------------------------------------------------------------------------------ -- -- -- GNAT RUNTIME COMPONENTS -- -- -- -- G N A T . T A B L E -- -- -- -- S p e c -- -- -- -- -- -- 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 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; 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;