Mojo: Armed Watchers

mojo/edk/system/watcher_set.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/watcher_set.h"
 
-#include "mojo/edk/system/request_context.h"
-#include "mojo/public/c/system/types.h"
+#include <utility>
 
 namespace mojo {
 namespace edk {
 
-WatcherSet::WatcherSet() {}
+WatcherSet::WatcherSet(Dispatcher* owner) : owner_(owner) {}
 
-WatcherSet::~WatcherSet() {}
+WatcherSet::~WatcherSet() = default;
 
-void WatcherSet::NotifyForStateChange(const HandleSignalsState& state) {
+void WatcherSet::NotifyState(const HandleSignalsState& state) {
+  // Avoid notifying watchers if they have already seen this state.
+  if (last_known_state_.has_value() && state.equals(last_known_state_.value()))
+    return;
+  last_known_state_ = state;
   for (const auto& entry : watchers_)
-    entry.second->NotifyForStateChange(state);
+    entry.first->NotifyHandleState(owner_, state);
 }
 
 void WatcherSet::NotifyClosed() {
   for (const auto& entry : watchers_)
-    entry.second->NotifyClosed();
+    entry.first->NotifyHandleClosed(owner_);
 }
 
-MojoResult WatcherSet::Add(MojoHandleSignals signals,
-                           const Watcher::WatchCallback& callback,
+MojoResult WatcherSet::Add(const scoped_refptr<WatcherDispatcher>& watcher,
                            uintptr_t context,
                            const HandleSignalsState& current_state) {
-  auto it = watchers_.find(context);
-  if (it != watchers_.end())
+  auto it = watchers_.find(watcher.get());
+  if (it == watchers_.end()) {
+    auto result =
+        watchers_.insert(std::make_pair(watcher.get(), Entry{watcher}));
+    it = result.first;
+  }
+
+  if (!it->second.contexts.insert(context).second)
     return MOJO_RESULT_ALREADY_EXISTS;
 
-  if (!current_state.can_satisfy(signals))
-    return MOJO_RESULT_FAILED_PRECONDITION;
+  if (last_known_state_.has_value() &&
+      !current_state.equals(last_known_state_.value())) {
+    // This new state may be relevant to everyone, in which case we just
+    // notify everyone.
+    NotifyState(current_state);
+  } else {
+    // Otherwise only notify the newly added Watcher.
+    watcher->NotifyHandleState(owner_, current_state);
+  }
+  return MOJO_RESULT_OK;
+}
 
-  scoped_refptr<Watcher> watcher(new Watcher(signals, callback));
-  watchers_.insert(std::make_pair(context, watcher));
+MojoResult WatcherSet::Remove(WatcherDispatcher* watcher, uintptr_t context) {
+  auto it = watchers_.find(watcher);
+  if (it == watchers_.end())
+    return MOJO_RESULT_NOT_FOUND;
 
-  watcher->NotifyForStateChange(current_state);
+  ContextSet& contexts = it->second.contexts;
+  auto context_it = contexts.find(context);
+  if (context_it == contexts.end())
+    return MOJO_RESULT_NOT_FOUND;
+
+  contexts.erase(context_it);
+  if (contexts.empty())
+    watchers_.erase(it);
 
   return MOJO_RESULT_OK;
 }
 
-MojoResult WatcherSet::Remove(uintptr_t context) {
-  auto it = watchers_.find(context);
-  if (it == watchers_.end())
-    return MOJO_RESULT_INVALID_ARGUMENT;
+WatcherSet::Entry::Entry(const scoped_refptr<WatcherDispatcher>& dispatcher)
+    : dispatcher(dispatcher) {}
 
-  RequestContext::current()->AddWatchCancelFinalizer(it->second);
-  watchers_.erase(it);
-  return MOJO_RESULT_OK;
-}
+WatcherSet::Entry::Entry(Entry&& other) = default;
+
+WatcherSet::Entry::~Entry() = default;
+
+WatcherSet::Entry& WatcherSet::Entry::operator=(Entry&& other) = default;
 
 }  // namespace edk
 }  // namespace mojo