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// Copyright 2014 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 <cstddef>
#include <string>
#include <utility>
#include "base/macros.h"
#include "base/optional.h"
#include "base/sequenced_task_runner.h"
#include "mojo/public/cpp/bindings/connection_group.h"
#include "mojo/public/cpp/bindings/disconnect_reason.h"
#include "mojo/public/cpp/bindings/interface_ptr.h"
#include "mojo/public/cpp/bindings/lib/bindings_internal.h"
#include "mojo/public/cpp/bindings/lib/pending_receiver_state.h"
#include "mojo/public/cpp/bindings/lib/serialization_context.h"
#include "mojo/public/cpp/bindings/pipe_control_message_proxy.h"
#include "mojo/public/cpp/system/message_pipe.h"
namespace mojo {
// Represents a request from a remote client for an implementation of Interface
// over a specified message pipe. The implementor of the interface should
// remove the message pipe by calling PassMessagePipe() and bind it to the
// implementation. If this is not done, the InterfaceRequest will automatically
// close the pipe on destruction. Can also represent the absence of a request
// if the client did not provide a message pipe.
template <typename Interface>
class InterfaceRequest {
// Constructs an empty InterfaceRequest, representing that the client is not
// requesting an implementation of Interface.
InterfaceRequest() {}
InterfaceRequest(std::nullptr_t) {}
explicit InterfaceRequest(ScopedMessagePipeHandle handle)
: state_(std::move(handle)) {}
// Takes the message pipe from another InterfaceRequest.
InterfaceRequest(InterfaceRequest&& other) = default;
InterfaceRequest& operator=(InterfaceRequest&& other) = default;
// Assigning to nullptr resets the InterfaceRequest to an empty state,
// closing the message pipe currently bound to it (if any).
InterfaceRequest& operator=(std::nullptr_t) {
return *this;
// Indicates whether the request currently contains a valid message pipe.
bool is_pending() const { return state_.pipe.is_valid(); }
explicit operator bool() const { return is_pending(); }
// Removes the message pipe from the request and returns it.
ScopedMessagePipeHandle PassMessagePipe() { return std::move(state_.pipe); }
bool Equals(const InterfaceRequest& other) const {
if (this == &other)
return true;
// Now that the two refer to different objects, they are equivalent if
// and only if they are both invalid.
return !is_pending() && !other.is_pending();
void ResetWithReason(uint32_t custom_reason, const std::string& description) {
if (!is_pending())
Message message =
kMasterInterfaceId, DisconnectReason(custom_reason, description));
MojoResult result =
WriteMessageNew(state_.pipe.get(), message.TakeMojoMessage(),
// Assigns this InterfaceRequest to the ConnectionGroup referenced by |ref|.
// Any Receiver which binds this InterfaceRequest will inherit the Ref.
void set_connection_group(ConnectionGroup::Ref ref) {
state_.connection_group = std::move(ref);
const ConnectionGroup::Ref& connection_group() const {
return state_.connection_group;
// Passes ownership of this InterfaceRequest's ConnectionGroup Ref, removing
// it from its group.
ConnectionGroup::Ref PassConnectionGroupRef() {
return std::move(state_.connection_group);
// For internal Mojo use only.
internal::PendingReceiverState* internal_state() { return &state_; }
internal::PendingReceiverState state_;
// Creates a new message pipe over which Interface is to be served. Binds the
// specified InterfacePtr to one end of the message pipe, and returns an
// InterfaceRequest bound to the other. The InterfacePtr should be passed to
// the client, and the InterfaceRequest should be passed to whatever will
// provide the implementation. The implementation should typically be bound to
// the InterfaceRequest using the Binding or StrongBinding classes. The client
// may begin to issue calls even before an implementation has been bound, since
// messages sent over the pipe will just queue up until they are consumed by
// the implementation.
// Example #1: Requesting a remote implementation of an interface.
// ===============================================================
// Given the following interface:
// interface Database {
// OpenTable(Table& table);
// }
// The client would have code similar to the following:
// DatabasePtr database = ...; // Connect to database.
// TablePtr table;
// database->OpenTable(MakeRequest(&table));
// Upon return from MakeRequest, |table| is ready to have methods called on it.
// Example #2: Registering a local implementation with a remote service.
// =====================================================================
// Given the following interface
// interface Collector {
// RegisterSource(Source source);
// }
// The client would have code similar to the following:
// CollectorPtr collector = ...; // Connect to Collector.
// SourcePtr source;
// InterfaceRequest<Source> source_request(&source);
// collector->RegisterSource(std::move(source));
// CreateSource(std::move(source_request)); // Create implementation locally.
template <typename Interface>
InterfaceRequest<Interface> MakeRequest(
InterfacePtr<Interface>* ptr,
scoped_refptr<base::SequencedTaskRunner> runner = nullptr) {
MessagePipe pipe;
ptr->Bind(InterfacePtrInfo<Interface>(std::move(pipe.handle0), 0u),
return InterfaceRequest<Interface>(std::move(pipe.handle1));
// Similar to the constructor above, but binds one end of the message pipe to
// an InterfacePtrInfo instance.
template <typename Interface>
InterfaceRequest<Interface> MakeRequest(InterfacePtrInfo<Interface>* ptr_info) {
MessagePipe pipe;
return InterfaceRequest<Interface>(std::move(pipe.handle1));
// Fuses an InterfaceRequest<T> endpoint with an InterfacePtrInfo<T> endpoint.
// Returns |true| on success or |false| on failure.
template <typename Interface>
bool FuseInterface(InterfaceRequest<Interface> request,
InterfacePtrInfo<Interface> proxy_info) {
MojoResult result = FuseMessagePipes(request.PassMessagePipe(),
return result == MOJO_RESULT_OK;
} // namespace mojo