shared_mutex.hpp

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/*
 * Copyright 2016-2018, Intel Corporation
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *       notice, this list of conditions and the following disclaimer.
 *
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in
 *       the documentation and/or other materials provided with the
 *       distribution.
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 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#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 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 lock_error(ret, std::system_category(),
                     "Failed to lock a shared mutex.");
    }

    void
    lock_shared()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        if (int ret = pmemobj_rwlock_rdlock(pop, &this->plock))
            throw 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 lock_error(ret, std::system_category(),
                     "Failed to lock a shared mutex.");
    }

    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 lock_error(ret, std::system_category(),
                     "Failed to lock a shared mutex.");
    }

    void
    unlock()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        (void)pmemobj_rwlock_unlock(pop, &this->plock);
    }

    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 */