1 files changed, 117 insertions, 0 deletions
diff --git a/gr-dtv/lib/atsc_randomize.cc b/gr-dtv/lib/atsc_randomize.cc
new file mode 100644
index 0000000000..769b08587a
--- /dev/null
+++ b/gr-dtv/lib/atsc_randomize.cc
@@ -0,0 +1,117 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2014 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 "atsc_randomize.h"
+
+namespace gr {
+  namespace dtv {
+
+    unsigned char atsc_randomize::s_output_map[1 << 14];
+    bool atsc_randomize::s_output_map_initialized_p = false;
+
+    atsc_randomize::atsc_randomize ()
+    {
+      d_state = PRELOAD_VALUE;
+
+      if (!s_output_map_initialized_p)
+        initialize_output_map ();
+    }
+
+    /*!
+     * \brief Generate the table used in the fast_output_map function.
+     *
+     * The table has 16K byte entries, but because of how is is used, only
+     * 256 entries end up being resident in the cache.  This seems
+     * like a good use of memory.  We can get away with a 16K table
+     * because the low two bits of the state do not affect the output
+     * function.  By shifting right those two bits we shrink the table,
+     * and also get better cache line utilization.
+     */
+    void
+    atsc_randomize::initialize_output_map ()
+    {
+      s_output_map_initialized_p = true;
+
+      for (int i = 0; i < (1 << 14); i++)
+        s_output_map[i] = slow_output_map (i << 2);
+    }
+
+
+    void
+    atsc_randomize::reset ()
+    {
+      d_state = PRELOAD_VALUE;
+    }
+
+    void
+    atsc_randomize::randomize (atsc_mpeg_packet_no_sync &out, const atsc_mpeg_packet &in)
+    {
+      assert (in.data[0] == MPEG_SYNC_BYTE);	// confirm it's there, then drop
+
+      for (int i = 0; i < ATSC_MPEG_DATA_LENGTH; i++)
+        out.data[i] = in.data[i + 1] ^ output_and_clk ();
+    }
+
+    void
+    atsc_randomize::derandomize (atsc_mpeg_packet &out, const atsc_mpeg_packet_no_sync &in)
+    {
+      out.data[0] = MPEG_SYNC_BYTE;		// add sync byte to beginning of packet
+
+      for (int i = 0; i < ATSC_MPEG_DATA_LENGTH; i++)
+        out.data[i + 1] = in.data[i] ^ output_and_clk ();
+    }
+
+
+    unsigned char
+    atsc_randomize::slow_output_map (int st)
+    {
+      int	output = 0;
+
+      if (st & 0x8000)
+        output |= 0x01;
+
+      if (st & 0x2000)
+        output |= 0x02;
+
+      if (st & 0x1000)
+        output |= 0x04;
+
+      if (st & 0x0200)
+        output |= 0x08;
+
+      if (st & 0x0020)
+        output |= 0x10;
+
+      if (st & 0x0010)
+        output |= 0x20;
+
+      if (st & 0x0008)
+        output |= 0x40;
+
+      if (st & 0x0004)
+        output |= 0x80;
+
+      return output;
+    }
+
+  } /* namespace dtv */
+} /* namespace gr */