Math Forum Discussions

Kwok

Posts: 8
Registered: 5/31/12

create object in C++ mex S-function
Posted: Nov 26, 2012 11:11 AM

Plain Text

When I create object of a class by calling myClass* p_myClass = new myClass(); outside all the S-function method, it will work for the first run. When I run the model again, it outputs a really small number, which doesn't seem to work properly. When I put create the object and store the pointer using PWork vector inside mdlStart, it works. What is the difference?
Below is my simple code to test this.

#define S_FUNCTION_LEVEL 2
#define S_FUNCTION_NAME test_1
#include "simstruc.h"
#include "myClass.h"
#define NumInput 0
#define NumOutput 1

// this does not work properly
myClass* p_myClass = new myClass();

static void mdlInitializeSizes(SimStruct *S){
int PortIndex;
ssSetNumSFcnParams(S, 0); /* Number of expected parameters */
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
/* Return if number of expected != number of actual parameters */
return;
}
ssSetNumContStates(S, 0);
ssSetNumDiscStates(S, 0);
// InputPort
if (!ssSetNumInputPorts(S, NumInput)) return; //no input
// OutputPort
if (!ssSetNumOutputPorts(S, NumOutput)) return;
for (PortIndex=0; PortIndex<NumOutput; PortIndex++){
ssSetOutputPortWidth(S, PortIndex, 1);
}
ssSetNumSampleTimes(S, 1);
ssSetNumPWork( S, 1);
ssSetSimStateCompliance(S, USE_DEFAULT_SIM_STATE);
ssSetOptions(S, 0);
}

static void mdlInitializeSampleTimes(SimStruct *S){
ssSetSampleTime(S, 0, CONTINUOUS_SAMPLE_TIME);
ssSetOffsetTime(S, 0, 0.0);
}

#define MDL_START
#if defined(MDL_START)
static void mdlStart(SimStruct *S){
// This will work properly.
//myClass* p_myClass = new myClass();
ssGetPWork(S)[0] = (void *) p_myClass;
}
#endif

static void mdlOutputs(SimStruct *S, int_T tid)
{
myClass* p_myClass = (myClass *) ssGetPWork(S)[0];
real_T *y0 = ssGetOutputPortRealSignal(S,0);

y0[0]=p_myClass->GetVar1();
}

static void mdlTerminate(SimStruct *S){
myClass* p_myClass = (myClass *) ssGetPWork(S)[0];
delete p_myClass;
}

#ifdef MATLAB_MEX_FILE /* Is this file being compiled as a MEX-file? */
#include "simulink.c" /* MEX-file interface mechanism */
#else
#include "cg_sfun.h" /* Code generation registration function */
#endif

-----------------------------------------------------------------------------------------------------
class myClass{
private:
double var1;
int var2;
double* ptr;
public:
myClass();
~myClass();
double GetVar1(){
return var1;
}
int GetVar2(){
return var2;
}
double AddVariable(){
return var1+double(var2);
}
double GetEntry2(){
return ptr[1];
}

};

myClass::myClass(){
var1=2.55;
var2=5;
ptr = new double [3];
for(int count=0;count<3;count++){
ptr[count]=count*10+1000;
}
}

myClass::~myClass(){
printf("deleted allocated memory\n");
delete[] ptr;
}