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_);
  21 }
  22
  23 WaitableEvent::WaitableEvent(HANDLE handle)
  24     : handle_(handle) {
  25   CHECK(handle) << "Tried to create WaitableEvent from NULL handle";
  26 }
  27
  28 WaitableEvent::~WaitableEvent() {
  29   CloseHandle(handle_);
  30 }
  31
  32 HANDLE WaitableEvent::Release() {
  33   HANDLE rv = handle_;
  34   handle_ = INVALID_HANDLE_VALUE;
  35   return rv;
  36 }
  37
  38 void WaitableEvent::Reset() {
  39   ResetEvent(handle_);
  40 }
  41
  42 void WaitableEvent::Signal() {
  43   SetEvent(handle_);
  44 }
  45
  46 bool WaitableEvent::IsSignaled() {
  47   return TimedWait(TimeDelta::FromMilliseconds(0));
  48 }
  49
  50 void WaitableEvent::Wait() {
  51   base::ThreadRestrictions::AssertWaitAllowed();
  52   DWORD result = WaitForSingleObject(handle_, INFINITE);
  53   // It is most unexpected that this should ever fail.  Help consumers learn
  54   // about it if it should ever fail.
  55   DCHECK_EQ(WAIT_OBJECT_0, result) << "WaitForSingleObject failed";
  56 }
  57
  58 bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
  59   base::ThreadRestrictions::AssertWaitAllowed();
  60   DCHECK(max_time >= TimeDelta::FromMicroseconds(0));
  61   // Be careful here.  TimeDelta has a precision of microseconds, but this API
  62   // is in milliseconds.  If there are 5.5ms left, should the delay be 5 or 6?
  63   // It should be 6 to avoid returning too early.
  64   double timeout = ceil(max_time.InMillisecondsF());
  65   DWORD result = WaitForSingleObject(handle_, static_cast<DWORD>(timeout));
  66   switch (result) {
  67     case WAIT_OBJECT_0:
  68       return true;
  69     case WAIT_TIMEOUT:
  70       return false;
  71   }
  72   // It is most unexpected that this should ever fail.  Help consumers learn
  73   // about it if it should ever fail.
  74   NOTREACHED() << "WaitForSingleObject failed";
  75   return false;
  76 }
  77
  78 // static
  79 size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count) {
  80   base::ThreadRestrictions::AssertWaitAllowed();
  81   HANDLE handles[MAXIMUM_WAIT_OBJECTS];
  82   CHECK_LE(count, MAXIMUM_WAIT_OBJECTS)
  83       << "Can only wait on " << MAXIMUM_WAIT_OBJECTS << " with WaitMany";
  84
  85   for (size_t i = 0; i < count; ++i)
  86     handles[i] = events[i]->handle();
  87
  88   // The cast is safe because count is small - see the CHECK above.
  89   DWORD result =
  90       WaitForMultipleObjects(static_cast<DWORD>(count),
  91                              handles,
  92                              FALSE,      // don't wait for all the objects
  93                              INFINITE);  // no timeout
  94   if (result >= WAIT_OBJECT_0 + count) {
  95     DLOG_GETLASTERROR(FATAL) << "WaitForMultipleObjects failed";
  96     return 0;
  97   }
  98
  99   return result - WAIT_OBJECT_0;
 100 }
 101
 102 }  // namespace base