reader_writer_lock.h

/*
    Copyright 2005-2016 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks. Threading Building Blocks is free software;
    you can redistribute it and/or modify it under the terms of the GNU General Public License
    version 2  as  published  by  the  Free Software Foundation.  Threading Building Blocks is
    distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the
    implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
    See  the GNU General Public License for more details.   You should have received a copy of
    the  GNU General Public License along with Threading Building Blocks; if not, write to the
    Free Software Foundation, Inc.,  51 Franklin St,  Fifth Floor,  Boston,  MA 02110-1301 USA

    As a special exception,  you may use this file  as part of a free software library without
    restriction.  Specifically,  if other files instantiate templates  or use macros or inline
    functions from this file, or you compile this file and link it with other files to produce
    an executable,  this file does not by itself cause the resulting executable to be covered
    by the GNU General Public License. This exception does not however invalidate any other
    reasons why the executable file might be covered by the GNU General Public License.
*/

#ifndef __TBB_reader_writer_lock_H
#define __TBB_reader_writer_lock_H

#include "tbb_thread.h"
#include "tbb_allocator.h"
#include "atomic.h"

namespace tbb {
namespace interface5 {

    class reader_writer_lock : tbb::internal::no_copy {
 public:
    friend class scoped_lock;
    friend class scoped_lock_read;

    enum status_t { waiting_nonblocking, waiting, active, invalid };

    reader_writer_lock() {
        internal_construct();
    }

    ~reader_writer_lock() {
        internal_destroy();
    }


    class scoped_lock : tbb::internal::no_copy {
    public:
        friend class reader_writer_lock;

        scoped_lock(reader_writer_lock& lock) {
            internal_construct(lock);
        }

        ~scoped_lock() {
            internal_destroy();
        }

        void* operator new(size_t s) {
            return tbb::internal::allocate_via_handler_v3(s);
        }
        void operator delete(void* p) {
            tbb::internal::deallocate_via_handler_v3(p);
        }

    private:
        reader_writer_lock *mutex;
        scoped_lock* next;
        atomic<status_t> status;

        scoped_lock();

        void __TBB_EXPORTED_METHOD internal_construct(reader_writer_lock&);
        void __TBB_EXPORTED_METHOD internal_destroy();
   };

    class scoped_lock_read : tbb::internal::no_copy {
    public:
        friend class reader_writer_lock;

        scoped_lock_read(reader_writer_lock& lock) {
            internal_construct(lock);
        }

        ~scoped_lock_read() {
            internal_destroy();
        }

        void* operator new(size_t s) {
            return tbb::internal::allocate_via_handler_v3(s);
        }
        void operator delete(void* p) {
            tbb::internal::deallocate_via_handler_v3(p);
        }

    private:
        reader_writer_lock *mutex;
        scoped_lock_read *next;
        atomic<status_t> status;

        scoped_lock_read();

        void __TBB_EXPORTED_METHOD internal_construct(reader_writer_lock&);
        void __TBB_EXPORTED_METHOD internal_destroy();
    };


    void __TBB_EXPORTED_METHOD lock();


    bool __TBB_EXPORTED_METHOD try_lock();


    void __TBB_EXPORTED_METHOD lock_read();


    bool __TBB_EXPORTED_METHOD try_lock_read();

    void __TBB_EXPORTED_METHOD unlock();

 private:
    void __TBB_EXPORTED_METHOD internal_construct();
    void __TBB_EXPORTED_METHOD internal_destroy();


    bool start_write(scoped_lock *);
    void set_next_writer(scoped_lock *w);
    void end_write(scoped_lock *);
    bool is_current_writer();


    void start_read(scoped_lock_read *);
    void unblock_readers();
    void end_read();

    atomic<scoped_lock_read*> reader_head;
    atomic<scoped_lock*> writer_head;
    atomic<scoped_lock*> writer_tail;
    tbb_thread::id my_current_writer;
    atomic<uintptr_t> rdr_count_and_flags; // used with __TBB_AtomicOR, which assumes uintptr_t
};

} // namespace interface5

using interface5::reader_writer_lock;

} // namespace tbb

#endif /* __TBB_reader_writer_lock_H */