------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- G N A T . D Y N A M I C _ T A B L E S -- -- -- -- S p e c -- -- -- -- -- -- 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 accommodate 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;