4 files changed, 104 insertions, 17 deletions
diff --git a/gr-digital/include/gnuradio/digital/additive_scrambler_bb.h b/gr-digital/include/gnuradio/digital/additive_scrambler_bb.h
index 73fd395d67..e88ac5a48c 100644
--- a/gr-digital/include/gnuradio/digital/additive_scrambler_bb.h
+++ b/gr-digital/include/gnuradio/digital/additive_scrambler_bb.h
@@ -57,15 +57,17 @@ namespace gr {
        * \param mask   Polynomial mask for LFSR
        * \param seed   Initial shift register contents
        * \param len    Shift register length
-       * \param count  Number of bits after which shift register is reset, 0=never
-       *
+       * \param count  Number of bytes after which shift register is reset, 0=never
+       * \param bits_per_byte Number of bits per byte
+       * \param reset_tag When a tag with this key is detected, the shift register is reset (when this is set, count is ignored!)
        */
-      static sptr make(int mask, int seed, int len, int count=0);
+      static sptr make(int mask, int seed, int len, int count=0, int bits_per_byte=1, const std::string &reset_tag_key="");
 
       virtual int mask() const = 0;
       virtual int seed() const = 0;
       virtual int len() const = 0;
       virtual int count() const = 0;
+      virtual int bits_per_byte() = 0;
     };
 
   } /* namespace digital */
diff --git a/gr-digital/lib/additive_scrambler_bb_impl.cc b/gr-digital/lib/additive_scrambler_bb_impl.cc
index 8f2229e6b6..96e1fbbc25 100644
--- a/gr-digital/lib/additive_scrambler_bb_impl.cc
+++ b/gr-digital/lib/additive_scrambler_bb_impl.cc
@@ -31,23 +31,35 @@ namespace gr {
   namespace digital {
     
     additive_scrambler_bb::sptr
-    additive_scrambler_bb::make(int mask, int seed, int len, int count)
+    additive_scrambler_bb::make (int mask, int seed,
+				 int len, int count,
+				 int bits_per_byte,
+				 const std::string &reset_tag_key)
     {
       return gnuradio::get_initial_sptr(new additive_scrambler_bb_impl
-					(mask, seed, len, count));
+					(mask, seed, len, count, bits_per_byte, reset_tag_key));
     }
 
     additive_scrambler_bb_impl::additive_scrambler_bb_impl(int mask,
 							   int seed,
 							   int len,
-							   int count)
+							   int count,
+							   int bits_per_byte,
+							   const std::string &reset_tag_key)
       : sync_block("additive_scrambler_bb",
 		      io_signature::make(1, 1, sizeof(unsigned char)),
 		      io_signature::make(1, 1, sizeof(unsigned char))),
 	d_lfsr(mask, seed, len),
-	d_count(count),
-	d_bits(0), d_len(len), d_seed(seed)
+	d_count(reset_tag_key.empty() ? count : -1),
+	d_bytes(0), d_len(len), d_seed(seed),
+	d_bits_per_byte(bits_per_byte), d_reset_tag_key(pmt::string_to_symbol(reset_tag_key))
     {
+      if (d_count < -1) {
+      	throw std::invalid_argument("count must be non-negative!");
+      }
+      if (d_bits_per_byte < 1 || d_bits_per_byte > 8) {
+      	throw std::invalid_argument("bits_per_byte must be in [1, 8]");
+      }
     }
 
     additive_scrambler_bb_impl::~additive_scrambler_bb_impl()
@@ -78,6 +90,28 @@ namespace gr {
       return d_count;
     }
 
+    int additive_scrambler_bb_impl::_get_next_reset_index(int noutput_items, int last_reset_index /* = -1 */)
+    {
+      int reset_index = noutput_items; // This is a value that gets never reached in the for loop
+      if (d_count == -1) {
+	std::vector<gr::tag_t> tags;
+	get_tags_in_range(tags, 0, nitems_read(0), nitems_read(0)+noutput_items, d_reset_tag_key);
+	for (unsigned i = 0; i < tags.size(); i++) {
+	  int reset_pos = tags[i].offset - nitems_read(0);
+	  if (reset_pos < reset_index && reset_pos > last_reset_index) {
+	    reset_index = reset_pos;
+	  };
+	}
+      } else {
+	if (last_reset_index == -1) {
+	  reset_index = d_count - d_bytes;
+	} else {
+	  reset_index = last_reset_index + d_count;
+	}
+      }
+      return reset_index;
+    }
+
     int
     additive_scrambler_bb_impl::work(int noutput_items,
 				     gr_vector_const_void_star &input_items,
@@ -85,14 +119,19 @@ namespace gr {
     {
       const unsigned char *in = (const unsigned char *)input_items[0];
       unsigned char *out = (unsigned char *)output_items[0];
+      int reset_index = _get_next_reset_index(noutput_items);
 
       for(int i = 0; i < noutput_items; i++) {
-	out[i] = in[i]^d_lfsr.next_bit();
-	if(d_count > 0) {
-	  if(++d_bits == d_count) {
-	    d_lfsr.reset();
-	    d_bits = 0;
-	  }
+	unsigned char scramble_byte = 0x00;
+	for (int k = 0; k < d_bits_per_byte; k++) {
+	  scramble_byte ^= (d_lfsr.next_bit() << k);
+	}
+	out[i] = in[i] ^ scramble_byte;
+	d_bytes++;
+	if (i == reset_index) {
+	  d_lfsr.reset();
+	  d_bytes = 0;
+	  reset_index = _get_next_reset_index(noutput_items, reset_index);
 	}
       }
 
diff --git a/gr-digital/lib/additive_scrambler_bb_impl.h b/gr-digital/lib/additive_scrambler_bb_impl.h
index b621637e67..5f28203709 100644
--- a/gr-digital/lib/additive_scrambler_bb_impl.h
+++ b/gr-digital/lib/additive_scrambler_bb_impl.h
@@ -34,20 +34,27 @@ namespace gr {
     {
     private:
       digital::lfsr d_lfsr;
-      int      d_count;
-      int      d_bits;
+      int      d_count; //! Reset the LFSR after this many bytes (not bits)
+      int      d_bytes; //! Count the processed bytes
       int      d_len;
       int      d_seed;
+      int      d_bits_per_byte;
+      pmt::pmt_t d_reset_tag_key;
+
+      int _get_next_reset_index(int noutput_items, int last_reset_index=-1);
 
     public:
       additive_scrambler_bb_impl(int mask, int seed,
-				 int len, int count=0);
+				 int len, int count=0,
+				 int bits_per_byte=1, const std::string &reset_tag_key="");
       ~additive_scrambler_bb_impl();
 
       int mask() const;
       int seed() const;
       int len() const;
       int count() const;
+      int bits_per_byte() { return d_bits_per_byte; };
+
       
       int work(int noutput_items,
 	       gr_vector_const_void_star &input_items,
diff --git a/gr-digital/python/digital/qa_scrambler.py b/gr-digital/python/digital/qa_scrambler.py
index 05daebd389..e19e963cd3 100755
--- a/gr-digital/python/digital/qa_scrambler.py
+++ b/gr-digital/python/digital/qa_scrambler.py
@@ -21,6 +21,7 @@
 #
 
 from gnuradio import gr, gr_unittest, digital, blocks
+import pmt
 
 class test_scrambler(gr_unittest.TestCase):
 
@@ -60,5 +61,43 @@ class test_scrambler(gr_unittest.TestCase):
         self.tb.run()
         self.assertEqual(src_data, dst.data())
 
+    def test_additive_scrambler_reset_3bpb(self):
+        src_data = (5,)*2000
+        src = blocks.vector_source_b(src_data, False)
+        scrambler = digital.additive_scrambler_bb(0x8a, 0x7f, 7, 100, 3)
+        descrambler = digital.additive_scrambler_bb(0x8a, 0x7f, 7, 100, 3)
+        dst = blocks.vector_sink_b()
+        dst2 = blocks.vector_sink_b()
+        self.tb.connect(src, scrambler, descrambler, dst)
+        self.tb.connect(scrambler, dst2)
+        self.tb.run()
+        if not (src_data == dst.data()):
+            self.fail('Not equal.')
+        self.assertEqual(src_data, src_data)
+
+    def test_additive_scrambler_tags(self):
+        print 'tags'
+        src_data = (1,)*1000
+        src = blocks.vector_source_b(src_data, False)
+        scrambler = digital.additive_scrambler_bb(0x8a, 0x7f, 7, 100)
+        descrambler = digital.additive_scrambler_bb(0x8a, 0x7f, 7, 100)
+        reset_tag_key = 'reset_lfsr'
+        reset_tag1 = gr.tag_t()
+        reset_tag1.key = pmt.string_to_symbol(reset_tag_key)
+        reset_tag1.offset = 17
+        reset_tag2 = gr.tag_t()
+        reset_tag2.key = pmt.string_to_symbol(reset_tag_key)
+        reset_tag2.offset = 110
+        reset_tag3 = gr.tag_t()
+        reset_tag3.key = pmt.string_to_symbol(reset_tag_key)
+        reset_tag3.offset = 523
+        src = blocks.vector_source_b(src_data, False, 1, (reset_tag1, reset_tag2, reset_tag3))
+        scrambler = digital.additive_scrambler_bb(0x8a, 0x7f, 7, 100, 1, reset_tag_key)
+        descrambler = digital.additive_scrambler_bb(0x8a, 0x7f, 7, 100, 1, reset_tag_key)
+        dst = blocks.vector_sink_b()
+        self.tb.connect(src, scrambler, descrambler, dst)
+        self.tb.run()
+        self.assertEqual(src_data, dst.data())
+
 if __name__ == '__main__':
     gr_unittest.run(test_scrambler, "test_scrambler.xml")