shared_mutex.hpp

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// SPDX-License-Identifier: BSD-3-Clause
/* Copyright 2016-2020, Intel Corporation */
 
#ifndef LIBPMEMOBJ_CPP_SHARED_MUTEX_HPP
#define LIBPMEMOBJ_CPP_SHARED_MUTEX_HPP
 
#include <libpmemobj/thread.h>
#include <libpmemobj/tx_base.h>
 
namespace pmem
{
 
namespace obj
{
 
class shared_mutex {
public:
    typedef PMEMrwlock *native_handle_type;
 
    shared_mutex()
    {
        PMEMobjpool *pop;
        if ((pop = pmemobj_pool_by_ptr(&plock)) == nullptr)
            throw pmem::lock_error(
                1, std::generic_category(),
                "Persistent shared mutex not from persistent memory.");
 
        pmemobj_rwlock_zero(pop, &plock);
    }
 
    ~shared_mutex() = default;
 
    void
    lock()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        if (int ret = pmemobj_rwlock_wrlock(pop, &this->plock))
            throw pmem::lock_error(ret, std::system_category(),
                           "Failed to lock a shared mutex.")
                .with_pmemobj_errormsg();
    }
 
    void
    lock_shared()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        if (int ret = pmemobj_rwlock_rdlock(pop, &this->plock))
            throw pmem::lock_error(
                ret, std::system_category(),
                "Failed to shared lock a shared mutex.");
    }
 
    bool
    try_lock()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        int ret = pmemobj_rwlock_trywrlock(pop, &this->plock);
 
        if (ret == 0)
            return true;
        else if (ret == EBUSY)
            return false;
        else
            throw pmem::lock_error(ret, std::system_category(),
                           "Failed to lock a shared mutex.")
                .with_pmemobj_errormsg();
    }
 
    bool
    try_lock_shared()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        int ret = pmemobj_rwlock_tryrdlock(pop, &this->plock);
 
        if (ret == 0)
            return true;
        else if (ret == EBUSY)
            return false;
        else
            throw pmem::lock_error(ret, std::system_category(),
                           "Failed to lock a shared mutex.")
                .with_pmemobj_errormsg();
    }
 
    void
    unlock()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        int ret = pmemobj_rwlock_unlock(pop, &this->plock);
        if (ret)
            throw pmem::lock_error(
                ret, std::system_category(),
                "Failed to unlock a shared mutex.")
                .with_pmemobj_errormsg();
    }
 
    void
    unlock_shared()
    {
        this->unlock();
    }
 
    native_handle_type
    native_handle() noexcept
    {
        return &this->plock;
    }
 
    enum pobj_tx_param
    lock_type() const noexcept
    {
        return TX_PARAM_RWLOCK;
    }
 
    shared_mutex &operator=(const shared_mutex &) = delete;
 
    shared_mutex(const shared_mutex &) = delete;
 
private:
    PMEMrwlock plock;
};
 
} /* namespace obj */
 
} /* namespace pmem */
 
#endif /* LIBPMEMOBJ_CPP_SHARED_MUTEX_HPP */