Mojo: Add BindingsSupportImpl on top of HandleWatcher

mojo/common/bindings_support_impl.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/common/bindings_support_impl.h"
+
+#include "base/atomic_ref_count.h"
+#include "base/bind.h"
+#include "mojo/common/handle_watcher.h"
+
+namespace mojo {
+namespace common {
+
+// The Context struct is used to track the number of HandleWatcher objects in

[sky, 2013/11/11 17:23:50]

nit: struct -> class

+// use by a particular BindingsSupportImpl instance.
+class BindingsSupportImpl::Context
+    : public base::RefCountedThreadSafe<BindingsSupportImpl::Context> {
+ public:
+  void CallOnHandleReady(HandleWatcher* watcher,
+                         AsyncWaitCallback* callback,
+                         MojoResult result) {
+    delete watcher;
+    callback->OnHandleReady(result);
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<Context>;
+  virtual ~Context() {}
+};
+
+BindingsSupportImpl::BindingsSupportImpl()
+    : context_(new Context()) {
+}
+
+BindingsSupportImpl::~BindingsSupportImpl() {
+  // All HandleWatcher instances created through this interface should have
+  // been destroyed.
+  DCHECK(context_->HasOneRef());
+}
+
+BindingsSupport::AsyncWaitID BindingsSupportImpl::AsyncWait(
+    Handle handle,
+    MojoWaitFlags flags,
+    AsyncWaitCallback* callback) {
+  HandleWatcher* watcher = new HandleWatcher();

[sky, 2013/11/11 17:23:50]

nit: document destroyed when done or canceled.

+
+  // TODO(darin): Standardize on mojo::Handle instead of MojoHandle?
+  watcher->Start(handle.value,
+                 flags,
+                 MOJO_DEADLINE_INDEFINITE,
+                 base::Bind(&Context::CallOnHandleReady,
+                            context_,
+                            watcher,
+                            callback));
+  return watcher;
+}
+
+void BindingsSupportImpl::CancelWait(AsyncWaitID async_wait_id) {
+  HandleWatcher* watcher = static_cast<HandleWatcher*>(async_wait_id);
+  delete watcher;
+}
+
+}  // namespace common
+}  // namespace mojo