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