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Unified Diff: mojo/edk/system/channel_endpoint.h

Issue 814543006: Move //mojo/{public, edk} underneath //third_party (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Rebase Created 5 years, 11 months ago
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Index: mojo/edk/system/channel_endpoint.h
diff --git a/mojo/edk/system/channel_endpoint.h b/mojo/edk/system/channel_endpoint.h
deleted file mode 100644
index 90ee86b758399f912c93baac0d54b643e4d39036..0000000000000000000000000000000000000000
--- a/mojo/edk/system/channel_endpoint.h
+++ /dev/null
@@ -1,210 +0,0 @@
-// 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.
-
-#ifndef MOJO_EDK_SYSTEM_CHANNEL_ENDPOINT_H_
-#define MOJO_EDK_SYSTEM_CHANNEL_ENDPOINT_H_
-
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/synchronization/lock.h"
-#include "mojo/edk/system/channel_endpoint_id.h"
-#include "mojo/edk/system/message_in_transit_queue.h"
-#include "mojo/edk/system/system_impl_export.h"
-
-namespace mojo {
-namespace system {
-
-class Channel;
-class ChannelEndpointClient;
-class MessageInTransit;
-
-// TODO(vtl): The plan:
-// - (Done.) Move |Channel::Endpoint| to |ChannelEndpoint|. Make it
-// refcounted, and not copyable. Make |Channel| a friend. Make things work.
-// - (Done.) Give |ChannelEndpoint| a lock. The lock order (in order of
-// allowable acquisition) is: |MessagePipe|, |ChannelEndpoint|, |Channel|.
-// - (Done) Stop having |Channel| as a friend.
-// - (Done) Move logic from |ProxyMessagePipeEndpoint| into |ChannelEndpoint|.
-// Right now, we have to go through lots of contortions to manipulate state
-// owned by |ProxyMessagePipeEndpoint| (in particular, |Channel::Endpoint|
-// doesn't know about the remote ID; the local ID is duplicated in two
-// places). Hollow out |ProxyMessagePipeEndpoint|, and have it just own a
-// reference to |ChannelEndpoint| (hence the refcounting).
-// - In essence, |ChannelEndpoint| becomes the thing that knows about
-// channel-specific aspects of an endpoint (notably local and remote IDs,
-// and knowledge about handshaking), and mediates between the |Channel| and
-// the |MessagePipe|.
-// - In the end state, |Channel| should no longer need to know about
-// |MessagePipe| and ports (but only |ChannelEndpoint|) and
-// |ProxyMessagePipeEndpoint| should no longer need to know about |Channel|
-// (ditto).
-//
-// Things as they are now, before I change everything (TODO(vtl): update this
-// comment appropriately):
-//
-// Terminology:
-// - "Message pipe endpoint": In the implementation, a |MessagePipe| owns
-// two |MessagePipeEndpoint| objects, one for each port. The
-// |MessagePipeEndpoint| objects are only accessed via the |MessagePipe|
-// (which has the lock), with the additional information of the port
-// number. So as far as the channel is concerned, a message pipe endpoint
-// is a pointer to a |MessagePipe| together with the port number.
-// - The value of |port| in |EndpointInfo| refers to the
-// |ProxyMessagePipeEndpoint| (i.e., the endpoint that is logically on
-// the other side). Messages received by a channel for a message pipe
-// are thus written to the *peer* of this port.
-// - "Attached"/"detached": A message pipe endpoint is attached to a channel
-// if it has a pointer to it. It must be detached before the channel gives
-// up its pointer to it in order to break a reference cycle. (This cycle
-// is needed to allow a channel to be shut down cleanly, without shutting
-// down everything else first.)
-// - "Running" (message pipe endpoint): A message pipe endpoint is running
-// if messages written to it (via some |MessagePipeDispatcher|, to which
-// some |MojoHandle| is assigned) are being transmitted through the
-// channel.
-// - Before a message pipe endpoint is run, it will queue messages.
-// - When a message pipe endpoint is detached from a channel, it is also
-// taken out of the running state. After that point, messages should
-// no longer be written to it.
-// - "Normal" message pipe endpoint (state): The channel itself does not
-// have knowledge of whether a message pipe endpoint has started running
-// yet. It will *receive* messages for a message pipe in either state (but
-// the message pipe endpoint won't *send* messages to the channel if it
-// has not started running).
-// - "Zombie" message pipe endpoint (state): A message pipe endpoint is a
-// zombie if it is still in |local_id_to_endpoint_info_map_|, but the
-// channel is no longer forwarding messages to it (even if it may still be
-// receiving messages for it).
-// - There are various types of zombies, depending on the reason the
-// message pipe endpoint cannot yet be removed.
-// - If the remote side is closed, it will send a "remove" control
-// message. After the channel receives that message (to which it
-// responds with a "remove ack" control message), it knows that it
-// shouldn't receive any more messages for that message pipe endpoint
-// (local ID), but it must wait for the endpoint to detach. (It can't
-// do so without a race, since it can't call into the message pipe
-// under |lock_|.) [TODO(vtl): When I add remotely-allocated IDs,
-// we'll have to remove the |EndpointInfo| from
-// |local_id_to_endpoint_info_map_| -- i.e., remove the local ID,
-// since it's no longer valid and may be reused by the remote side --
-// and keep the |EndpointInfo| alive in some other way.]
-// - If the local side is closed and the message pipe endpoint was
-// already running (so there are no queued messages left to send), it
-// will detach the endpoint, and send a "remove" control message.
-// However, the channel may still receive messages for that endpoint
-// until it receives a "remove ack" control message.
-// - If the local side is closed but the message pipe endpoint was not
-// yet running , the detaching is delayed until after it is run and
-// all the queued messages are sent to the channel. On being detached,
-// things proceed as in one of the above cases. The endpoint is *not*
-// a zombie until it is detached (or a "remove" message is received).
-// [TODO(vtl): Maybe we can get rid of this case? It'd only not yet be
-// running since under the current scheme it wouldn't have a remote ID
-// yet.]
-// - Note that even if the local side is closed, it may still receive a
-// "remove" message from the other side (if the other side is closed
-// simultaneously, and both sides send "remove" messages). In that
-// case, it must still remain alive until it receives the "remove
-// ack" (and it must ack the "remove" message that it received).
-class MOJO_SYSTEM_IMPL_EXPORT ChannelEndpoint
- : public base::RefCountedThreadSafe<ChannelEndpoint> {
- public:
- // Constructor for a |ChannelEndpoint| with the given client (specified by
- // |client| and |client_port|). Optionally takes messages from
- // |*message_queue| if |message_queue| is non-null.
- //
- // |client| may be null if this endpoint will never need to receive messages,
- // in which case |message_queue| should not be null. In that case, this
- // endpoint will simply send queued messages upon being attached to a
- // |Channel| and immediately detach itself.
- ChannelEndpoint(ChannelEndpointClient* client,
- unsigned client_port,
- MessageInTransitQueue* message_queue = nullptr);
-
- // Methods called by |ChannelEndpointClient|:
-
- // Called to enqueue an outbound message. (If |AttachAndRun()| has not yet
- // been called, the message will be enqueued and sent when |AttachAndRun()| is
- // called.)
- bool EnqueueMessage(scoped_ptr<MessageInTransit> message);
-
- // Called to *replace* current client with a new client (which must differ
- // from the existing client). This must not be called after
- // |DetachFromClient()| has been called.
- //
- // This returns true in the typical case, and false if this endpoint has been
- // detached from the channel, in which case the caller should probably call
- // its (new) client's |OnDetachFromChannel()|.
- bool ReplaceClient(ChannelEndpointClient* client, unsigned client_port);
-
- // Called before the |ChannelEndpointClient| gives up its reference to this
- // object.
- void DetachFromClient();
-
- // Methods called by |Channel|:
-
- // Called when the |Channel| takes a reference to this object. This will send
- // all queue messages (in |channel_message_queue_|).
- // TODO(vtl): Maybe rename this "OnAttach"?
- void AttachAndRun(Channel* channel,
- ChannelEndpointId local_id,
- ChannelEndpointId remote_id);
-
- // Called when the |Channel| receives a message for the |ChannelEndpoint|.
- void OnReadMessage(scoped_ptr<MessageInTransit> message);
-
- // Called before the |Channel| gives up its reference to this object.
- void DetachFromChannel();
-
- private:
- friend class base::RefCountedThreadSafe<ChannelEndpoint>;
- ~ChannelEndpoint();
-
- // Must be called with |lock_| held.
- bool WriteMessageNoLock(scoped_ptr<MessageInTransit> message);
-
- // Resets |channel_| to null (and sets |is_detached_from_channel_|). This may
- // only be called if |channel_| is non-null. Must be called with |lock_| held.
- void ResetChannelNoLock();
-
- // Protects the members below.
- base::Lock lock_;
-
- // |client_| must be valid whenever it is non-null. Before |*client_| gives up
- // its reference to this object, it must call |DetachFromClient()|.
- // NOTE: This is a |scoped_refptr<>|, rather than a raw pointer, since the
- // |Channel| needs to keep the |MessagePipe| alive for the "proxy-proxy" case.
- // Possibly we'll be able to eliminate that case when we have full
- // multiprocess support.
- // WARNING: |ChannelEndpointClient| methods must not be called under |lock_|.
- // Thus to make such a call, a reference must first be taken under |lock_| and
- // the lock released.
- // WARNING: Beware of interactions with |ReplaceClient()|. By the time the
- // call is made, the client may have changed. This must be detected and dealt
- // with.
- scoped_refptr<ChannelEndpointClient> client_;
- unsigned client_port_;
-
- // |channel_| must be valid whenever it is non-null. Before |*channel_| gives
- // up its reference to this object, it must call |DetachFromChannel()|.
- // |local_id_| and |remote_id_| are valid if and only |channel_| is non-null.
- Channel* channel_;
- ChannelEndpointId local_id_;
- ChannelEndpointId remote_id_;
- // This distinguishes the two cases of |channel| being null: not yet attached
- // versus detached.
- bool is_detached_from_channel_;
-
- // This queue is used before we're running on a channel and ready to send
- // messages to the channel.
- MessageInTransitQueue channel_message_queue_;
-
- DISALLOW_COPY_AND_ASSIGN(ChannelEndpoint);
-};
-
-} // namespace system
-} // namespace mojo
-
-#endif // MOJO_EDK_SYSTEM_CHANNEL_ENDPOINT_H_
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