libstdc++-v3/testsuite/ext/pb_ds/example/hash_illegal_resize.cc

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006, 2009 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 terms
   7 // of the GNU General Public License as published by the Free Software
   8 // Foundation; either version 3, or (at your option) any later
   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
  17 // along with this library; see the file COPYING3.  If not see
  18 // <http://www.gnu.org/licenses/>.
  19
  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_illegal_resize_example.cpp
  34  * An example of illegally
  35  *    externally resizing a hash-based container object.
  36  */
  37
  38 /**
  39  * This example shows the case where a hash-based container object is
  40  * resized to a value which it cannot accomodate at runtime. Illegal
  41  * runtime resizes cause an exception.
  42  */
  43
  44 #include <ext/pb_ds/assoc_container.hpp>
  45 #include <ext/pb_ds/hash_policy.hpp>
  46 #include <ext/pb_ds/exception.hpp>
  47 #include <cassert>
  48
  49 using namespace std;
  50 using namespace __gnu_pbds;
  51
  52 // A simple hash functor.
  53 // hash could serve instead of this functor, but it is not yet
  54 // standard everywhere.
  55 struct int_hash : public unary_function<int, size_t>
  56 {
  57   inline size_t
  58   operator()(const int& r_i) const
  59   { return r_i; }
  60 };
  61
  62
  63 int main()
  64 {
  65   // A probing hash table mapping ints to chars.
  66   typedef
  67     gp_hash_table<
  68     int,
  69     int,
  70     int_hash,
  71     equal_to<
  72     int>,
  73     // Combining function.
  74     direct_mod_range_hashing<>,
  75     // Probe function.
  76     quadratic_probe_fn<>,
  77     // Resize policy.
  78     hash_standard_resize_policy<
  79     hash_prime_size_policy,
  80     hash_load_check_resize_trigger<>,
  81     /* Allow external access to size.
  82      *     Without setting this to true, external resizing
  83      *     is not possible.
  84      */
  85     true> >
  86     map_t;
  87
  88   map_t g;
  89
  90   // Insert some elements.
  91   int i;
  92
  93   for (i = 0; i < 1000; ++i)
  94     g[i] = 2*  i;
  95
  96   // Check all ok.
  97   assert(g.size() == 1000);
  98   for (i = 0; i < 1000; ++i)
  99     assert(g.find(i) != g.end()&&  g.find(i)->second == 2*  i);
 100
 101   // Now attempt to resize the table to 200 (impossible).
 102   bool ex_thrown = false;
 103
 104   try
 105     {
 106       g.resize(200);
 107     }
 108   catch(__gnu_pbds::resize_error& )
 109     {
 110       ex_thrown = true;
 111     }
 112
 113   // Assert an exception was thrown. A probing table cannot contain
 114   // 1000 entries in less than 1000 places.
 115   assert(ex_thrown);
 116
 117   // Irrespective of the fact that the resize was not successful, the
 118   // container object should still be in a valid state; the following
 119   // checks this.
 120   // Check all ok.
 121   assert(g.size() == 1000);
 122   for (i = 0; i < 1000; ++i)
 123     assert(g.find(i) != g.end()&&  g.find(i)->second == 2*  i);
 124
 125   return 0;
 126 }
 127