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// Copyright (c) 2012 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 <stddef.h>
#include <set>
#include "base/component_export.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "ipc/ipc_channel.h"
namespace IPC {
namespace internal {
// This class provides common pipe reading functionality for the
// platform-specific IPC channel implementations.
// It does the common input buffer management and message dispatch, while the
// platform-specific parts provide the pipe management through a virtual
// interface implemented on a per-platform basis.
// Note that there is no "writer" corresponding to this because the code for
// writing to the channel is much simpler and has very little common
// functionality that would benefit from being factored out. If we add
// something like that in the future, it would be more appropriate to add it
// here (and rename appropriately) rather than writing a different class.
class COMPONENT_EXPORT(IPC) ChannelReader {
explicit ChannelReader(Listener* listener);
virtual ~ChannelReader();
void set_listener(Listener* listener) { listener_ = listener; }
// This type is returned by ProcessIncomingMessages to indicate the effect of
// the method.
enum DispatchState {
// All messages were successfully dispatched, or there were no messages to
// dispatch.
// There was a channel error.
// Dispatching messages is blocked on receiving more information from the
// broker.
// Call to process messages received from the IPC connection and dispatch
// them.
DispatchState ProcessIncomingMessages();
// Handles asynchronously read data.
// Optionally call this after returning READ_PENDING from ReadData to
// indicate that buffer was filled with the given number of bytes of
// data. See ReadData for more.
DispatchState AsyncReadComplete(int bytes_read);
// Returns true if the given message is internal to the IPC implementation,
// like the "hello" message sent on channel set-up.
bool IsInternalMessage(const Message& m);
// Returns true if the given message is an Hello message
// sent on channel set-up.
bool IsHelloMessage(const Message& m);
Listener* listener() const { return listener_; }
// Subclasses should call this method in their destructor to give this class a
// chance to clean up state that might be dependent on subclass members.
void CleanUp();
// Populates the given buffer with data from the pipe.
// Returns the state of the read. On READ_SUCCESS, the number of bytes
// read will be placed into |*bytes_read| (which can be less than the
// buffer size). On READ_FAILED, the channel will be closed.
// If the return value is READ_PENDING, it means that there was no data
// ready for reading. The implementation is then responsible for either
// calling AsyncReadComplete with the number of bytes read into the
// buffer, or ProcessIncomingMessages to try the read again (depending
// on whether the platform's async I/O is "try again" or "write
// asynchronously into your buffer").
virtual ReadState ReadData(char* buffer, int buffer_len, int* bytes_read) = 0;
// Loads the required file desciptors into the given message. Returns true
// on success. False means a fatal channel error.
// This will read from the input_fds_ and read more handles from the FD
// pipe if necessary.
virtual bool ShouldDispatchInputMessage(Message* msg) = 0;
// Overridden by subclasses to get attachments that are sent alongside the IPC
// channel.
// Returns true on success. False means a fatal channel error.
virtual bool GetAttachments(Message* msg) = 0;
// Performs post-dispatch checks. Called when all input buffers are empty,
// though there could be more data ready to be read from the OS.
virtual bool DidEmptyInputBuffers() = 0;
// Handles internal messages, like the hello message sent on channel startup.
virtual void HandleInternalMessage(const Message& msg) = 0;
// Exposed for testing purposes only.
virtual void DispatchMessage(Message* m);
FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, AttachmentAlreadyBrokered);
FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, AttachmentNotYetBrokered);
FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, ResizeOverflowBuffer);
FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, InvalidMessageSize);
FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, TrimBuffer);
// Takes the data received from the IPC channel and translates it into
// Messages. Complete messages are passed to HandleTranslatedMessage().
// Returns |false| on unrecoverable error.
bool TranslateInputData(const char* input_data, int input_data_len);
// Internal messages and messages bound for the attachment broker are
// immediately dispatched. Other messages are passed to
// HandleExternalMessage().
// Returns |false| on unrecoverable error.
bool HandleTranslatedMessage(Message* translated_message);
// Populates the message with brokered and non-brokered attachments. If
// possible, the message is immediately dispatched. Otherwise, a deep copy of
// the message is added to |queued_messages_|. |blocked_ids_| are updated if
// necessary.
bool HandleExternalMessage(Message* external_message);
// If there was a dispatch error, informs |listener_|.
void HandleDispatchError(const Message& message);
// Checks that |size| is a valid message size. Has side effects if it's not.
bool CheckMessageSize(size_t size);
Listener* listener_;
// We read from the pipe into this buffer. Managed by DispatchInputData, do
// not access directly outside that function.
char input_buf_[Channel::kReadBufferSize];
// Large messages that span multiple pipe buffers, get built-up using
// this buffer.
std::string input_overflow_buf_;
// Maximum overflow buffer size, see Channel::kMaximumReadBufferSize.
// This is not a constant because we update it to reflect the reality
// of std::string::reserve() implementation.
size_t max_input_buffer_size_;
} // namespace internal
} // namespace IPC