Mojo: Abstract out the endpoints of MessagePipes.

mojo/system/message_pipe.cc

 // Copyright 2013 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 "mojo/system/message_pipe.h"
 
 #include "base/logging.h"
 #include "base/stl_util.h"
+#include "mojo/system/local_message_pipe_endpoint.h"
 #include "mojo/system/message_in_transit.h"
+#include "mojo/system/message_pipe_endpoint.h"
 
 namespace mojo {
 namespace system {
 
 namespace {
 
 unsigned DestinationPortFromSourcePort(unsigned port) {
   DCHECK(port == 0 || port == 1);
   return port ^ 1;
 }
 
 }  // namespace
 
 MessagePipe::MessagePipe() {
-  is_open_[0] = is_open_[1] = true;
+  endpoints_[0].reset(new LocalMessagePipeEndpoint());

[darin (slow to review), 2013/10/15 06:50:36]

I see. This is the connected pair case.

+  endpoints_[1].reset(new LocalMessagePipeEndpoint());
 }
 
 void MessagePipe::CancelAllWaiters(unsigned port) {
   DCHECK(port == 0 || port == 1);
 
   base::AutoLock locker(lock_);
-  DCHECK(is_open_[port]);
-
-  waiter_lists_[port].CancelAllWaiters();
+  DCHECK(endpoints_[port].get());
+  endpoints_[port]->CancelAllWaiters();
 }
 
 void MessagePipe::Close(unsigned port) {
   DCHECK(port == 0 || port == 1);
 
   unsigned destination_port = DestinationPortFromSourcePort(port);
 
   base::AutoLock locker(lock_);
-  DCHECK(is_open_[port]);
+  DCHECK(endpoints_[port].get());
 
-  // Record the old state of the other (destination) port, so we can tell if it
-  // changes.
-  // TODO(vtl): Maybe the |WaiterList| should track the old state, so that we
-  // don't have to do this.
-  MojoWaitFlags old_dest_satisfied_flags = MOJO_WAIT_FLAG_NONE;
-  MojoWaitFlags old_dest_satisfiable_flags = MOJO_WAIT_FLAG_NONE;
-  bool dest_is_open = is_open_[destination_port];
-  if (dest_is_open) {
-    old_dest_satisfied_flags = SatisfiedFlagsNoLock(destination_port);
-    old_dest_satisfiable_flags = SatisfiableFlagsNoLock(destination_port);
-  }
+  endpoints_[port]->Close();
+  if (endpoints_[destination_port].get())
+    endpoints_[destination_port]->OnPeerClose();
 
-  is_open_[port] = false;
-  STLDeleteElements(&message_queues_[port]);  // Clear incoming queue for port.
-
-  // Notify the other (destination) port if its state has changed.
-  if (dest_is_open) {
-    MojoWaitFlags new_dest_satisfied_flags =
-        SatisfiedFlagsNoLock(destination_port);
-    MojoWaitFlags new_dest_satisfiable_flags =
-        SatisfiableFlagsNoLock(destination_port);
-    if (new_dest_satisfied_flags != old_dest_satisfied_flags ||
-        new_dest_satisfiable_flags != old_dest_satisfiable_flags) {
-      waiter_lists_[destination_port].AwakeWaitersForStateChange(
-          new_dest_satisfied_flags, new_dest_satisfiable_flags);
-    }
-  }
+  endpoints_[port].reset();
 }
 
 // TODO(vtl): Handle flags.
 MojoResult MessagePipe::WriteMessage(
     unsigned port,
     const void* bytes, uint32_t num_bytes,
     const MojoHandle* handles, uint32_t num_handles,
-    MojoWriteMessageFlags /*flags*/) {
+    MojoWriteMessageFlags flags) {
   DCHECK(port == 0 || port == 1);
 
   unsigned destination_port = DestinationPortFromSourcePort(port);
 
   base::AutoLock locker(lock_);
-  DCHECK(is_open_[port]);
+  DCHECK(endpoints_[port].get());
 
   // The destination port need not be open, unlike the source port.
-  if (!is_open_[destination_port])
+  if (!endpoints_[destination_port].get())
     return MOJO_RESULT_FAILED_PRECONDITION;
 
-  bool dest_was_empty = message_queues_[destination_port].empty();
-
-  // TODO(vtl): Eventually (with C++11), this should be an |emplace_back()|.
-  message_queues_[destination_port].push_back(
-      MessageInTransit::Create(bytes, num_bytes));
-  // TODO(vtl): Support sending handles.
-
-  // The other (destination) port was empty and now isn't, so it should now be
-  // readable. Wake up anyone waiting on this.
-  if (dest_was_empty) {
-    waiter_lists_[destination_port].AwakeWaitersForStateChange(
-        SatisfiedFlagsNoLock(destination_port),
-        SatisfiableFlagsNoLock(destination_port));
-  }
-
-  return MOJO_RESULT_OK;
+  return endpoints_[destination_port]->EnqueueMessage(bytes, num_bytes,
+                                                      handles, num_handles,
+                                                      flags);
 }
 
 MojoResult MessagePipe::ReadMessage(unsigned port,
                                     void* bytes, uint32_t* num_bytes,
                                     MojoHandle* handles, uint32_t* num_handles,
                                     MojoReadMessageFlags flags) {
   DCHECK(port == 0 || port == 1);
 
-  const uint32_t max_bytes = num_bytes ? *num_bytes : 0;
-  // TODO(vtl): We'll need this later:
-  //  const uint32_t max_handles = num_handles ? *num_handles : 0;
+  base::AutoLock locker(lock_);
+  DCHECK(endpoints_[port].get());
 
-  base::AutoLock locker(lock_);
-  DCHECK(is_open_[port]);
-
-  if (message_queues_[port].empty())
-    return MOJO_RESULT_NOT_FOUND;
-
-  // TODO(vtl): If |flags & MOJO_READ_MESSAGE_FLAG_MAY_DISCARD|, we could pop
-  // and release the lock immediately.
-  bool not_enough_space = false;
-  MessageInTransit* const message = message_queues_[port].front();
-  if (num_bytes)
-    *num_bytes = message->data_size();
-  if (message->data_size() <= max_bytes)
-    memcpy(bytes, message->data(), message->data_size());
-  else
-    not_enough_space = true;
-
-  // TODO(vtl): Support receiving handles.
-  if (num_handles)
-    *num_handles = 0;
-
-  if (!not_enough_space || (flags & MOJO_READ_MESSAGE_FLAG_MAY_DISCARD)) {
-    message_queues_[port].pop_front();
-    message->Destroy();
-
-    // Now it's empty, thus no longer readable.
-    if (message_queues_[port].empty()) {
-      // It's currently not possible to wait for non-readability, but we should
-      // do the state change anyway.
-      waiter_lists_[port].AwakeWaitersForStateChange(
-          SatisfiedFlagsNoLock(port), SatisfiableFlagsNoLock(port));
-    }
-  }
-
-  if (not_enough_space)
-    return MOJO_RESULT_RESOURCE_EXHAUSTED;
-
-  return MOJO_RESULT_OK;
+  return endpoints_[port]->ReadMessage(bytes, num_bytes,
+                                       handles, num_handles,
+                                       flags);
 }
 
 MojoResult MessagePipe::AddWaiter(unsigned port,
                                   Waiter* waiter,
                                   MojoWaitFlags flags,
                                   MojoResult wake_result) {
   DCHECK(port == 0 || port == 1);
 
   base::AutoLock locker(lock_);
-  DCHECK(is_open_[port]);
+  DCHECK(endpoints_[port].get());
 
-  if ((flags & SatisfiedFlagsNoLock(port)))
-    return MOJO_RESULT_ALREADY_EXISTS;
-  if (!(flags & SatisfiableFlagsNoLock(port)))
-    return MOJO_RESULT_FAILED_PRECONDITION;
-
-  waiter_lists_[port].AddWaiter(waiter, flags, wake_result);
-  return MOJO_RESULT_OK;
+  return endpoints_[port]->AddWaiter(waiter, flags, wake_result);
 }
 
 void MessagePipe::RemoveWaiter(unsigned port, Waiter* waiter) {
   DCHECK(port == 0 || port == 1);
 
   base::AutoLock locker(lock_);
-  DCHECK(is_open_[port]);
+  DCHECK(endpoints_[port].get());
 
-  waiter_lists_[port].RemoveWaiter(waiter);
+  endpoints_[port]->RemoveWaiter(waiter);
 }
 
 MessagePipe::~MessagePipe() {
   // Owned by the dispatchers. The owning dispatchers should only release us via
   // their |Close()| method, which should inform us of being closed via our
   // |Close()|. Thus these should already be null.
-  DCHECK(!is_open_[0]);
-  DCHECK(!is_open_[1]);
-}
-
-MojoWaitFlags MessagePipe::SatisfiedFlagsNoLock(unsigned port) {
-  DCHECK(port == 0 || port == 1);
-
-  unsigned destination_port = DestinationPortFromSourcePort(port);
-
-  lock_.AssertAcquired();
-
-  MojoWaitFlags satisfied_flags = 0;
-  if (!message_queues_[port].empty())
-    satisfied_flags |= MOJO_WAIT_FLAG_READABLE;
-  if (is_open_[destination_port])
-    satisfied_flags |= MOJO_WAIT_FLAG_WRITABLE;
-
-  return satisfied_flags;
-}
-
-MojoWaitFlags MessagePipe::SatisfiableFlagsNoLock(unsigned port) {
-  DCHECK(port == 0 || port == 1);
-
-  unsigned destination_port = DestinationPortFromSourcePort(port);
-
-  lock_.AssertAcquired();
-
-  MojoWaitFlags satisfiable_flags = 0;
-  if (!message_queues_[port].empty() || is_open_[destination_port])
-    satisfiable_flags |= MOJO_WAIT_FLAG_READABLE;
-  if (is_open_[destination_port])
-    satisfiable_flags |= MOJO_WAIT_FLAG_WRITABLE;
-
-  return satisfiable_flags;
+  DCHECK(!endpoints_[0].get());
+  DCHECK(!endpoints_[1].get());
 }
 
 }  // namespace system
 }  // namespace mojo