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// Copyright 2017 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 CONTENT_COMMON_MESSAGE_PORT_H_
#define CONTENT_COMMON_MESSAGE_PORT_H_
#include <vector>
#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/lock.h"
#include "content/common/content_export.h"
#include "mojo/public/cpp/system/message_pipe.h"
#include "mojo/public/cpp/system/watcher.h"
namespace content {
// MessagePort corresponds to a HTML MessagePort. It is a thin wrapper around a
// Mojo MessagePipeHandle and provides methods for reading and writing messages.
//
// A MessagePort is only actively listening for incoming messages once
// SetCallback has been called with a valid callback. If ClearCallback is
// called (or if SetCallback is called with a null callback), then the
// MessagePort will stop listening for incoming messages. The callback runs on
// an unspecified background thread.
//
// Upon destruction, if the MessagePort is listening for incoming messages,
// then the destructor will first synchronize with the background thread,
// waiting for it to finish any in-process callback before closing the
// underlying MessagePipeHandle. This synchronization ensures that any code
// running in the callback can be sure to not worry about the MessagePort
// becoming invalid during callback execution.
//
// MessagePort methods may be used from any thread; however, care must be taken
// when using ReleaseHandle, ReleaseHandles or when destroying a MessagePort
// instance. The MessagePort class does not synchronize those methods with
// methods like PostMessage, GetMessage and SetCallback that use the underlying
// MessagePipeHandle.
//
// TODO(darin): Make this class move-only once no longer used with Chrome IPC.
//
class CONTENT_EXPORT MessagePort {
public:
~MessagePort();
MessagePort();
// Shallow copy, resulting in multiple references to the same port.
MessagePort(const MessagePort& other);
MessagePort& operator=(const MessagePort& other);
explicit MessagePort(mojo::ScopedMessagePipeHandle handle);
const mojo::ScopedMessagePipeHandle& GetHandle() const;
mojo::ScopedMessagePipeHandle ReleaseHandle() const;
static std::vector<mojo::ScopedMessagePipeHandle> ReleaseHandles(
const std::vector<MessagePort>& ports);
// Sends an encoded message (along with ports to transfer) to this port's
// peer.
void PostMessage(const uint8_t* encoded_message,
size_t encoded_message_size,
std::vector<MessagePort> ports);
// Get the next available encoded message if any. Returns true if a message
// was read.
bool GetMessage(std::vector<uint8_t>* encoded_message,
std::vector<MessagePort>* ports);
// This callback will be invoked on a background thread when messages are
// available to be read via GetMessage. It must not synchronously call back
// into the MessagePort instance.
void SetCallback(const base::Closure& callback);
// Clears any callback specified by a prior call to SetCallback.
void ClearCallback();
private:
class State : public base::RefCountedThreadSafe<State> {
public:
State();
State(mojo::ScopedMessagePipeHandle handle);
void StartWatching(const base::Closure& callback);
void StopWatching();
mojo::ScopedMessagePipeHandle TakeHandle();
const mojo::ScopedMessagePipeHandle& handle() const { return handle_; }
private:
friend class base::RefCountedThreadSafe<State>;
~State();
void ArmWatcher();
void OnHandleReady(MojoResult result);
static void CallOnHandleReady(uintptr_t context,
MojoResult result,
MojoHandleSignalsState signals_state,
MojoWatcherNotificationFlags flags);
// Guards access to the fields below.
base::Lock lock_;
mojo::ScopedWatcherHandle watcher_handle_;
mojo::ScopedMessagePipeHandle handle_;
// Callback to invoke when the State is notified about a change to
// |handle_|'s signaling state.
base::Closure callback_;
};
mutable scoped_refptr<State> state_;
};
} // namespace content
#endif // CONTENT_COMMON_MESSAGE_PORT_H_