------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- T A B L E -- -- -- -- S p e c -- -- -- -- Copyright (C) 1992-2005, 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, 51 Franklin Street, Fifth Floor, -- -- Boston, MA 02110-1301, 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. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- 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; 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. -- WARNING: On HPPA, the virtual addressing approach used in this unit -- is incompatible with the indexing instructions on the HPPA. So when -- using this unit, compile your application with -mdisable-indexing. -- WARNING: If the table is reallocated, then the address of all its -- components will change. So do not capture the address of an element -- and then use the address later after the table may be reallocated. -- One tricky case of this is passing an element of the table to a -- subprogram by reference where the table gets reallocated during -- the execution of the subprogram. The best rule to follow is never -- to pass a table element as a parameter except for the case of IN -- mode parameters with scalar values. 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 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 -- 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;