/*
 * sfuntmpl_basic.c: Basic 'C' template for a level 2 S-function.
 *
 *  -------------------------------------------------------------------------
 *  | See matlabroot/simulink/src/sfuntmpl_doc.c for a more detailed template |
 *  -------------------------------------------------------------------------
 *
 * Copyright 1990-2001 The MathWorks, Inc.
 * $Revision: 1.26 $
 */


/*
 * You must specify the S_FUNCTION_NAME as the name of your S-function
 * (i.e. replace sfuntmpl_basic with the name of your S-function).
 */

#define S_FUNCTION_NAME  sfun_han
#define S_FUNCTION_LEVEL 2

/*
 * Need to include simstruc.h for the definition of the SimStruct and
 * its associated macro definitions.
 */
#include "simstruc.h"
#include "math.h"

/* Error handling
 * --------------
 *
 * You should use the following technique to report errors encountered within
 * an S-function:
 *
 *       ssSetErrorStatus(S,"Error encountered due to ...");
 *       return;
 *
 * Note that the 2nd argument to ssSetErrorStatus must be persistent memory.
 * It cannot be a local variable. For example the following will cause
 * unpredictable errors:
 *
 *      mdlOutputs()
 *      {
 *         char msg[256];         {ILLEGAL: to fix use "static char msg[256];"}
 *         sprintf(msg,"Error due to %s", string);
 *         ssSetErrorStatus(S,msg);
 *         return;
 *      }
 *
 * See matlabroot/simulink/src/sfuntmpl_doc.c for more details.
 */

 double sign(double x)
{
   double f;
   f=1; if (x<=0) f=-1; return(f);
}

double fst(real_T *x, const real_T *u, const real_T *p1, const real_T *p2)
{
   double delta, delta0, a0, a, y, r, h;
   r=p1[0]; h=p2[0];
   delta=r*h; delta0=delta*h;
   y=x[0]-u[0]+h*x[1]; 
   a0=sqrt(delta*delta+8.0*r*fabs(y));
   if (fabs(y) <= delta0) a=x[1]+y/h;
   else a=x[1]+0.5*(a0-delta)*sign(y);
   if (fabs(a) <= delta) return (-r*a/delta);
   else return(-r*sign(a));
}

/*====================*
 * S-function methods *
 *====================*/

/* Function: mdlInitializeSizes ===============================================
 * Abstract:
 *    The sizes information is used by Simulink to determine the S-function
 *    block's characteristics (number of inputs, outputs, states, etc.).
 */
static void mdlInitializeSizes(SimStruct *S)
{
    /* See sfuntmpl_doc.c for more details on the macros below */

    ssSetNumSFcnParams(S, 3);  /* number of extra parameters */
    if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
        /* Return if number of expected != number of actual parameters */
        return;
    }

    ssSetNumContStates(S, 0);
    ssSetNumDiscStates(S, 2);

    if (!ssSetNumInputPorts(S, 1)) return;
    ssSetInputPortWidth(S, 0, 1);
    ssSetInputPortRequiredContiguous(S, 0, true); /*direct input signal access*/
    /*
     * Set direct feedthrough flag (1=yes, 0=no).
     * A port has direct feedthrough if the input is used in either
     * the mdlOutputs or mdlGetTimeOfNextVarHit functions.
     * See matlabroot/simulink/src/sfuntmpl_directfeed.txt.
     */
    ssSetInputPortDirectFeedThrough(S, 0, 0);

    if (!ssSetNumOutputPorts(S, 1)) return;
    ssSetOutputPortWidth(S, 0, 2);

    ssSetNumSampleTimes(S, 1);
    ssSetNumRWork(S, 3);
    ssSetNumIWork(S, 0);
    ssSetNumPWork(S, 0);
    ssSetNumModes(S, 0);
    ssSetNumNonsampledZCs(S, 0);

    ssSetOptions(S, 0);
}

/* Function: mdlInitializeSampleTimes =========================================
 * Abstract:
 *    This function is used to specify the sample time(s) for your
 *    S-function. You must register the same number of sample times as
 *    specified in ssSetNumSampleTimes.
 */
static void mdlInitializeSampleTimes(SimStruct *S)
{
    ssSetSampleTime(S, 0, *mxGetPr(ssGetSFcnParam(S,2)));
    ssSetOffsetTime(S, 0, 0.0);
}

#define MDL_INITIALIZE_CONDITIONS   /* Change to #undef to remove function */
#if defined(MDL_INITIALIZE_CONDITIONS)
  /* Function: mdlInitializeConditions ========================================
   * Abstract:
   *    In this function, you should initialize the continuous and discrete
   *    states for your S-function block.  The initial states are placed
   *    in the state vector, ssGetContStates(S) or ssGetRealDiscStates(S).
   *    You can also perform any other initialization activities that your
   *    S-function may require. Note, this routine will be called at the
   *    start of simulation and if it is present in an enabled subsystem
   *    configured to reset states, it will be call when the enabled subsystem
   *    restarts execution to reset the states.
   */
  static void mdlInitializeConditions(SimStruct *S)
  {
  }
#endif /* MDL_INITIALIZE_CONDITIONS */

#define MDL_START  /* Change to #undef to remove function */
#if defined(MDL_START) 
  /* Function: mdlStart =======================================================
   * Abstract:
   *    This function is called once at start of model execution. If you
   *    have states that should be initialized once, this is the place
   *    to do it.
   */
  static void mdlStart(SimStruct *S)
  {
  }
#endif /*  MDL_START */

/* Function: mdlOutputs =======================================================
 * Abstract:
 *    In this function, you compute the outputs of your S-function
 *    block. Generally outputs are placed in the output vector, ssGetY(S).
 */
static void mdlOutputs(SimStruct *S, int_T tid)
{
    const real_T *x = ssGetRealDiscStates(S);
    real_T       *y = ssGetOutputPortSignal(S,0);
    y[0] = x[0];
    y[1] = x[1];
}

#define MDL_UPDATE  /* Change to #undef to remove function */
#if defined(MDL_UPDATE)
  /* Function: mdlUpdate ======================================================
   * Abstract:
   *    This function is called once for every major integration time step.
   *    Discrete states are typically updated here, but this function is useful
   *    for performing any tasks that should only take place once per
   *    integration step.
   */
  static void mdlUpdate(SimStruct *S, int_T tid)
  {
    real_T       *x = ssGetRealDiscStates(S);
    const real_T *u = (const real_T*) ssGetInputPortSignal(S,0);
    const real_T *r = mxGetPr(ssGetSFcnParam(S,0));
    const real_T *h = mxGetPr(ssGetSFcnParam(S,1));
    const real_T *T = mxGetPr(ssGetSFcnParam(S,2));
    real_T tempX[2] = {0.0, 0.0};
    tempX[0] = x[0] + T[0]*x[1]; 
    tempX[1] = x[1] + T[0]*fst(x,u,r,h);
/*    printf("%f, %f, %f\n",tempX[0],tempX[1],fst(x,u,r,h));*/
    x[0] = tempX[0]; x[1] = tempX[1];
  }
#endif /* MDL_UPDATE */

#define MDL_DERIVATIVES  /* Change to #undef to remove function */
#if defined(MDL_DERIVATIVES)
  /* Function: mdlDerivatives =================================================
   * Abstract:
   *    In this function, you compute the S-function block's derivatives.
   *    The derivatives are placed in the derivative vector, ssGetdX(S).
   */
  static void mdlDerivatives(SimStruct *S)
  {
  }
#endif /* MDL_DERIVATIVES */

/* Function: mdlTerminate =====================================================
 * Abstract:
 *    In this function, you should perform any actions that are necessary
 *    at the termination of a simulation.  For example, if memory was
 *    allocated in mdlStart, this is the place to free it.
 */
static void mdlTerminate(SimStruct *S)
{
}

/*======================================================*
 * See sfuntmpl_doc.c for the optional S-function methods *
 *======================================================*/

/*=============================*
 * Required S-function trailer *
 *=============================*/

#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