New Language: Ada

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+------------------------------------------------------------------------------
+--                                                                          --
+--                         GNAT COMPILER COMPONENTS                         --
+--                                                                          --
+--                                T A B L E                                 --
+--                                                                          --
+--                                 S p e c                                  --
+--                                                                          --
+--                            $Revision: 1.38 $
+--                                                                          --
+--          Copyright (C) 1992-2001 Free Software Foundation, Inc.          --
+--                                                                          --
+-- GNAT is free software;  you can  redistribute it  and/or modify it under --
+-- terms of the  GNU General Public License as published  by the Free Soft- --
+-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
+-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
+-- OUT 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  distributed with GNAT;  see file COPYING.  If not, write --
+-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
+-- MA 02111-1307, USA.                                                      --
+--                                                                          --
+-- As a special exception,  if other files  instantiate  generics from this --
+-- unit, or you link  this unit with other files  to produce an executable, --
+-- this  unit  does not  by itself cause  the resulting  executable  to  be --
+-- covered  by the  GNU  General  Public  License.  This exception does not --
+-- however invalidate  any other reasons why  the executable file  might be --
+-- covered by the  GNU Public License.                                      --
+--                                                                          --
+-- GNAT was originally developed  by the GNAT team at  New York University. --
+-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
+--                                                                          --
+------------------------------------------------------------------------------
+
+--  This package provides an implementation of dynamically resizable one
+--  dimensional arrays. The idea is to mimic the normal Ada semantics for
+--  arrays as closely as possible with the one additional capability of
+--  dynamically modifying the value of the Last attribute.
+
+--  Note that this interface should remain synchronized with those in
+--  GNAT.Table and GNAT.Dynamic_Tables to keep coherency between these
+--  three related units.
+
+with Types; use Types;
+
+package Table is
+pragma Elaborate_Body (Table);
+
+   generic
+      type Table_Component_Type is private;
+      type Table_Index_Type     is range <>;
+
+      Table_Low_Bound  : Table_Index_Type;
+      Table_Initial    : Pos;
+      Table_Increment  : Nat;
+      Table_Name       : String;
+
+   package Table is
+
+      --  Table_Component_Type and Table_Index_Type specify the type of the
+      --  array, Table_Low_Bound is the lower bound. Index_type must be an
+      --  integer type. The effect is roughly to declare:
+
+      --    Table : array (Table_Index_Type range Table_Low_Bound .. <>)
+      --                       of Table_Component_Type;
+
+      --    Note: since the upper bound can be one less than the lower
+      --    bound for an empty array, the table index type must be able
+      --    to cover this range, e.g. if the lower bound is 1, then the
+      --    Table_Index_Type should be Natural rather than Positive.
+
+      --  Table_Component_Type may be any Ada type, except that controlled
+      --  types are not supported. Note however that default initialization
+      --  will NOT occur for array components.
+
+      --  The Table_Initial values controls the allocation of the table when
+      --  it is first allocated, either by default, or by an explicit Init
+      --  call. The value used is Opt.Table_Factor * Table_Initial.
+
+      --  The Table_Increment value controls the amount of increase, if the
+      --  table has to be increased in size. The value given is a percentage
+      --  value (e.g. 100 = increase table size by 100%, i.e. double it).
+
+      --  The Table_Name parameter is simply use in debug output messages it
+      --  has no other usage, and is not referenced in non-debugging mode.
+
+      --  The Last and Set_Last subprograms provide control over the current
+      --  logical allocation. They are quite efficient, so they can be used
+      --  freely (expensive reallocation occurs only at major granularity
+      --  chunks controlled by the allocation parameters).
+
+      --  Note: we do not make the table components aliased, since this would
+      --  restict the use of table for discriminated types. If it is necessary
+      --  to take the access of a table element, use Unrestricted_Access.
+
+      type Table_Type is
+        array (Table_Index_Type range <>) of Table_Component_Type;
+
+      subtype Big_Table_Type is
+        Table_Type (Table_Low_Bound .. Table_Index_Type'Last);
+      --  We work with pointers to a bogus array type that is constrained
+      --  with the maximum possible range bound. This means that the pointer
+      --  is a thin pointer, which is more efficient. Since subscript checks
+      --  in any case must be on the logical, rather than physical bounds,
+      --  safety is not compromised by this approach.
+
+      type Table_Ptr is access all Big_Table_Type;
+      --  The table is actually represented as a pointer to allow reallocation
+
+      Table : aliased Table_Ptr := null;
+      --  The table itself. The lower bound is the value of Low_Bound.
+      --  Logically the upper bound is the current value of Last (although
+      --  the actual size of the allocated table may be larger than this).
+      --  The program may only access and modify Table entries in the range
+      --  First .. Last.
+
+      Locked : Boolean := False;
+      --  Table expansion is permitted only if this switch is set to False. A
+      --  client may set Locked to True, in which case any attempt to expand
+      --  the table will cause an assertion failure. Note that while a table
+      --  is locked, its address in memory remains fixed and unchanging. This
+      --  feature is used to control table expansion during Gigi processing.
+      --  Gigi assumes that tables other than the Uint and Ureal tables do
+      --  not move during processing, which means that they cannot be expanded.
+      --  The Locked flag is used to enforce this restriction.
+
+      procedure Init;
+      --  This procedure allocates a new table of size Initial (freeing any
+      --  previously allocated larger table). It is not necessary to call
+      --  Init when a table is first instantiated (since the instantiation does
+      --  the same initialization steps). However, it is harmless to do so, and
+      --  Init is convenient in reestablishing a table for new use.
+
+      function Last return Table_Index_Type;
+      pragma Inline (Last);
+      --  Returns the current value of the last used entry in the table, which
+      --  can then be used as a subscript for Table. Note that the only way to
+      --  modify Last is to call the Set_Last procedure. Last must always be
+      --  used to determine the logically last entry.
+
+      procedure Release;
+      --  Storage is allocated in chunks according to the values given in the
+      --  Initial and Increment parameters. A call to Release releases all
+      --  storage that is allocated, but is not logically part of the current
+      --  array value. Current array values are not affected by this call.
+
+      procedure Free;
+      --  Free all allocated memory for the table. A call to init is required
+      --  before any use of this table after calling Free.
+
+      First : constant Table_Index_Type := Table_Low_Bound;
+      --  Export First as synonym for Low_Bound (parallel with use of Last)
+
+      procedure Set_Last (New_Val : Table_Index_Type);
+      pragma Inline (Set_Last);
+      --  This procedure sets Last to the indicated value. If necessary the
+      --  table is reallocated to accomodate the new value (i.e. on return
+      --  the allocated table has an upper bound of at least Last). If Set_Last
+      --  reduces the size of the table, then logically entries are removed
+      --  from the table. If Set_Last increases the size of the table, then
+      --  new entries are logically added to the table.
+
+      procedure Increment_Last;
+      pragma Inline (Increment_Last);
+      --  Adds 1 to Last (same as Set_Last (Last + 1).
+
+      procedure Decrement_Last;
+      pragma Inline (Decrement_Last);
+      --  Subtracts 1 from Last (same as Set_Last (Last - 1).
+
+      procedure Append (New_Val : Table_Component_Type);
+      pragma Inline (Append);
+      --  Equivalent to:
+      --    x.Increment_Last;
+      --    x.Table (x.Last) := New_Val;
+      --  i.e. the table size is increased by one, and the given new item
+      --  stored in the newly created table element.
+
+      procedure Set_Item
+        (Index : Table_Index_Type;
+         Item  : Table_Component_Type);
+      pragma Inline (Set_Item);
+      --  Put Item in the table at position Index. The table is expanded if
+      --  current table length is less than Index and in that case Last is set
+      --  to Index. Item will replace any value already present in the table
+      --  at this position.
+
+      type Saved_Table is private;
+      --  Type used for Save/Restore subprograms
+
+      function Save return Saved_Table;
+      --  Resets table to empty, but saves old contents of table in returned
+      --  value, for possible later restoration by a call to Restore.
+
+      procedure Restore (T : Saved_Table);
+      --  Given a Saved_Table value returned by a prior call to Save, restores
+      --  the table to the state it was in at the time of the Save call.
+
+      procedure Tree_Write;
+      --  Writes out contents of table using Tree_IO
+
+      procedure Tree_Read;
+      --  Initializes table by reading contents previously written
+      --  with the Tree_Write call (also using Tree_IO)
+
+   private
+
+      Last_Val : Int;
+      --  Current value of Last. Note that we declare this in the private part
+      --  because we don't want the client to modify Last except through one of
+      --  the official interfaces (since a modification to Last may require a
+      --  reallocation of the table).
+
+      Max : Int;
+      --  Subscript of the maximum entry in the currently allocated table
+
+      type Saved_Table is record
+         Last_Val : Int;
+         Max      : Int;
+         Table    : Table_Ptr;
+      end record;
+
+   end Table;
+end Table;