| // Copyright 2018 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef SERVICES_AUDIO_GROUP_COORDINATOR_H_ |
| #define SERVICES_AUDIO_GROUP_COORDINATOR_H_ |
| |
| #include <algorithm> |
| #include <utility> |
| #include <vector> |
| |
| #include "base/callback.h" |
| #include "base/check.h" |
| #include "base/macros.h" |
| #include "base/sequence_checker.h" |
| #include "base/stl_util.h" |
| #include "base/unguessable_token.h" |
| |
| namespace audio { |
| |
| // Manages a registry of group members and notifies observers as membership in |
| // the group changes. |
| template <typename Member> |
| class GroupCoordinator { |
| public: |
| // Interface for entities that wish to montior and take action as members |
| // join/leave a particular group. |
| class Observer { |
| public: |
| virtual void OnMemberJoinedGroup(Member* member) = 0; |
| virtual void OnMemberLeftGroup(Member* member) = 0; |
| |
| protected: |
| virtual ~Observer(); |
| }; |
| |
| GroupCoordinator(); |
| ~GroupCoordinator(); |
| |
| // Registers/Unregisters a group |member|. The member must remain valid until |
| // after UnregisterMember() is called. |
| void RegisterMember(const base::UnguessableToken& group_id, Member* member); |
| void UnregisterMember(const base::UnguessableToken& group_id, Member* member); |
| |
| void AddObserver(const base::UnguessableToken& group_id, Observer* observer); |
| void RemoveObserver(const base::UnguessableToken& group_id, |
| Observer* observer); |
| |
| // Runs a |callback| for each member associated with the given |group_id|. |
| void ForEachMemberInGroup( |
| const base::UnguessableToken& group_id, |
| base::RepeatingCallback<void(Member*)> callback) const; |
| |
| protected: |
| // Returns the current members in the group having the given |group_id|. Note |
| // that the validity of the returned reference is uncertain once any of the |
| // other non-const methods are called. |
| const std::vector<Member*>& GetCurrentMembersUnsafe( |
| const base::UnguessableToken& group_id) const; |
| |
| private: |
| struct Group { |
| std::vector<Member*> members; |
| std::vector<Observer*> observers; |
| |
| Group(); |
| ~Group(); |
| Group(Group&& other); |
| Group& operator=(Group&& other); |
| |
| private: |
| DISALLOW_COPY_AND_ASSIGN(Group); |
| }; |
| |
| using GroupMap = std::vector<std::pair<base::UnguessableToken, Group>>; |
| |
| // Returns an iterator to the entry associated with the given |group_id|, |
| // creating a new one if necessary. |
| typename GroupMap::iterator FindGroup(const base::UnguessableToken& group_id); |
| |
| // Deletes the entry in |groups_| if it has no members or observers remaining. |
| void MaybePruneGroupMapEntry(typename GroupMap::iterator it); |
| |
| GroupMap groups_; |
| |
| #if DCHECK_IS_ON() |
| // Incremented with each mutation, and used to sanity-check that there aren't |
| // any possible re-entrancy bugs. It's okay if this rolls over, since the |
| // implementation is only doing DCHECK_EQ's. |
| size_t mutation_count_ = 0; |
| #endif |
| |
| SEQUENCE_CHECKER(sequence_checker_); |
| |
| DISALLOW_COPY_AND_ASSIGN(GroupCoordinator); |
| }; |
| |
| } // namespace audio |
| |
| #endif // SERVICES_AUDIO_GROUP_COORDINATOR_H_ |