1 // Copyright 2017 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "mojo/public/cpp/bindings/sync_event_watcher.h"
6
7 #include <algorithm>
8
9 #include "base/containers/stack_container.h"
10 #include "base/logging.h"
11
12 namespace mojo {
13
SyncEventWatcher(base::WaitableEvent * event,const base::Closure & callback)14 SyncEventWatcher::SyncEventWatcher(base::WaitableEvent* event,
15 const base::Closure& callback)
16 : event_(event),
17 callback_(callback),
18 registry_(SyncHandleRegistry::current()),
19 destroyed_(new base::RefCountedData<bool>(false)) {}
20
~SyncEventWatcher()21 SyncEventWatcher::~SyncEventWatcher() {
22 DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
23 if (registered_)
24 registry_->UnregisterEvent(event_, callback_);
25 destroyed_->data = true;
26 }
27
AllowWokenUpBySyncWatchOnSameThread()28 void SyncEventWatcher::AllowWokenUpBySyncWatchOnSameThread() {
29 DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
30 IncrementRegisterCount();
31 }
32
SyncWatch(const bool ** stop_flags,size_t num_stop_flags)33 bool SyncEventWatcher::SyncWatch(const bool** stop_flags,
34 size_t num_stop_flags) {
35 DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
36 IncrementRegisterCount();
37 if (!registered_) {
38 DecrementRegisterCount();
39 return false;
40 }
41
42 // This object may be destroyed during the Wait() call. So we have to preserve
43 // the boolean that Wait uses.
44 auto destroyed = destroyed_;
45
46 constexpr size_t kFlagStackCapacity = 4;
47 base::StackVector<const bool*, kFlagStackCapacity> should_stop_array;
48 should_stop_array.container().push_back(&destroyed->data);
49 std::copy(stop_flags, stop_flags + num_stop_flags,
50 std::back_inserter(should_stop_array.container()));
51 bool result = registry_->Wait(should_stop_array.container().data(),
52 should_stop_array.container().size());
53
54 // This object has been destroyed.
55 if (destroyed->data)
56 return false;
57
58 DecrementRegisterCount();
59 return result;
60 }
61
IncrementRegisterCount()62 void SyncEventWatcher::IncrementRegisterCount() {
63 register_request_count_++;
64 if (!registered_) {
65 registry_->RegisterEvent(event_, callback_);
66 registered_ = true;
67 }
68 }
69
DecrementRegisterCount()70 void SyncEventWatcher::DecrementRegisterCount() {
71 DCHECK_GT(register_request_count_, 0u);
72 register_request_count_--;
73 if (register_request_count_ == 0 && registered_) {
74 registry_->UnregisterEvent(event_, callback_);
75 registered_ = false;
76 }
77 }
78
79 } // namespace mojo
80