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