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 <windows.h>
   8
   9 #include "base/logging.h"
  10 #include "base/numerics/safe_conversions.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(win::ScopedHandle handle)
  24     : handle_(handle.Pass()) {
  25   CHECK(handle_.IsValid()) << "Tried to create WaitableEvent from NULL handle";
  26 }
  27
  28 WaitableEvent::~WaitableEvent() {
  29 }
  30
  31 void WaitableEvent::Reset() {
  32   ResetEvent(handle_.Get());
  33 }
  34
  35 void WaitableEvent::Signal() {
  36   SetEvent(handle_.Get());
  37 }
  38
  39 bool WaitableEvent::IsSignaled() {
  40   return TimedWait(TimeDelta());
  41 }
  42
  43 void WaitableEvent::Wait() {
  44   base::ThreadRestrictions::AssertWaitAllowed();
  45   DWORD result = WaitForSingleObject(handle_.Get(), INFINITE);
  46   // It is most unexpected that this should ever fail.  Help consumers learn
  47   // about it if it should ever fail.
  48   DCHECK_EQ(WAIT_OBJECT_0, result) << "WaitForSingleObject failed";
  49 }
  50
  51 bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
  52   base::ThreadRestrictions::AssertWaitAllowed();
  53   DCHECK_GE(max_time, TimeDelta());
  54   // Truncate the timeout to milliseconds. The API specifies that this method
  55   // can return in less than |max_time| (when returning false), as the argument
  56   // is the maximum time that a caller is willing to wait.
  57   DWORD timeout = saturated_cast<DWORD>(max_time.InMilliseconds());
  58
  59   DWORD result = WaitForSingleObject(handle_.Get(), timeout);
  60   switch (result) {
  61     case WAIT_OBJECT_0:
  62       return true;
  63     case WAIT_TIMEOUT:
  64       return false;
  65   }
  66   // It is most unexpected that this should ever fail.  Help consumers learn
  67   // about it if it should ever fail.
  68   NOTREACHED() << "WaitForSingleObject failed";
  69   return false;
  70 }
  71
  72 // static
  73 size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count) {
  74   base::ThreadRestrictions::AssertWaitAllowed();
  75   HANDLE handles[MAXIMUM_WAIT_OBJECTS];
  76   CHECK_LE(count, static_cast<size_t>(MAXIMUM_WAIT_OBJECTS))
  77       << "Can only wait on " << MAXIMUM_WAIT_OBJECTS << " with WaitMany";
  78
  79   for (size_t i = 0; i < count; ++i)
  80     handles[i] = events[i]->handle();
  81
  82   // The cast is safe because count is small - see the CHECK above.
  83   DWORD result =
  84       WaitForMultipleObjects(static_cast<DWORD>(count),
  85                              handles,
  86                              FALSE,      // don't wait for all the objects
  87                              INFINITE);  // no timeout
  88   if (result >= WAIT_OBJECT_0 + count) {
  89     DPLOG(FATAL) << "WaitForMultipleObjects failed";
  90     return 0;
  91   }
  92
  93   return result - WAIT_OBJECT_0;
  94 }
  95
  96 }  // namespace base