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.

10 files changed, 123 insertions, 62 deletions

diff --git a/src/cache.c b/src/cache.c
index 424aaae84..ec3d9d17b 100644
--- a/src/cache.c
+++ b/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 */
 		}
diff --git a/src/describe.c b/src/describe.c
index 2cfa75f40..62d8860b6 100644
--- a/src/describe.c
+++ b/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(
diff --git a/src/merge.c b/src/merge.c
index 22df380b8..b8bb1947f 100644
--- a/src/merge.c
+++ b/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 {
diff --git a/src/odb_mempack.c b/src/odb_mempack.c
index c68e5932e..e66f2e942 100644
--- a/src/odb_mempack.c
+++ b/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;
diff --git a/src/oidmap.c b/src/oidmap.c
index 6b2180766..1e2b8124b 100644
--- a/src/oidmap.c
+++ b/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);
diff --git a/src/oidmap.h b/src/oidmap.h
index c44f7228e..799fec402 100644
--- a/src/oidmap.h
+++ b/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);
 
diff --git a/src/pack-objects.c b/src/pack-objects.c
index 4ccc84d4b..094317a80 100644
--- a/src/pack-objects.c
+++ b/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;
 
diff --git a/src/pack.c b/src/pack.c
index 88af6afd4..650d20346 100644
--- a/src/pack.c
+++ b/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
diff --git a/src/revwalk.c b/src/revwalk.c
index b28c341b1..a052a646d 100644
--- a/src/revwalk.c
+++ b/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)
diff --git a/tests/core/oidmap.c b/tests/core/oidmap.c
index 519b5875e..0e66b7291 100644
--- a/tests/core/oidmap.c
+++ b/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);
+}