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<?xml version="1.0" encoding="UTF-8" standalone="no"?>

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<CFile xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.w3.org/2001/XMLSchema" xsi:schemaLocation="cext_xsd.xsd">

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  <includes>

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<![CDATA[#include "stdio.h"]]>

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  </includes>

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  <variables>

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    <variable name="TestInput" type="SINT" class="input"/>

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    <variable name="TestOutput" type="SINT" class="output"/>

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  </variables>

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  <globals>

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<![CDATA[volatile long Lock=0;

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volatile char PtoC=1,CtoP=2;

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extern long AtomicCompareExchange(long*,long, long);

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int Simple_C_Call(int val){

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  return val+1;

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}

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int Python_to_C_Call(char toC, char *fromC){

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  /* Code called by python should never touch to 

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     variables modified by PLC thread directly

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     AtomicCompareExchange comes from 

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     beremiz' runtime implementation */

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  int res = 0;

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  if(!AtomicCompareExchange((long*)&Lock, 0, 1)){

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    PtoC=toC;

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    *fromC=CtoP;

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    AtomicCompareExchange((long*)&Lock, 1, 0);

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    res=1;

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  }

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  printf("C code called by Python: toC %d fromC %d\n",toC,*fromC);

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  return res;

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}

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int PLC_C_Call(char fromPLC, char *toPLC){

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  /* PLC also have to be realy carefull not to 

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     conflict with asynchronous python access */

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  if(!AtomicCompareExchange((long*)&Lock, 0, 1)){

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      CtoP = fromPLC;

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      *toPLC = PtoC;

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      AtomicCompareExchange((long*)&Lock, 1, 0);

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      return 1;

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  }

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  return 0;

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}]]>

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  </globals>

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  <initFunction>

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<![CDATA[]]>

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  </initFunction>

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  <cleanUpFunction>

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<![CDATA[]]>

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  </cleanUpFunction>

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  <retrieveFunction>

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<![CDATA[]]>

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  </retrieveFunction>

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  <publishFunction>

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<![CDATA[if(!AtomicCompareExchange((long*)&Lock, 0, 1)){

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    TestInput = CtoP + PtoC + TestOutput;

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    AtomicCompareExchange((long*)&Lock, 1, 0);

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}]]>

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  </publishFunction>

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</CFile>