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
 * are met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       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
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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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);
        int ret = pmemobj_rwlock_unlock(pop, &this->plock);
        if (ret)
            throw lock_error(ret, std::system_category(),
                     "Failed to unlock a shared mutex.");
    }
 
    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 */