1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- G N A T . H T A B L E --
9 -- Copyright (C) 1995-2008, AdaCore --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 -- Hash table searching routines
36 -- This package contains two separate packages. The Simple_HTable package
37 -- provides a very simple abstraction that associates one element to one
38 -- key value and takes care of all allocations automatically using the heap.
39 -- The Static_HTable package provides a more complex interface that allows
40 -- complete control over allocation.
42 -- Note: actual code is found in System.HTable (s-htable.ads/adb) since
43 -- this facility is accessed from run time routines, but clients should
44 -- always access the version supplied via GNAT.HTable.
50 package GNAT
.HTable
is
52 pragma Elaborate_Body
;
53 -- The elaborate body is because we have a dummy body to deal with
54 -- bootstrap path problems (we used to have a real body, and now we don't
55 -- need it any more, but the bootstrap requires that we have a dummy body,
56 -- since otherwise the old body gets picked up.
62 -- A simple hash table abstraction, easy to instantiate, easy to use.
63 -- The table associates one element to one key with the procedure Set.
64 -- Get retrieves the Element stored for a given Key. The efficiency of
65 -- retrieval is function of the size of the Table parameterized by
66 -- Header_Num and the hashing function Hash.
68 generic package Simple_HTable
renames System
.HTable
.Simple_HTable
;
70 -- For convenience of reference here is what this package has in it:
73 -- type Header_Num is range <>;
74 -- -- An integer type indicating the number and range of hash headers
76 -- type Element is private;
77 -- -- The type of element to be stored
79 -- No_Element : Element;
80 -- -- The object that is returned by Get when no element has been set
83 -- type Key is private;
84 -- with function Hash (F : Key) return Header_Num;
85 -- with function Equal (F1, F2 : Key) return Boolean;
87 -- package Simple_HTable is
89 -- procedure Set (K : Key; E : Element);
90 -- -- Associates an element with a given key. Overrides any previously
91 -- -- associated element.
94 -- -- Removes and frees all elements in the table
96 -- function Get (K : Key) return Element;
97 -- -- Returns the Element associated with a key or No_Element if the
98 -- -- given key has not associated element
100 -- procedure Remove (K : Key);
101 -- -- Removes the latest inserted element pointer associated with the
102 -- -- given key if any, does nothing if none.
104 -- function Get_First return Element;
105 -- -- Returns No_Element if the HTable is empty, otherwise returns one
106 -- -- non specified element. There is no guarantee that 2 calls to
107 -- -- this function will return the same element.
109 -- function Get_Next return Element;
110 -- -- Returns a non-specified element that has not been returned by the
111 -- -- same function since the last call to Get_First or No_Element if
112 -- -- there is no such element. If there is no call to 'Set' in between
113 -- -- Get_Next calls, all the elements of the HTable will be traversed.
114 -- end Simple_HTable;
120 -- A low-level Hash-Table abstraction, not as easy to instantiate as
121 -- Simple_HTable but designed to allow complete control over the
122 -- allocation of necessary data structures. Particularly useful when
123 -- dynamic allocation is not desired. The model is that each Element
124 -- contains its own Key that can be retrieved by Get_Key. Furthermore,
125 -- Element provides a link that can be used by the HTable for linking
126 -- elements with same hash codes:
130 -- +-------------------+
132 -- +-------------------+
134 -- +-------------------+
136 -- +-------------------+
138 generic package Static_HTable
renames System
.HTable
.Static_HTable
;
140 -- For convenience of reference here is what this package has in it:
143 -- type Header_Num is range <>;
144 -- -- An integer type indicating the number and range of hash headers.
146 -- type Element (<>) is limited private;
147 -- -- The type of element to be stored
149 -- type Elmt_Ptr is private;
150 -- -- The type used to reference an element (will usually be an
151 -- -- access type, but could be some other form of type such as
152 -- -- an integer type).
154 -- Null_Ptr : Elmt_Ptr;
155 -- -- The null value of the Elmt_Ptr type.
157 -- with procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr);
158 -- with function Next (E : Elmt_Ptr) return Elmt_Ptr;
159 -- -- The type must provide an internal link for the sake of the
160 -- -- staticness of the HTable.
162 -- type Key is limited private;
163 -- with function Get_Key (E : Elmt_Ptr) return Key;
164 -- with function Hash (F : Key) return Header_Num;
165 -- with function Equal (F1, F2 : Key) return Boolean;
167 -- package Static_HTable is
170 -- -- Resets the hash table by setting all its elements to Null_Ptr.
171 -- -- The effect is to clear the hash table so that it can be reused.
172 -- -- For the most common case where Elmt_Ptr is an access type, and
173 -- -- Null_Ptr is null, this is only needed if the same table is
174 -- -- reused in a new context. If Elmt_Ptr is other than an access
175 -- -- type, or Null_Ptr is other than null, then Reset must be called
176 -- -- before the first use of the hash table.
178 -- procedure Set (E : Elmt_Ptr);
179 -- -- Insert the element pointer in the HTable
181 -- function Get (K : Key) return Elmt_Ptr;
182 -- -- Returns the latest inserted element pointer with the given Key
183 -- -- or null if none.
185 -- procedure Remove (K : Key);
186 -- -- Removes the latest inserted element pointer associated with the
187 -- -- given key if any, does nothing if none.
189 -- function Get_First return Elmt_Ptr;
190 -- -- Returns Null_Ptr if the HTable is empty, otherwise returns one
191 -- -- non specified element. There is no guarantee that 2 calls to
192 -- -- this function will return the same element.
194 -- function Get_Next return Elmt_Ptr;
195 -- -- Returns a non-specified element that has not been returned by
196 -- -- the same function since the last call to Get_First or Null_Ptr
197 -- -- if there is no such element or Get_First has never been called.
198 -- -- If there is no call to 'Set' in between Get_Next calls, all
199 -- -- the elements of the HTable will be traversed.
201 -- end Static_HTable;
207 -- A generic hashing function working on String keys
209 generic function Hash
renames System
.HTable
.Hash
;
212 -- type Header_Num is range <>;
213 -- function Hash (Key : String) return Header_Num;