1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
|
------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- S Y S T E M . H T A B L E --
-- --
-- S p e c --
-- --
-- Copyright (C) 1995-2008, 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 2, 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. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- 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.
pragma Warnings (Off);
pragma Compiler_Unit;
pragma Warnings (On);
package System.HTable is
pragma Preelaborate;
-------------------
-- 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
procedure Set (K : Key; E : Element);
-- Associates an element with a given key. Overrides any previously
-- associated element.
procedure Reset;
-- Removes and frees all elements in the table
function Get (K : Key) return Element;
-- Returns the Element associated with a key or No_Element if the
-- given key has not associated element
procedure Remove (K : Key);
-- Removes the latest inserted element pointer associated with the
-- given key if any, does nothing if none.
function Get_First return Element;
-- Returns No_Element 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 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.
end Simple_HTable;
-------------------
-- 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. This is historically part of the
-- interface, even though it is not used at all in the operations of
-- the package.
pragma Warnings (Off, Element);
-- We have to kill warnings here, because Element is and always
-- has been unreferenced, but we cannot remove it at this stage,
-- since this unit is in wide use, and it certainly seems harmless.
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
procedure Reset;
-- Resets the hash table by setting all its elements to Null_Ptr. The
-- effect is to clear the hash table so that it can be reused. 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 (E : Elmt_Ptr);
-- Insert the element pointer in the HTable
function Get (K : Key) return Elmt_Ptr;
-- Returns the latest inserted element pointer with the given Key
-- or null if none.
procedure Remove (K : Key);
-- Removes the latest inserted element pointer associated with the
-- given key if any, does nothing if none.
function Get_First 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 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.
end Static_HTable;
----------
-- Hash --
----------
-- A generic hashing function working on String keys
generic
type Header_Num is range <>;
function Hash (Key : String) return Header_Num;
end System.HTable;
|
