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diff --git a/gnuradio-runtime/lib/gr_vmcircbuf.h b/gnuradio-runtime/lib/gr_vmcircbuf.h
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+++ b/gnuradio-runtime/lib/gr_vmcircbuf.h
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+/* -*- c++ -*- */
+/*
+ * Copyright 2003 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 _GR_VMCIRCBUF_H_
+#define _GR_VMCIRCBUF_H_
+
+#include <gr_runtime_api.h>
+#include <vector>
+
+/*!
+ * \brief abstract class to implement doubly mapped virtual memory circular buffers
+ * \ingroup internal
+ */
+class GR_RUNTIME_API gr_vmcircbuf {
+ protected:
+  int	 d_size;
+  char	*d_base;
+
+  // CREATORS
+  gr_vmcircbuf (int size) : d_size (size), d_base (0) {};
+
+ public:
+  virtual ~gr_vmcircbuf ();
+
+  // ACCESSORS
+  void *pointer_to_first_copy ()  const { return d_base; }
+  void *pointer_to_second_copy () const { return d_base + d_size; }
+};
+
+/*!
+ * \brief abstract factory for creating circular buffers
+ */
+class GR_RUNTIME_API gr_vmcircbuf_factory {
+ protected:
+  gr_vmcircbuf_factory () {};
+  virtual ~gr_vmcircbuf_factory ();
+
+ public:
+
+  /*!
+   * \brief return name of this factory
+   */
+  virtual const char *name () const = 0;
+
+  /*!
+   * \brief return granularity of mapping, typically equal to page size
+   */
+  virtual int granularity () = 0;
+
+  /*!
+   * \brief return a gr_vmcircbuf, or 0 if unable.
+   *
+   * Call this to create a doubly mapped circular buffer.
+   */
+  virtual gr_vmcircbuf *make (int size) = 0;
+};
+
+/*
+ * \brief pulls together all implementations of gr_vmcircbuf
+ */
+class GR_RUNTIME_API gr_vmcircbuf_sysconfig {
+ public:
+
+  /*
+   * \brief return the single instance of the default factory.
+   *
+   * returns the default factory to use if it's already defined,
+   * else find the first working factory and use it.
+   */
+  static gr_vmcircbuf_factory *get_default_factory ();
+
+
+  static int granularity () 	       { return get_default_factory()->granularity(); }
+  static gr_vmcircbuf *make (int size) { return get_default_factory()->make(size);    }
+
+
+  // N.B. not all factories are guaranteed to work.
+  // It's too hard to check everything at config time, so we check at runtime
+  static std::vector<gr_vmcircbuf_factory *> all_factories ();
+
+  // make this factory the default
+  static void set_default_factory (gr_vmcircbuf_factory *f);
+
+  /*!
+   * \brief  Does this factory really work?
+   *
+   * verbose = 0: silent
+   * verbose = 1: names of factories tested and results
+   * verbose = 2: all intermediate results
+   */
+  static bool test_factory (gr_vmcircbuf_factory *f, int verbose);
+
+  /*!
+   * \brief Test all factories, return true if at least one of them works
+   * verbose = 0: silent
+   * verbose = 1: names of factories tested and results
+   * verbose = 2: all intermediate results
+   */
+  static bool test_all_factories (int verbose);
+};
+
+
+#endif /* _GR_VMCIRCBUF_H_ */