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/time.h"
  12
  13 namespace base {
  14
  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
  22 WaitableEvent::WaitableEvent(HANDLE handle)
  23     : handle_(handle) {
  24   CHECK(handle) << "Tried to create WaitableEvent from NULL handle";
  25 }
  26
  27 WaitableEvent::~WaitableEvent() {
  28   CloseHandle(handle_);
  29 }
  30
  31 HANDLE WaitableEvent::Release() {
  32   HANDLE rv = handle_;
  33   handle_ = INVALID_HANDLE_VALUE;
  34   return rv;
  35 }
  36
  37 void WaitableEvent::Reset() {
  38   ResetEvent(handle_);
  39 }
  40
  41 void WaitableEvent::Signal() {
  42   SetEvent(handle_);
  43 }
  44
  45 bool WaitableEvent::IsSignaled() {
  46   return TimedWait(TimeDelta::FromMilliseconds(0));
  47 }
  48
  49 void 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_EQ(WAIT_OBJECT_0, result) << "WaitForSingleObject failed";
  54 }
  55
  56 bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
  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_, static_cast<DWORD>(timeout));
  63   switch (result) {
  64     case WAIT_OBJECT_0:
  65       return true;
  66     case WAIT_TIMEOUT:
  67       return false;
  68   }
  69   // It is most unexpected that this should ever fail.  Help consumers learn
  70   // about it if it should ever fail.
  71   NOTREACHED() << "WaitForSingleObject failed";
  72   return false;
  73 }
  74
  75 // static
  76 size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count) {
  77   HANDLE handles[MAXIMUM_WAIT_OBJECTS];
  78   CHECK_LE(count, MAXIMUM_WAIT_OBJECTS)
  79       << "Can only wait on " << MAXIMUM_WAIT_OBJECTS << " with WaitMany";
  80
  81   for (size_t i = 0; i < count; ++i)
  82     handles[i] = events[i]->handle();
  83
  84   // The cast is safe because count is small - see the CHECK above.
  85   DWORD result =
  86       WaitForMultipleObjects(static_cast<DWORD>(count),
  87                              handles,
  88                              FALSE,      // don't wait for all the objects
  89                              INFINITE);  // no timeout
  90   if (result >= WAIT_OBJECT_0 + count) {
  91     NOTREACHED() << "WaitForMultipleObjects failed: " << GetLastError();
  92     return 0;
  93   }
  94
  95   return result - WAIT_OBJECT_0;
  96 }
  97
  98 }  // namespace base