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1 | // -*- C++ -*- |
2 | ||
748086b7 | 3 | // Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc. |
4569a895 AT |
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 terms | |
7 | // of the GNU General Public License as published by the Free Software | |
748086b7 | 8 | // Foundation; either version 3, or (at your option) any later |
4569a895 AT |
9 | // version. |
10 | ||
11 | // This library is distributed in the hope that it will be useful, but | |
12 | // WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | // General Public License for more details. | |
15 | ||
16 | // You should have received a copy of the GNU General Public License | |
748086b7 JJ |
17 | // along with this library; see the file COPYING3. If not see |
18 | // <http://www.gnu.org/licenses/>. | |
19 | ||
4569a895 AT |
20 | |
21 | // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL. | |
22 | ||
23 | // Permission to use, copy, modify, sell, and distribute this software | |
24 | // is hereby granted without fee, provided that the above copyright | |
25 | // notice appears in all copies, and that both that copyright notice | |
26 | // and this permission notice appear in supporting documentation. None | |
27 | // of the above authors, nor IBM Haifa Research Laboratories, make any | |
28 | // representation about the suitability of this software for any | |
29 | // purpose. It is provided "as is" without express or implied | |
30 | // warranty. | |
31 | ||
32 | /** | |
33 | * @file hash_resize_example.cpp | |
34 | * An example of externally resizing a map. | |
35 | */ | |
36 | ||
37 | /** | |
38 | * This example shows how to externally manipulate the size of a hash-based | |
39 | * container object throught its resize-policy object. | |
40 | **/ | |
41 | ||
42 | #include <functional> | |
43 | #include <cassert> | |
44 | #include <ext/pb_ds/assoc_container.hpp> | |
45 | #include <ext/pb_ds/hash_policy.hpp> | |
46 | ||
47 | using namespace std; | |
5e11f978 | 48 | using namespace __gnu_pbds; |
4569a895 AT |
49 | |
50 | // A simple hash functor. | |
51 | // hash could serve instead of this functor, but it is not yet | |
52 | // standard everywhere. | |
53 | struct int_hash : public unary_function<int, size_t> | |
54 | { | |
55 | inline size_t | |
56 | operator()(const int& r_i) const | |
57 | { return r_i; } | |
58 | }; | |
59 | ||
60 | int main() | |
61 | { | |
62 | // A probing hash table mapping ints to chars. | |
63 | typedef | |
64 | gp_hash_table< | |
65 | int, | |
66 | char, | |
67 | int_hash, | |
68 | equal_to< | |
69 | int>, | |
70 | // Combining function. | |
71 | direct_mask_range_hashing<>, | |
72 | // Probe function. | |
73 | linear_probe_fn<>, | |
74 | // Resize policy. | |
75 | hash_standard_resize_policy< | |
76 | hash_exponential_size_policy<>, | |
77 | hash_load_check_resize_trigger<>, | |
78 | /* Allow external access to size. | |
79 | * Without setting this to true, external resizing | |
80 | * is not possible. | |
81 | */ | |
82 | true> > | |
83 | map_t; | |
84 | ||
85 | map_t g; | |
86 | ||
87 | // Check the actual size of the container object. In this case, this | |
88 | // should be the initial size given by the size policy object. | |
89 | assert(g.get_actual_size() == 8); | |
90 | ||
91 | // Insert some elements. | |
92 | g[1] = 'a'; | |
93 | g[2] = 'b'; | |
94 | g[3] = 'c'; | |
95 | ||
96 | // Now resize the table upward. | |
97 | g.resize(200); | |
98 | ||
99 | // Check the actual size of the container object. | |
100 | // For the policy used in this example, the nearest larger size than | |
101 | // 200 is 256. | |
102 | assert(g.get_actual_size() == 256); | |
103 | ||
104 | g[67] = 'g'; | |
105 | g[22] = 'f'; | |
106 | ||
107 | // Regardless of the internal size, the logical size should be 5. | |
108 | assert(g.size() == 5); | |
109 | ||
110 | // Now resize the table downward. | |
111 | g.resize(106); | |
112 | ||
113 | // Check the actual size of the container object. | |
114 | // For the policy used in this example, the nearest larger size than | |
115 | // 106 is 128. | |
116 | assert(g.get_actual_size() == 128); | |
117 | ||
118 | g[37] = 'f'; | |
119 | ||
120 | // Regardless of the internal size, the logical size should be 5. | |
121 | assert(g.size() == 6); | |
122 | ||
123 | return 0; | |
124 | } | |
125 |