README change

1 files changed, 78 insertions, 0 deletions

diff --git a/gr-blocks/lib/count_bits.cc b/gr-blocks/lib/count_bits.cc
new file mode 100644
index 000000000..167396b57
--- /dev/null
+++ b/gr-blocks/lib/count_bits.cc
@@ -0,0 +1,78 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2003,2013 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.
+ */
+
+#include <blocks/count_bits.h>
+
+/*
+ * these are slow and obvious.  If you need something faster, fix these
+ *
+ * Can probably replace with VOLK's popcount
+ */
+
+namespace gr {
+  namespace blocks {
+
+    unsigned int
+    count_bits8(unsigned int x)
+    {
+      int count = 0;
+
+      for(int i = 0; i < 8; i++) {
+        if(x & (1 << i))
+          count++;
+      }
+
+      return count;
+    }
+
+    unsigned int
+    count_bits16(unsigned int x)
+    {
+      int count = 0;
+
+      for(int i = 0; i < 16; i++) {
+        if(x & (1 << i))
+          count++;
+      }
+
+      return count;
+    }
+
+    unsigned int
+    count_bits32(unsigned int x)
+    {
+      unsigned res = (x & 0x55555555) + ((x >> 1) & 0x55555555);
+      res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
+      res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F);
+      res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF);
+      return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF);
+    }
+
+    unsigned int
+    count_bits64(unsigned long long x)
+    {
+      return count_bits32((x >> 32) & 0xffffffff) + \
+        count_bits32(x & 0xffffffff);
+    }
+
+  } /* namespace blocks */
+} /* namespace gr */