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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 MOJO_EDK_EMBEDDER_PENDING_PROCESS_CONNECTION_H_
#define MOJO_EDK_EMBEDDER_PENDING_PROCESS_CONNECTION_H_
#include <string>
#include "base/callback.h"
#include "base/macros.h"
#include "base/process/process_handle.h"
#include "mojo/edk/embedder/connection_params.h"
#include "mojo/edk/embedder/scoped_platform_handle.h"
#include "mojo/edk/system/system_impl_export.h"
#include "mojo/public/cpp/system/message_pipe.h"
namespace mojo {
namespace edk {
using ProcessErrorCallback = base::Callback<void(const std::string& error)>;
// Represents a potential connection to an external process. Use this object
// to make other processes reachable from this one via Mojo IPC. Typical usage
// might look something like:
//
// PendingProcessConnection connection;
//
// std::string pipe_token;
// ScopedMessagePipeHandle pipe = connection.CreateMessagePipe(&pipe_token);
//
// // New pipes to the process are fully functional and can be used right
// // away, even if the process doesn't exist yet.
// GoDoSomethingInteresting(std::move(pipe));
//
// ScopedPlatformChannelPair channel;
//
// // Give the pipe token to the child process via command-line.
// child_command_line.AppendSwitchASCII("yer-pipe", pipe_token);
//
// // Magic child process launcher which gives one end of the pipe to the
// // new process.
// LaunchProcess(child_command_line, channel.PassClientHandle());
//
// // Some time later...
// connection.Connect(new_process, channel.PassServerHandle());
//
// If at any point during the above process, |connection| is destroyed before
// Connect() can be called, |pipe| will imminently behave as if its peer has
// been closed.
//
// Otherwise, if the remote process in this example eventually calls:
//
// mojo::edk::SetParentPipeHandle(std::move(client_channel_handle));
//
// std::string token = command_line.GetSwitchValueASCII("yer-pipe");
// ScopedMessagePipeHandle pipe = mojo::edk::CreateChildMessagePipe(token);
//
// it will be connected to this process, and its |pipe| will be connected to
// this process's |pipe|.
//
// If the remote process exits or otherwise closes its client channel handle
// before calling CreateChildMessagePipe for a given message pipe token,
// this process's end of the corresponding message pipe will imminently behave
// as if its peer has been closed.
//
class MOJO_SYSTEM_IMPL_EXPORT PendingProcessConnection {
public:
PendingProcessConnection();
~PendingProcessConnection();
// Creates a message pipe associated with a new globally unique string value
// which will be placed in |*token|.
//
// The other end of the new pipe is obtainable in the remote process (or in
// this process, to facilitate "single-process mode" in some applications) by
// passing the new |*token| value to mojo::edk::CreateChildMessagePipe. It's
// the caller's responsibility to communicate the value of |*token| to the
// remote process by any means available, e.g. a command-line argument on
// process launch, or some other out-of-band communication channel for an
// existing process.
//
// NOTES: This may be called any number of times to create multiple message
// pipes to the same remote process. This call ALWAYS succeeds, returning
// a valid message pipe handle and populating |*token| with a new unique
// string value.
ScopedMessagePipeHandle CreateMessagePipe(std::string* token);
// Connects to the process. This must be called at most once, with the process
// handle in |process|.
//
// |connection_param| contains the platform handle of an OS pipe which can be
// used to communicate with the connected process. The other end of that pipe
// must ultimately be passed to mojo::edk::SetParentPipeHandle in the remote
// process, and getting that end of the pipe into the other process is the
// embedder's responsibility.
//
// If this method is not called by the time the PendingProcessConnection is
// destroyed, it's assumed that the process is unavailable (e.g. process
// launch failed or the process has otherwise been terminated early), and
// any associated resources, such as remote endpoints of messages pipes
// created by CreateMessagePipe above) will be cleaned up at that time.
void Connect(
base::ProcessHandle process,
ConnectionParams connection_params,
const ProcessErrorCallback& error_callback = ProcessErrorCallback());
private:
// A GUID representing a potential new process to be connected to this one.
const std::string process_token_;
// Indicates whether this object has been used to create new message pipes.
bool has_message_pipes_ = false;
// Indicates whether Connect() has been called yet.
bool connected_ = false;
DISALLOW_COPY_AND_ASSIGN(PendingProcessConnection);
};
} // namespace edk
} // namespace mojo
#endif // MOJO_EDK_EMBEDDER_PENDING_PROCESS_CONNECTION_H_
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