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https://github.com/kidfromjupiter/nearby.git
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78 lines
2.7 KiB
C++
78 lines
2.7 KiB
C++
// Copyright 2020 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "platform/impl/windows/count_down_latch.h"
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namespace location {
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namespace nearby {
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namespace windows {
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// A synchronization aid that allows one or more threads to wait until a set of
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// operations being performed in other threads completes.
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//
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// Creates or opens a named or unnamed event object.
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// https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CountDownLatch.html
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CountDownLatch::CountDownLatch(int count) {
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if (count < 0) {
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throw(std::invalid_argument("count"));
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}
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// https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-createeventa
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h_count_down_latch_event_ =
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CreateEvent(NULL, // default security attributes
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TRUE, // manual-reset event
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FALSE, // initial state is nonsignaled
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TEXT("LatchEvent") // object name
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);
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count_ = count;
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}
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Exception CountDownLatch::Await() {
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// Waits until the specified object is in the signaled state or the time-out
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// interval elapses.
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// https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-waitforsingleobject
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if (WaitForSingleObject(h_count_down_latch_event_, INFINITE) ==
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WAIT_OBJECT_0) {
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return Exception{Exception::kSuccess};
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}
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return Exception{Exception::kFailed};
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}
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ExceptionOr<bool> CountDownLatch::Await(absl::Duration timeout) {
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auto result = WaitForSingleObject(h_count_down_latch_event_,
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absl::ToInt64Milliseconds(timeout));
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if (result == WAIT_OBJECT_0) {
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return ExceptionOr<bool>(true);
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}
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if (result == WAIT_TIMEOUT) {
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return ExceptionOr<bool>{Exception::kTimeout};
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}
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return ExceptionOr<bool>{Exception::kFailed};
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}
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void CountDownLatch::CountDown() {
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// Decrements (decreases by one) the value of the specified 32-bit variable as
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// an atomic operation.
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// https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockeddecrement
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InterlockedDecrement(&count_);
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if (count_ == 0) {
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SetEvent(h_count_down_latch_event_);
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}
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}
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} // namespace windows
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} // namespace nearby
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} // namespace location
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