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+------------------------------------------------------------------------------
+-- --
+-- GNAT COMPILER COMPONENTS --
+-- --
+-- G N A T . D Y N A M I C _ T A B L E S --
+-- --
+-- S p e c --
+-- --
+-- $Revision: 1.11 $
+-- --
+-- Copyright (C) 2000-2001 Ada Core Technologies, 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 is maintained by Ada Core Technologies Inc (http://www.gnat.com). --
+-- --
+------------------------------------------------------------------------------
+
+-- Resizable one dimensional array support
+
+-- 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.
+
+-- This package provides a facility similar to that of GNAT.Table, except
+-- that this package declares a type that can be used to define dynamic
+-- instances of the table, while an instantiation of GNAT.Table creates a
+-- single instance of the table type.
+
+-- Note that this interface should remain synchronized with those in
+-- GNAT.Table and the GNAT compiler source unit Table to keep as much
+-- coherency as possible between these three related units.
+
+generic
+ type Table_Component_Type is private;
+ type Table_Index_Type is range <>;
+
+ Table_Low_Bound : Table_Index_Type;
+ Table_Initial : Positive;
+ Table_Increment : Natural;
+
+package GNAT.Dynamic_Tables 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_Low_Bound .. <>) of Table_Component_Type;
+
+ -- 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 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 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
+ -- restrict 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.
+
+ type Table_Private is private;
+ -- table private data that is not exported in Instance.
+
+ type Instance is record
+ 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.
+
+ P : Table_Private;
+ end record;
+
+ procedure Init (T : in out Instance);
+ -- This procedure allocates a new table of size Initial (freeing any
+ -- previously allocated larger table). Init must be called before using
+ -- the table. Init is convenient in reestablishing a table for new use.
+
+ function Last (T : in Instance) 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 (T : in out Instance);
+ -- 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 (T : in out Instance);
+ -- 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 (T : in out Instance; 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 (T : in out Instance);
+ pragma Inline (Increment_Last);
+ -- Adds 1 to Last (same as Set_Last (Last + 1).
+
+ procedure Decrement_Last (T : in out Instance);
+ pragma Inline (Decrement_Last);
+ -- Subtracts 1 from Last (same as Set_Last (Last - 1).
+
+ procedure Append (T : in out Instance; New_Val : Table_Component_Type);
+ pragma Inline (Append);
+ -- Equivalent to:
+ -- Increment_Last (T);
+ -- T.Table (T.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
+ (T : in out Instance;
+ 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.
+
+ procedure Allocate (T : in out Instance; Num : Integer := 1);
+ pragma Inline (Allocate);
+ -- Adds Num to Last.
+
+private
+
+ type Table_Private is record
+ Max : Integer;
+ -- Subscript of the maximum entry in the currently allocated table
+
+ Length : Integer := 0;
+ -- Number of entries in currently allocated table. The value of zero
+ -- ensures that we initially allocate the table.
+
+ Last_Val : Integer;
+ -- Current value of Last.
+ end record;
+
+end GNAT.Dynamic_Tables;