atomicoperations.h

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// The DAGFrameScheduler is a Multi-Threaded lock free and wait free scheduling library.
// © Copyright 2010 - 2016 BlackTopp Studios Inc.
/* This file is part of The DAGFrameScheduler.

    The DAGFrameScheduler is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
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    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with The DAGFrameScheduler.  If not, see <http://www.gnu.org/licenses/>.
*/
/* The original authors have included a copy of the license specified above in the
   'doc' folder. See 'gpl.txt'
*/
/* We welcome the use of the DAGFrameScheduler to anyone, including companies who wish to
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*/
#ifndef _atomic_black_ops_would_be_an_awesome_name_for_a_cheezy_game_h
#define _atomic_black_ops_would_be_an_awesome_name_for_a_cheezy_game_h

#include "datatypes.h"

/// @file
/// @brief Simple thread safe ways to check and change a specified variable atomically.

namespace Mezzanine
{
    namespace Threading
    {
#if !(defined(SWIG) && defined(MEZZLUA51)) // Stop Swig from making lua bindings but allow other languages
        /// @brief Atomically Compares And Swaps a 32 bit value.
        /// @details In such a way that this cannot be interupted by another thread this performs a number of steps.
        /// First, it compares the dereferenced value VariableToChange to OldValue. Then if they match it writes NewValue
        /// to the memory location VariableToChange points to. If they did not match, no work is performed except the dereferencing.
        /// In either case since VariableToChange has been derefenced the value stored before any exchange that might have
        /// occured is returned.
        /// @param VariableToChange A pointer to the value to compare and if it matches OldValue Atomically change.
        /// @param OldValue what is expected to be at the other end of VariableToChange.
        /// @param NewValue The value to be written to VariableToChange if at the time the actual CPU instruction is executed OldValue Matches *VariableToChange.
        /// @note This very specific semantics of this function are useless in most scripting so it is not included in Lua and other scripting languages.
        /// @return This always returns the value that was pointed to by VariableToChange immediately before this call.
        Int32 MEZZ_LIB AtomicCompareAndSwap32(Int32* VariableToChange, const Int32& OldValue, const Int32& NewValue);
/*
        // @brief Atomically Compares And Swaps a 64 bit value.
        // @details In such a way that this cannot be interupted by another thread this performs a number of steps.
        // First, it compares the dereferenced value VariableToChange to OldValue. Then if they match it writes NewValue
        // to the memory location VariableToChange points to. If they did not match, no work is performed except the dereferencing.
        // In either case since VariableToChange has been derefenced the value stored before any exchange that might have
        // occured is returned.
        // @param VariableToChange A pointer to the value to compare and if it matches OldValue Atomically change.
        // @param OldValue what is expected to be at the other end of VariableToChange.
        // @param NewValue The value to be written to VariableToChange if at the time the actual CPU instruction is executed OldValue Matches *VariableToChange.
        // @return This always returns the value that was pointed to by VariableToChange immediately before this call.
        Int64 MEZZ_LIB AtomicCompareAndSwap64(Int64* VariableToChange, const Int64& OldValue, const Int64& NewValue);
*/
        /// @brief Increments a value in a way guaranteed to not lose any atomic increments.
        /// @param VariableToChange A pointer to the 32 bit integer to increment by the amount specified.
        /// @param Value The amount to increment the VariableToChange by.
        /// @note This very specific semantics of this function are useless in most scripting so it is not included in Lua and other scripting languages.
        /// @return The value just before being incremented. This is not always *VariableToChange. If another thread attempted an atomic operation on this at the same time the result could be an unexpected value.
        Int32 MEZZ_LIB AtomicAdd(Int32* VariableToChange, Int32 Value);
#endif
    }//Threading
}//Mezzanine

#endif