223 lines
9.9 KiB
Ada
223 lines
9.9 KiB
Ada
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------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME COMPONENTS --
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-- --
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-- S Y S T E M . H T A B L E --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1995-2013, AdaCore --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- Hash table searching routines
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-- This package contains two separate packages. The Simple_HTable package
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-- provides a very simple abstraction that associates one element to one
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-- key value and takes care of all allocations automatically using the heap.
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-- The Static_HTable package provides a more complex interface that allows
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-- complete control over allocation.
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pragma Compiler_Unit_Warning;
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package System.HTable is
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pragma Preelaborate;
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-------------------
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-- Simple_HTable --
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-------------------
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-- A simple hash table abstraction, easy to instantiate, easy to use.
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-- The table associates one element to one key with the procedure Set.
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-- Get retrieves the Element stored for a given Key. The efficiency of
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-- retrieval is function of the size of the Table parameterized by
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-- Header_Num and the hashing function Hash.
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generic
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type Header_Num is range <>;
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-- An integer type indicating the number and range of hash headers
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type Element is private;
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-- The type of element to be stored
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No_Element : Element;
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-- The object that is returned by Get when no element has been set for
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-- a given key
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type Key is private;
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with function Hash (F : Key) return Header_Num;
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with function Equal (F1, F2 : Key) return Boolean;
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package Simple_HTable is
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procedure Set (K : Key; E : Element);
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-- Associates an element with a given key. Overrides any previously
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-- associated element.
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procedure Reset;
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-- Removes and frees all elements in the table
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function Get (K : Key) return Element;
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-- Returns the Element associated with a key or No_Element if the
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-- given key has no associated element.
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procedure Remove (K : Key);
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-- Removes the latest inserted element pointer associated with the
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-- given key if any, does nothing if none.
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function Get_First return Element;
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-- Returns No_Element if the HTable is empty, otherwise returns one
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-- non specified element. There is no guarantee that two calls to this
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-- function will return the same element.
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function Get_Next return Element;
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-- Returns a non-specified element that has not been returned by the
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-- same function since the last call to Get_First or No_Element if
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-- there is no such element. If there is no call to Set in between
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-- Get_Next calls, all the elements of the HTable will be traversed.
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procedure Get_First (K : in out Key; E : out Element);
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-- This version of the iterator returns a key/element pair. A non-
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-- specified entry is returned, and there is no guarantee that two
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-- calls to this procedure will return the same element. If the table
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-- is empty, E is set to No_Element, and K is unchanged, otherwise
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-- K and E are set to the first returned entry.
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procedure Get_Next (K : in out Key; E : out Element);
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-- This version of the iterator returns a key/element pair. It returns
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-- a non-specified element that has not been returned since the last
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-- call to Get_First. If there is no remaining element, then E is set
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-- to No_Element, and the value in K is unchanged, otherwise K and E
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-- are set to the next entry. If there is no call to Set in between
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-- Get_Next calls, all the elements of the HTable will be traversed.
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end Simple_HTable;
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-------------------
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-- Static_HTable --
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-------------------
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-- A low-level Hash-Table abstraction, not as easy to instantiate as
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-- Simple_HTable but designed to allow complete control over the
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-- allocation of necessary data structures. Particularly useful when
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-- dynamic allocation is not desired. The model is that each Element
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-- contains its own Key that can be retrieved by Get_Key. Furthermore,
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-- Element provides a link that can be used by the HTable for linking
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-- elements with same hash codes:
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-- Element
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-- +-------------------+
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-- | Key |
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-- +-------------------+
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-- : other data :
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-- +-------------------+
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-- | Next Elmt |
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-- +-------------------+
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generic
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type Header_Num is range <>;
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-- An integer type indicating the number and range of hash headers
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type Element (<>) is limited private;
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-- The type of element to be stored. This is historically part of the
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-- interface, even though it is not used at all in the operations of
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-- the package.
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pragma Warnings (Off, Element);
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-- We have to kill warnings here, because Element is and always
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-- has been unreferenced, but we cannot remove it at this stage,
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-- since this unit is in wide use, and it certainly seems harmless.
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type Elmt_Ptr is private;
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-- The type used to reference an element (will usually be an access
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-- type, but could be some other form of type such as an integer type).
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Null_Ptr : Elmt_Ptr;
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-- The null value of the Elmt_Ptr type
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with procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr);
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with function Next (E : Elmt_Ptr) return Elmt_Ptr;
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-- The type must provide an internal link for the sake of the
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-- staticness of the HTable.
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type Key is limited private;
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with function Get_Key (E : Elmt_Ptr) return Key;
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with function Hash (F : Key) return Header_Num;
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with function Equal (F1, F2 : Key) return Boolean;
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package Static_HTable is
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procedure Reset;
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-- Resets the hash table by setting all its elements to Null_Ptr. The
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-- effect is to clear the hash table so that it can be reused. For the
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-- most common case where Elmt_Ptr is an access type, and Null_Ptr is
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-- null, this is only needed if the same table is reused in a new
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-- context. If Elmt_Ptr is other than an access type, or Null_Ptr is
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-- other than null, then Reset must be called before the first use
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-- of the hash table.
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procedure Set (E : Elmt_Ptr);
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-- Insert the element pointer in the HTable
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function Get (K : Key) return Elmt_Ptr;
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-- Returns the latest inserted element pointer with the given Key
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-- or null if none.
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function Present (K : Key) return Boolean;
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-- True if an element whose Get_Key is K is in the table
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function Set_If_Not_Present (E : Elmt_Ptr) return Boolean;
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-- If Present (Get_Key (E)), returns False. Otherwise, does Set (E), and
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-- then returns True. Present (Get_Key (E)) is always True afterward,
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-- and the result True indicates E is newly Set.
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procedure Remove (K : Key);
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-- Removes the latest inserted element pointer associated with the
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-- given key if any, does nothing if none.
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function Get_First return Elmt_Ptr;
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-- Returns Null_Ptr if the HTable is empty, otherwise returns one
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-- non specified element. There is no guarantee that two calls to this
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-- function will return the same element.
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function Get_Next return Elmt_Ptr;
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-- Returns a non-specified element that has not been returned by the
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-- same function since the last call to Get_First or Null_Ptr if
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-- there is no such element or Get_First has never been called. If
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-- there is no call to 'Set' in between Get_Next calls, all the
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-- elements of the HTable will be traversed.
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end Static_HTable;
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----------
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-- Hash --
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----------
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-- A generic hashing function working on String keys
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generic
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type Header_Num is range <>;
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function Hash (Key : String) return Header_Num;
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end System.HTable;
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