385 lines
8.5 KiB
Plaintext
385 lines
8.5 KiB
Plaintext
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/* DECODE.C - Decode blocks of received data. */
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/* Copyright (c) 1995-2012 by Radford M. Neal.
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*
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* Permission is granted for anyone to copy, use, modify, and distribute
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* these programs and accompanying documents for any purpose, provided
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* this copyright notice is retained and prominently displayed, and note
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* is made of any changes made to these programs. These programs and
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* documents are distributed without any warranty, express or implied.
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* As the programs were written for research purposes only, they have not
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* been tested to the degree that would be advisable in any important
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* application. All use of these programs is entirely at the user's own
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* risk.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include "rand.h"
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#include "alloc.h"
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#include "blockio.h"
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#include "open.h"
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#include "mod2sparse.h"
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#include "mod2dense.h"
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#include "mod2convert.h"
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#include "channel.h"
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#include "rcode.h"
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#include "check.h"
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#include "dec.h"
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void usage(void);
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/* MAIN PROGRAM. */
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int main
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( int argc,
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char **argv
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)
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{
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char *pchk_file, *rfile, *dfile, *pfile;
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char **meth;
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FILE *rf, *df, *pf;
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char *dblk, *pchk;
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double *lratio;
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double *bitpr;
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double *awn_data; /* Places to store channel data */
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int *bsc_data;
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unsigned iters; /* Unsigned because can be huge for enum */
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double tot_iter; /* Double because can be huge for enum */
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double chngd, tot_changed; /* Double because can be fraction if lratio==1*/
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int tot_valid;
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char junk;
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int valid;
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int i, j, k;
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/* Look at initial flag arguments. */
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ldpc_table = 0;
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blockio_flush = 0;
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while (argc>1)
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{
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if (strcmp(argv[1],"-t")==0)
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{ if (ldpc_table!=0) usage();
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ldpc_table = 1;
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}
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else if (strcmp(argv[1],"-T")==0)
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{ if (ldpc_table!=0) usage();
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ldpc_table = 2;
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}
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else if (strcmp(argv[1],"-f")==0)
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{ if (blockio_flush!=0) usage();
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blockio_flush = 1;
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}
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else
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{ break;
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}
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argc -= 1;
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argv += 1;
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}
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/* Look at arguments up to the decoding method specification. */
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if (!(pchk_file = argv[1])
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|| !(rfile = argv[2])
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|| !(dfile = argv[3]))
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{ usage();
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}
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if (argv[4]==0 || argv[5]==0) usage();
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k = channel_parse(argv+4,argc-4);
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if (k<=0)
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{ pfile = argv[4];
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k = channel_parse(argv+5,argc-5);
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if (k<=0) usage();
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meth = argv+5+k;
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}
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else
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{ pfile = 0;
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meth = argv+4+k;
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}
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/* Look at the specification of the decoding method, which starts at meth and
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continues to the end of the command line (marked by a zero pointer). */
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if (!meth[0]) usage();
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if (strcmp(meth[0],"prprp")==0)
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{ dec_method = Prprp;
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if (!meth[1] || sscanf(meth[1],"%d%c",&max_iter,&junk)!=1 || meth[2])
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{ usage();
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}
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}
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else if (strcmp(meth[0],"enum-block")==0)
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{ dec_method = Enum_block;
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if (!(gen_file = meth[1]) || meth[2]) usage();
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}
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else if (strcmp(meth[0],"enum-bit")==0)
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{ dec_method = Enum_bit;
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if (!(gen_file = meth[1]) || meth[2]) usage();
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}
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else
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{ usage();
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}
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/* Check that we aren't overusing standard input or output. */
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if ((strcmp(pchk_file,"-")==0)
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+ (strcmp(rfile,"-")==0) > 1)
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{ fprintf(stderr,"Can't read more than one stream from standard input\n");
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exit(1);
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}
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if ((ldpc_table>0)
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+ (strcmp(dfile,"-")==0)
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+ (pfile!=0 && strcmp(pfile,"-")==0) > 1)
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{ fprintf(stderr,"Can't send more than one stream to standard output\n");
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exit(1);
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}
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/* Read parity check file. */
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read_pchk(pchk_file);
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if (N<=M)
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{ fprintf(stderr,
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"Number of bits (%d) should be greater than number of checks (%d)\n",N,M);
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exit(1);
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}
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/* Open file of received data. */
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rf = open_file_std(rfile,"r");
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if (rf==NULL)
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{ fprintf(stderr,"Can't open file of received data: %s\n",rfile);
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exit(1);
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}
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/* Create file for decoded data. */
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df = open_file_std(dfile,"w");
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if (df==NULL)
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{ fprintf(stderr,"Can't create file for decoded data: %s\n",dfile);
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exit(1);
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}
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/* Create file for bit probabilities, if specified. */
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if (pfile)
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{ pf = open_file_std(pfile,"w");
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if (pf==NULL)
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{ fprintf(stderr,"Can't create file for bit probabilities: %s\n",pfile);
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exit(1);
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}
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}
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/* Allocate space for data from channel. */
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switch (channel)
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{ case BSC:
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{ bsc_data = chk_alloc (N, sizeof *bsc_data);
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break;
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}
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case AWGN: case AWLN:
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{ awn_data = chk_alloc (N, sizeof *awn_data);
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break;
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}
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default:
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{ abort();
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}
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}
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/* Allocate other space. */
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dblk = chk_alloc (N, sizeof *dblk);
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lratio = chk_alloc (N, sizeof *lratio);
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pchk = chk_alloc (M, sizeof *pchk);
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bitpr = chk_alloc (N, sizeof *bitpr);
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/* Print header for summary table. */
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if (ldpc_table==1)
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{ printf(" block iterations valid changed\n");
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}
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/* Do the setup for the decoding method. */
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switch (dec_method)
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{ case Prprp:
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{ prprp_decode_setup();
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break;
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}
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case Enum_block: case Enum_bit:
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{ enum_decode_setup();
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break;
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}
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default: abort();
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}
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/* Read received blocks, decode, and write decoded blocks. */
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tot_iter = 0;
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tot_valid = 0;
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tot_changed = 0;
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for (block_no = 0; ; block_no++)
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{
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/* Read block from received file, exit if end-of-file encountered. */
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for (i = 0; i<N; i++)
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{ int c;
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switch (channel)
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{ case BSC:
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{ c = fscanf(rf,"%1d",&bsc_data[i]);
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break;
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}
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case AWGN: case AWLN:
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{ c = fscanf(rf,"%lf",&awn_data[i]);
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break;
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}
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default: abort();
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}
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if (c==EOF)
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{ if (i>0)
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{ fprintf(stderr,
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"Warning: Short block (%d long) at end of received file ignored\n",i);
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}
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goto done;
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}
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if (c<1 || channel==BSC && bsc_data[i]!=0 && bsc_data[i]!=1)
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{ fprintf(stderr,"File of received data is garbled\n");
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exit(1);
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}
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}
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/* Find likelihood ratio for each bit. */
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switch (channel)
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{ case BSC:
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{ for (i = 0; i<N; i++)
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{ lratio[i] = bsc_data[i]==1 ? (1-error_prob) / error_prob
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: error_prob / (1-error_prob);
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}
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break;
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}
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case AWGN:
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{ for (i = 0; i<N; i++)
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{ lratio[i] = exp(2*awn_data[i]/(std_dev*std_dev));
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}
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break;
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}
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case AWLN:
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{ for (i = 0; i<N; i++)
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{ double e, d1, d0;
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e = exp(-(awn_data[i]-1)/lwidth);
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d1 = 1 / ((1+e)*(1+1/e));
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e = exp(-(awn_data[i]+1)/lwidth);
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d0 = 1 / ((1+e)*(1+1/e));
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lratio[i] = d1/d0;
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}
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break;
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}
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default: abort();
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}
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/* Try to decode using the specified method. */
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switch (dec_method)
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{ case Prprp:
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{ iters = prprp_decode (H, lratio, dblk, pchk, bitpr);
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break;
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}
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case Enum_block: case Enum_bit:
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{ iters = enum_decode (lratio, dblk, bitpr, dec_method==Enum_block);
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break;
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}
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default: abort();
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}
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/* See if it worked, and how many bits were changed. */
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valid = check(H,dblk,pchk)==0;
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chngd = changed(lratio,dblk,N);
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tot_iter += iters;
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tot_valid += valid;
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tot_changed += chngd;
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/* Print summary table entry. */
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if (ldpc_table==1)
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{ printf ("%7d %10f %d %8.1f\n",
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block_no, (double)iters, valid, (double)chngd);
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/* iters is printed as a double to avoid problems if it's >= 2^31 */
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fflush(stdout);
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}
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/* Write decoded block. */
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blockio_write(df,dblk,N);
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/* Write bit probabilities, if asked to. */
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if (pfile)
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{ for (j = 0; j<N; j++)
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{ fprintf(pf," %.5f",bitpr[j]);
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}
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fprintf(pf,"\n");
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}
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/* Check for errors when writing. */
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if (ferror(df) || pfile && ferror(pf))
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{ break;
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}
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}
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/* Finish up. */
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done:
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fprintf(stderr,
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"Decoded %d blocks, %d valid. Average %.1f iterations, %.0f%% bit changes\n",
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block_no, tot_valid, (double)tot_iter/block_no,
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100.0*(double)tot_changed/(N*block_no));
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if (ferror(df) || fclose(df)!=0)
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{ fprintf(stderr,"Error writing decoded blocks to %s\n",dfile);
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exit(1);
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}
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if (pfile)
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{ if (ferror(pf) || fclose(pf)!=0)
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{ fprintf(stderr,"Error writing bit probabilities to %s\n",dfile);
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exit(1);
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}
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}
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exit(0);
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}
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/* PRINT USAGE MESSAGE AND EXIT. */
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void usage(void)
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{ fprintf(stderr,"Usage:\n");
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fprintf(stderr,
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" decode [ -f ] [ -t | -T ] pchk-file received-file decoded-file [ bp-file ] channel method\n");
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channel_usage();
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fprintf(stderr,
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"Method: enum-block gen-file | enum-bit gen-file | prprp [-]max-iterations\n");
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exit(1);
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}
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