1 ------------------------------------------------------------------------------
3 -- GNAT RUNTIME COMPONENTS --
5 -- G N A T . H T A B L E --
10 -- Copyright (C) 1995-2001 Ada Core Technologies, Inc. --
12 -- GNAT is free software; you can redistribute it and/or modify it under --
13 -- terms of the GNU General Public License as published by the Free Soft- --
14 -- ware Foundation; either version 2, or (at your option) any later ver- --
15 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
16 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
17 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
18 -- for more details. You should have received a copy of the GNU General --
19 -- Public License distributed with GNAT; see file COPYING. If not, write --
20 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
21 -- MA 02111-1307, USA. --
23 -- As a special exception, if other files instantiate generics from this --
24 -- unit, or you link this unit with other files to produce an executable, --
25 -- this unit does not by itself cause the resulting executable to be --
26 -- covered by the GNU General Public License. This exception does not --
27 -- however invalidate any other reasons why the executable file might be --
28 -- covered by the GNU Public License. --
30 -- GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). --
32 ------------------------------------------------------------------------------
34 -- Hash table searching routines
36 -- This package contains two separate packages. The Simple_Htable package
37 -- provides a very simple abstraction that asosicates one element to one
38 -- key values and takes care of all allocation automatically using the heap.
39 -- The Static_Htable package provides a more complex interface that allows
40 -- complete control over allocation.
42 package GNAT
.HTable
is
43 pragma Preelaborate
(HTable
);
49 -- A simple hash table abstraction, easy to instantiate, easy to use.
50 -- The table associates one element to one key with the procedure Set.
51 -- Get retrieves the Element stored for a given Key. The efficiency of
52 -- retrieval is function of the size of the Table parameterized by
53 -- Header_Num and the hashing function Hash.
56 type Header_Num
is range <>;
57 -- An integer type indicating the number and range of hash headers.
59 type Element
is private;
60 -- The type of element to be stored
63 -- The object that is returned by Get when no element has been set for
67 with function Hash
(F
: Key
) return Header_Num
;
68 with function Equal
(F1
, F2
: Key
) return Boolean;
70 package Simple_HTable
is
72 procedure Set
(K
: Key
; E
: Element
);
73 -- Associates an element with a given key. Overrides any previously
74 -- associated element.
77 -- Removes and frees all elements in the table
79 function Get
(K
: Key
) return Element
;
80 -- Returns the Element associated with a key or No_Element if the
81 -- given key has not associated element
83 procedure Remove
(K
: Key
);
84 -- Removes the latest inserted element pointer associated with the
85 -- given key if any, does nothing if none.
87 function Get_First
return Element
;
88 -- Returns No_Element if the Htable is empty, otherwise returns one
89 -- non specified element. There is no guarantee that 2 calls to this
90 -- function will return the same element.
92 function Get_Next
return Element
;
93 -- Returns a non-specified element that has not been returned by the
94 -- same function since the last call to Get_First or No_Element if
95 -- there is no such element. If there is no call to 'Set' in between
96 -- Get_Next calls, all the elements of the Htable will be traversed.
103 -- A low-level Hash-Table abstraction, not as easy to instantiate as
104 -- Simple_HTable but designed to allow complete control over the
105 -- allocation of necessary data structures. Particularly useful when
106 -- dynamic allocation is not desired. The model is that each Element
107 -- contains its own Key that can be retrieved by Get_Key. Furthermore,
108 -- Element provides a link that can be used by the HTable for linking
109 -- elements with same hash codes:
113 -- +-------------------+
115 -- +-------------------+
117 -- +-------------------+
119 -- +-------------------+
122 type Header_Num
is range <>;
123 -- An integer type indicating the number and range of hash headers.
125 type Element
(<>) is limited private;
126 -- The type of element to be stored
128 type Elmt_Ptr
is private;
129 -- The type used to reference an element (will usually be an access
130 -- type, but could be some other form of type such as an integer type).
133 -- The null value of the Elmt_Ptr type.
135 with procedure Set_Next
(E
: Elmt_Ptr
; Next
: Elmt_Ptr
);
136 with function Next
(E
: Elmt_Ptr
) return Elmt_Ptr
;
137 -- The type must provide an internal link for the sake of the
138 -- staticness of the HTable.
140 type Key
is limited private;
141 with function Get_Key
(E
: Elmt_Ptr
) return Key
;
142 with function Hash
(F
: Key
) return Header_Num
;
143 with function Equal
(F1
, F2
: Key
) return Boolean;
145 package Static_HTable
is
148 -- Resets the hash table by setting all its elements to Null_Ptr. The
149 -- effect is to clear the hash table so that it can be reused. For the
150 -- most common case where Elmt_Ptr is an access type, and Null_Ptr is
151 -- null, this is only needed if the same table is reused in a new
152 -- context. If Elmt_Ptr is other than an access type, or Null_Ptr is
153 -- other than null, then Reset must be called before the first use
154 -- of the hash table.
156 procedure Set
(E
: Elmt_Ptr
);
157 -- Insert the element pointer in the HTable
159 function Get
(K
: Key
) return Elmt_Ptr
;
160 -- Returns the latest inserted element pointer with the given Key
163 procedure Remove
(K
: Key
);
164 -- Removes the latest inserted element pointer associated with the
165 -- given key if any, does nothing if none.
167 function Get_First
return Elmt_Ptr
;
168 -- Returns Null_Ptr if the Htable is empty, otherwise returns one
169 -- non specified element. There is no guarantee that 2 calls to this
170 -- function will return the same element.
172 function Get_Next
return Elmt_Ptr
;
173 -- Returns a non-specified element that has not been returned by the
174 -- same function since the last call to Get_First or Null_Ptr if
175 -- there is no such element or Get_First has bever been called. If
176 -- there is no call to 'Set' in between Get_Next calls, all the
177 -- elements of the Htable will be traversed.
185 -- A generic hashing function working on String keys
188 type Header_Num
is range <>;
189 function Hash
(Key
: String) return Header_Num
;