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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.
#include <memory>
#include <utility>
#include <vector>
#include "base/macros.h"
#include "base/optional.h"
#include "mojo/core/channel.h"
#include "mojo/core/dispatcher.h"
#include "mojo/core/ports/event.h"
#include "mojo/core/ports/name.h"
#include "mojo/core/ports/port_ref.h"
#include "mojo/core/ports/user_message.h"
#include "mojo/core/system_impl_export.h"
#include "mojo/public/c/system/message_pipe.h"
#include "mojo/public/c/system/types.h"
namespace mojo {
namespace core {
// UserMessageImpl is the sole implementation of ports::UserMessage used to
// attach message data to any ports::UserMessageEvent.
// A UserMessageImpl may be either serialized or unserialized. Unserialized
// instances are serialized lazily only when necessary, i.e., if and when
// Serialize() is called to obtain a serialized message for wire transfer.
class MOJO_SYSTEM_IMPL_EXPORT UserMessageImpl : public ports::UserMessage {
static const TypeInfo kUserMessageTypeInfo;
// Determines how ExtractSerializedHandles should behave when it encounters an
// unrecoverable serialized handle.
enum ExtractBadHandlePolicy {
// Continue extracting handles upon encountering a bad handle. The bad
// handle will be extracted with an invalid handle value.
// Abort the extraction process, leaving any valid serialized handles still
// in the message.
~UserMessageImpl() override;
// Creates a new ports::UserMessageEvent with an attached UserMessageImpl.
static std::unique_ptr<ports::UserMessageEvent> CreateEventForNewMessage();
// Creates a new ports::UserMessageEvent with an attached serialized
// UserMessageImpl. May fail iff one or more |dispatchers| fails to serialize
// (e.g. due to it being in an invalid state.)
// Upon success, MOJO_RESULT_OK is returned and the new UserMessageEvent is
// stored in |*out_event|.
static MojoResult CreateEventForNewSerializedMessage(
uint32_t num_bytes,
const Dispatcher::DispatcherInTransit* dispatchers,
uint32_t num_dispatchers,
std::unique_ptr<ports::UserMessageEvent>* out_event);
// Creates a new UserMessageImpl from an existing serialized message buffer
// which was read from a Channel. Takes ownership of |channel_message|.
// |payload| and |payload_size| represent the range of bytes within
// |channel_message| which should be parsed by this call.
static std::unique_ptr<UserMessageImpl> CreateFromChannelMessage(
ports::UserMessageEvent* message_event,
Channel::MessagePtr channel_message,
void* payload,
size_t payload_size);
// Extracts the serialized Channel::Message from the UserMessageEvent in
// |event|. |event| must have a serialized UserMessageImpl instance attached.
// |message_event| is serialized into the front of the message payload before
// returning.
static Channel::MessagePtr FinalizeEventMessage(
std::unique_ptr<ports::UserMessageEvent> event);
bool HasContext() const { return context_ != 0; }
uintptr_t context() const { return context_; }
bool IsSerialized() const {
if (HasContext()) {
return false;
return !!channel_message_;
bool IsTransmittable() const { return !IsSerialized() || is_committed_; }
void* user_payload() {
return user_payload_;
const void* user_payload() const {
return user_payload_;
size_t user_payload_size() const {
return user_payload_size_;
size_t user_payload_capacity() const;
size_t num_handles() const;
void set_source_node(const ports::NodeName& name) { source_node_ = name; }
const ports::NodeName& source_node() const { return source_node_; }
MojoResult SetContext(uintptr_t context,
MojoMessageContextSerializer serializer,
MojoMessageContextDestructor destructor);
MojoResult AppendData(uint32_t additional_payload_size,
const MojoHandle* handles,
uint32_t num_handles);
MojoResult CommitSize();
// If this message is not already serialized, this serializes it.
MojoResult SerializeIfNecessary();
// Extracts handles from this (serialized) message.
// Returns |MOJO_RESULT_OK|
// if sucessful, |MOJO_RESULT_FAILED_PRECONDITION| if this isn't a serialized
// message, |MOJO_RESULT_NOT_FOUND| if all serialized handles have already
// been extracted, or |MOJO_RESULT_ABORTED| if one or more handles failed
// extraction.
// On success, |handles| is populated with |num_handles()| extracted handles,
// whose ownership is thereby transferred to the caller.
MojoResult ExtractSerializedHandles(ExtractBadHandlePolicy bad_handle_policy,
MojoHandle* handles);
// Forces all handle serialization to fail. Serialization can fail in
// production for a few different reasons (e.g. file descriptor exhaustion
// when duping data pipe buffer handles) which may be difficult to control in
// testing environments. This forces the common serialization code path to
// always behave as if the underlying implementation signaled failure,
// allowing tests to exercise those cases.
static void FailHandleSerializationForTesting(bool fail);
// Creates an unserialized UserMessageImpl with an associated |context| and
// |thunks|. If the message is ever going to be routed to another node (see
// |WillBeRoutedExternally()| below), it will be serialized at that time using
// operations provided by |thunks|.
UserMessageImpl(ports::UserMessageEvent* message_event);
// Creates a serialized UserMessageImpl backed by an existing Channel::Message
// object. |header| and |user_payload| must be pointers into
// |channel_message|'s own storage, and |user_payload_size| is the number of
// bytes comprising the user message contents at |user_payload|.
UserMessageImpl(ports::UserMessageEvent* message_event,
Channel::MessagePtr channel_message,
void* header,
size_t header_size,
void* user_payload,
size_t user_payload_size);
// UserMessage:
bool WillBeRoutedExternally() override;
size_t GetSizeIfSerialized() const override;
// The event which owns this serialized message. Not owned.
ports::UserMessageEvent* const message_event_;
// Unserialized message state.
uintptr_t context_ = 0;
MojoMessageContextSerializer context_serializer_ = nullptr;
MojoMessageContextDestructor context_destructor_ = nullptr;
// Serialized message contents. May be null if this is not a serialized
// message.
Channel::MessagePtr channel_message_;
// Indicates whether any handles serialized within |channel_message_| have
// yet to be extracted.
bool has_serialized_handles_ = false;
// Indicates whether the serialized message's contents (if any) have been
// committed yet.
bool is_committed_ = false;
// Only valid if |channel_message_| is non-null. |header_| is the address
// of the UserMessageImpl's internal MessageHeader structure within the
// serialized message buffer. |user_payload_| is the address of the first byte
// after any serialized dispatchers, with the payload comprising the remaining
// |user_payload_size_| bytes of the message.
void* header_ = nullptr;
size_t header_size_ = 0;
void* user_payload_ = nullptr;
size_t user_payload_size_ = 0;
// Handles which have been attached to the serialized message but which have
// not yet been serialized.
std::vector<Dispatcher::DispatcherInTransit> pending_handle_attachments_;
// The node name from which this message was received, iff it came from
// out-of-process and the source is known.
ports::NodeName source_node_ = ports::kInvalidNodeName;
} // namespace core
} // namespace mojo