171 lines
3.6 KiB
C
Executable File
171 lines
3.6 KiB
C
Executable File
/* TRANSMIT.C - Simulate transmission of bits through a channel. */
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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 "channel.h"
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#include "open.h"
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#include "rand.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 *tfile, *rfile;
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FILE *tf, *rf;
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int block_size, n_bits;
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char junk;
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int seed;
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int cnt;
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int n, b;
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/* Look at arguments. The arguments specifying the channel are looked
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at by channel_parse in channel.c */
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if (!(tfile = argv[1])
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|| !(rfile = argv[2])
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|| !argv[3] || sscanf(argv[3],"%d%c",&seed,&junk)!=1)
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{ usage();
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}
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n = channel_parse(argv+4,argc-4);
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if (n<=0 || argc-4-n!=0)
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{ usage();
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}
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/* See if the source is all zeros or a file. */
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if (sscanf(tfile,"%d%c",&n_bits,&junk)==1 && n_bits>0)
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{ block_size = 1;
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tf = NULL;
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}
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else if (sscanf(tfile,"%dx%d%c",&block_size,&n_bits,&junk)==2
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&& block_size>0 && n_bits>0)
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{ n_bits *= block_size;
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tf = NULL;
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}
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else
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{ tf = open_file_std(tfile,"r");
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if (tf==NULL)
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{ fprintf(stderr,"Can't open encoded file to transmit: %s\n",tfile);
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exit(1);
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}
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}
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/* Open output file. */
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rf = open_file_std(rfile,"w");
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if (rf==NULL)
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{ fprintf(stderr,"Can't create file for received data: %s\n",rfile);
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exit(1);
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}
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/* Set random seed to avoid duplications with other programs. */
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rand_seed(10*seed+3);
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/* Transmit bits. */
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for (cnt = 0; ; cnt++)
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{
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/* Get next bit to transmit. */
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if (tf) /* Data comes from a file */
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{
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for (;;)
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{ b = getc(tf);
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if (b!=' ' && b!='\t' && b!='\n' && b!='\r')
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{ break;
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}
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putc(b,rf);
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}
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if (b==EOF) break;
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if (b!='0' && b!='1')
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{ fprintf(stderr,"Bad character (code %d) file being transmitted\n",b);
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exit(1);
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}
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}
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else /* Data is all zeros */
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{
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if (cnt>0 && cnt%block_size==0)
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{ putc('\n',rf);
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}
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if (cnt==n_bits) break;
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b = '0';
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}
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b = b=='1';
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/* Produce the channel output for this transmitted bit. */
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switch (channel)
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{ case BSC:
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{ int bsc_noise;
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bsc_noise = rand_uniform() < error_prob;
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fprintf (rf, "%d", b^bsc_noise);
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break;
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}
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case AWGN:
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{ double awgn_noise;
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awgn_noise = std_dev * rand_gaussian();
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fprintf (rf, " %+5.2f", b ? 1+awgn_noise : -1+awgn_noise);
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break;
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}
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case AWLN:
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{ double awln_noise;
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awln_noise = lwidth * rand_logistic();
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fprintf (rf, " %+5.2f", b ? 1+awln_noise : -1+awln_noise);
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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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}
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fprintf(stderr,"Transmitted %d bits\n",cnt);
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if (ferror(rf) || fclose(rf)!=0)
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{ fprintf(stderr,"Error writing received bits to %s\n",rfile);
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exit(1);
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}
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return 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,
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"Usage: transmit encoded-file|n-zeros received-file seed channel\n");
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channel_usage();
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exit(1);
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}
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