mirror of
https://github.com/jart/cosmopolitan.git
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93 lines
2.7 KiB
C++
93 lines
2.7 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include <mutex>
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#include <shared_mutex>
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#if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
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# pragma comment(lib, "pthread")
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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// Shared Mutex Base
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__shared_mutex_base::__shared_mutex_base() : __state_(0) {}
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// Exclusive ownership
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void __shared_mutex_base::lock() {
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unique_lock<mutex> lk(__mut_);
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while (__state_ & __write_entered_)
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__gate1_.wait(lk);
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__state_ |= __write_entered_;
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while (__state_ & __n_readers_)
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__gate2_.wait(lk);
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}
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bool __shared_mutex_base::try_lock() {
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unique_lock<mutex> lk(__mut_);
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if (__state_ == 0) {
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__state_ = __write_entered_;
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return true;
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}
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return false;
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}
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void __shared_mutex_base::unlock() {
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lock_guard<mutex> _(__mut_);
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__state_ = 0;
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__gate1_.notify_all();
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}
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// Shared ownership
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void __shared_mutex_base::lock_shared() {
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unique_lock<mutex> lk(__mut_);
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while ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_)
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__gate1_.wait(lk);
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unsigned num_readers = (__state_ & __n_readers_) + 1;
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__state_ &= ~__n_readers_;
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__state_ |= num_readers;
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}
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bool __shared_mutex_base::try_lock_shared() {
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unique_lock<mutex> lk(__mut_);
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unsigned num_readers = __state_ & __n_readers_;
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if (!(__state_ & __write_entered_) && num_readers != __n_readers_) {
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++num_readers;
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__state_ &= ~__n_readers_;
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__state_ |= num_readers;
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return true;
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}
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return false;
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}
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void __shared_mutex_base::unlock_shared() {
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lock_guard<mutex> _(__mut_);
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unsigned num_readers = (__state_ & __n_readers_) - 1;
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__state_ &= ~__n_readers_;
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__state_ |= num_readers;
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if (__state_ & __write_entered_) {
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if (num_readers == 0)
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__gate2_.notify_one();
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} else {
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if (num_readers == __n_readers_ - 1)
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__gate1_.notify_one();
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}
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}
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// Shared Timed Mutex
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// These routines are here for ABI stability
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shared_timed_mutex::shared_timed_mutex() : __base_() {}
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void shared_timed_mutex::lock() { return __base_.lock(); }
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bool shared_timed_mutex::try_lock() { return __base_.try_lock(); }
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void shared_timed_mutex::unlock() { return __base_.unlock(); }
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void shared_timed_mutex::lock_shared() { return __base_.lock_shared(); }
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bool shared_timed_mutex::try_lock_shared() { return __base_.try_lock_shared(); }
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void shared_timed_mutex::unlock_shared() { return __base_.unlock_shared(); }
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_LIBCPP_END_NAMESPACE_STD
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