[mojo-edk] Add MojoWatch and MojoCancelWatch APIs

mojo/edk/system/request_context.cc

+// Copyright 2016 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/edk/system/request_context.h"
+
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/threading/thread_local.h"
+
+namespace mojo {
+namespace edk {
+
+namespace {
+
+base::LazyInstance<base::ThreadLocalPointer<RequestContext>>::Leaky
+    g_current_context;
+
+}  // namespace
+
+RequestContext::RequestContext() {
+  // We allow nested RequestContexts to exist as long as they aren't actually
+  // used for anything.
+  if (!g_current_context.Pointer()->Get())
+    g_current_context.Pointer()->Set(this);
+}
+
+RequestContext::~RequestContext() {
+  // NOTE: Callbacks invoked by this destructor are allowed to initiate new
+  // EDK requests on this thread, so we need to reset the thread-local context
+  // pointer before calling them.
+  if (IsCurrent())
+    g_current_context.Pointer()->Set(nullptr);
+
+  for (const WatchNotifyFinalizer& watch : watch_notify_finalizers_.container())
+    watch.watcher->MaybeInvokeCallback(watch.result, watch.state);
+
+  for (const scoped_refptr<Watcher>& watcher :
+          watch_cancel_finalizers_.container())
+    watcher->Cancel();
+}
+
+// static
+RequestContext* RequestContext::current() {
+  DCHECK(g_current_context.Pointer()->Get());
+  return g_current_context.Pointer()->Get();
+}
+
+void RequestContext::AddWatchNotifyFinalizer(
+    scoped_refptr<Watcher> watcher,
+    MojoResult result,
+    const HandleSignalsState& state) {
+  DCHECK(IsCurrent());
+  watch_notify_finalizers_->push_back(
+      WatchNotifyFinalizer(watcher, result, state));
+}
+
+void RequestContext::AddWatchCancelFinalizer(scoped_refptr<Watcher> watcher) {
+  DCHECK(IsCurrent());
+  watch_cancel_finalizers_->push_back(watcher);
+}
+
+bool RequestContext::IsCurrent() const {
+  return g_current_context.Pointer()->Get() == this;
+}
+
+RequestContext::WatchNotifyFinalizer::WatchNotifyFinalizer(
+    scoped_refptr<Watcher> watcher,
+    MojoResult result,
+    const HandleSignalsState& state)
+    : watcher(watcher), result(result), state(state) {
+}
+
+RequestContext::WatchNotifyFinalizer::~WatchNotifyFinalizer() {}
+
+}  // namespace edk
+}  // namespace mojo