100 lines
2.1 KiB
C++
100 lines
2.1 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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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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* http://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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*/
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#include <folly/portability/Semaphore.h>
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#include <folly/portability/Windows.h>
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#include <cerrno>
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#include <mutex>
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#ifdef _WIN32
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namespace folly::portability::semaphore {
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struct sem_t_ {
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std::mutex mtx{};
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HANDLE sema{INVALID_HANDLE_VALUE};
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int32_t value{0};
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};
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int sem_init(sem_t* s, int shared, unsigned int value) {
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// Don't support cross-process shared semaphores.
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if (shared != 0) {
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return -1;
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}
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auto sem = CreateSemaphoreA(nullptr, 0, SEM_VALUE_MAX, nullptr);
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if (sem == 0) {
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return -1;
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}
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auto ret = new sem_t_();
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ret->sema = sem;
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ret->value = value;
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*s = ret;
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return 0;
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}
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int sem_destroy(sem_t* s) {
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if (!CloseHandle((*s)->sema)) {
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return -1;
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}
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delete *s;
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*s = nullptr;
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return 0;
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}
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int sem_post(sem_t* s) {
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std::lock_guard<std::mutex> lock{(*s)->mtx};
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if ((*s)->value < SEM_VALUE_MAX) {
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if (++(*s)->value <= 0 && !ReleaseSemaphore((*s)->sema, 1, nullptr)) {
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--(*s)->value;
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errno = EINVAL;
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return -1;
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}
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} else {
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errno = ERANGE;
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return -1;
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}
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return 0;
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}
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int sem_trywait(sem_t* s) {
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std::lock_guard<std::mutex> lock{(*s)->mtx};
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if ((*s)->value > 0) {
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(*s)->value--;
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return 0;
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} else {
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errno = EAGAIN;
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return -1;
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}
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}
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int sem_wait(sem_t* s) {
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int32_t value = 0;
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{
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std::lock_guard<std::mutex> lock{(*s)->mtx};
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value = --(*s)->value;
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}
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if (value < 0) {
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if (WaitForSingleObject((*s)->sema, INFINITE) != WAIT_OBJECT_0) {
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errno = EINVAL;
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return -1;
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}
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}
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return 0;
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}
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} // namespace folly::portability::semaphore
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#endif
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