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------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- G N A T . D Y N A M I C _ H T A B L E S -- -- -- -- S p e c -- -- -- -- Copyright (C) 1995-2010, AdaCore -- -- -- -- 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 3, 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. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- <http://www.gnu.org/licenses/>. -- -- -- -- 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. -- This package provides a facility similar to that of GNAT.HTable, except -- that this package declares types that can be used to define dynamic -- instances of hash tables, while instantiations in GNAT.HTable creates a -- single instance of the hash table. -- Note that this interface should remain synchronized with those in -- GNAT.HTable to keep as much coherency as possible between these two -- related units. with Ada.Unchecked_Deallocation; package GNAT.Dynamic_HTables is ------------------- -- 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 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 type Instance is private; Nil : constant Instance; procedure Reset (T : in out Instance); -- Resets the hash table by releasing all memory associated with -- it. The hash table can safely be reused after this call. 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 (T : in out Instance; E : Elmt_Ptr); -- Insert the element pointer in the HTable function Get (T : Instance; K : Key) return Elmt_Ptr; -- Returns the latest inserted element pointer with the given Key -- or null if none. procedure Remove (T : Instance; K : Key); -- Removes the latest inserted element pointer associated with the -- given key if any, does nothing if none. function Get_First (T : Instance) 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 (T : Instance) 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 never been called. If -- there is no call to 'Set' in between Get_Next calls, all the -- elements of the Htable will be traversed. private type Instance_Data; type Instance is access all Instance_Data; Nil : constant Instance := null; end Static_HTable; ------------------- -- 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 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 type Instance is private; Nil : constant Instance; procedure Set (T : in out Instance; K : Key; E : Element); -- Associates an element with a given key. Overrides any previously -- associated element. procedure Reset (T : in out Instance); -- Releases all memory associated with the table. The table can be -- reused after this call (it is automatically allocated on the first -- access to the table). function Get (T : Instance; K : Key) return Element; -- Returns the Element associated with a key or No_Element if the -- given key has not associated element procedure Remove (T : Instance; K : Key); -- Removes the latest inserted element pointer associated with the -- given key if any, does nothing if none. function Get_First (T : Instance) return Element; -- Returns No_Element if the Htable is empty, otherwise returns one -- non specified element. There is no guarantee that two calls to this -- function will return the same element, if the Htable has been -- modified between the two calls. function Get_Next (T : Instance) 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. -- To guarantee that all the elements of the Htable will be traversed, -- no modification of the Htable (Set, Reset, Remove) should occur -- between a call to Get_First and subsequent consecutive calls to -- Get_Next, until one of these calls returns No_Element. private type Element_Wrapper; type Elmt_Ptr is access all Element_Wrapper; type Element_Wrapper is record K : Key; E : Element; Next : Elmt_Ptr; end record; procedure Free is new Ada.Unchecked_Deallocation (Element_Wrapper, Elmt_Ptr); procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr); function Next (E : Elmt_Ptr) return Elmt_Ptr; function Get_Key (E : Elmt_Ptr) return Key; package Tab is new Static_HTable (Header_Num => Header_Num, Element => Element_Wrapper, Elmt_Ptr => Elmt_Ptr, Null_Ptr => null, Set_Next => Set_Next, Next => Next, Key => Key, Get_Key => Get_Key, Hash => Hash, Equal => Equal); type Instance is new Tab.Instance; Nil : constant Instance := Instance (Tab.Nil); end Simple_HTable; end GNAT.Dynamic_HTables;
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