oidmap: introduce high-level getter for values

The current way of looking up an entry from a map is tightly coupled with the
map implementation, as one first has to look up the index of the key and then
retrieve the associated value by using the index. As a caller, you usually do
not care about any indices at all, though, so this is more complicated than
really necessary. Furthermore, it invites for errors to happen if the correct
error checking sequence is not being followed.

Introduce a new high-level function `git_oidmap_get` that takes a map and a key
and returns a pointer to the associated value if such a key exists. Otherwise,
a `NULL` pointer is returned. Adjust all callers that can trivially be
converted.

Author: pks-t

src/cache.c

@@ -151,16 +151,12 @@ static bool cache_should_store(git_object_t object_type, size_t object_size)
 
 static void *cache_get(git_cache *cache, const git_oid *oid, unsigned int flags)
 {
-	size_t pos;
-	git_cached_obj *entry = NULL;
+	git_cached_obj *entry;
 
 	if (!git_cache__enabled || git_rwlock_rdlock(&cache->lock) < 0)
 		return NULL;
 
-	pos = git_oidmap_lookup_index(cache->map, oid);
-	if (git_oidmap_valid_index(cache->map, pos)) {
-		entry = git_oidmap_value_at(cache->map, pos);
-
+	if ((entry = git_oidmap_get(cache->map, oid)) != NULL) {
 		if (flags && entry->flags != flags) {
 			entry = NULL;
 		} else {
@@ -175,7 +171,7 @@ static void *cache_get(git_cache *cache, const git_oid *oid, unsigned int flags)
 
 static void *cache_store(git_cache *cache, git_cached_obj *entry)
 {
-	size_t pos;
+	git_cached_obj *stored_entry;
 
 	git_cached_obj_incref(entry);
 
@@ -194,10 +190,8 @@ static void *cache_store(git_cache *cache, git_cached_obj *entry)
 	if (git_cache__current_storage.val > git_cache__max_storage)
 		cache_evict_entries(cache);
 
-	pos = git_oidmap_lookup_index(cache->map, &entry->oid);
-
 	/* not found */
-	if (!git_oidmap_valid_index(cache->map, pos)) {
+	if ((stored_entry = git_oidmap_get(cache->map, &entry->oid)) == NULL) {
 		int rval;
 
 		git_oidmap_insert(cache->map, &entry->oid, entry, &rval);
@@ -209,19 +203,18 @@ static void *cache_store(git_cache *cache, git_cached_obj *entry)
 	}
 	/* found */
 	else {
-		git_cached_obj *stored_entry = git_oidmap_value_at(cache->map, pos);
-
 		if (stored_entry->flags == entry->flags) {
 			git_cached_obj_decref(entry);
 			git_cached_obj_incref(stored_entry);
 			entry = stored_entry;
 		} else if (stored_entry->flags == GIT_CACHE_STORE_RAW &&
-			entry->flags == GIT_CACHE_STORE_PARSED) {
+			   entry->flags == GIT_CACHE_STORE_PARSED) {
+			int rval;
+
 			git_cached_obj_decref(stored_entry);
 			git_cached_obj_incref(entry);
 
-			git_oidmap_set_key_at(cache->map, pos, &entry->oid);
-			git_oidmap_set_value_at(cache->map, pos, entry);
+			git_oidmap_insert(cache->map, &entry->oid, entry, &rval);
 		} else {
 			/* NO OP */
 		}

src/describe.c

@@ -36,12 +36,7 @@ struct commit_name {
 
 static void *oidmap_value_bykey(git_oidmap *map, const git_oid *key)
 {
-	size_t pos = git_oidmap_lookup_index(map, key);
-
-	if (!git_oidmap_valid_index(map, pos))
-		return NULL;
-
-	return git_oidmap_value_at(map, pos);
+	return git_oidmap_get(map, key);
 }
 
 static struct commit_name *find_commit_name(

src/merge.c

@@ -1104,14 +1104,13 @@ static void deletes_by_oid_free(git_oidmap *map) {
 	git_oidmap_free(map);
 }
 
-static int deletes_by_oid_enqueue(git_oidmap *map, git_pool* pool, const git_oid *id, size_t idx) {
-	size_t pos;
+static int deletes_by_oid_enqueue(git_oidmap *map, git_pool* pool, const git_oid *id, size_t idx)
+{
 	deletes_by_oid_queue *queue;
 	size_t *array_entry;
 	int error;
 
-	pos = git_oidmap_lookup_index(map, id);
-	if (!git_oidmap_valid_index(map, pos)) {
+	if ((queue = git_oidmap_get(map, id)) == NULL) {
 		queue = git_pool_malloc(pool, sizeof(deletes_by_oid_queue));
 		GIT_ERROR_CHECK_ALLOC(queue);
 
@@ -1123,7 +1122,6 @@ static int deletes_by_oid_enqueue(git_oidmap *map, git_pool* pool, const git_oid
 		if (error < 0)
 			return -1;
 	} else {
-		queue = git_oidmap_value_at(map, pos);
 		array_entry = git_array_alloc(queue->arr);
 		GIT_ERROR_CHECK_ALLOC(array_entry);
 		*array_entry = idx;
@@ -1132,18 +1130,14 @@ static int deletes_by_oid_enqueue(git_oidmap *map, git_pool* pool, const git_oid
 	return 0;
 }
 
-static int deletes_by_oid_dequeue(size_t *idx, git_oidmap *map, const git_oid *id) {
-	size_t pos;
+static int deletes_by_oid_dequeue(size_t *idx, git_oidmap *map, const git_oid *id)
+{
 	deletes_by_oid_queue *queue;
 	size_t *array_entry;
 
-	pos = git_oidmap_lookup_index(map, id);
-
-	if (!git_oidmap_valid_index(map, pos))
+	if ((queue = git_oidmap_get(map, id)) == NULL)
 		return GIT_ENOTFOUND;
 
-	queue = git_oidmap_value_at(map, pos);
-
 	if (queue->next_pos == 0) {
 		*idx = queue->first_entry;
 	} else {

src/odb_mempack.c

@@ -79,15 +79,11 @@ static int impl__exists(git_odb_backend *backend, const git_oid *oid)
 static int impl__read(void **buffer_p, size_t *len_p, git_object_t *type_p, git_odb_backend *backend, const git_oid *oid)
 {
 	struct memory_packer_db *db = (struct memory_packer_db *)backend;
-	struct memobject *obj = NULL;
-	size_t pos;
+	struct memobject *obj;
 
-	pos = git_oidmap_lookup_index(db->objects, oid);
-	if (!git_oidmap_valid_index(db->objects, pos))
+	if ((obj = git_oidmap_get(db->objects, oid)) == NULL)
 		return GIT_ENOTFOUND;
 
-	obj = git_oidmap_value_at(db->objects, pos);
-
 	*len_p = obj->len;
 	*type_p = obj->type;
 	*buffer_p = git__malloc(obj->len);
@@ -100,15 +96,11 @@ static int impl__read(void **buffer_p, size_t *len_p, git_object_t *type_p, git_
 static int impl__read_header(size_t *len_p, git_object_t *type_p, git_odb_backend *backend, const git_oid *oid)
 {
 	struct memory_packer_db *db = (struct memory_packer_db *)backend;
-	struct memobject *obj = NULL;
-	size_t pos;
+	struct memobject *obj;
 
-	pos = git_oidmap_lookup_index(db->objects, oid);
-	if (!git_oidmap_valid_index(db->objects, pos))
+	if ((obj = git_oidmap_get(db->objects, oid)) == NULL)
 		return GIT_ENOTFOUND;
 
-	obj = git_oidmap_value_at(db->objects, pos);
-
 	*len_p = obj->len;
 	*type_p = obj->type;
 	return 0;

src/oidmap.c

@@ -48,6 +48,15 @@ size_t git_oidmap_size(git_oidmap *map)
 	return kh_size(map);
 }
 
+void *git_oidmap_get(git_oidmap *map, const git_oid *key)
+{
+	size_t idx = git_oidmap_lookup_index(map, key);
+	if (!git_oidmap_valid_index(map, idx) ||
+	    !git_oidmap_has_data(map, idx))
+		return NULL;
+	return kh_val(map, idx);
+}
+
 size_t git_oidmap_lookup_index(git_oidmap *map, const git_oid *key)
 {
 	return kh_get(oid, map, key);

src/oidmap.h

@@ -52,6 +52,15 @@ void git_oidmap_clear(git_oidmap *map);
  */
 size_t git_oidmap_size(git_oidmap *map);
 
+/**
+ * Return value associated with the given key.
+ *
+ * @param map map to search key in
+ * @param key key to search for
+ * @return value associated with the given key or NULL if the key was not found
+ */
+void *git_oidmap_get(git_oidmap *map, const git_oid *key);
+
 size_t git_oidmap_lookup_index(git_oidmap *map, const git_oid *key);
 int git_oidmap_valid_index(git_oidmap *map, size_t idx);
 

src/pack-objects.c

@@ -512,15 +512,12 @@ static int cb_tag_foreach(const char *name, git_oid *oid, void *data)
 {
 	git_packbuilder *pb = data;
 	git_pobject *po;
-	size_t pos;
 
 	GIT_UNUSED(name);
 
-	pos = git_oidmap_lookup_index(pb->object_ix, oid);
-	if (!git_oidmap_valid_index(pb->object_ix, pos))
+	if ((po = git_oidmap_get(pb->object_ix, oid)) == NULL)
 		return 0;
 
-	po = git_oidmap_value_at(pb->object_ix, pos);
 	po->tagged = 1;
 
 	/* TODO: peel objects */
@@ -1537,14 +1534,10 @@ static int lookup_walk_object(struct walk_object **out, git_packbuilder *pb, con
 
 static int retrieve_object(struct walk_object **out, git_packbuilder *pb, const git_oid *id)
 {
-	int error;
-	size_t pos;
 	struct walk_object *obj;
+	int error;
 
-	pos = git_oidmap_lookup_index(pb->walk_objects, id);
-	if (git_oidmap_valid_index(pb->walk_objects, pos)) {
-		obj = git_oidmap_value_at(pb->walk_objects, pos);
-	} else {
+	if ((obj = git_oidmap_get(pb->walk_objects, id)) == NULL) {
 		if ((error = lookup_walk_object(&obj, pb, id)) < 0)
 			return error;
 

src/pack.c

@@ -957,14 +957,13 @@ git_off_t get_delta_base(
 	} else if (type == GIT_OBJECT_REF_DELTA) {
 		/* If we have the cooperative cache, search in it first */
 		if (p->has_cache) {
+			struct git_pack_entry *entry;
 			git_oid oid;
-			size_t k;
 
 			git_oid_fromraw(&oid, base_info);
-			k = git_oidmap_lookup_index(p->idx_cache, &oid);
-			if (git_oidmap_valid_index(p->idx_cache, k)) {
+			if ((entry = git_oidmap_get(p->idx_cache, &oid)) != NULL) {
 				*curpos += 20;
-				return ((struct git_pack_entry *)git_oidmap_value_at(p->idx_cache, k))->offset;
+				return entry->offset;
 			} else {
 				/* If we're building an index, don't try to find the pack
 				 * entry; we just haven't seen it yet.  We'll make

src/revwalk.c

@@ -25,9 +25,8 @@ git_commit_list_node *git_revwalk__commit_lookup(
 	int ret;
 
 	/* lookup and reserve space if not already present */
-	pos = git_oidmap_lookup_index(walk->commits, oid);
-	if (git_oidmap_valid_index(walk->commits, pos))
-		return git_oidmap_value_at(walk->commits, pos);
+	if ((commit = git_oidmap_get(walk->commits, oid)) != NULL)
+		return commit;
 
 	commit = git_commit_list_alloc_node(walk);
 	if (commit == NULL)

tests/core/oidmap.c

@@ -104,3 +104,81 @@ void test_core_oidmap__hash_collision(void)
 
 	git_oidmap_free(map);
 }
+
+void test_core_oidmap__get_succeeds_with_existing_keys(void)
+{
+	git_oidmap *map;
+	oidmap_item items[NITEMS];
+	uint32_t i, j;
+
+	for (i = 0; i < NITEMS; ++i) {
+		uint32_t segment = i / 8;
+		int modi = i - (segment * 8);
+
+		items[i].extra = i;
+
+		for (j = 0; j < GIT_OID_RAWSZ / 4; ++j) {
+			items[i].oid.id[j * 4    ] = (unsigned char)modi;
+			items[i].oid.id[j * 4 + 1] = (unsigned char)(modi >> 8);
+			items[i].oid.id[j * 4 + 2] = (unsigned char)(modi >> 16);
+			items[i].oid.id[j * 4 + 3] = (unsigned char)(modi >> 24);
+		}
+
+		items[i].oid.id[ 8] = (unsigned char)i;
+		items[i].oid.id[ 9] = (unsigned char)(i >> 8);
+		items[i].oid.id[10] = (unsigned char)(i >> 16);
+		items[i].oid.id[11] = (unsigned char)(i >> 24);
+	}
+
+	cl_git_pass(git_oidmap_new(&map));
+
+	for (i = 0; i < NITEMS; ++i) {
+		int ret;
+		git_oidmap_insert(map, &items[i].oid, &items[i], &ret);
+		cl_assert(ret == 1);
+	}
+
+	for (i = 0; i < NITEMS; ++i)
+		cl_assert_equal_p(git_oidmap_get(map, &items[i].oid), &items[i]);
+
+	git_oidmap_free(map);
+}
+
+void test_core_oidmap__get_fails_with_nonexisting_key(void)
+{
+	git_oidmap *map;
+	oidmap_item items[NITEMS];
+	uint32_t i, j;
+
+	for (i = 0; i < NITEMS; ++i) {
+		uint32_t segment = i / 8;
+		int modi = i - (segment * 8);
+
+		items[i].extra = i;
+
+		for (j = 0; j < GIT_OID_RAWSZ / 4; ++j) {
+			items[i].oid.id[j * 4    ] = (unsigned char)modi;
+			items[i].oid.id[j * 4 + 1] = (unsigned char)(modi >> 8);
+			items[i].oid.id[j * 4 + 2] = (unsigned char)(modi >> 16);
+			items[i].oid.id[j * 4 + 3] = (unsigned char)(modi >> 24);
+		}
+
+		items[i].oid.id[ 8] = (unsigned char)i;
+		items[i].oid.id[ 9] = (unsigned char)(i >> 8);
+		items[i].oid.id[10] = (unsigned char)(i >> 16);
+		items[i].oid.id[11] = (unsigned char)(i >> 24);
+	}
+
+	cl_git_pass(git_oidmap_new(&map));
+
+	/* Do _not_ add last OID to verify that we cannot look it up */
+	for (i = 0; i < NITEMS - 1; ++i) {
+		int ret;
+		git_oidmap_insert(map, &items[i].oid, &items[i], &ret);
+		cl_assert(ret == 1);
+	}
+
+	cl_assert_equal_p(git_oidmap_get(map, &items[NITEMS - 1].oid), NULL);
+
+	git_oidmap_free(map);
+}