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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/synchronization/waitable_event.h"
#include <math.h>
#include <windows.h>
#include "base/logging.h"
#include "base/threading/thread_restrictions.h"
#include "base/time/time.h"
namespace base {
WaitableEvent::WaitableEvent(bool manual_reset, bool signaled)
: handle_(CreateEvent(NULL, manual_reset, signaled, NULL)) {
// We're probably going to crash anyways if this is ever NULL, so we might as
// well make our stack reports more informative by crashing here.
CHECK(handle_);
}
WaitableEvent::WaitableEvent(HANDLE handle)
: handle_(handle) {
CHECK(handle) << "Tried to create WaitableEvent from NULL handle";
}
WaitableEvent::~WaitableEvent() {
CloseHandle(handle_);
}
HANDLE WaitableEvent::Release() {
HANDLE rv = handle_;
handle_ = INVALID_HANDLE_VALUE;
return rv;
}
void WaitableEvent::Reset() {
ResetEvent(handle_);
}
void WaitableEvent::Signal() {
SetEvent(handle_);
}
bool WaitableEvent::IsSignaled() {
return TimedWait(TimeDelta::FromMilliseconds(0));
}
void WaitableEvent::Wait() {
base::ThreadRestrictions::AssertWaitAllowed();
DWORD result = WaitForSingleObject(handle_, INFINITE);
// It is most unexpected that this should ever fail. Help consumers learn
// about it if it should ever fail.
DCHECK_EQ(WAIT_OBJECT_0, result) << "WaitForSingleObject failed";
}
bool WaitableEvent::TimedWait(const TimeDelta& max_time) {
base::ThreadRestrictions::AssertWaitAllowed();
DCHECK(max_time >= TimeDelta::FromMicroseconds(0));
// Be careful here. TimeDelta has a precision of microseconds, but this API
// is in milliseconds. If there are 5.5ms left, should the delay be 5 or 6?
// It should be 6 to avoid returning too early.
double timeout = ceil(max_time.InMillisecondsF());
DWORD result = WaitForSingleObject(handle_, static_cast<DWORD>(timeout));
switch (result) {
case WAIT_OBJECT_0:
return true;
case WAIT_TIMEOUT:
return false;
}
// It is most unexpected that this should ever fail. Help consumers learn
// about it if it should ever fail.
NOTREACHED() << "WaitForSingleObject failed";
return false;
}
// static
size_t WaitableEvent::WaitMany(WaitableEvent** events, size_t count) {
base::ThreadRestrictions::AssertWaitAllowed();
HANDLE handles[MAXIMUM_WAIT_OBJECTS];
CHECK_LE(count, MAXIMUM_WAIT_OBJECTS)
<< "Can only wait on " << MAXIMUM_WAIT_OBJECTS << " with WaitMany";
for (size_t i = 0; i < count; ++i)
handles[i] = events[i]->handle();
// The cast is safe because count is small - see the CHECK above.
DWORD result =
WaitForMultipleObjects(static_cast<DWORD>(count),
handles,
FALSE, // don't wait for all the objects
INFINITE); // no timeout
if (result >= WAIT_OBJECT_0 + count) {
DPLOG(FATAL) << "WaitForMultipleObjects failed";
return 0;
}
return result - WAIT_OBJECT_0;
}
} // namespace base
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