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------------------------------------------------------------------------------
-- --
-- GNAT RUNTIME COMPONENTS --
-- --
-- G N A T . T A B L E --
-- --
-- S p e c --
-- --
-- $Revision: 1.12 $
-- --
-- Copyright (C) 1998-2001 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.Dynamic_Tables,
-- except that this package declares a single instance of the table type,
-- while an instantiation of GNAT.Dynamic_Tables creates a type that can be
-- used to define dynamic instances of the table.
-- Note that this interface should remain synchronized with those in
-- GNAT.Dynamic_Tables 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.Table is
pragma Elaborate_Body (Table);
-- 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 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
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.
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 the
-- 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.
function Allocate (Num : Integer := 1) return Table_Index_Type;
pragma Inline (Allocate);
-- Adds Num to Last, and returns the old value of Last + 1. Note that
-- this function has the possible side effect of reallocating the table.
-- This means that a reference X.Table (X.Allocate) is incorrect, since
-- the call to X.Allocate may modify the results of calling X.Table.
end GNAT.Table;
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