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diff --git a/gnuradio-runtime/include/gnuradio/buffer.h b/gnuradio-runtime/include/gnuradio/buffer.h
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+++ b/gnuradio-runtime/include/gnuradio/buffer.h
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+/* -*- c++ -*- */
+/*
+ * Copyright 2004,2009-2011,2013 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.
+ */
+
+#ifndef INCLUDED_GR_RUNTIME_BUFFER_H
+#define INCLUDED_GR_RUNTIME_BUFFER_H
+
+#include <gnuradio/api.h>
+#include <gnuradio/runtime_types.h>
+#include <gnuradio/tags.h>
+#include <boost/weak_ptr.hpp>
+#include <gnuradio/thread/thread.h>
+#include <deque>
+
+namespace gr {
+  
+  class vmcircbuf;
+
+  /*!
+   * \brief Allocate a buffer that holds at least \p nitems of size \p sizeof_item.
+   *
+   * The total size of the buffer will be rounded up to a system
+   * dependent boundary. This is typically the system page size, but
+   * under MS windows is 64KB.
+   *
+   * \param nitems is the minimum number of items the buffer will hold.
+   * \param sizeof_item is the size of an item in bytes.
+   * \param link is the block that writes to this buffer.
+   */
+  GR_RUNTIME_API buffer_sptr make_buffer(int nitems, size_t sizeof_item,
+                                         block_sptr link=block_sptr());
+
+  /*!
+   * \brief Single writer, multiple reader fifo.
+   * \ingroup internal
+   */
+  class GR_RUNTIME_API buffer
+  {
+  public:
+    virtual ~buffer();
+
+    /*!
+     * \brief return number of items worth of space available for writing
+     */
+    int space_available();
+
+    /*!
+     * \brief return size of this buffer in items
+     */
+    int bufsize() const { return d_bufsize; }
+
+    /*!
+     * \brief return pointer to write buffer.
+     *
+     * The return value points at space that can hold at least
+     * space_available() items.
+     */
+    void *write_pointer();
+
+    /*!
+     * \brief tell buffer that we wrote \p nitems into it
+     */
+    void update_write_pointer(int nitems);
+
+    void set_done(bool done);
+    bool done() const { return d_done; }
+
+    /*!
+     * \brief Return the block that writes to this buffer.
+     */
+    block_sptr link() { return block_sptr(d_link); }
+
+    size_t nreaders() const { return d_readers.size(); }
+    buffer_reader* reader(size_t index) { return d_readers[index]; }
+
+    gr::thread::mutex *mutex() { return &d_mutex; }
+
+    uint64_t nitems_written() { return d_abs_write_offset; }
+
+    size_t get_sizeof_item() { return d_sizeof_item; }
+
+    /*!
+     * \brief  Adds a new tag to the buffer.
+     *
+     * \param tag        the new tag
+     */
+    void add_item_tag(const tag_t &tag);
+
+    /*!
+     * \brief  Removes an existing tag from the buffer.
+     *
+     * If no such tag is found, does nothing.
+     *
+     * \param tag        the tag that needs to be removed
+     */
+    void remove_item_tag(const tag_t &tag);
+
+    /*!
+     * \brief  Removes all tags before \p max_time from buffer
+     *
+     * \param max_time        the time (item number) to trim up until.
+     */
+    void prune_tags(uint64_t max_time);
+
+    std::deque<tag_t>::iterator get_tags_begin() { return d_item_tags.begin(); }
+    std::deque<tag_t>::iterator get_tags_end() { return d_item_tags.end(); }
+
+    // -------------------------------------------------------------------------
+
+  private:
+    friend class buffer_reader;
+    friend GR_RUNTIME_API buffer_sptr make_buffer(int nitems, size_t sizeof_item, block_sptr link);
+    friend GR_RUNTIME_API buffer_reader_sptr buffer_add_reader(buffer_sptr buf, int nzero_preload, block_sptr link);
+
+  protected:
+    char			       *d_base;		// base address of buffer
+    unsigned int			d_bufsize;	// in items
+  private:
+    gr::vmcircbuf		       *d_vmcircbuf;
+    size_t	 			d_sizeof_item;	// in bytes
+    std::vector<buffer_reader *>	d_readers;
+    boost::weak_ptr<block>		d_link;		// block that writes to this buffer
+
+    //
+    // The mutex protects d_write_index, d_abs_write_offset, d_done, d_item_tags
+    // and the d_read_index's and d_abs_read_offset's in the buffer readers.
+    //
+    gr::thread::mutex			d_mutex;
+    unsigned int			d_write_index;	// in items [0,d_bufsize)
+    uint64_t                            d_abs_write_offset; // num items written since the start
+    bool				d_done;
+    std::deque<tag_t>                d_item_tags;
+    uint64_t                            d_last_min_items_read;
+
+    unsigned index_add(unsigned a, unsigned b)
+    {
+      unsigned s = a + b;
+
+      if(s >= d_bufsize)
+        s -= d_bufsize;
+
+      assert(s < d_bufsize);
+      return s;
+    }
+
+    unsigned index_sub(unsigned a, unsigned b)
+    {
+      int s = a - b;
+
+      if(s < 0)
+        s += d_bufsize;
+
+      assert((unsigned) s < d_bufsize);
+      return s;
+    }
+
+    virtual bool allocate_buffer(int nitems, size_t sizeof_item);
+
+    /*!
+     * \brief constructor is private.  Use gr_make_buffer to create instances.
+     *
+     * Allocate a buffer that holds at least \p nitems of size \p sizeof_item.
+     *
+     * \param nitems is the minimum number of items the buffer will hold.
+     * \param sizeof_item is the size of an item in bytes.
+     * \param link is the block that writes to this buffer.
+     *
+     * The total size of the buffer will be rounded up to a system
+     * dependent boundary.  This is typically the system page size, but
+     * under MS windows is 64KB.
+     */
+    buffer(int nitems, size_t sizeof_item, block_sptr link);
+
+    /*!
+     * \brief disassociate \p reader from this buffer
+     */
+    void drop_reader(buffer_reader *reader);
+  };
+
+  /*!
+   * \brief Create a new gr::buffer_reader and attach it to buffer \p buf
+   * \param buf is the buffer the \p gr::buffer_reader reads from.
+   * \param nzero_preload -- number of zero items to "preload" into buffer.
+   * \param link is the block that reads from the buffer using this gr::buffer_reader.
+   */
+  GR_RUNTIME_API buffer_reader_sptr
+    buffer_add_reader(buffer_sptr buf, int nzero_preload, block_sptr link=block_sptr());
+
+  //! returns # of buffers currently allocated
+  GR_RUNTIME_API long buffer_ncurrently_allocated();
+
+
+  // ---------------------------------------------------------------------------
+
+  /*!
+   * \brief How we keep track of the readers of a gr::buffer.
+   * \ingroup internal
+   */
+  class GR_RUNTIME_API buffer_reader
+  {
+  public:
+    ~buffer_reader();
+
+    /*!
+     * \brief Return number of items available for reading.
+     */
+    int items_available() const;
+
+    /*!
+     * \brief Return buffer this reader reads from.
+     */
+    buffer_sptr buffer() const { return d_buffer; }
+
+    /*!
+     * \brief Return maximum number of items that could ever be available for reading.
+     * This is used as a sanity check in the scheduler to avoid looping forever.
+     */
+    int max_possible_items_available() const { return d_buffer->d_bufsize - 1; }
+
+    /*!
+     * \brief return pointer to read buffer.
+     *
+     * The return value points to items_available() number of items
+     */
+    const void *read_pointer();
+
+    /*
+     * \brief tell buffer we read \p items from it
+     */
+    void update_read_pointer(int nitems);
+
+    void set_done(bool done) { d_buffer->set_done(done); }
+    bool done() const { return d_buffer->done(); }
+
+    gr::thread::mutex *mutex() { return d_buffer->mutex(); }
+
+    uint64_t nitems_read() { return d_abs_read_offset; }
+
+    size_t get_sizeof_item() { return d_buffer->get_sizeof_item(); }
+
+    /*!
+     * \brief Return the block that reads via this reader.
+     *
+     */
+    block_sptr link() { return block_sptr(d_link); }
+
+    /*!
+     * \brief Given a [start,end), returns a vector all tags in the range.
+     *
+     * Get a vector of tags in given range. Range of counts is from start to end-1.
+     *
+     * Tags are tuples of:
+     *      (item count, source id, key, value)
+     *
+     * \param v            a vector reference to return tags into
+     * \param abs_start    a uint64 count of the start of the range of interest
+     * \param abs_end      a uint64 count of the end of the range of interest
+     */
+    void get_tags_in_range(std::vector<tag_t> &v,
+                           uint64_t abs_start,
+                           uint64_t abs_end);
+
+    // -------------------------------------------------------------------------
+
+  private:
+    friend class buffer;
+    friend GR_RUNTIME_API buffer_reader_sptr
+      buffer_add_reader(buffer_sptr buf, int nzero_preload, block_sptr link);
+
+    buffer_sptr  d_buffer;
+    unsigned int d_read_index;       // in items [0,d->buffer.d_bufsize)
+    uint64_t     d_abs_read_offset;  // num items seen since the start
+    boost::weak_ptr<block> d_link;   // block that reads via this buffer reader
+
+    //! constructor is private.  Use gr::buffer::add_reader to create instances
+    buffer_reader(buffer_sptr buffer, unsigned int read_index, block_sptr link);
+  };
+
+  //! returns # of buffer_readers currently allocated
+  GR_RUNTIME_API long buffer_reader_ncurrently_allocated ();
+
+} /* namespace gr */
+
+#endif /* INCLUDED_GR_RUNTIME_BUFFER_H */