1 // Copyright (c) 2006-2008 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 "base/waitable_event.h"
6
7 #include <math.h>
8 #include <windows.h>
9
10 #include "base/logging.h"
11 #include "base/time.h"
12
13 namespace base {
14
WaitableEvent(bool manual_reset,bool signaled)15 WaitableEvent::WaitableEvent(bool manual_reset, bool signaled)
16 : handle_(CreateEvent(NULL, manual_reset, signaled, NULL)) {
17 // We're probably going to crash anyways if this is ever NULL, so we might as
18 // well make our stack reports more informative by crashing here.
19 CHECK(handle_);
20 }
21
WaitableEvent(HANDLE handle)22 WaitableEvent::WaitableEvent(HANDLE handle)
23 : handle_(handle) {
24 CHECK(handle) << "Tried to create WaitableEvent from NULL handle";
25 }
26
~WaitableEvent()27 WaitableEvent::~WaitableEvent() {
28 CloseHandle(handle_);
29 }
30
Release()31 HANDLE WaitableEvent::Release() {
32 HANDLE rv = handle_;
33 handle_ = INVALID_HANDLE_VALUE;
34 return rv;
35 }
36
Reset()37 void WaitableEvent::Reset() {
38 ResetEvent(handle_);
39 }
40
Signal()41 void WaitableEvent::Signal() {
42 SetEvent(handle_);
43 }
44
IsSignaled()45 bool WaitableEvent::IsSignaled() {
46 return TimedWait(TimeDelta::FromMilliseconds(0));
47 }
48
Wait()49 bool WaitableEvent::Wait() {
50 DWORD result = WaitForSingleObject(handle_, INFINITE);
51 // It is most unexpected that this should ever fail. Help consumers learn
52 // about it if it should ever fail.
53 DCHECK(result == WAIT_OBJECT_0) << "WaitForSingleObject failed";
54 return result == WAIT_OBJECT_0;
55 }
56
TimedWait(const TimeDelta & max_time)57 bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
58 DCHECK(max_time >= TimeDelta::FromMicroseconds(0));
59 // Be careful here. TimeDelta has a precision of microseconds, but this API
60 // is in milliseconds. If there are 5.5ms left, should the delay be 5 or 6?
61 // It should be 6 to avoid returning too early.
62 double timeout = ceil(max_time.InMillisecondsF());
63 DWORD result = WaitForSingleObject(handle_, static_cast<DWORD>(timeout));
64 switch (result) {
65 case WAIT_OBJECT_0:
66 return true;
67 case WAIT_TIMEOUT:
68 return false;
69 }
70 // It is most unexpected that this should ever fail. Help consumers learn
71 // about it if it should ever fail.
72 NOTREACHED() << "WaitForSingleObject failed";
73 return false;
74 }
75
76 // static
WaitMany(WaitableEvent ** events,size_t count)77 size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count) {
78 HANDLE handles[MAXIMUM_WAIT_OBJECTS];
79 CHECK(count <= MAXIMUM_WAIT_OBJECTS)
80 << "Can only wait on " << MAXIMUM_WAIT_OBJECTS << " with WaitMany";
81
82 for (size_t i = 0; i < count; ++i)
83 handles[i] = events[i]->handle();
84
85 // The cast is safe because count is small - see the CHECK above.
86 DWORD result =
87 WaitForMultipleObjects(static_cast<DWORD>(count),
88 handles,
89 FALSE, // don't wait for all the objects
90 INFINITE); // no timeout
91 if (result >= WAIT_OBJECT_0 + count) {
92 NOTREACHED() << "WaitForMultipleObjects failed: " << GetLastError();
93 return 0;
94 }
95
96 return result - WAIT_OBJECT_0;
97 }
98
99 } // namespace base
100