gfplus.c

来自「Proakis《contemporarycommunication system」· C语言 代码 · 共 72 行

#include <math.h>
#include "mex.h"
/*
 * GFPLUS  Galois Field addition (vectorized)
 *         k = gfplus(i,j,alpha,beta)
 */

/*
 * Wes Wang, Cleve Moler, 10/5/95
 * Copyright (c) 1995-96 The MathWorks, Inc.
 * All Rights Reserved
 * $Revision: 1.1 $  $Date: 1996/04/01 18:14:36 $
 */
void mexFunction(int nlhs, Matrix *plhs[], int nrhs, Matrix *prhs[])
{
   int mi,ni,mj,nj,m,n,k,r,inci,incj, indi, indj, nalpha;
   double *pi,*pj,*pr,*alpha,*beta;

   mi = mxGetM(prhs[0]);
   ni = mxGetN(prhs[0]);
   mj = mxGetM(prhs[1]);
   nj = mxGetN(prhs[1]);
   alpha = mxGetPr(prhs[2]);
   beta = mxGetPr(prhs[3]);
   nalpha = mxGetN(prhs[2]) * mxGetM(prhs[2]);
   if (nalpha != mxGetN(prhs[3]) * mxGetM(prhs[3]))
       mexErrMsgTxt("Dimensions of Alpha and Beta must agree.");
   nalpha = nalpha - 1;
   if ((mi == 1) & (ni == 1) & (mj == 1) & (nj == 1)) {
       r = ((int) alpha[(int) mxGetScalar(prhs[0]) % nalpha + 1]) ^ 
             ((int) alpha[(int) mxGetScalar(prhs[1]) % nalpha + 1]);
       *mxGetPr(plhs[0] = mxCreateFull(1,1,0)) = (double) (beta[r]-1);
       return;
   } else if ((mi == mj) & (ni == nj)) {
       m = mi;
       n = ni;
       inci = 1;
       incj = 1;
   } else if ((mj == 1) & (nj == 1)) {
       m = mi;
       n = ni;
       inci = 1;
       incj = 0;
   } else if ((mi == 1) & (ni == 1)) {
       m = mj;
       n = nj;
       inci = 0;
       incj = 1;
   } else {
       mexErrMsgTxt("Matrix dimensions must agree.");
   }
   pi = mxGetPr(prhs[0]);
   pj = mxGetPr(prhs[1]);
   pr = mxGetPr(plhs[0] = mxCreateFull(m,n,0));
   for (k = 0; k < m*n; k++) {
/*           indi = (int)*pi+1;
              indj = (int)*pj+1;
              if (indi < 0)
             indi = 0;
             if (indj < 0)
             indj = 0;
 */
      indi = (*pi < 0) ? 0 : (int)*pi % nalpha + 1;
      indj = (*pj < 0) ? 0 : (int)*pj % nalpha + 1;
      r = ((int) alpha[indi]) ^ ((int) alpha[indj]);
      *pr++ = (double) (beta[r]-1);
       pi += inci;
       pj += incj;
   }
   return;
}