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-- Copyright (C) 1996 Morgan Kaufmann Publishers, Inc
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-- This file is part of VESTs (Vhdl tESTs).
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-- VESTs is free software; you can redistribute it and/or modify it
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-- under the terms of the GNU General Public License as published by the
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-- Free Software Foundation; either version 2 of the License, or (at
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-- your option) any later version. 
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-- VESTs is distributed in the hope that it will be useful, but WITHOUT
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-- ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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-- FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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-- for more details. 
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-- You should have received a copy of the GNU General Public License
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-- along with VESTs; if not, write to the Free Software Foundation,
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-- Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
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-- ---------------------------------------------------------------------
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--
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-- $Id: ch_19_tkfifo-b.vhd,v 1.3 2001-10-26 16:29:36 paw Exp $
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-- $Revision: 1.3 $
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--
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-- ---------------------------------------------------------------------
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package body token_fifo_adt is
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  function new_fifo return fifo_type is
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  begin
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    return new fifo_record'( null, null );
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  end function new_fifo;
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  procedure test_empty ( variable fifo : in fifo_type;
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                         variable is_empty : out boolean ) is
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  begin
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    is_empty := fifo.head_entry = null;
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  end procedure test_empty;
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  procedure insert ( fifo : inout fifo_type;
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                     element : in element_type ) is
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    variable new_entry : fifo_entry
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      := new fifo_entry_record'( next_entry => null,
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                                 element => element );
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  begin
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    if fifo.tail_entry /= null then
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      fifo.tail_entry.next_entry := new_entry;
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    else
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      fifo.head_entry := new_entry;
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    end if;
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    fifo.tail_entry := new_entry;
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  end procedure insert;
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  procedure remove ( fifo : inout fifo_type;
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                     element : out element_type ) is
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    variable empty_fifo : boolean;
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    variable removed_entry : fifo_entry;
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  begin
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    test_empty(fifo, empty_fifo);
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    if empty_fifo then
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      report "remove from empty fifo" severity failure;
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    else
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      removed_entry := fifo.head_entry;
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      element := removed_entry.element;
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      fifo.head_entry := removed_entry.next_entry;
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      if fifo.head_entry = null then  -- fifo now empty
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        fifo.tail_entry := null;
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      end if;
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      deallocate(removed_entry);
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    end if;
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  end procedure remove;
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end package body token_fifo_adt;
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