www.pudn.com > ldpca.zip > decodeBits.c

//Author:  David Varodayan (varodayan@stanford.edu)
//Date:    May 8, 2006

#include "mex.h"
#include 
#include 

#define max(a,b) (((a)>(b))?(a):(b))

//C-MEX wrapper
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
    double *LLR_intrinsic, *accumulatedSyndrome, *source, *decoded, *rate, *numErrors;
    char ladderFile[50];
    FILE *fp;
    int n;
    
    LLR_intrinsic = mxGetPr(prhs[0]);
    accumulatedSyndrome = mxGetPr(prhs[1]);
    source = mxGetPr(prhs[2]);
    mxGetString(prhs[3], ladderFile, 50); 
    
    fp = fopen(ladderFile, "r");
    fscanf(fp, "%d", &n);
    fscanf(fp, "%d", &n);
    fclose(fp);    
    
    plhs[0] = mxCreateDoubleMatrix(1, n, mxREAL);
    decoded = mxGetPr(plhs[0]);
    plhs[1] = mxCreateDoubleMatrix(1, 1, mxREAL);
    rate = mxGetPr(plhs[1]);
    plhs[2] = mxCreateDoubleMatrix(1, 1, mxREAL);
    numErrors = mxGetPr(plhs[2]);
    
    decodeBits(LLR_intrinsic, accumulatedSyndrome, source, ladderFile, decoded, rate, numErrors);
}

//decodeBits() finds the minimum rate for which the decoded bitstream matches
//the transmitted portion of the accumulated syndrome.
//The number of residual bit errors is also calculated.
void decodeBits(double *LLR_intrinsic, double *accumulatedSyndrome, double *source, char *ladderFile,
                double *decoded, double *rate, double *numErrors)
{
    FILE *fp;
    int n, m, nzmax, *ir, *jc;
    int numCodes, totalNumInc, numInc, *txSeq;
    int code, k, currIndex, prevIndex;
    double *syndrome;
    
    fp = fopen(ladderFile, "r");
 
    fscanf(fp, "%d", &numCodes);
    fscanf(fp, "%d", &n);
    fscanf(fp, "%d", &nzmax);
    fscanf(fp, "%d", &totalNumInc);
        
    ir = mxCalloc(nzmax, sizeof(int));
    jc = mxCalloc(n+1, sizeof(int));
    txSeq = mxCalloc(totalNumInc, sizeof(int)); //actual length: numInc
    syndrome = mxCalloc(n, sizeof(double)); //actual length: m
    
    for(k=0; k