From 8861aef9c8533782e299f8bbea295c16f6185323 Mon Sep 17 00:00:00 2001
From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date: Thu, 16 Jul 2020 15:02:27 -0700
Subject: [PATCH] shared/gatt-db: Add support for notifying attribute changes

This enables to get notified when an attribute has been changed e.g.
it is being removed so the code can detect changes changes at attribute
level.
---
 src/shared/gatt-db.c | 103 +++++++++++++++++++++++++++++++++++++++++++
 src/shared/gatt-db.h |   8 ++++
 2 files changed, 111 insertions(+)

diff --git a/src/shared/gatt-db.c b/src/shared/gatt-db.c
index 5eccab3b9..e939ddc3a 100644
--- a/src/shared/gatt-db.c
+++ b/src/shared/gatt-db.c
@@ -81,6 +81,13 @@ struct notify {
 	void *user_data;
 };
 
+struct attribute_notify {
+	unsigned int id;
+	gatt_db_attribute_cb_t removed;
+	gatt_db_destroy_func_t destroy;
+	void *user_data;
+};
+
 struct pending_read {
 	struct gatt_db_attribute *attrib;
 	unsigned int id;
@@ -114,6 +121,9 @@ struct gatt_db_attribute {
 
 	unsigned int write_id;
 	struct queue *pending_writes;
+
+	unsigned int next_notify_id;
+	struct queue *notify_list;
 };
 
 struct gatt_db_service {
@@ -171,6 +181,16 @@ static void pending_write_free(void *data)
 	pending_write_result(p, -ECANCELED);
 }
 
+static void attribute_notify_destroy(void *data)
+{
+	struct attribute_notify *notify = data;
+
+	if (notify->destroy)
+		notify->destroy(notify->user_data);
+
+	free(notify);
+}
+
 static void attribute_destroy(struct gatt_db_attribute *attribute)
 {
 	/* Attribute was not initialized by user */
@@ -179,6 +199,7 @@ static void attribute_destroy(struct gatt_db_attribute *attribute)
 
 	queue_destroy(attribute->pending_reads, pending_read_free);
 	queue_destroy(attribute->pending_writes, pending_write_free);
+	queue_destroy(attribute->notify_list, attribute_notify_destroy);
 
 	free(attribute->value);
 	free(attribute);
@@ -208,6 +229,7 @@ static struct gatt_db_attribute *new_attribute(struct gatt_db_service *service,
 
 	attribute->pending_reads = queue_new();
 	attribute->pending_writes = queue_new();
+	attribute->notify_list = queue_new();
 
 	return attribute;
 
@@ -352,12 +374,38 @@ static bool db_hash_update(void *user_data)
 	return false;
 }
 
+static void handle_attribute_notify(void *data, void *user_data)
+{
+	struct attribute_notify *notify = data;
+	struct gatt_db_attribute *attrib = user_data;
+
+	if (notify->removed)
+		notify->removed(attrib, notify->user_data);
+}
+
+static void notify_attribute_changed(struct gatt_db_service *service)
+{
+	int i;
+
+	for (i = 0; i < service->num_handles; i++) {
+		struct gatt_db_attribute *attr = service->attributes[i];
+
+		if (!attr)
+			continue;
+
+		queue_foreach(attr->notify_list, handle_attribute_notify, attr);
+	}
+}
+
 static void notify_service_changed(struct gatt_db *db,
 						struct gatt_db_service *service,
 						bool added)
 {
 	struct notify_data data;
 
+	if (!added)
+		notify_attribute_changed(service);
+
 	if (queue_isempty(db->notify_list))
 		return;
 
@@ -1993,3 +2041,58 @@ void *gatt_db_attribute_get_user_data(struct gatt_db_attribute *attrib)
 
 	return attrib->user_data;
 }
+
+static bool match_attribute_notify_id(const void *a, const void *b)
+{
+	const struct attribute_notify *notify = a;
+	unsigned int id = PTR_TO_UINT(b);
+
+	return notify->id == id;
+}
+
+unsigned int gatt_db_attribute_register(struct gatt_db_attribute *attrib,
+					gatt_db_attribute_cb_t removed,
+					void *user_data,
+					gatt_db_destroy_func_t destroy)
+{
+	struct attribute_notify *notify;
+
+	if (!attrib || !removed)
+		return 0;
+
+	notify = new0(struct attribute_notify, 1);
+	notify->removed = removed;
+	notify->destroy = destroy;
+	notify->user_data = user_data;
+
+	if (attrib->next_notify_id < 1)
+		attrib->next_notify_id = 1;
+
+	notify->id = attrib->next_notify_id++;
+
+	if (!queue_push_tail(attrib->notify_list, notify)) {
+		free(notify);
+		return 0;
+	}
+
+	return notify->id;
+}
+
+bool gatt_db_attribute_unregister(struct gatt_db_attribute *attrib,
+						unsigned int id)
+{
+	struct attribute_notify *notify;
+
+	if (!attrib || !id)
+		return false;
+
+	notify = queue_find(attrib->notify_list, match_attribute_notify_id,
+						UINT_TO_PTR(id));
+	if (!notify)
+		return false;
+
+	queue_remove(attrib->notify_list, notify);
+	attribute_notify_destroy(notify);
+
+	return true;
+}
diff --git a/src/shared/gatt-db.h b/src/shared/gatt-db.h
index a0fd66c53..5bf19d302 100644
--- a/src/shared/gatt-db.h
+++ b/src/shared/gatt-db.h
@@ -281,3 +281,11 @@ bool gatt_db_attribute_write_result(struct gatt_db_attribute *attrib,
 bool gatt_db_attribute_reset(struct gatt_db_attribute *attrib);
 
 void *gatt_db_attribute_get_user_data(struct gatt_db_attribute *attrib);
+
+unsigned int gatt_db_attribute_register(struct gatt_db_attribute *attrib,
+					gatt_db_attribute_cb_t removed,
+					void *user_data,
+					gatt_db_destroy_func_t destroy);
+
+bool gatt_db_attribute_unregister(struct gatt_db_attribute *attrib,
+						unsigned int id);
-- 
2.47.3