encode_blockmex.c

本程序利用改进的CHOW算法

/* Convolutional Encoder
   pass in generating polynomials g m-by-3 (m=1 to 7)
   outputs encoded bitstream
   written by Joe Williams - Southern Methodist University as ugrad,
   now Stanford grad student in EE.
   if you use this, you must give the author proper credit
*/

#include "mex.h"
#include "mat.h"
#include <math.h>
#define  output_bits plhs[0]
#define	 g_in prhs[0]
#define	 input_bits prhs[1]

void mexFunction(int nlhs, 
                     mxArray *plhs[],
                     int nrhs, 
                     const mxArray *prhs[])
    {
	mxArray *inputs[3];
	double *bits_output,*bits_input,*state_i,*state_o,*output_val;
	bool g[7][3];//now largest g matrix is a 7x3
	int n,k,m,i,j,temp,col,row,L_total,L_info,a,b;
	int input_val;
	int *test;

	n = mxGetM(g_in);//get the size of the g matrix 
	k = mxGetN(g_in);
	m = k-1;

	for(col=0;col<k;col++){//Create a c-matrix
	  for(row=0;row<n;row++){
		g[row][col]=(mxGetPr(g_in))[row+col*mxGetM(g_in)];
	  }
	}
	bits_input = mxGetPr(input_bits);
	L_info = mxGetN(input_bits);
	L_total = L_info+m;

	output_val=mxCalloc(n,sizeof(double));

	output_bits = mxCreateDoubleMatrix(1, (L_total)*n, mxREAL);
    //output_bits = mxCreateDoubleMatrix(1, (L_info)*n, mxREAL);
	bits_output = mxGetPr(output_bits);
   state_o = mxCalloc(1,m*sizeof(double));
   state_i = mxCalloc(1,m*sizeof(double));

	for(i=0;i<L_total;i++){
      //[output_bits, state] = encode_bit(g, input_bit, state);
 	  input_val=(int)bits_input[i];
	  for(j=0;j<=m-1;j++)
		state_i[j]=state_o[j];

	  for(a=0;a<n;a++){//encode the bit
        output_val[a]=g[a][0]*bits_input[i];
  		for(j=1;j<k;j++){
	      temp=g[a][j]*state_i[j-1];
          output_val[a]=(int)output_val[a]^temp;
	    }
	  }
	  state_o[0]=bits_input[i];
	  for(a=1;a<=m-1;a++)
	    state_o[a]=state_i[a-1];
	  for(j=n*i,a=0;j<n*(i+1)-1,a<n;j++,a++){
       bits_output[j]=output_val[a];
	  }
	}
   mxFree(output_val);
   mxFree(state_o);
   mxFree(state_i);
}