Initial Commit

2018-02-08 21:28:33 -05:00
commit 678c1d3966
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+/* CHANNEL.C - Procedures and variables regarding channels. */
+
+/* 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"
+
+
+/* GLOBAL VARIABLES.  Declared in channel.h. */
+
+channel_type channel;	/* Type of channel */
+
+double error_prob;	/* Error probability for BSC */
+double std_dev;		/* Noise standard deviation for AWGN */
+double lwidth;		/* Width of noise distribution for AWLN */
+
+
+/* PARSE A COMMAND-LINE SPECIFICATION OF A CHANNEL.  Takes a pointer to an
+   argument list and an argument count; returns the number of arguments that 
+   make up a channel specification at this point in the command line.  Returns
+   zero if the argument list does not start with a channel specification.
+   Returns -1 if there seems to be a channel specification here, but it's 
+   invalid.
+
+   Sets the variables declared in channel.h to the type and parameters of
+   the channel.
+ */
+
+int channel_parse
+( char **argv,		/* Pointer to argument list */
+  int argc		/* Number of arguments in list */
+)
+{ 
+  char junk;
+
+  if (argc==0) return 0;
+
+  if (strcmp(argv[0],"bsc")==0  || strcmp(argv[0],"BSC")==0)
+  { 
+    channel = BSC;
+    if (argc<2 || sscanf(argv[1],"%lf%c",&error_prob,&junk)!=1 
+     || error_prob<=0 || error_prob>=1)
+    { return -1;
+    }
+    else
+    { return 2;
+    }
+  }
+  else if (strcmp(argv[0],"awgn")==0 || strcmp(argv[0],"AWGN")==0)
+  { 
+    channel = AWGN;
+    if (argc<2 || sscanf(argv[1],"%lf%c",&std_dev,&junk)!=1 
+     || std_dev<=0)
+    { return -1;
+    }
+    else
+    { return 2;
+    }
+  }
+  else if (strcmp(argv[0],"awln")==0 || strcmp(argv[0],"AWLN")==0)
+  {
+    channel = AWLN;
+    if (argc<2 || sscanf(argv[1],"%lf%c",&lwidth,&junk)!=1 
+     || lwidth<=0)
+    { return -1;
+    }
+    else
+    { return 2;
+    }
+  }
+  else
+  { 
+    return 0;
+  }
+}
+
+
+/* PRINT USAGE MESSAGE REGARDING CHANNEL SPECIFICATIONS. */
+
+void channel_usage(void)
+{
+  fprintf(stderr,
+    "Channel: bsc error-probability | awgn standard-deviation | awln width\n");
+}