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// 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/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_