leansdrcat: Add --block, --nonblock, --cbrN

src/apps/leansdrcat.cc

@@ -9,19 +9,43 @@
 void fatal(const char *s) { perror(s); exit(1); }
 
 void usage(const char *name, FILE *f, int c) {
-  fprintf(f, "Usage: %s [--cbr bits_per_sec]\n", name);
-  fprintf(f, "Forward from stdin to stdout at constant rate.\n");
+  fprintf(f, "Usage: %s [options]\n", name);
+  fprintf(f,
+	  "Forward from stdin to stdout at constant rate.\n"
+	  "\nOptions:\n"
+	  "  --block      Pause when stdout is busy (default: '#' on stderr)\n"
+	  "  --nonblock   Silently ignore when stdout is busy\n"
+	  "  --cbr R      Set rate in bits per second\n"
+	  "  --cbr8 R     Set rate in bytes per second\n"
+	  "  --cbr16 R    Set rate in 16-bit words per second\n"
+	  "  --cbr32 R    Set rate in 32-bit words per second\n"
+	  "  --cbr64 R    Set rate in 64-bit words per second\n"
+	  "  -h           Display this help message and exit\n"
+	  );
   exit(c);
 }
 
 int main(int argc, const char *argv[]) {
+  bool block=false, nonblock=false;
   int bytespersec = 2400000 * 2;
 
   for ( int i=1; i<argc; ++i ) {
     if      ( ! strcmp(argv[i], "-h") )
       usage(argv[0], stdout, 0);
+    else if ( ! strcmp(argv[i], "--block") )
+      block = true;
+    else if ( ! strcmp(argv[i], "--nonblock") )
+      nonblock = true;
     else if ( ! strcmp(argv[i], "--cbr") && i+1<argc )
       bytespersec = atoll(argv[++i]) / 8;
+    else if ( ! strcmp(argv[i], "--cbr8") && i+1<argc )
+      bytespersec = atoll(argv[++i]);
+    else if ( ! strcmp(argv[i], "--cbr16") && i+1<argc )
+      bytespersec = atoll(argv[++i]) * 2;
+    else if ( ! strcmp(argv[i], "--cbr32") && i+1<argc )
+      bytespersec = atoll(argv[++i]) * 4;
+    else if ( ! strcmp(argv[i], "--cbr64") && i+1<argc )
+      bytespersec = atoll(argv[++i]) * 8;
     else
       usage(argv[0], stderr, 1);
   }
@@ -31,9 +55,11 @@ int main(int argc, const char *argv[]) {
   if ( bytespersec < blocksize )
     blocksize = bytespersec;
 
-  long flags = fcntl(1, F_GETFL);
-  flags |= O_NONBLOCK;
-  if ( fcntl(1, F_SETFL, flags) ) fatal("fcntl(F_SETFL)");
+  if ( ! block ) {
+    long flags = fcntl(1, F_GETFL);
+    flags |= O_NONBLOCK;
+    if ( fcntl(1, F_SETFL, flags) ) fatal("fcntl(F_SETFL)");
+  }
 
   struct timeval tv0;
   if ( gettimeofday(&tv0, NULL) ) fatal("gettimeofday");
@@ -59,12 +85,22 @@ int main(int argc, const char *argv[]) {
       if ( nr < 0 ) fatal("read");
       if ( ! nr ) return 0;
       current += nr;
-      ssize_t nw = write(1, buf, nr);
-      if ( nw < 0 ) {
-	if ( errno == EWOULDBLOCK ) fprintf(stderr, "#");
-	else fatal("write");
-      } else if ( ! nw ) fatal("write: EOF");
-      else if ( nw < nr ) fprintf(stderr, "#");
+      for ( unsigned char *p=buf; nr; ) {
+	ssize_t nw = write(1, p, nr);
+	if ( nw < 0 ) {
+	  if ( errno == EWOULDBLOCK ) {
+	    if ( ! nonblock ) fprintf(stderr, "#");
+	    nr = 0;
+	  } else
+	    fatal("write");
+	} else if ( ! nw ) fatal("write: EOF");
+	else {
+	  // Try again.  If stdout is really busy we will get
+	  // EWOULDBLOCK eventually, unless --block was set.
+	  p += nw;
+	  nr -= nw;
+	}
+      }
     }
   }