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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;