Split the IPC code into ipc/

This splits the ipc code from the common project.  The 'common' project pulls in
all of webkit, the v8 bindings, skia, googleurl, and a number of other projects
which makes it very difficult to deal with especially for external projects
wanting just to use some of Chromium's infrastructure.  This puts the ipc code
into its top-level ipc/ directory with a dependency only on base.  The common
project depends on the new ipc/ipc.gyp:ipc target so that all projects currently
pulling common in to get the IPC code still have it available.  This mostly
follows agl's pre-gyp attempt to do this which was r13062.

Known issues:
- Currently a number of projects depend on chrome/chrome.gyp:common in order to
use the IPC infrastructure.  Rather than fixing all of these dependencies I have
made common depend on ipc/ipc.gyp:ipc and added "ipc" to the include_rules
section of DEPS so that checkdeps.py doesn't complain.  Over time projects that
need IPC should depend on the IPC project themselves and dependencies on common
removed, although I don't think many projects that need IPC will be able to get
away without common currently.
- ipc/ipc_message_macros.h still has #include "chrome/common/..." inside of a
ipc/ should not refer to files in chrome/... now.  I'm not sure how to resolve
this since it's really an IDE bug
- the named pipe name (windows+linux) and the logging event name (all) + env
variable (posix) refer explicitly to 'Chrome' which somewhat hurts the illusion
of ipc/ being an independent library.  I think this should be examined in a
subsequent, much smaller patch.
- I've eliminated the IPC.SendMsgCount counter since it was implemented in a way
to create a dependency from ipc/ to chrome/common/chrome_counters. This is the
same approach that r13062 took.

http://codereview.chromium.org/155905

(Patch from James Robinson)


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@21342 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 209 insertions, 0 deletions

diff --git a/ipc/ipc_channel_proxy.h b/ipc/ipc_channel_proxy.h
new file mode 100644
index 0000000..1aed33e
--- /dev/null
+++ b/ipc/ipc_channel_proxy.h
@@ -0,0 +1,209 @@
+// Copyright (c) 2006-2008 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 IPC_IPC_CHANNEL_PROXY_H__
+#define IPC_IPC_CHANNEL_PROXY_H__
+
+#include <vector>
+
+#include "base/ref_counted.h"
+#include "ipc/ipc_channel.h"
+
+class MessageLoop;
+
+namespace IPC {
+
+//-----------------------------------------------------------------------------
+// IPC::ChannelProxy
+//
+// This class is a helper class that is useful when you wish to run an IPC
+// channel on a background thread.  It provides you with the option of either
+// handling IPC messages on that background thread or having them dispatched to
+// your main thread (the thread on which the IPC::ChannelProxy is created).
+//
+// The API for an IPC::ChannelProxy is very similar to that of an IPC::Channel.
+// When you send a message to an IPC::ChannelProxy, the message is routed to
+// the background thread, where it is then passed to the IPC::Channel's Send
+// method.  This means that you can send a message from your thread and your
+// message will be sent over the IPC channel when possible instead of being
+// delayed until your thread returns to its message loop.  (Often IPC messages
+// will queue up on the IPC::Channel when there is a lot of traffic, and the
+// channel will not get cycles to flush its message queue until the thread, on
+// which it is running, returns to its message loop.)
+//
+// An IPC::ChannelProxy can have a MessageFilter associated with it, which will
+// be notified of incoming messages on the IPC::Channel's thread.  This gives
+// the consumer of IPC::ChannelProxy the ability to respond to incoming
+// messages on this background thread instead of on their own thread, which may
+// be bogged down with other processing.  The result can be greatly improved
+// latency for messages that can be handled on a background thread.
+//
+// The consumer of IPC::ChannelProxy is responsible for allocating the Thread
+// instance where the IPC::Channel will be created and operated.
+//
+class ChannelProxy : public Message::Sender {
+ public:
+  // A class that receives messages on the thread where the IPC channel is
+  // running.  It can choose to prevent the default action for an IPC message.
+  class MessageFilter : public base::RefCountedThreadSafe<MessageFilter> {
+   public:
+    virtual ~MessageFilter() {}
+
+    // Called on the background thread to provide the filter with access to the
+    // channel.  Called when the IPC channel is initialized or when AddFilter
+    // is called if the channel is already initialized.
+    virtual void OnFilterAdded(Channel* channel) {}
+
+    // Called on the background thread when the filter has been removed from
+    // the ChannelProxy and when the Channel is closing.  After a filter is
+    // removed, it will not be called again.
+    virtual void OnFilterRemoved() {}
+
+    // Called to inform the filter that the IPC channel is connected and we
+    // have received the internal Hello message from the peer.
+    virtual void OnChannelConnected(int32 peer_pid) {}
+
+    // Called when there is an error on the channel, typically that the channel
+    // has been closed.
+    virtual void OnChannelError() {}
+
+    // Called to inform the filter that the IPC channel will be destroyed.
+    // OnFilterRemoved is called immediately after this.
+    virtual void OnChannelClosing() {}
+
+    // Return true to indicate that the message was handled, or false to let
+    // the message be handled in the default way.
+    virtual bool OnMessageReceived(const Message& message) {
+      return false;
+    }
+  };
+
+  // Initializes a channel proxy.  The channel_id and mode parameters are
+  // passed directly to the underlying IPC::Channel.  The listener is called on
+  // the thread that creates the ChannelProxy.  The filter's OnMessageReceived
+  // method is called on the thread where the IPC::Channel is running.  The
+  // filter may be null if the consumer is not interested in handling messages
+  // on the background thread.  Any message not handled by the filter will be
+  // dispatched to the listener.  The given message loop indicates where the
+  // IPC::Channel should be created.
+  ChannelProxy(const std::string& channel_id, Channel::Mode mode,
+               Channel::Listener* listener, MessageFilter* filter,
+               MessageLoop* ipc_thread_loop);
+
+  ~ChannelProxy() {
+    Close();
+  }
+
+  // Close the IPC::Channel.  This operation completes asynchronously, once the
+  // background thread processes the command to close the channel.  It is ok to
+  // call this method multiple times.  Redundant calls are ignored.
+  //
+  // WARNING: The MessageFilter object held by the ChannelProxy is also
+  // released asynchronously, and it may in fact have its final reference
+  // released on the background thread.  The caller should be careful to deal
+  // with / allow for this possibility.
+  void Close();
+
+  // Send a message asynchronously.  The message is routed to the background
+  // thread where it is passed to the IPC::Channel's Send method.
+  virtual bool Send(Message* message);
+
+  // Used to intercept messages as they are received on the background thread.
+  //
+  // Ordinarily, messages sent to the ChannelProxy are routed to the matching
+  // listener on the worker thread.  This API allows code to intercept messages
+  // before they are sent to the worker thread.
+  void AddFilter(MessageFilter* filter);
+  void RemoveFilter(MessageFilter* filter);
+
+#if defined(OS_POSIX)
+  // Calls through to the underlying channel's methods.
+  // TODO(playmobil): For now this is only implemented in the case of
+  // create_pipe_now = true, we need to figure this out for the latter case.
+  int GetClientFileDescriptor() const;
+#endif  // defined(OS_POSIX)
+
+ protected:
+  class Context;
+  // A subclass uses this constructor if it needs to add more information
+  // to the internal state.  If create_pipe_now is true, the pipe is created
+  // immediately.  Otherwise it's created on the IO thread.
+  ChannelProxy(const std::string& channel_id, Channel::Mode mode,
+               MessageLoop* ipc_thread_loop, Context* context,
+               bool create_pipe_now);
+
+  // Used internally to hold state that is referenced on the IPC thread.
+  class Context : public base::RefCountedThreadSafe<Context>,
+                  public Channel::Listener {
+   public:
+    Context(Channel::Listener* listener, MessageFilter* filter,
+            MessageLoop* ipc_thread);
+    virtual ~Context() { }
+    MessageLoop* ipc_message_loop() const { return ipc_message_loop_; }
+    const std::string& channel_id() const { return channel_id_; }
+
+    // Dispatches a message on the listener thread.
+    void OnDispatchMessage(const Message& message);
+
+   protected:
+    // IPC::Channel::Listener methods:
+    virtual void OnMessageReceived(const Message& message);
+    virtual void OnChannelConnected(int32 peer_pid);
+    virtual void OnChannelError();
+
+    // Like OnMessageReceived but doesn't try the filters.
+    void OnMessageReceivedNoFilter(const Message& message);
+
+    // Gives the filters a chance at processing |message|.
+    // Returns true if the message was processed, false otherwise.
+    bool TryFilters(const Message& message);
+
+    // Like Open and Close, but called on the IPC thread.
+    virtual void OnChannelOpened();
+    virtual void OnChannelClosed();
+
+    // Called on the consumers thread when the ChannelProxy is closed.  At that
+    // point the consumer is telling us that they don't want to receive any
+    // more messages, so we honor that wish by forgetting them!
+    virtual void Clear() { listener_ = NULL; }
+
+   private:
+    friend class ChannelProxy;
+    // Create the Channel
+    void CreateChannel(const std::string& id, const Channel::Mode& mode);
+
+    // Methods called via InvokeLater:
+    void OnSendMessage(Message* message_ptr);
+    void OnAddFilter(MessageFilter* filter);
+    void OnRemoveFilter(MessageFilter* filter);
+    void OnDispatchConnected();
+    void OnDispatchError();
+
+    MessageLoop* listener_message_loop_;
+    Channel::Listener* listener_;
+
+    // List of filters.  This is only accessed on the IPC thread.
+    std::vector<scoped_refptr<MessageFilter> > filters_;
+    MessageLoop* ipc_message_loop_;
+    Channel* channel_;
+    std::string channel_id_;
+    int peer_pid_;
+    bool channel_connected_called_;
+  };
+
+  Context* context() { return context_; }
+
+ private:
+  void Init(const std::string& channel_id, Channel::Mode mode,
+            MessageLoop* ipc_thread_loop, bool create_pipe_now);
+
+  // By maintaining this indirection (ref-counted) to our internal state, we
+  // can safely be destroyed while the background thread continues to do stuff
+  // that involves this data.
+  scoped_refptr<Context> context_;
+};
+
+}  // namespace IPC
+
+#endif  // IPC_IPC_CHANNEL_PROXY_H__