[mojo-edk] Add MojoWatch and MojoCancelWatch APIs

mojo/edk/system/watcher.cc

Index: mojo/edk/system/watcher.cc
diff --git a/mojo/edk/system/watcher.cc b/mojo/edk/system/watcher.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4bc9dbbede1e0c485421cf00623b54d4375406cd
--- /dev/null
+++ b/mojo/edk/system/watcher.cc
@@ -0,0 +1,52 @@
+// 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/watcher.h"
+
+#include "mojo/edk/system/handle_signals_state.h"
+#include "mojo/edk/system/request_context.h"
+
+namespace mojo {
+namespace edk {
+
+Watcher::Watcher(MojoHandleSignals signals, const WatchCallback& callback)
+    : signals_(signals), callback_(callback) {
+}
+
+void Watcher::MaybeInvokeCallback(MojoResult result,
+                                  const HandleSignalsState& state) {
+  base::AutoLock lock(lock_);
+  if (is_cancelled_)
+    return;
+
+  callback_.Run(result, state);
+}
+
+void Watcher::NotifyForStateChange(const HandleSignalsState& signals_state) {
+  RequestContext* request_context = RequestContext::current();
+  if (signals_state.satisfies(signals_)) {
+    request_context->AddWatchNotifyFinalizer(
+        make_scoped_refptr(this), MOJO_RESULT_OK, signals_state);
+  } else if (!signals_state.can_satisfy(signals_)) {
+    request_context->AddWatchNotifyFinalizer(make_scoped_refptr(this),
+                                             MOJO_RESULT_FAILED_PRECONDITION,
+                                             signals_state);
+  }
+}
+
+void Watcher::NotifyClosed() {
+  static const HandleSignalsState closed_state = {0, 0};
+  RequestContext::current()->AddWatchNotifyFinalizer(
+      make_scoped_refptr(this), MOJO_RESULT_CANCELLED, closed_state);
+}
+
+void Watcher::Cancel() {
+  base::AutoLock lock(lock_);
+  is_cancelled_ = true;
+}
+
+Watcher::~Watcher() {}
+
+}  // namespace edk
+}  // namespace mojo