1// -*- C++ -*-
2
3// Copyright (C) 2005 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 2, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// You should have received a copy of the GNU General Public License along
17// with this library; see the file COPYING.  If not, write to the Free
18// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
19// USA.
20
21// As a special exception, you may use this file as part of a free software
22// library without restriction.  Specifically, if other files instantiate
23// templates or use macros or inline functions from this file, or you compile
24// this file and link it with other files to produce an executable, this
25// file does not by itself cause the resulting executable to be covered by
26// the GNU General Public License.  This exception does not however
27// invalidate any other reasons why the executable file might be covered by
28// the GNU General Public License.
29
30// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
31
32// Permission to use, copy, modify, sell, and distribute this software
33// is hereby granted without fee, provided that the above copyright
34// notice appears in all copies, and that both that copyright notice and
35// this permission notice appear in supporting documentation. None of
36// the above authors, nor IBM Haifa Research Laboratories, make any
37// representation about the suitability of this software for any
38// purpose. It is provided "as is" without express or implied warranty.
39
40/**
41 * @file hash_resize_example.cpp
42 * An example of externally resizing a map.
43 */
44
45// For gp_hash_assoc_cntnr.
46#include <ext/pb_assoc/assoc_cntnr.hpp>
47// For hash-related policies.
48#include <ext/pb_assoc/hash_policy.hpp>
49// For unary_function.
50#include <functional>
51// For assert
52#include <cassert>
53
54/*
55 * A simple hash functor.
56 *	std::hash could serve instead of this functor,
57 *	but it is not yet standard everywhere.
58 */
59struct int_hash : public std::unary_function<
60  int,
61	     size_t>
62{
63  inline size_t
64  operator()(const int& r_i) const
65  {
66    return (r_i);
67  }
68};
69
70int
71main()
72{
73  /*
74   * A probing hash table mapping ints to chars.
75   */
76  typedef
77    pb_assoc::gp_hash_assoc_cntnr<
78    int,
79    char,
80    int_hash,
81    std::equal_to<
82    int>,
83    // Combining function.
84    pb_assoc::direct_mask_range_hashing<>,
85    // Probe function.
86    pb_assoc::linear_probe_fn<
87    int>,
88    // Resize policy.
89    pb_assoc::hash_standard_resize_policy<
90    pb_assoc::hash_exponential_size_policy<>,
91    pb_assoc::hash_load_check_resize_trigger<>,
92    /* Allow external access to size.
93     *	Without setting this to true, external resizing
94     *	is not possible.
95     */
96    true> >
97    map_t;
98
99  map_t g;
100
101  /*
102   * Check the actual size of the container object. In this case,
103   *	this should be the initial size given by the size policy object.
104   **/
105  assert(g.get_actual_size() == 8);
106
107  // Insert some elements.
108
109  g[1] = 'a';
110  g[2] = 'b';
111  g[3] = 'c';
112
113  // Now resize the table upward.
114
115  g.resize(200);
116
117  /*
118   * Check the actual size of the container object.
119   *	For the policy used in this example, the
120   *	nearest larger size than 200 is 256.
121   **/
122  assert(g.get_actual_size() == 256);
123
124  g[67] = 'g';
125  g[22] = 'f';
126
127  // Regardless of the internal size, the logical size should be 5.
128  assert(g.size() == 5);
129
130  // Now resize the table downward.
131
132  g.resize(106);
133
134  /*
135   * Check the actual size of the container object.
136   *	For the policy used in this example, the
137   *	nearest larger size than 106 is 128.
138   **/
139  assert(g.get_actual_size() == 128);
140
141  g[37] = 'f';
142
143  // Regardless of the internal size, the logical size should be 5.
144  assert(g.size() == 6);
145}
146
147