base/synchronization/waitable_event_win.cc

   1 // Copyright (c) 2011 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/synchronization/waitable_event.h"
   6
   7 #include <math.h>
   8 #include <windows.h>
   9
  10 #include "base/logging.h"
  11 #include "base/threading/thread_restrictions.h"
  12 #include "base/time/time.h"
  13
  14 namespace base {
  15
  16 WaitableEvent::WaitableEvent(bool manual_reset, bool signaled)
  17     : handle_(CreateEvent(NULL, manual_reset, signaled, NULL)) {
  18   // We're probably going to crash anyways if this is ever NULL, so we might as
  19   // well make our stack reports more informative by crashing here.
  20   CHECK(handle_.IsValid());
  21 }
  22
  23 WaitableEvent::WaitableEvent(HANDLE handle)
  24     : handle_(handle) {
  25   CHECK(handle_.IsValid()) << "Tried to create WaitableEvent from NULL handle";
  26 }
  27
  28 WaitableEvent::~WaitableEvent() {
  29 }
  30
  31 HANDLE WaitableEvent::Release() {
  32   return handle_.Take();
  33 }
  34
  35 void WaitableEvent::Reset() {
  36   ResetEvent(handle_.Get());
  37 }
  38
  39 void WaitableEvent::Signal() {
  40   SetEvent(handle_.Get());
  41 }
  42
  43 bool WaitableEvent::IsSignaled() {
  44   return TimedWait(TimeDelta::FromMilliseconds(0));
  45 }
  46
  47 void WaitableEvent::Wait() {
  48   base::ThreadRestrictions::AssertWaitAllowed();
  49   DWORD result = WaitForSingleObject(handle_.Get(), INFINITE);
  50   // It is most unexpected that this should ever fail.  Help consumers learn
  51   // about it if it should ever fail.
  52   DCHECK_EQ(WAIT_OBJECT_0, result) << "WaitForSingleObject failed";
  53 }
  54
  55 bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
  56   base::ThreadRestrictions::AssertWaitAllowed();
  57   DCHECK(max_time >= TimeDelta::FromMicroseconds(0));
  58   // Be careful here.  TimeDelta has a precision of microseconds, but this API
  59   // is in milliseconds.  If there are 5.5ms left, should the delay be 5 or 6?
  60   // It should be 6 to avoid returning too early.
  61   double timeout = ceil(max_time.InMillisecondsF());
  62   DWORD result = WaitForSingleObject(handle_.Get(),
  63                                      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
  77 size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count) {
  78   base::ThreadRestrictions::AssertWaitAllowed();
  79   HANDLE handles[MAXIMUM_WAIT_OBJECTS];
  80   CHECK_LE(count, MAXIMUM_WAIT_OBJECTS)
  81       << "Can only wait on " << MAXIMUM_WAIT_OBJECTS << " with WaitMany";
  82
  83   for (size_t i = 0; i < count; ++i)
  84     handles[i] = events[i]->handle();
  85
  86   // The cast is safe because count is small - see the CHECK above.
  87   DWORD result =
  88       WaitForMultipleObjects(static_cast<DWORD>(count),
  89                              handles,
  90                              FALSE,      // don't wait for all the objects
  91                              INFINITE);  // no timeout
  92   if (result >= WAIT_OBJECT_0 + count) {
  93     DPLOG(FATAL) << "WaitForMultipleObjects failed";
  94     return 0;
  95   }
  96
  97   return result - WAIT_OBJECT_0;
  98 }
  99
 100 }  // namespace base