read_write_lock.hpp

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/****************************************************************************
 *
 *  Copyright (c) 2017, Michael Becker (michael.f.becker@gmail.com)
 *
 *  This file is part of the FreeRTOS Add-ons project.
 *
 *  Source Code:
 *  https://github.com/michaelbecker/freertos-addons
 *
 *  Project Page:
 *  http://michaelbecker.github.io/freertos-addons/
 *
 *  On-line Documentation:
 *  http://michaelbecker.github.io/freertos-addons/docs/html/index.html
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a
 *  copy of this software and associated documentation files
 *  (the "Software"), to deal in the Software without restriction, including
 *  without limitation the rights to use, copy, modify, merge, publish,
 *  distribute, sublicense, and/or sell copies of the Software, and to
 *  permit persons to whom the Software is furnished to do so,subject to the
 *  following conditions:
 *
 *  + The above copyright notice and this permission notice shall be included
 *    in all copies or substantial portions of the Software.
 *  + Credit is appreciated, but not required, if you find this project
 *    useful enough to include in your application, product, device, etc.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 *  OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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 *  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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 *  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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 ***************************************************************************/


#ifndef READ_WRITE_LOCK_HPP_
#define READ_WRITE_LOCK_HPP_


#ifndef CPP_FREERTOS_NO_EXCEPTIONS
#include <exception>
#include <string>
#include <cstdio>
#ifdef CPP_FREERTOS_NO_CPP_STRINGS
#error "FreeRTOS-Addons require C++ Strings if you are using exceptions"
#endif
#endif
#include "FreeRTOS.h"
#include "semphr.h"


namespace cpp_freertos {


#ifndef CPP_FREERTOS_NO_EXCEPTIONS

class ReadWriteLockCreateException : public std::exception {

    public:
        ReadWriteLockCreateException()
        {
            sprintf(errorString, "ReadWriteLock Constructor Failed");
        }

        virtual const char *what() const throw()
        {
            return errorString;
        }

    private:
        char errorString[80];
};
#endif


class ReadWriteLock {

    //
    //  Public API
    //
    public:
        ReadWriteLock();

        virtual ~ReadWriteLock();

        virtual void ReaderLock() = 0;

        virtual void ReaderUnlock() = 0;

        virtual void WriterLock() = 0;

        virtual void WriterUnlock() = 0;

    //
    //  Protected API
    //  Not intended for use by application code.
    //
    protected:
        int ReadCount;

        SemaphoreHandle_t ReadLock;

        SemaphoreHandle_t ResourceLock;
};


class ReadWriteLockPreferReader : public ReadWriteLock {

    //
    //  Public API
    //
    public:
        virtual void ReaderLock();

        virtual void ReaderUnlock();

        virtual void WriterLock();

        virtual void WriterUnlock();
};


class ReadWriteLockPreferWriter : public ReadWriteLock {

    //
    //  Public API
    //
    public:
        ReadWriteLockPreferWriter();

        virtual ~ReadWriteLockPreferWriter();

        virtual void ReaderLock();

        virtual void ReaderUnlock();

        virtual void WriterLock();

        virtual void WriterUnlock();

    //
    //  Private API
    //  The internals of this wrapper class.
    //
    private:
        int WriteCount;

        SemaphoreHandle_t WriteLock;

        SemaphoreHandle_t BlockReadersLock;
};


}
#endif