reader_writer_lock.h

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/*
    Copyright 2005-2010 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<unsigned> rdr_count_and_flags;
};

} // namespace interface5

using interface5::reader_writer_lock;

} // namespace tbb

#endif /* __TBB_reader_writer_lock_H */