1 // Copyright 2024 The Chromium Authors
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 "base/synchronization/cancelable_event.h"
6
7 #include <windows.h>
8
9 #include <synchapi.h>
10 #include <winbase.h>
11
12 #include <tuple>
13
14 #include "base/synchronization/lock.h"
15
16 namespace base {
17
CancelableEvent()18 CancelableEvent::CancelableEvent() {
19 native_handle_ = ::CreateSemaphoreA(nullptr, 0, 1, nullptr);
20 PCHECK(!!native_handle_);
21 }
22
~CancelableEvent()23 CancelableEvent::~CancelableEvent() {
24 const bool result = ::CloseHandle(native_handle_);
25 PCHECK(result);
26 }
27
SignalImpl()28 void CancelableEvent::SignalImpl() {
29 LONG prev_count;
30 const bool result = ::ReleaseSemaphore(native_handle_, 1, &prev_count);
31 PCHECK(result);
32 CHECK_EQ(prev_count, 0);
33 }
34
CancelImpl()35 bool CancelableEvent::CancelImpl() {
36 const DWORD result = ::WaitForSingleObject(native_handle_, 0);
37 return result == WAIT_OBJECT_0;
38 }
39
TimedWaitImpl(TimeDelta timeout)40 bool CancelableEvent::TimedWaitImpl(TimeDelta timeout) {
41 const DWORD wait_ms = saturated_cast<DWORD>(timeout.InMilliseconds());
42 const TimeTicks start = TimeTicks::Now();
43 DWORD result;
44 // WaitForSingleObject has been shown to experience spurious wakeups (on the
45 // order of 10ms before when it was supposed to wake up), so retry until at
46 // least `timeout` has passed.
47 do {
48 result = ::WaitForSingleObject(native_handle_, wait_ms);
49 if (result == WAIT_OBJECT_0) {
50 return true;
51 }
52 } while (TimeTicks::Now() <= start + timeout);
53 CHECK_EQ(result, static_cast<DWORD>(WAIT_TIMEOUT));
54 return false;
55 }
56
57 } // namespace base
58