Mojo C++ bindings: refactor SyncHandleWatcher.

mojo/public/cpp/bindings/lib/sync_handle_registry.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/public/cpp/bindings/lib/sync_handle_watcher.h"
+#include "mojo/public/cpp/bindings/lib/sync_handle_registry.h"
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "base/threading/thread_local.h"
 #include "mojo/public/c/system/core.h"
 
 namespace mojo {
 namespace internal {
 namespace {
 
-base::LazyInstance<base::ThreadLocalPointer<SyncHandleWatcher>>
+base::LazyInstance<base::ThreadLocalPointer<SyncHandleRegistry>>
     g_current_sync_handle_watcher = LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
 
 // static
-SyncHandleWatcher* SyncHandleWatcher::current() {
-  SyncHandleWatcher* result = g_current_sync_handle_watcher.Pointer()->Get();
+SyncHandleRegistry* SyncHandleRegistry::current() {
+  SyncHandleRegistry* result = g_current_sync_handle_watcher.Pointer()->Get();
   if (!result) {
-    // This object will be destroyed when the current message loop goes away.
-    result = new SyncHandleWatcher();
+    result = new SyncHandleRegistry();
     DCHECK_EQ(result, g_current_sync_handle_watcher.Pointer()->Get());
   }
   return result;
 }
 
-bool SyncHandleWatcher::RegisterHandle(const Handle& handle,
-                                       MojoHandleSignals handle_signals,
-                                       const HandleCallback& callback) {
+bool SyncHandleRegistry::RegisterHandle(const Handle& handle,
+                                        MojoHandleSignals handle_signals,
+                                        const HandleCallback& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   if (ContainsKey(handles_, handle))
     return false;
 
   MojoResult result = MojoAddHandle(wait_set_handle_.get().value(),
                                     handle.value(), handle_signals);
   if (result != MOJO_RESULT_OK)
     return false;
 
   handles_[handle] = callback;
   return true;
 }
 
-void SyncHandleWatcher::UnregisterHandle(const Handle& handle) {
+void SyncHandleRegistry::UnregisterHandle(const Handle& handle) {
   DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK(ContainsKey(handles_, handle));
+  if (!ContainsKey(handles_, handle))
+    return;
 
   MojoResult result =
       MojoRemoveHandle(wait_set_handle_.get().value(), handle.value());
   DCHECK_EQ(MOJO_RESULT_OK, result);
-
   handles_.erase(handle);
 }
 
-bool SyncHandleWatcher::WatchAllHandles(const bool* should_stop[],
-                                        size_t count) {
+bool SyncHandleRegistry::WatchAllHandles(const bool* should_stop[],
+                                         size_t count) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   MojoResult result;
   uint32_t num_ready_handles;
   MojoHandle ready_handle;
   MojoResult ready_handle_result;
 
-  while (true) {
+  // This object may be destroyed during a callback. So we have to preserve
+  // the boolean.
+  scoped_refptr<base::RefCountedData<bool>> destroyed = destroyed_;
+  while (!destroyed->data) {
     for (size_t i = 0; i < count; ++i)
       if (*should_stop[i])
         return true;
     do {
       result = Wait(wait_set_handle_.get(), MOJO_HANDLE_SIGNAL_READABLE,
                     MOJO_DEADLINE_INDEFINITE, nullptr);
       if (result != MOJO_RESULT_OK)
         return false;
 
       // TODO(yzshen): Theoretically it can reduce sync call re-entrancy if we
       // give priority to the handle that is waiting for sync response.
       num_ready_handles = 1;
       result = MojoGetReadyHandles(wait_set_handle_.get().value(),
                                    &num_ready_handles, &ready_handle,
                                    &ready_handle_result, nullptr);
       if (result != MOJO_RESULT_OK && result != MOJO_RESULT_SHOULD_WAIT)
         return false;
     } while (result == MOJO_RESULT_SHOULD_WAIT);
 
     const auto iter = handles_.find(Handle(ready_handle));
     iter->second.Run(ready_handle_result);
   };
 
-  return true;
+  return false;
 }
 
-SyncHandleWatcher::SyncHandleWatcher() {
+SyncHandleRegistry::SyncHandleRegistry()
+    : destroyed_(new base::RefCountedData<bool>(false)) {
   MojoHandle handle;
   MojoResult result = MojoCreateWaitSet(&handle);
   CHECK_EQ(MOJO_RESULT_OK, result);
   wait_set_handle_.reset(Handle(handle));
   CHECK(wait_set_handle_.is_valid());
 
   DCHECK(!g_current_sync_handle_watcher.Pointer()->Get());
   g_current_sync_handle_watcher.Pointer()->Set(this);
 
   base::MessageLoop::current()->AddDestructionObserver(this);
 }
 
-SyncHandleWatcher::~SyncHandleWatcher() {
+SyncHandleRegistry::~SyncHandleRegistry() {
   DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK(handles_.empty());
+  destroyed_->data = true;
   g_current_sync_handle_watcher.Pointer()->Set(nullptr);
 }
 
-void SyncHandleWatcher::WillDestroyCurrentMessageLoop() {
+void SyncHandleRegistry::WillDestroyCurrentMessageLoop() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_EQ(this, g_current_sync_handle_watcher.Pointer()->Get());
 
   base::MessageLoop::current()->RemoveDestructionObserver(this);
+
   delete this;
 }
 
 }  // namespace internal
 }  // namespace mojo