const struct object_id *oid)
+{
+	int pos = bitmap_position_packfile(bitmap_git, oid);
+	return (pos >= 0) ? pos : bitmap_position_extended(bitmap_git, oid);
+}
+
+static int ext_index_add_object(struct bitmap_index *bitmap_git,
+				struct object *object, const char *name)
+{
+	struct eindex *eindex = &bitmap_git->ext_index;
+
+	khiter_t hash_pos;
+	int hash_ret;
+	int bitmap_pos;
+
+	hash_pos = kh_put_oid_pos(eindex->positions, object->oid, &hash_ret);
+	if (hash_ret > 0) {
+		if (eindex->count >= eindex->alloc) {
+			eindex->alloc = (eindex->alloc + 16) * 3 / 2;
+			REALLOC_ARRAY(eindex->objects, eindex->alloc);
+			REALLOC_ARRAY(eindex->hashes, eindex->alloc);
+		}
+
+		bitmap_pos = eindex->count;
+		eindex->objects[eindex->count] = object;
+		eindex->hashes[eindex->count] = pack_name_hash(name);
+		kh_value(eindex->positions, hash_pos) = bitmap_pos;
+		eindex->count++;
+	} else {
+		bitmap_pos = kh_value(eindex->positions, hash_pos);
+	}
+
+	return bitmap_pos + bitmap_git->pack->num_objects;
+}
+
+struct bitmap_show_data {
+	struct bitmap_index *bitmap_git;
+	struct bitmap *base;
+};
+
+static void show_object(struct object *object, const char *name, void *data_)
+{
+	struct bitmap_show_data *data = data_;
+	int bitmap_pos;
+
+	bitmap_pos = bitmap_position(data->bitmap_git, &object->oid);
+
+	if (bitmap_pos < 0)
+		bitmap_pos = ext_index_add_object(data->bitmap_git, object,
+						  name);
+
+	bitmap_set(data->base, bitmap_pos);
+}
+
+static void show_commit(struct commit *commit, void *data)
+{
+}
+
+static int add_to_include_set(struct bitmap_index *bitmap_git,
+			      struct include_data *data,
+			      const struct object_id *oid,
+			      int bitmap_pos)
+{
+	khiter_t hash_pos;
+
+	if (data->seen && bitmap_get(data->seen, bitmap_pos))
+		return 0;
+
+	if (bitmap_get(data->base, bitmap_pos))
+		return 0;
+
+	hash_pos = kh_get_oid_map(bitmap_git->bitmaps, *oid);
+	if (hash_pos < kh_end(bitmap_git->bitmaps)) {
+		struct stored_bitmap *st = kh_value(bitmap_git->bitmaps, hash_pos);
+		bitmap_or_ewah(data->base, lookup_stored_bitmap(st));
+		return 0;
+	}
+
+	bitmap_set(data->base, bitmap_pos);
+	return 1;
+}
+
+static int should_include(struct commit *commit, void *_data)
+{
+	struct include_data *data = _data;
+	int bitmap_pos;
+
+	bitmap_pos = bitmap_position(data->bitmap_git, &commit->object.oid);
+	if (bitmap_pos < 0)
+		bitmap_pos = ext_index_add_object(data->bitmap_git,
+						  (struct object *)commit,
+						  NULL);
+
+	if (!add_to_include_set(data->bitmap_git, data, &commit->object.oid,
+				bitmap_pos)) {
+		struct commit_list *parent = commit->parents;
+
+		while (parent) {
+			parent->item->object.flags |= SEEN;
+			parent = parent->next;
+		}
+
+		return 0;
+	}
+
+	return 1;
+}
+
+static struct bitmap *find_objects(struct bitmap_index *bitmap_git,
+				   struct rev_info *revs,
+				   struct object_list *roots,
+				   struct bitmap *seen)
+{
+	struct bitmap *base = NULL;
+	int needs_walk = 0;
+
+	struct object_list *not_mapped = NULL;
+
+	/*
+	 * Go through all the roots for the walk. The ones that have bitmaps
+	 * on the bitmap index will be `or`ed together to form an initial
+	 * global reachability analysis.
+	 *
+	 * The ones without bitmaps in the index will be stored in the
+	 * `not_mapped_list` for further processing.
+	 */
+	while (roots) {
+		struct object *object = roots->item;
+		roots = roots->next;
+
+		if (object->type == OBJ_COMMIT) {
+			khiter_t pos = kh_get_oid_map(bitmap_git->bitmaps, object->oid);
+
+			if (pos < kh_end(bitmap_git->bitmaps)) {
+				struct stored_bitmap *st = kh_value(bitmap_git->bitmaps, pos);
+				struct ewah_bitmap *or_with = lookup_stored_bitmap(st);
+
+				if (base == NULL)
+					base = ewah_to_bitmap(or_with);
+				else
+					bitmap_or_ewah(base, or_with);
+
+				object->flags |= SEEN;
+				continue;
+			}
+		}
+
+		object_list_insert(object, &not_mapped);
+	}
+
+	/*
+	 * Best case scenario: We found bitmaps for all the roots,
+	 * so the resulting `or` bitmap has the full reachability analysis
+	 */
+	if (not_mapped == NULL)
+		return base;
+
+	roots = not_mapped;
+
+	/*
+	 * Let's iterate through all the roots that don't have bitmaps to
+	 * check if we can determine them to be reachable from the existing
+	 * global bitmap.
+	 *
+	 * If we cannot find them in the existing global bitmap, we'll need
+	 * to push them to an actual walk and run it until we can confirm
+	 * they are reachable
+	 */
+	while (roots) {
+		struct object *object = roots->item;
+		int pos;
+
+		roots = roots->next;
+		pos = bitmap_position(bitmap_git, &object->oid);
+
+		if (pos < 0 || base == NULL || !bitmap_get(base, pos)) {
+			object->flags &= ~UNINTERESTING;
+			add_pending_object(revs, object, "");
+			needs_walk = 1;
+		} else {
+			object->flags |= SEEN;
+		}
+	}
+
+	if (needs_walk) {
+		struct include_data incdata;
+		struct bitmap_show_data show_data;
+
+		if (base == NULL)
+			base = bitmap_new();
+
+		incdata.bitmap_git = bitmap_git;
+		incdata.base = base;
+		incdata.seen = seen;
+
+		revs->include_check = should_include;
+		revs->include_check_data = &incdata;
+
+		if (prepare_revision_walk(revs))
+			die("revision walk setup failed");
+
+		show_data.bitmap_git = bitmap_git;
+		show_data.base = base;
+
+		traverse_commit_list(revs, show_commit, show_object,
+				     &show_data);
+	}
+
+	return base;
+}
+
+static void show_extended_objects(struct bitmap_index *bitmap_git,
+				  show_reachable_fn show_reach)
+{
+	struct bitmap *objects = bitmap_git->result;
+	struct eindex *eindex = &bitmap_git->ext_index;
+	uint32_t i;
+
+	for (i = 0; i < eindex->count; ++i) {
+		struct object *obj;
+
+		if (!bitmap_get(objects, bitmap_git->pack->num_objects + i))
+			continue;
+
+		obj = eindex->objects[i];
+		show_reach(&obj->oid, obj->type, 0, eindex->hashes[i], NULL, 0);
+	}
+}
+
+static void show_objects_for_type(
+	struct bitmap_index *bitmap_git,
+	struct ewah_bitmap *type_filter,
+	enum object_type object_type,
+	show_reachable_fn show_reach)
+{
+	size_t pos = 0, i = 0;
+	uint32_t offset;
+
+	struct ewah_iterator it;
+	eword_t filter;
+
+	struct bitmap *objects = bitmap_git->result;
+
+	if (bitmap_git->reuse_objects == bitmap_git->pack->num_objects)
+		return;
+
+	ewah_iterator_init(&it, type_filter);
+
+	while (i < objects->word_alloc && ewah_iterator_next(&filter, &it)) {
+		eword_t word = objects->words[i] & filter;
+
+		for (offset = 0; offset < BITS_IN_EWORD; ++offset) {
+			struct object_id oid;
+			struct revindex_entry *entry;
+			uint32_t hash = 0;
+
+			if ((word >> offset) == 0)
+				break;
+
+			offset += ewah_bit_ctz64(word >> offset);
+
+			if (pos + offset < bitmap_git->reuse_objects)
+				continue;
+
+			entry = &bitmap_git->pack->revindex[pos + offset];
+			nth_packed_object_oid(&oid, bitmap_git->pack, entry->nr);
+
+			if (bitmap_git->hashes)
+				hash = get_be32(bitmap_git->hashes + entry->nr);
+
+			show_reach(&oid, object_type, 0, hash, bitmap_git->pack, entry->offset);
+		}
+
+		pos += BITS_IN_EWORD;
+		i++;
+	}
+}
+
+static int in_bitmapped_pack(struct bitmap_index *bitmap_git,
+			     struct object_list *roots)
+{
+	while (roots) {
+		struct object *object = roots->item;
+		roots = roots->next;
+
+		if (find_pack_entry_one(object->oid.hash, bitmap_git->pack) > 0)
+			return 1;
+	}
+
+	return 0;
+}
+
+struct bitmap_index *prepare_bitmap_walk(struct rev_info *revs)
+{
+	unsigned int i;
+
+	struct object_list *wants = NULL;
+	struct object_list *haves = NULL;
+
+	struct bitmap *wants_bitmap = NULL;
+	struct bitmap *haves_bitmap = NULL;
+
+	struct bitmap_index *bitmap_git = xcalloc(1, sizeof(*bitmap_git));
+	/* try to open a bitmapped pack, but don't parse it yet
+	 * because we may not need to use it */
+	if (open_pack_bitmap(revs->repo, bitmap_git) < 0)
+		goto cleanup;
+
+	for (i = 0; i < revs->pending.nr; ++i) {
+		struct object *object = revs->pending.objects[i].item;
+
+		if (object->type == OBJ_NONE)
+			parse_object_or_die(&object->oid, NULL);
+
+		while (object->type == OBJ_TAG) {
+			struct tag *tag = (struct tag *) object;
+
+			if (object->flags & UNINTERESTING)
+				object_list_insert(object, &haves);
+			else
+				object_list_insert(object, &wants);
+
+			if (!tag->tagged)
+				die("bad tag");
+			object = parse_object_or_die(&tag->tagged->oid, NULL);
+		}
+
+		if (object->flags & UNINTERESTING)
+			object_list_insert(object, &haves);
+		else
+			object_list_insert(object, &wants);
+	}
+
+	/*
+	 * if we have a HAVES list, but none of those haves is contained
+	 * in the packfile that has a bitmap, we don't have anything to
+	 * optimize here
+	 */
+	if (haves && !in_bitmapped_pack(bitmap_git, haves))
+		goto cleanup;
+
+	/* if we don't want anything, we're done here */
+	if (!wants)
+		goto cleanup;
+
+	/*
+	 * now we're going to use bitmaps, so load the actual bitmap entries
+	 * from disk. this is the point of no return; after this the rev_list
+	 * becomes invalidated and we must perform the revwalk through bitmaps
+	 */
+	if (load_pack_bitmap(bitmap_git) < 0)
+		goto cleanup;
+
+	object_array_clear(&revs->pending);
+
+	if (haves) {
+		revs->ignore_missing_links = 1;
+		haves_bitmap = find_objects(bitmap_git, revs, haves, NULL);
+		reset_revision_walk();
+		revs->ignore_missing_links = 0;
+
+		if (haves_bitmap == NULL)
+			BUG("failed to perform bitmap walk");
+	}
+
+	wants_bitmap = find_objects(bitmap_git, revs, wants, haves_bitmap);
+
+	if (!wants_bitmap)
+		BUG("failed to perform bitmap walk");
+
+	if (haves_bitmap)
+		bitmap_and_not(wants_bitmap, haves_bitmap);
+
+	bitmap_git->result = wants_bitmap;
+	bitmap_git->haves = haves_bitmap;
+
+	return bitmap_git;
+
+cleanup:
+	free_bitmap_index(bitmap_git);
+	return NULL;
+}
+
+int reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git,
+				       struct packed_git **packfile,
+				       uint32_t *entries,
+				       off_t *up_to)
+{
+	/*
+	 * Reuse the packfile content if we need more than
+	 * 90% of its objects
+	 */
+	static const double REUSE_PERCENT = 0.9;
+
+	struct bitmap *result = bitmap_git->result;
+	uint32_t reuse_threshold;
+	uint32_t i, reuse_objects = 0;
+
+	assert(result);
+
+	for (i = 0; i < result->word_alloc; ++i) {
+		if (result->words[i] != (eword_t)~0) {
+			reuse_objects += ewah_bit_ctz64(~result->words[i]);
+			break;
+		}
+
+		reuse_objects += BITS_IN_EWORD;
+	}
+
+#ifdef GIT_BITMAP_DEBUG
+	{
+		const unsigned char *sha1;
+		struct revindex_entry *entry;
+
+		entry = &bitmap_git->reverse_index->revindex[reuse_objects];
+		sha1 = nth_packed_object_sha1(bitmap_git->pack, entry->nr);
+
+		fprintf(stderr, "Failed to reuse at %d (%016llx)\n",
+			reuse_objects, result->words[i]);
+		fprintf(stderr, " %s\n", hash_to_hex(sha1));
+	}
+#endif
+
+	if (!reuse_objects)
+		return -1;
+
+	if (reuse_objects >= bitmap_git->pack->num_objects) {
+		bitmap_git->reuse_objects = *entries = bitmap_git->pack->num_objects;
+		*up_to = -1; /* reuse the full pack */
+		*packfile = bitmap_git->pack;
+		return 0;
+	}
+
+	reuse_threshold = bitmap_popcount(bitmap_git->result) * REUSE_PERCENT;
+
+	if (reuse_objects < reuse_threshold)
+		return -1;
+
+	bitmap_git->reuse_objects = *entries = reuse_objects;
+	*up_to = bitmap_git->pack->revindex[reuse_objects].offset;
+	*packfile = bitmap_git->pack;
+
+	return 0;
+}
+
+void traverse_bitmap_commit_list(struct bitmap_index *bitmap_git,
+				 show_reachable_fn show_reachable)
+{
+	assert(bitmap_git->result);
+
+	show_objects_for_type(bitmap_git, bitmap_git->commits,
+		OBJ_COMMIT, show_reachable);
+	show_objects_for_type(bitmap_git, bitmap_git->trees,
+		OBJ_TREE, show_reachable);
+	show_objects_for_type(bitmap_git, bitmap_git->blobs,
+		OBJ_BLOB, show_reachable);
+	show_objects_for_type(bitmap_git, bitmap_git->tags,
+		OBJ_TAG, show_reachable);
+
+	show_extended_objects(bitmap_git, show_reachable);
+}
+
+static uint32_t count_object_type(struct bitmap_index *bitmap_git,
+				  enum object_type type)
+{
+	struct bitmap *objects = bitmap_git->result;
+	struct eindex *eindex = &bitmap_git->ext_index;
+
+	uint32_t i = 0, count = 0;
+	struct ewah_iterator it;
+	eword_t filter;
+
+	switch (type) {
+	case OBJ_COMMIT:
+		ewah_iterator_init(&it, bitmap_git->commits);
+		break;
+
+	case OBJ_TREE:
+		ewah_iterator_init(&it, bitmap_git->trees);
+		break;
+
+	case OBJ_BLOB:
+		ewah_iterator_init(&it, bitmap_git->blobs);
+		break;
+
+	case OBJ_TAG:
+		ewah_iterator_init(&it, bitmap_git->tags);
+		break;
+
+	default:
+		return 0;
+	}
+
+	while (i < objects->word_alloc && ewah_iterator_next(&filter, &it)) {
+		eword_t word = objects->words[i++] & filter;
+		count += ewah_bit_popcount64(word);
+	}
+
+	for (i = 0; i < eindex->count; ++i) {
+		if (eindex->objects[i]->type == type &&
+			bitmap_get(objects, bitmap_git->pack->num_objects + i))
+			count++;
+	}
+
+	return count;
+}
+
+void count_bitmap_commit_list(struct bitmap_index *bitmap_git,
+			      uint32_t *commits, uint32_t *trees,
+			      uint32_t *blobs, uint32_t *tags)
+{
+	assert(bitmap_git->result);
+
+	if (commits)
+		*commits = count_object_type(bitmap_git, OBJ_COMMIT);
+
+	if (trees)
+		*trees = count_object_type(bitmap_git, OBJ_TREE);
+
+	if (blobs)
+		*blobs = count_object_type(bitmap_git, OBJ_BLOB);
+
+	if (tags)
+		*tags = count_object_type(bitmap_git, OBJ_TAG);
+}
+
+struct bitmap_test_data {
+	struct bitmap_index *bitmap_git;
+	struct bitmap *base;
+	struct progress *prg;
+	size_t seen;
+};
+
+static void test_show_object(struct object *object, const char *name,
+			     void *data)
+{
+	struct bitmap_test_data *tdata = data;
+	int bitmap_pos;
+
+	bitmap_pos = bitmap_position(tdata->bitmap_git, &object->oid);
+	if (bitmap_pos < 0)
+		die("Object not in bitmap: %s\n", oid_to_hex(&object->oid));
+
+	bitmap_set(tdata->base, bitmap_pos);
+	display_progress(tdata->prg, ++tdata->seen);
+}
+
+static void test_show_commit(struct commit *commit, void *data)
+{
+	struct bitmap_test_data *tdata = data;
+	int bitmap_pos;
+
+	bitmap_pos = bitmap_position(tdata->bitmap_git,
+				     &commit->object.oid);
+	if (bitmap_pos < 0)
+		die("Object not in bitmap: %s\n", oid_to_hex(&commit->object.oid));
+
+	bitmap_set(tdata->base, bitmap_pos);
+	display_progress(tdata->prg, ++tdata->seen);
+}
+
+void test_bitmap_walk(struct rev_info *revs)
+{
+	struct object *root;
+	struct bitmap *result = NULL;
+	khiter_t pos;
+	size_t result_popcnt;
+	struct bitmap_test_data tdata;
+	struct bitmap_index *bitmap_git;
+
+	if (!(bitmap_git = prepare_bitmap_git(revs->repo)))
+		die("failed to load bitmap indexes");
+
+	if (revs->pending.nr != 1)
+		die("you must specify exactly one commit to test");
+
+	fprintf(stderr, "Bitmap v%d test (%d entries loaded)\n",
+		bitmap_git->version, bitmap_git->entry_count);
+
+	root = revs->pending.objects[0].item;
+	pos = kh_get_oid_map(bitmap_git->bitmaps, root->oid);
+
+	if (pos < kh_end(bitmap_git->bitmaps)) {
+		struct stored_bitmap *st = kh_value(bitmap_git->bitmaps, pos);
+		struct ewah_bitmap *bm = lookup_stored_bitmap(st);
+
+		fprintf(stderr, "Found bitmap for %s. %d bits / %08x checksum\n",
+			oid_to_hex(&root->oid), (int)bm->bit_size, ewah_checksum(bm));
+
+		result = ewah_to_bitmap(bm);
+	}
+
+	if (result == NULL)
+		die("Commit %s doesn't have an indexed bitmap", oid_to_hex(&root->oid));
+
+	revs->tag_objects = 1;
+	revs->tree_objects = 1;
+	revs->blob_objects = 1;
+
+	result_popcnt = bitmap_popcount(result);
+
+	if (prepare_revision_walk(revs))
+		die("revision walk setup failed");
+
+	tdata.bitmap_git = bitmap_git;
+	tdata.base = bitmap_new();
+	tdata.prg = start_progress("Verifying bitmap entries", result_popcnt);
+	tdata.seen = 0;
+
+	traverse_commit_list(revs, &test_show_commit, &test_show_object, &tdata);
+
+	stop_progress(&tdata.prg);
+
+	if (bitmap_equals(result, tdata.base))
+		fprintf(stderr, "OK!\n");
+	else
+		fprintf(stderr, "Mismatch!\n");
+
+	free_bitmap_index(bitmap_git);
+}
+
+static int rebuild_bitmap(uint32_t *reposition,
+			  struct ewah_bitmap *source,
+			  struct bitmap *dest)
+{
+	uint32_t pos = 0;
+	struct ewah_iterator it;
+	eword_t word;
+
+	ewah_iterator_init(&it, source);
+
+	while (ewah_iterator_next(&word, &it)) {
+		uint32_t offset, bit_pos;
+
+		for (offset = 0; offset < BITS_IN_EWORD; ++offset) {
+			if ((word >> offset) == 0)
+				break;
+
+			offset += ewah_bit_ctz64(word >> offset);
+
+			bit_pos = reposition[pos + offset];
+			if (bit_pos > 0)
+				bitmap_set(dest, bit_pos - 1);
+			else /* can't reuse, we don't have the object */
+				return -1;
+		}
+
+		pos += BITS_IN_EWORD;
+	}
+	return 0;
+}
+
+int rebuild_existing_bitmaps(struct bitmap_index *bitmap_git,
+			     struct packing_data *mapping,
+			     kh_oid_map_t *reused_bitmaps,
+			     int show_progress)
+{
+	uint32_t i, num_objects;
+	uint32_t *reposition;
+	struct bitmap *rebuild;
+	struct stored_bitmap *stored;
+	struct progress *progress = NULL;
+
+	khiter_t hash_pos;
+	int hash_ret;
+
+	num_objects = bitmap_git->pack->num_objects;
+	reposition = xcalloc(num_objects, sizeof(uint32_t));
+
+	for (i = 0; i < num_objects; ++i) {
+		struct object_id oid;
+		struct revindex_entry *entry;
+		struct object_entry *oe;
+
+		entry = &bitmap_git->pack->revindex[i];
+		nth_packed_object_oid(&oid, bitmap_git->pack, entry->nr);
+		oe = packlist_find(mapping, &oid, NULL);
+
+		if (oe)
+			reposition[i] = oe_in_pack_pos(mapping, oe) + 1;
+	}
+
+	rebuild = bitmap_new();
+	i = 0;
+
+	if (show_progress)
+		progress = start_progress("Reusing bitmaps", 0);
+
+	kh_foreach_value(bitmap_git->bitmaps, stored, {
+		if (stored->flags & BITMAP_FLAG_REUSE) {
+			if (!rebuild_bitmap(reposition,
+					    lookup_stored_bitmap(stored),
+					    rebuild)) {
+				hash_pos = kh_put_oid_map(reused_bitmaps,
+							  stored->oid,
+							  &hash_ret);
+				kh_value(reused_bitmaps, hash_pos) =
+					bitmap_to_ewah(rebuild);
+			}
+			bitmap_reset(rebuild);
+			display_progress(progress, ++i);
+		}
+	});
+
+	stop_progress(&progress);
+
+	free(reposition);
+	bitmap_free(rebuild);
+	return 0;
+}
+
+void free_bitmap_index(struct bitmap_index *b)
+{
+	if (!b)
+		return;
+
+	if (b->map)
+		munmap(b->map, b->map_size);
+	ewah_pool_free(b->commits);
+	ewah_pool_free(b->trees);
+	ewah_pool_free(b->blobs);
+	ewah_pool_free(b->tags);
+	kh_destroy_oid_map(b->bitmaps);
+	free(b->ext_index.objects);
+	free(b->ext_index.hashes);
+	bitmap_free(b->result);
+	bitmap_free(b->haves);
+	free(b);
+}
+
+int bitmap_has_oid_in_uninteresting(struct bitmap_index *bitmap_git,
+				    const struct object_id *oid)
+{
+	int pos;
+
+	if (!bitmap_git)
+		return 0; /* no bitmap loaded */
+	if (!bitmap_git->haves)
+		return 0; /* walk had no "haves" */
+
+	pos = bitmap_position_packfile(bitmap_git, oid);
+	if (pos < 0)
+		return 0;
+
+	return bitmap_get(bitmap_git->haves, pos);
+}
-- 
cgit 1.4.1