simrscod.c

数字通信第四版原书的例程

/*============================================================================
 * Syntax: [sys, x0, str, ts] = simrscod(t, x, u, flag, n, k, pg, tp, dim);
 *SIMBCHDC SIMULINK S-function for Reed-Solomon encode.
 *       The m-dile is designed to be used in a SIMULINK S-Function block.
 *       This function will encode the input integer vector using RS-code.
 *       Parameters: n -- length of code word.
 *                   k -- length of message.
 *                   pg-- generator polynomial
 *                   tp-- list of all GF(2^M) elements. n=2^M-1.
 *                   dim -- M.
 *
 *       The output has length n.
 *============================================================================
 *     Original designed by Wes Wang,
 *     Jun Wu,     The Mathworks, Inc.
 *     Feb-07, 1996
 *
 *     Copyright (c) 1996 by The MAthWorks, Inc.
 *     All Rights Reserved
 *     $Revision: 1.1 $  $Date: 1996/04/01 19:05:00 $
 *============================================================================
 */
#define S_FUNCTION_NAME simrscod

/* need to include simstruc.h for the definition of the SimStruct and
 * its associated macro definitions.
 */ 
#include "simstruc.h"
#include "gflib.c"

#ifdef MATLAB_MEX_FILE
#include "mex.h"        /* needed for declaration of mexErrMsgTxt */
#endif

#define NUM_ARGS    5           /* five additional input arguments */
#define N       ssGetArg(S,0)
#define K       ssGetArg(S,1)
#define PG      ssGetArg(S,2)
#define P       ssGetArg(S,3)
#define DIM     ssGetArg(S,4)

/*elseif flag == 0
 *    if 2^dim-1 ~= n
 *        error('Reed-Solomon encode has illegal code word length')
 *    end;
 *    sys(1) = 0; % no continuous state
 *    sys(2) = 0;
 *    sys(3) = n;   % number of output, code word length plus one.
 *    sys(4) = k + 1;       % number of input, message length.
 *    sys(5) = 0;
 *    sys(6) = 1;       % direct through flag.
 *    sys(7) = 1;       % one sample rate
 *    x0 = [];
 *    ts = [-1, 0];
 *else
 *    sys = [];
 *end;
 */
static void mdlInitializeSizes(S)
     SimStruct *S;
{
  int     i, np, len_pg;
  int     n = (int)mxGetPr(N)[0];
  int     k = (int)mxGetPr(K)[0];
  int     dim = (int)mxGetPr(DIM)[0];
  
  len_pg = mxGetM(PG)*mxGetN(PG);
  np = 1;
  for(i=0; i < dim; i++)
    np = np*2;
  
  if ( np-1 != n ){
#ifdef MATLAB_MEX_FILE
    mexErrMsgTxt("Reed-Solomon encode has illegal code word length");
#endif
  }
  
  ssSetNumContStates(     S, 0);          /* no continuous states */
  ssSetNumDiscStates(     S, 0);          /* no discrete states */
  ssSetNumOutputs(        S, n);          /* number of output, code word length plus one*/
  ssSetNumInputs(         S, k+1);        /* number of inputs, message length*/
  ssSetDirectFeedThrough( S, 1);          /* direct feedthrough flag */
  ssSetNumSampleTimes(    S, 1);          /* number of sample times */
  ssSetNumInputArgs(      S, NUM_ARGS);   /* number of input arguments*/
  ssSetNumRWork(          S, 0);
  ssSetNumIWork(          S, (n+3)*dim+len_pg+3*n+6);
  /* (n+1)*dim    --- *pp
   * len_pg-1 ------- *pgg
   * n -------------- *msg
   * 1 -------------- *tmpMul
   * 1 -------------- *len
   * n+3+dim -------- Iwork for gfpmul()
   * n+2+dim -------- Iwork for gfpadd()
   */
  ssSetNumPWork(          S, 0);
}

/*
 * mdlInitializeConditions - initialize the states
 * Initialize the states, Integers and real-numbers
 */
static void mdlInitializeConditions(x0, S)
     double *x0;
     SimStruct *S;
{
  int     i, len_pg;
  int     *pp, *pgg, *msg, *tmpMul, *len, *IworkMul, *IworkAdd;
  int     n = (int)mxGetPr(N)[0];
  int     k = (int)mxGetPr(K)[0];
  int     dim = (int)mxGetPr(DIM)[0];
  
  len_pg = mxGetM(PG)*mxGetN(PG);
    
  pp =       ssGetIWork(S);
  pgg =      ssGetIWork(S)+(n+1)*dim;
  msg =      ssGetIWork(S)+(n+1)*dim+len_pg-1;
  tmpMul =   ssGetIWork(S)+(n+1)*dim+len_pg-1+n;
  len =      ssGetIWork(S)+(n+1)*dim+len_pg-1+n+1;
  IworkMul = ssGetIWork(S)+(n+1)*dim+len_pg-1+n+2;
  IworkAdd = ssGetIWork(S)+(n+1)*dim+len_pg-1+n+2+n+3+dim;
  
  for( i=0; i<(n+1)*dim; i++ )
    pp[i] = (int)mxGetPr(P)[i];
  for(i=0; i<len_pg-1; i++)
    pgg[i] = (int)mxGetPr(PG)[len_pg-2-i];
}
/*
 * mdlInitializeSampleTimes - initialize the sample times array
 *
 * This function is used to specify the sample time(s) for your S-function.
 * If your S-function is continuous, you must specify a sample time of 0.0.
 * Sample times must be registered in ascending order.
 */
static void mdlInitializeSampleTimes(S)
     SimStruct *S;
{
  ssSetSampleTimeEvent(S, 0,  0.0);
  ssSetOffsetTimeEvent(S, 0,  0.0);
}

/*if (flag == 3)
 *    % refresh the state only when there is a trigger signal
 *    len_u = length(u);
 *    if u(len_u)
 *        % main calculation
 *        t2 = n - k;
 *        pgg = fliplr(pg(1:length(pg)-1));       % pg is a monic polynomial
 *        msg = [flipud(msg); -ones(t2,1)];
 *        for main_j = 1 : len_u-1
 *            if msg(main_j)>= 0
 *                for main_k = 1: t2
 *                    msg(main_j + main_k) = gfadd(msg(main_j + main_k), gfmul(msg(main_j), pgg(main_k), tp), tp);
 *                end;
 *            end;
 *        end;
 *        sys = [flipud(msg(len_u:n))+1; u(1:len_u-1)];
 *        indx = find(~(sys >= 0));
 *        sys(indx) = indx - indx;
 *    else
 *        % if there is no trigger, no calculation.
 *        sys = zeros(n, 1);
 *    end;
 */
/* mdlOutputs - compute the outputs
 * In this function, you compute the outputs of your S-function
 * block.  The outputs are placed in the y variable.
 */
static void mdlOutputs(y, x, u, S, tid)
     double *y, *x, *u; 
     SimStruct *S;
     int tid;
{
  int     i, len_pg, t2, main_j, main_k;
  int     *pp, *pgg, *msg, *tmpMul, *len, *IworkMul, *IworkAdd;
  int     n = (int)mxGetPr(N)[0];
  int     k = (int)mxGetPr(K)[0];
  int     dim = (int)mxGetPr(DIM)[0];
  
  len_pg = mxGetM(PG)*mxGetN(PG);
  
  pp =       ssGetIWork(S);
  pgg =      ssGetIWork(S)+(n+1)*dim;
  msg =      ssGetIWork(S)+(n+1)*dim+len_pg-1;
  tmpMul =   ssGetIWork(S)+(n+1)*dim+len_pg-1+n;
  len =      ssGetIWork(S)+(n+1)*dim+len_pg-1+n+1;
  IworkMul = ssGetIWork(S)+(n+1)*dim+len_pg-1+n+2;
  IworkAdd = ssGetIWork(S)+(n+1)*dim+len_pg-1+n+2+n+3+dim;
  
  if( u[k] != 0 ){
    for( i=0; i<(n+1)*dim; i++ )
      pp[i] = (int)mxGetPr(P)[i];
    for(i=0; i<len_pg-1; i++)
      pgg[i] = (int)mxGetPr(PG)[len_pg-2-i];
    
    t2 = n - k;
    for(i=0; i < n; i++){
      if(i < k) 
	msg[i] = (int)u[k-1-i] - 1;
      else
	msg[i] = -1;
    }
    for(main_j=0; main_j < k; main_j++){
      if (msg[main_j] >= 0){
	for(main_k=0; main_k < t2; main_k++){
	  tmpMul[0] = 0;
	  len[0] = 1;
	  gfpmul(&msg[main_j],1,&pgg[main_k],1,pp,n+1,dim,tmpMul,len,IworkMul);
	  gfpadd(&msg[main_j+main_k+1],1,tmpMul,1,pp,n+1,dim,&msg[main_j+main_k+1],len,IworkAdd);
	}
      }
    }
    for(i=0; i < n-k; i++)
      y[i] = (double)(msg[n-1-i] + 1);
    for(i=0; i < k; i++)
      y[i+n-k] = u[i];
    for(i=0; i < n; i++){
      if( y[i] < 0 )
	y[i] = 0;
    }   
  }else{
    /* % if there is no trigger, no calculation.*/
    for(i=0; i < n*dim; i++)
      y[i] = 0;
  }                
}
/*
 * mdlUpdate - perform action at major integration time step
 *
 * 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(x, u, S, tid)
     double *x, *u;
     SimStruct *S;
     int tid;
{
}

/*
 * mdlDerivatives - compute the derivatives
 *
 * In this function, you compute the S-function block's derivatives.
 * The derivatives are placed in the dx variable.
 */
static void mdlDerivatives(dx, x, u, S, tid)
     double *dx, *x, *u;
     SimStruct *S; 
     int tid;
{
}

/*
 * mdlTerminate - called when the simulation is terminated.
 *
 * In this function, you should perform any actions that are necessary
 * at the termination of a simulation.  For example, if memory was allocated
 * in mdlInitializeConditions, this is the place to free it.
 */
static void mdlTerminate(S)
     SimStruct *S;
{
}

#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