[mojo-edk] Add MojoWatch and MojoCancelWatch APIs

mojo/edk/system/watcher_set.cc

Index: mojo/edk/system/watcher_set.cc
diff --git a/mojo/edk/system/watcher_set.cc b/mojo/edk/system/watcher_set.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6a9c0b3fea17f2053e832712ffa327502f26d581
--- /dev/null
+++ b/mojo/edk/system/watcher_set.cc
@@ -0,0 +1,89 @@
+// 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_set.h"
+
+#include "base/bind.h"
+#include "base/containers/stack_container.h"

[Anand Mistry (off Chromium), 2016/02/29 12:03:35]

Unused?

[Ken Rockot(use gerrit already), 2016/02/29 20:59:06]

Removed

+
+namespace mojo {
+namespace edk {
+
+struct HandleSignalsState;

[Anand Mistry (off Chromium), 2016/02/29 12:03:35]

Remove and #include "mojo/edk/system/handle_signals_state.h".

[Ken Rockot(use gerrit already), 2016/02/29 20:59:06]

Done

+
+WatcherSet::Watcher::Watcher(MojoHandleSignals signals,
+                             const Dispatcher::WatchCallback& callback)
+    : signals(signals), callback(callback) {}
+
+WatcherSet::Watcher::~Watcher() {}
+
+WatcherSet::WatcherSet() {}
+
+WatcherSet::~WatcherSet() {}
+
+void WatcherSet::NotifyOfStateChange(
+    const HandleSignalsState& state,
+    Dispatcher::RequestContext* request_context) {
+  MojoHandleSignalsState signals_state;

[Anand Mistry (off Chromium), 2016/02/29 12:03:35]

Given that HandleSignalsSate inherits from MojoHandleSignalsState, you should be
able to just pass |state| through. You might need a static_cast in
MaybeNotifyWatcher(), but you get the advantage of avoiding the manual copy
(twice) and get to use HandleSignalsSate::satisfies().

[Ken Rockot(use gerrit already), 2016/02/29 20:59:06]

Ah right... static_cast :) Done

+  signals_state.satisfied_signals = state.satisfied_signals;
+  signals_state.satisfiable_signals = state.satisfiable_signals;
+  for (const auto& entry : watchers_)
+    MaybeNotifyWatcher(entry.second, signals_state, request_context);
+}
+
+void WatcherSet::CancelAll(Dispatcher::RequestContext* request_context) {
+  MojoHandleSignalsState signals_state = {0, 0};
+  for (const auto& entry : watchers_) {
+    request_context->AddFinalizer(base::Bind(
+        entry.second.callback, MOJO_RESULT_CANCELLED, signals_state));
+  }
+  watchers_.clear();
+}
+
+MojoResult WatcherSet::Add(MojoHandleSignals signals,
+                           const Dispatcher::WatchCallback& callback,
+                           uintptr_t context,
+                           const HandleSignalsState& current_state,
+                           Dispatcher::RequestContext* request_context) {
+  auto it = watchers_.find(context);
+  if (it != watchers_.end())
+    return MOJO_RESULT_ALREADY_EXISTS;
+
+  if (!current_state.can_satisfy(signals))
+    return MOJO_RESULT_FAILED_PRECONDITION;
+
+  Watcher watcher(signals, callback);
+  watchers_.insert(std::make_pair(context, watcher));
+
+  MojoHandleSignalsState signals_state;
+  signals_state.satisfied_signals = current_state.satisfied_signals;
+  signals_state.satisfiable_signals = current_state.satisfiable_signals;
+  MaybeNotifyWatcher(watcher, signals_state, request_context);
+
+  return MOJO_RESULT_OK;
+}
+
+MojoResult WatcherSet::Remove(uintptr_t context) {
+  auto it = watchers_.find(context);
+  if (it == watchers_.end())
+    return MOJO_RESULT_INVALID_ARGUMENT;
+  watchers_.erase(it);
+  return MOJO_RESULT_OK;
+}
+
+void WatcherSet::MaybeNotifyWatcher(
+    const Watcher& watcher,
+    const MojoHandleSignalsState& current_state,
+    Dispatcher::RequestContext* request_context) {
+  if (current_state.satisfied_signals & watcher.signals) {
+    request_context->AddFinalizer(
+        base::Bind(watcher.callback, MOJO_RESULT_OK, current_state));
+  } else if (!(current_state.satisfiable_signals & watcher.signals)) {
+    request_context->AddFinalizer(base::Bind(
+        watcher.callback, MOJO_RESULT_FAILED_PRECONDITION, current_state));
+  }
+}
+
+}  // namespace edk
+}  // namespace mojo