Block Modifications:

 digital.mpsk_receiver_cc: Set reasonable default parameter values for GRC definition
 digital.ofdm_insert_preamble: Expose enter_preamble() as public, to allow external state changes
                               Cleanup of incorrect forecast behavior
                               Make the flag port optional, incase external preamble triggers are preferred to in-band
 gr_vector_source: added set_data( data ) and rewind() public methods
 gr_head: added set_length(int) method to modify head length

New Blocks Added:
 gr_keep_m_in_n: Allows periodic extraction of M items instead of 1 (in keep_1_in_n)
 gr_pack_k_bits: Complementary block fo gr_unpack_k_bits
 gr_vector_insert_x: Complement to the gr_head block, inserts a vector into a stream then becomes a pass through

gnuradio-core/src/lib/general/CMakeLists.txt

@@ -228,6 +228,7 @@ set(gr_core_general_triple_threats
     gr_interleaved_short_to_complex
     gr_iqcomp_cc
     gr_keep_one_in_n
+    gr_keep_m_in_n
     gr_kludge_copy
     gr_lfsr_32k_source_s
     gr_map_bb
@@ -285,6 +286,7 @@ set(gr_core_general_triple_threats
     gr_vector_to_stream
     gr_vector_to_streams
     gr_unpack_k_bits_bb
+    gr_pack_k_bits_bb
     gr_descrambler_bb
     gr_scrambler_bb
     gr_probe_density_b

gnuradio-core/src/lib/general/general.i

@@ -37,6 +37,7 @@
 #include <gr_stream_to_vector.h>
 #include <gr_vector_to_stream.h>
 #include <gr_keep_one_in_n.h>
+#include <gr_keep_m_in_n.h>
 #include <gr_fft_vcc.h>
 #include <gr_fft_vfc.h>
 #include <gr_float_to_int.h>
@@ -100,6 +101,7 @@
 #include <gr_test_types.h>
 #include <gr_test.h>
 #include <gr_unpack_k_bits_bb.h>
+#include <gr_pack_k_bits_bb.h>
 #include <gr_diff_phasor_cc.h>
 #include <gr_diff_encoder_bb.h>
 #include <gr_diff_decoder_bb.h>
@@ -155,6 +157,7 @@
 %include "gr_stream_to_vector.i"
 %include "gr_vector_to_stream.i"
 %include "gr_keep_one_in_n.i"
+%include "gr_keep_m_in_n.i"
 %include "gr_fft_vcc.i"
 %include "gr_fft_vfc.i"
 %include "gr_float_to_int.i"
@@ -218,6 +221,7 @@
 %include "gr_test_types.h"
 %include "gr_test.i"
 %include "gr_unpack_k_bits_bb.i"
+%include "gr_pack_k_bits_bb.i"
 %include "gr_diff_phasor_cc.i"
 %include "gr_diff_encoder_bb.i"
 %include "gr_diff_decoder_bb.i"

gnuradio-core/src/lib/general/gr_head.h

@@ -51,6 +51,7 @@ class GR_CORE_API gr_head : public gr_sync_block
 		 gr_vector_void_star &output_items);
 
   void reset() { d_ncopied_items = 0; }
+  void set_length(int nitems) { d_nitems = nitems; }
 };
 
 GR_CORE_API gr_head_sptr

gnuradio-core/src/lib/general/gr_head.i

@@ -28,5 +28,6 @@ class gr_head : public gr_block {
   gr_head();
 public:
   void reset();
+  void set_length(int nitems);
 };
 

gnuradio-core/src/lib/general/gr_keep_m_in_n.cc

@@ -0,0 +1,85 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2004,2010 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 <gr_keep_m_in_n.h>
+#include <gr_io_signature.h>
+#include <string.h>
+#include <stdio.h>
+
+gr_keep_m_in_n_sptr
+gr_make_keep_m_in_n (size_t item_size, int m, int n, int offset)
+{
+  return gnuradio::get_initial_sptr(new gr_keep_m_in_n (item_size, m, n, offset));
+}
+
+
+/*
+*
+* offset = 0, starts with 0th item
+* offset = 1, starts with 1st item, etc...
+* 
+* we take m items out of each n
+*/
+gr_keep_m_in_n::gr_keep_m_in_n (size_t item_size, int m, int n, int offset)
+  : gr_sync_block ("keep_m_in_n",
+	      gr_make_io_signature (1, 1, n*item_size),
+	      gr_make_io_signature (1, 1, m*item_size)),
+    d_n(n),
+    d_m(m),
+    d_offset( offset )
+{
+    // sanity checking
+    assert(d_m > 0);
+    assert(d_n > 0);
+    assert(d_m <= d_n);
+    assert(d_offset <= (d_n-d_m));
+}
+
+
+void gr_keep_m_in_n::set_offset(int offset){
+    d_offset = offset;
+}
+
+
+int
+gr_keep_m_in_n::work (int noutput_items,
+				gr_vector_const_void_star &input_items,
+				gr_vector_void_star &output_items)
+{
+  uint8_t* out = (uint8_t*) output_items[0];
+  const uint8_t* in = (const uint8_t*) input_items[0];
+
+  int in_item( input_signature()->sizeof_stream_item(0) );
+  int out_item( output_signature()->sizeof_stream_item(0) );
+  int single_size = in_item/d_n;
+
+  // iterate over data blocks of size {n, input : m, output}
+  for(int i=0; i<noutput_items; i++){
+    memcpy( &out[out_item*i], &in[in_item*i + single_size*d_offset], out_item);
+    } 
+
+  return noutput_items;
+}

gnuradio-core/src/lib/general/gr_keep_m_in_n.h

@@ -0,0 +1,62 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2004 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.
+ */
+
+#ifndef INCLUDED_GR_KEEP_M_IN_N_H
+#define INCLUDED_GR_KEEP_M_IN_N_H
+
+#include <gr_core_api.h>
+#include <gr_sync_block.h>
+
+class gr_keep_m_in_n;
+typedef boost::shared_ptr<gr_keep_m_in_n> gr_keep_m_in_n_sptr;
+
+GR_CORE_API gr_keep_m_in_n_sptr 
+gr_make_keep_m_in_n (size_t item_size, int m, int n, int offset);
+
+
+/*!
+ * \brief decimate a stream, keeping one item out of every n.
+ * \ingroup slicedice_blk
+ */
+class GR_CORE_API gr_keep_m_in_n : public gr_sync_block
+{
+  friend GR_CORE_API gr_keep_m_in_n_sptr
+  gr_make_keep_m_in_n (size_t item_size, int m, int n, int offset);
+
+  int	d_n;
+  int	d_m;
+  int	d_count;
+  int   d_offset;
+
+ protected:
+  gr_keep_m_in_n (size_t item_size, int m, int n, int offset);
+
+ public:
+  int work (int noutput_items,
+		    gr_vector_const_void_star &input_items,
+		    gr_vector_void_star &output_items);
+
+    void set_offset(int offset);
+
+};
+
+#endif /* INCLUDED_GR_KEEP_M_IN_N_H */

gnuradio-core/src/lib/general/gr_keep_m_in_n.i

@@ -0,0 +1,35 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2004 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.
+ */
+
+GR_SWIG_BLOCK_MAGIC(gr,keep_m_in_n)
+
+gr_keep_m_in_n_sptr 
+gr_make_keep_m_in_n (size_t itemsize, int m, int n, int offset);
+
+class gr_keep_m_in_n : public gr_sync_block
+{
+ protected:
+  gr_keep_m_in_n (size_t itemsize, int m, int n, int offset);
+ public:
+    void set_offset(int offset);
+
+};

gnuradio-core/src/lib/general/gr_pack_k_bits_bb.cc

@@ -0,0 +1,69 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2005,2010 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.
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gr_pack_k_bits_bb.h>
+#include <gr_io_signature.h>
+#include <stdexcept>
+#include <iostream>
+
+gr_pack_k_bits_bb_sptr gr_make_pack_k_bits_bb (unsigned k)
+{
+  return gnuradio::get_initial_sptr(new gr_pack_k_bits_bb (k));
+}
+
+
+gr_pack_k_bits_bb::gr_pack_k_bits_bb (unsigned k)
+  : gr_sync_decimator ("pack_k_bits_bb",
+			  gr_make_io_signature (1, 1, sizeof (unsigned char)),
+			  gr_make_io_signature (1, 1, sizeof (unsigned char)),
+			  k),
+    d_k (k)
+{
+  if (d_k == 0)
+    throw std::out_of_range ("interpolation must be > 0");
+}
+
+gr_pack_k_bits_bb::~gr_pack_k_bits_bb ()
+{
+}
+
+int
+gr_pack_k_bits_bb::work (int noutput_items,
+			   gr_vector_const_void_star &input_items,
+			   gr_vector_void_star &output_items)
+{
+  const unsigned char *in = (const unsigned char *) input_items[0];
+  unsigned char *out = (unsigned char *) output_items[0];
+
+  for (int i = 0; i < noutput_items; i++){
+    out[i] = 0x00;
+    for (unsigned int j = 0; j < d_k; j++){
+        out[i] |=  (0x01 & in[i*d_k+j])<<j;
+    }
+  }
+
+  return noutput_items;
+}

gnuradio-core/src/lib/general/gr_pack_k_bits_bb.h

@@ -0,0 +1,56 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2006 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.
+ */
+
+#ifndef INCLUDED_GR_PACK_K_BITS_BB_H
+#define	INCLUDED_GR_PACK_K_BITS_BB_H
+
+#include <gr_core_api.h>
+#include <gr_sync_decimator.h>
+
+class gr_pack_k_bits_bb;
+typedef boost::shared_ptr<gr_pack_k_bits_bb> gr_pack_k_bits_bb_sptr;
+GR_CORE_API gr_pack_k_bits_bb_sptr gr_make_pack_k_bits_bb (unsigned k);
+
+class gr_pack_k_bits_bb;
+
+/*!
+ * \brief Converts a byte with k relevent bits to k output bytes with 1 bit in the LSB.
+ * \ingroup converter_blk
+ */
+class GR_CORE_API gr_pack_k_bits_bb : public gr_sync_decimator
+{
+ private:
+  friend GR_CORE_API gr_pack_k_bits_bb_sptr gr_make_pack_k_bits_bb (unsigned k);
+
+  gr_pack_k_bits_bb (unsigned k);
+
+  unsigned d_k;    // number of relevent bits to pack from k input bytes
+
+ public:
+  ~gr_pack_k_bits_bb ();
+
+  int work (int noutput_items,
+	    gr_vector_const_void_star &input_items,
+	    gr_vector_void_star &output_items);
+};
+
+#endif