gomp-20050608-branch/libstdc++-v3/testsuite/ext/pb_assoc/example/hash_resize.cc

   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  */
  59 struct 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
  70 int
  71 main()
  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