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// Copyright 2015 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.
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/process/process_handle.h"
#include "base/synchronization/lock.h"
#include "build/build_config.h"
#include "ipc/brokerable_attachment.h"
#include "ipc/ipc_export.h"
#include "ipc/ipc_listener.h"
// If the platform has no attachments that need brokering, then it shouldn't
// compile any code that calls member functions of AttachmentBroker. This
// prevents symbols only used by AttachmentBroker and its subclasses from
// making it into the binary.
#if defined(OS_WIN) || (defined(OS_MACOSX) && !defined(OS_IOS))
#endif // defined(OS_WIN)
namespace base {
class SequencedTaskRunner;
namespace IPC {
class AttachmentBroker;
class Endpoint;
// Classes that inherit from this abstract base class are capable of
// communicating with a broker to send and receive attachments to Chrome IPC
// messages.
class IPC_EXPORT SupportsAttachmentBrokering {
// Returns an AttachmentBroker used to broker attachments of IPC messages to
// other processes. There must be exactly one AttachmentBroker per process.
virtual AttachmentBroker* GetAttachmentBroker() = 0;
// Responsible for brokering attachments to Chrome IPC messages. On platforms
// that support attachment brokering, every IPC channel should have a reference
// to a AttachmentBroker.
// This class is not thread safe. The implementation of this class assumes that
// it is only ever used on the same thread as its consumers.
class IPC_EXPORT AttachmentBroker : public Listener {
// A standard observer interface that allows consumers of the AttachmentBroker
// to be notified when a new attachment has been received.
class Observer {
virtual void ReceivedBrokerableAttachmentWithId(
const BrokerableAttachment::AttachmentId& id) = 0;
// Each process has at most one attachment broker. The process is responsible
// for ensuring that |broker| stays alive for as long as the process is
// sending/receiving ipc messages.
static void SetGlobal(AttachmentBroker* broker);
static AttachmentBroker* GetGlobal();
~AttachmentBroker() override;
// Sends |attachment| to |destination_process|. The implementation uses an
// IPC::Channel to communicate with the broker process. This may be the same
// IPC::Channel that is requesting the brokering of an attachment.
// Returns true on success and false otherwise.
virtual bool SendAttachmentToProcess(
const scoped_refptr<BrokerableAttachment>& attachment,
base::ProcessId destination_process) = 0;
// Returns whether the attachment was available. If the attachment was
// available, populates the output parameter |attachment|.
bool GetAttachmentWithId(BrokerableAttachment::AttachmentId id,
scoped_refptr<BrokerableAttachment>* attachment);
// Any given observer should only ever add itself once to the observer list.
// Notifications to |observer| will be posted to |runner|.
// The |observer| is expected to call RemoveObserver() before being destroyed.
void AddObserver(Observer* observer,
const scoped_refptr<base::SequencedTaskRunner>& runner);
void RemoveObserver(Observer* observer);
// These two methods should only be called by the broker process.
// Each unprivileged process should have one IPC channel on which it
// communicates attachment information with the broker process. In the broker
// process, these channels must be registered and deregistered with the
// Attachment Broker as they are created and destroyed.
virtual void RegisterCommunicationChannel(Endpoint* endpoint);
virtual void DeregisterCommunicationChannel(Endpoint* endpoint);
using AttachmentVector = std::vector<scoped_refptr<BrokerableAttachment>>;
// Adds |attachment| to |attachments_|, and notifies the observers.
void HandleReceivedAttachment(
const scoped_refptr<BrokerableAttachment>& attachment);
// Informs the observers that a new BrokerableAttachment has been received.
void NotifyObservers(const BrokerableAttachment::AttachmentId& id);
// Informs the observer identified by |unique_id| that a new
// BrokerableAttachment has been received.
void NotifyObserver(int unique_id,
const BrokerableAttachment::AttachmentId& id);
// This method is exposed for testing only.
AttachmentVector* get_attachments() { return &attachments_; }
base::Lock* get_lock() { return &lock_; }
#if defined(OS_WIN)
#endif // defined(OS_WIN)
// A vector of BrokerableAttachments that have been received, but not yet
// consumed.
// A std::vector is used instead of a std::map because this container is
// expected to have few elements, for which a std::vector is expected to have
// better performance.
AttachmentVector attachments_;
struct ObserverInfo {
Observer* observer;
int unique_id;
// Notifications must be dispatched onto |runner|.
scoped_refptr<base::SequencedTaskRunner> runner;
std::vector<ObserverInfo> observers_;
// This member holds the last id given to an ObserverInfo.
int last_unique_id_;
// The AttachmentBroker can be accessed from any thread, so modifications to
// internal state must be guarded by a lock.
base::Lock lock_;
} // namespace IPC