Matlab Level 2 S-Function example: Sine wave (continous output)

#define S_FUNCTION_NAME  sine_wave_generator
#define S_FUNCTION_LEVEL 2

#include "simstruc.h"
#include <cmath>  // For sine wave generation

// Define constants
#define SAMPLING_RATE 1000 // 1kHz
#define WAVE_FREQUENCY 1   // 1Hz
#define PI 3.14159265358979323846

// Function: mdlInitializeSizes ===============================================
// Abstract:
//   Setup sizes of the various vectors.
static void mdlInitializeSizes(SimStruct *S)
{
    ssSetNumSFcnParams(S, 0);  // No parameters
    ssSetNumContStates(S, 0);  // No continuous states
    ssSetNumDiscStates(S, 0);  // No discrete states

    // 1 output port with 1 element
    if (!ssSetNumOutputPorts(S, 1)) return;
    ssSetOutputPortWidth(S, 0, 1);  // Output port width = 1 (sine wave value)
    ssSetOutputPortDataType(S, 0, SS_DOUBLE);
    ssSetOutputPortComplexSignal(S, 0, COMPLEX_NO);

    // Sample times
    ssSetNumSampleTimes(S, 1);  // Single sample time

    // No work vectors (if needed, allocate work vectors here)
    ssSetNumRWork(S, 0);  // Real work vector
    ssSetNumIWork(S, 0);  // Integer work vector
    ssSetNumPWork(S, 0);  // Pointer work vector
    ssSetNumModes(S, 0);  // Mode vector
    ssSetNumNonsampledZCs(S, 0);  // Zero crossings

    // Make the S-function block capable of being used in a Real-Time Workshop-generated model
    ssSetOptions(S, 0);
}

// Function: mdlInitializeSampleTimes =========================================
// Abstract:
//    Initialize the sample times to be 1ms (1kHz)
static void mdlInitializeSampleTimes(SimStruct *S)
{
    ssSetSampleTime(S, 0, 1.0 / SAMPLING_RATE);  // 1kHz sampling rate
    ssSetOffsetTime(S, 0, 0.0);
}

// Function: mdlOutputs =======================================================
// Abstract:
//      Calculate the sine wave output based on the simulation time.
static void mdlOutputs(SimStruct *S, int_T tid)
{
    real_T *y = ssGetOutputPortRealSignal(S, 0);  // Output pointer
    real_T time = ssGetT(S);  // Get the current simulation time

    // Calculate the sine wave value for 1Hz frequency
    y[0] = sin(2 * PI * WAVE_FREQUENCY * time);
}

// Function: mdlTerminate =====================================================
// Abstract:
//    This function is called at the end of simulation for cleanup.
static void mdlTerminate(SimStruct *S)
{
    // No cleanup required for this example
}

// Required S-function trailer
#ifdef MATLAB_MEX_FILE
#include "simulink.c"   // MEX-file interface mechanism
#else
#include "cg_sfun.h"    // Code generation interface
#endif