------------------------------------------------------------------------------ -- -- -- GNAT RUNTIME COMPONENTS -- -- -- -- G N A T . H T A B L E -- -- -- -- S p e c -- -- -- -- Copyright (C) 1995-2002 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 was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- Hash table searching routines -- This package contains two separate packages. The Simple_HTable package -- provides a very simple abstraction that associates one element to one -- key value and takes care of all allocations automatically using the heap. -- The Static_HTable package provides a more complex interface that allows -- complete control over allocation. -- Note: actual code is found in System.HTable (s-htable.ads/adb) since -- this facility is accessed from run time routines, but clients should -- always access the version supplied via GNAT.HTable. with System.HTable; package GNAT.HTable is pragma Preelaborate (HTable); pragma Elaborate_Body; -- The elaborate body is because we have a dummy body to deal with bootstrap -- path problems (we used to have a real body, and now we don't need it any -- more, but the bootstrap requires that we have a dummy body, since otherwise -- the old body gets picked up. ------------------- -- Simple_HTable -- ------------------- -- A simple hash table abstraction, easy to instantiate, easy to use. -- The table associates one element to one key with the procedure Set. -- Get retrieves the Element stored for a given Key. The efficiency of -- retrieval is function of the size of the Table parameterized by -- Header_Num and the hashing function Hash. generic package Simple_HTable renames System.HTable.Simple_HTable; -- For convenience of reference here is what this package has in it: -- generic -- type Header_Num is range <>; -- -- An integer type indicating the number and range of hash headers -- type Element is private; -- -- The type of element to be stored -- No_Element : Element; -- -- The object that is returned by Get when no element has been set -- -- for a given key -- type Key is private; -- with function Hash (F : Key) return Header_Num; -- with function Equal (F1, F2 : Key) return Boolean; -- package Simple_HTable is -- procedure Set (K : Key; E : Element); -- -- Associates an element with a given key. Overrides any previously -- -- associated element. -- procedure Reset; -- -- Removes and frees all elements in the table -- function Get (K : Key) return Element; -- -- Returns the Element associated with a key or No_Element if the -- -- given key has not associated element -- procedure Remove (K : Key); -- -- Removes the latest inserted element pointer associated with the -- -- given key if any, does nothing if none. -- function Get_First return Element; -- -- Returns No_Element if the HTable is empty, otherwise returns one -- -- non specified element. There is no guarantee that 2 calls to -- -- this function will return the same element. -- function Get_Next return Element; -- -- Returns a non-specified element that has not been returned by the -- -- same function since the last call to Get_First or No_Element if -- -- there is no such element. If there is no call to 'Set' in between -- -- Get_Next calls, all the elements of the HTable will be traversed. -- end Simple_HTable; ------------------- -- Static_HTable -- ------------------- -- A low-level Hash-Table abstraction, not as easy to instantiate as -- Simple_HTable but designed to allow complete control over the -- allocation of necessary data structures. Particularly useful when -- dynamic allocation is not desired. The model is that each Element -- contains its own Key that can be retrieved by Get_Key. Furthermore, -- Element provides a link that can be used by the HTable for linking -- elements with same hash codes: -- Element -- +-------------------+ -- | Key | -- +-------------------+ -- : other data : -- +-------------------+ -- | Next Elmt | -- +-------------------+ generic package Static_HTable renames System.HTable.Static_HTable; -- For convenience of reference here is what this package has in it: -- generic -- type Header_Num is range <>; -- -- An integer type indicating the number and range of hash headers. -- type Element (<>) is limited private; -- -- The type of element to be stored -- type Elmt_Ptr is private; -- -- The type used to reference an element (will usually be an -- -- access type, but could be some other form of type such as -- -- an integer type). -- Null_Ptr : Elmt_Ptr; -- -- The null value of the Elmt_Ptr type. -- with procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr); -- with function Next (E : Elmt_Ptr) return Elmt_Ptr; -- -- The type must provide an internal link for the sake of the -- -- staticness of the HTable. -- type Key is limited private; -- with function Get_Key (E : Elmt_Ptr) return Key; -- with function Hash (F : Key) return Header_Num; -- with function Equal (F1, F2 : Key) return Boolean; -- package Static_HTable is -- procedure Reset; -- -- Resets the hash table by setting all its elements to Null_Ptr. -- -- The effect is to clear the hash table so that it can be reused. -- -- For the most common case where Elmt_Ptr is an access type, and -- -- Null_Ptr is null, this is only needed if the same table is -- -- reused in a new context. If Elmt_Ptr is other than an access -- -- type, or Null_Ptr is other than null, then Reset must be called -- -- before the first use of the hash table. -- procedure Set (E : Elmt_Ptr); -- -- Insert the element pointer in the HTable -- function Get (K : Key) return Elmt_Ptr; -- -- Returns the latest inserted element pointer with the given Key -- -- or null if none. -- procedure Remove (K : Key); -- -- Removes the latest inserted element pointer associated with the -- -- given key if any, does nothing if none. -- function Get_First return Elmt_Ptr; -- -- Returns Null_Ptr if the HTable is empty, otherwise returns one -- -- non specified element. There is no guarantee that 2 calls to -- -- this function will return the same element. -- function Get_Next return Elmt_Ptr; -- -- Returns a non-specified element that has not been returned by -- -- the same function since the last call to Get_First or Null_Ptr -- -- if there is no such element or Get_First has bever been called. -- -- If there is no call to 'Set' in between Get_Next calls, all -- -- the elements of the HTable will be traversed. -- end Static_HTable; ---------- -- Hash -- ---------- -- A generic hashing function working on String keys generic function Hash renames System.HTable.Hash; -- generic -- type Header_Num is range <>; -- function Hash (Key : String) return Header_Num; end GNAT.HTable;