Initial Commit

lib/ldpc/transmit.c

@@ -0,0 +1,170 @@
+/* TRANSMIT.C - Simulate transmission of bits through a channel. */
+
+/* Copyright (c) 1995-2012 by Radford M. Neal.
+ *
+ * Permission is granted for anyone to copy, use, modify, and distribute
+ * these programs and accompanying documents for any purpose, provided
+ * this copyright notice is retained and prominently displayed, and note
+ * is made of any changes made to these programs.  These programs and
+ * documents are distributed without any warranty, express or implied.
+ * As the programs were written for research purposes only, they have not
+ * been tested to the degree that would be advisable in any important
+ * application.  All use of these programs is entirely at the user's own
+ * risk.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+#include "channel.h"
+#include "open.h"
+#include "rand.h"
+
+void usage(void);
+
+
+/* MAIN PROGRAM. */
+
+int main
+( int argc,
+  char **argv
+)
+{
+  char *tfile, *rfile;
+  FILE *tf, *rf;
+  int block_size, n_bits;
+  char junk;
+  int seed;
+  int cnt;
+  int n, b;
+
+  /* Look at arguments.  The arguments specifying the channel are looked
+     at by channel_parse in channel.c */
+
+  if (!(tfile = argv[1])
+   || !(rfile = argv[2])
+   || !argv[3] || sscanf(argv[3],"%d%c",&seed,&junk)!=1)
+  { usage();
+  }
+
+  n = channel_parse(argv+4,argc-4);
+  if (n<=0 || argc-4-n!=0) 
+  { usage();
+  }
+
+  /* See if the source is all zeros or a file. */
+
+  if (sscanf(tfile,"%d%c",&n_bits,&junk)==1 && n_bits>0)
+  { block_size = 1;
+    tf = NULL;
+  }
+  else if (sscanf(tfile,"%dx%d%c",&block_size,&n_bits,&junk)==2 
+            && block_size>0 && n_bits>0)
+  { n_bits *= block_size;
+    tf = NULL;
+  }
+  else
+  { tf = open_file_std(tfile,"r");
+    if (tf==NULL)
+    { fprintf(stderr,"Can't open encoded file to transmit: %s\n",tfile);
+      exit(1);
+    }
+  }
+
+  /* Open output file. */
+
+  rf = open_file_std(rfile,"w");
+  if (rf==NULL)
+  { fprintf(stderr,"Can't create file for received data: %s\n",rfile);
+    exit(1);
+  }
+
+  /* Set random seed to avoid duplications with other programs. */
+
+  rand_seed(10*seed+3);
+
+  /* Transmit bits. */
+
+  for (cnt = 0; ; cnt++)
+  { 
+    /* Get next bit to transmit. */
+
+    if (tf) /* Data comes from a file */
+    { 
+      for (;;)
+      { b = getc(tf);
+        if (b!=' ' && b!='\t' && b!='\n' && b!='\r')
+        { break;
+        }
+        putc(b,rf);
+      }
+
+      if (b==EOF) break;
+
+      if (b!='0' && b!='1')
+      { fprintf(stderr,"Bad character (code %d) file being transmitted\n",b);
+        exit(1);
+      }
+    }
+
+    else /* Data is all zeros */
+    { 
+      if (cnt>0 && cnt%block_size==0) 
+      { putc('\n',rf);
+      }
+
+      if (cnt==n_bits) break;
+
+      b = '0';
+    }
+
+    b = b=='1';
+
+    /* Produce the channel output for this transmitted bit. */
+    
+    switch (channel)
+    { case BSC:
+      { int bsc_noise;
+        bsc_noise = rand_uniform() < error_prob;
+        fprintf (rf, "%d", b^bsc_noise);
+        break;
+      }
+      case AWGN:
+      { double awgn_noise;
+        awgn_noise = std_dev * rand_gaussian();
+        fprintf (rf, " %+5.2f", b ? 1+awgn_noise : -1+awgn_noise);
+        break;
+      }
+      case AWLN:
+      { double awln_noise;
+        awln_noise = lwidth * rand_logistic();
+        fprintf (rf, " %+5.2f", b ? 1+awln_noise : -1+awln_noise);
+        break;
+      }
+      default:
+      { abort();
+      }
+    }
+  }
+
+  fprintf(stderr,"Transmitted %d bits\n",cnt);
+
+  if (ferror(rf) || fclose(rf)!=0)
+  { fprintf(stderr,"Error writing received bits to %s\n",rfile);
+    exit(1);
+  }
+
+  return 0;
+}
+
+
+/* PRINT USAGE MESSAGE AND EXIT. */
+
+void usage(void)
+{ fprintf(stderr,
+    "Usage:   transmit encoded-file|n-zeros received-file seed channel\n");
+  channel_usage();
+  exit(1);
+}