waitable_event_win.cc (2723B)
1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */ 3 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved. 4 // Use of this source code is governed by a BSD-style license that can be 5 // found in the LICENSE file. 6 7 #include "base/waitable_event.h" 8 9 #include <math.h> 10 #include <windows.h> 11 12 #include "base/logging.h" 13 #include "base/time.h" 14 15 namespace base { 16 17 WaitableEvent::WaitableEvent(bool manual_reset, bool signaled) 18 : handle_(CreateEvent(NULL, manual_reset, signaled, NULL)) { 19 // We're probably going to crash anyways if this is ever NULL, so we might as 20 // well make our stack reports more informative by crashing here. 21 CHECK(handle_); 22 } 23 24 WaitableEvent::~WaitableEvent() { CloseHandle(handle_); } 25 26 void WaitableEvent::Reset() { ResetEvent(handle_); } 27 28 void WaitableEvent::Signal() { SetEvent(handle_); } 29 30 bool WaitableEvent::IsSignaled() { 31 return TimedWait(TimeDelta::FromMilliseconds(0)); 32 } 33 34 bool WaitableEvent::Wait() { 35 DWORD result = WaitForSingleObject(handle_, INFINITE); 36 // It is most unexpected that this should ever fail. Help consumers learn 37 // about it if it should ever fail. 38 DCHECK(result == WAIT_OBJECT_0) << "WaitForSingleObject failed"; 39 return result == WAIT_OBJECT_0; 40 } 41 42 bool WaitableEvent::TimedWait(const TimeDelta& max_time) { 43 DCHECK(max_time >= TimeDelta::FromMicroseconds(0)); 44 // Be careful here. TimeDelta has a precision of microseconds, but this API 45 // is in milliseconds. If there are 5.5ms left, should the delay be 5 or 6? 46 // It should be 6 to avoid returning too early. 47 double timeout = ceil(max_time.InMillisecondsF()); 48 DWORD result = WaitForSingleObject(handle_, static_cast<DWORD>(timeout)); 49 switch (result) { 50 case WAIT_OBJECT_0: 51 return true; 52 case WAIT_TIMEOUT: 53 return false; 54 } 55 // It is most unexpected that this should ever fail. Help consumers learn 56 // about it if it should ever fail. 57 NOTREACHED() << "WaitForSingleObject failed"; 58 return false; 59 } 60 61 // static 62 size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count) { 63 HANDLE handles[MAXIMUM_WAIT_OBJECTS]; 64 CHECK(count <= MAXIMUM_WAIT_OBJECTS) 65 << "Can only wait on " << MAXIMUM_WAIT_OBJECTS << " with WaitMany"; 66 67 for (size_t i = 0; i < count; ++i) handles[i] = events[i]->handle(); 68 69 DWORD result = 70 WaitForMultipleObjects(count, handles, 71 FALSE, // don't wait for all the objects 72 INFINITE); // no timeout 73 if (result >= WAIT_OBJECT_0 + count) { 74 NOTREACHED() << "WaitForMultipleObjects failed: " << GetLastError(); 75 return 0; 76 } 77 78 return result - WAIT_OBJECT_0; 79 } 80 81 } // namespace base