1 files changed, 109 insertions, 0 deletions
diff --git a/gr-blocks/lib/keep_one_in_n_impl.cc b/gr-blocks/lib/keep_one_in_n_impl.cc
new file mode 100644
index 000000000..7ab6dc14d
--- /dev/null
+++ b/gr-blocks/lib/keep_one_in_n_impl.cc
@@ -0,0 +1,109 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2012 Free Software Foundation, Inc.
+ *
+ * This file is part of GNU Radio
+ *
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ *
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "keep_one_in_n_impl.h"
+#include <gr_io_signature.h>
+
+namespace gr {
+  namespace blocks {
+
+    keep_one_in_n::sptr keep_one_in_n::make(size_t itemsize, int n)
+    {
+      return gnuradio::get_initial_sptr(new keep_one_in_n_impl(itemsize, n));
+    }
+
+    keep_one_in_n_impl::keep_one_in_n_impl(size_t itemsize, int n)
+      : gr_block("keep_one_in_n",
+		 gr_make_io_signature (1, 1, itemsize),
+		 gr_make_io_signature (1, 1, itemsize)),
+	d_count(n)
+    {
+      // To avoid bad behavior with using set_relative_rate in this block with
+      // VERY large values of n, we will keep track of things ourselves. Using
+      // this to turn off automatic tag propagation, which will be handled
+      // locally in general_work().
+      set_tag_propagation_policy(TPP_DONT);
+
+      set_n(n);
+    }
+
+    void
+    keep_one_in_n_impl::set_n(int n)
+    {
+      if (n < 1)
+	n = 1;
+      
+      d_n = n;
+      d_count = n;
+
+      // keep our internal understanding of the relative rate of this block
+      // don't set the relative rate, though, and we will handle our own
+      // tag propagation.
+      d_decim_rate = 1.0/(float)d_n;
+    }
+
+    int
+    keep_one_in_n_impl::general_work(int noutput_items,
+				     gr_vector_int &ninput_items,
+				     gr_vector_const_void_star &input_items,
+				     gr_vector_void_star &output_items)
+    {
+      const char *in = (const char *) input_items[0];
+      char *out = (char *) output_items[0];
+      
+      size_t item_size = input_signature ()->sizeof_stream_item (0);
+      int	    ni = 0;
+      int	    no = 0;
+
+      while (ni < ninput_items[0] && no < noutput_items){
+	d_count--;
+	if (d_count <= 0){
+	  memcpy (out, in, item_size);		// copy 1 item
+	  out += item_size;
+	  no++;
+	  d_count = d_n;
+	}
+	in += item_size;
+	ni++;
+      }
+
+      // Because we have set TPP_DONT, we have to propagate the tags here manually.
+      // Adjustment of the tag sample value is done using the float d_decim_rate.
+      std::vector<gr_tag_t> tags;
+      std::vector<gr_tag_t>::iterator t;
+      get_tags_in_range(tags, 0, nitems_read(0), nitems_read(0)+ni);
+      for(t = tags.begin(); t != tags.end(); t++) {
+	gr_tag_t new_tag = *t;
+	new_tag.offset *= d_decim_rate;
+	add_item_tag(0, new_tag);
+      }
+
+      consume_each (ni);
+      return no;
+    }
+
+  } /* namespace blocks */
+} /* namespace gr */