Mojo: Abstract out the endpoints of MessagePipes.

mojo/system/local_message_pipe_endpoint.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/local_message_pipe_endpoint.h"
+
+#include <string.h>
+
+#include "base/logging.h"
+#include "base/stl_util.h"
+#include "mojo/system/message_in_transit.h"
+
+namespace mojo {
+namespace system {
+
+LocalMessagePipeEndpoint::LocalMessagePipeEndpoint()
+    : is_open_(true),
+      is_peer_open_(true) {
+}
+
+LocalMessagePipeEndpoint::~LocalMessagePipeEndpoint() {
+  DCHECK(!is_open_);
+}
+
+void LocalMessagePipeEndpoint::OnPeerClose() {
+  DCHECK(is_open_);
+  DCHECK(is_peer_open_);
+
+  MojoWaitFlags old_satisfied_flags = SatisfiedFlags();
+  MojoWaitFlags old_satisfiable_flags = SatisfiableFlags();
+  is_peer_open_ = false;
+  MojoWaitFlags new_satisfied_flags = SatisfiedFlags();
+  MojoWaitFlags new_satisfiable_flags = SatisfiableFlags();
+
+  if (new_satisfied_flags != old_satisfied_flags ||
+      new_satisfiable_flags != old_satisfiable_flags) {
+    waiter_list_.AwakeWaitersForStateChange(new_satisfied_flags,
+                                            new_satisfiable_flags);
+  }
+}
+
+MojoResult LocalMessagePipeEndpoint::EnqueueMessage(
+    const void* bytes, uint32_t num_bytes,
+    const MojoHandle* handles, uint32_t num_handles,
+    MojoWriteMessageFlags /*flags*/) {
+  DCHECK(is_open_);
+  DCHECK(is_peer_open_);
+
+  bool was_empty = message_queue_.empty();
+
+  // TODO(vtl): Eventually (with C++11), this should be an |emplace_back()|.
+  message_queue_.push_back(MessageInTransit::Create(bytes, num_bytes));
+  // TODO(vtl): Support sending handles.
+
+  if (was_empty) {
+    waiter_list_.AwakeWaitersForStateChange(SatisfiedFlags(),
+                                            SatisfiableFlags());
+  }
+
+  return MOJO_RESULT_OK;
+}
+
+void LocalMessagePipeEndpoint::CancelAllWaiters() {
+  DCHECK(is_open_);
+  waiter_list_.CancelAllWaiters();
+}
+
+void LocalMessagePipeEndpoint::Close() {
+  DCHECK(is_open_);
+  is_open_ = false;
+  STLDeleteElements(&message_queue_);
+}
+
+MojoResult LocalMessagePipeEndpoint::ReadMessage(
+    void* bytes, uint32_t* num_bytes,
+    MojoHandle* handles, uint32_t* num_handles,
+    MojoReadMessageFlags flags) {
+  DCHECK(is_open_);
+
+  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;
+
+  if (message_queue_.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_queue_.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_queue_.pop_front();
+    message->Destroy();
+
+    // Now it's empty, thus no longer readable.
+    if (message_queue_.empty()) {
+      // It's currently not possible to wait for non-readability, but we should
+      // do the state change anyway.
+      waiter_list_.AwakeWaitersForStateChange(SatisfiedFlags(),
+                                              SatisfiableFlags());
+    }
+  }
+
+  if (not_enough_space)
+    return MOJO_RESULT_RESOURCE_EXHAUSTED;
+
+  return MOJO_RESULT_OK;
+}
+
+MojoResult LocalMessagePipeEndpoint::AddWaiter(Waiter* waiter,
+                                               MojoWaitFlags flags,
+                                               MojoResult wake_result) {
+  DCHECK(is_open_);
+
+  if ((flags & SatisfiedFlags()))
+    return MOJO_RESULT_ALREADY_EXISTS;
+  if (!(flags & SatisfiableFlags()))
+    return MOJO_RESULT_FAILED_PRECONDITION;
+
+  waiter_list_.AddWaiter(waiter, flags, wake_result);
+  return MOJO_RESULT_OK;
+}
+
+void LocalMessagePipeEndpoint::RemoveWaiter(Waiter* waiter) {
+  DCHECK(is_open_);
+  waiter_list_.RemoveWaiter(waiter);
+}
+
+MojoWaitFlags LocalMessagePipeEndpoint::SatisfiedFlags() {
+  MojoWaitFlags satisfied_flags = 0;
+  if (!message_queue_.empty())
+    satisfied_flags |= MOJO_WAIT_FLAG_READABLE;
+  if (is_peer_open_)
+    satisfied_flags |= MOJO_WAIT_FLAG_WRITABLE;
+  return satisfied_flags;
+}
+
+MojoWaitFlags LocalMessagePipeEndpoint::SatisfiableFlags() {
+  MojoWaitFlags satisfiable_flags = 0;
+  if (!message_queue_.empty() || is_peer_open_)
+    satisfiable_flags |= MOJO_WAIT_FLAG_READABLE;
+  if (is_peer_open_)
+    satisfiable_flags |= MOJO_WAIT_FLAG_WRITABLE;
+  return satisfiable_flags;
+}
+
+}  // namespace system
+}  // namespace mojo
+