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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006 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 2, 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 COPYING.  If not, write to
  18 // the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
  19 // MA 02111-1307, USA.
  20
  21 // As a special exception, you may use this file as part of a free
  22 // software library without restriction.  Specifically, if other files
  23 // instantiate templates or use macros or inline functions from this
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  25 // produce an executable, this file does not by itself cause the
  26 // resulting executable to be covered by the GNU General Public
  27 // License.  This exception does not however invalidate any other
  28 // reasons why the executable file might be covered by the GNU General
  29 // Public License.
  30
  31 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  32
  33 // Permission to use, copy, modify, sell, and distribute this software
  34 // is hereby granted without fee, provided that the above copyright
  35 // notice appears in all copies, and that both that copyright notice
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  37 // of the above authors, nor IBM Haifa Research Laboratories, make any
  38 // representation about the suitability of this software for any
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  40 // warranty.
  41
  42 /**
  43  * @file hash_illegal_resize_example.cpp
  44  * An example of illegally
  45  *    externally resizing a hash-based container object.
  46  */
  47
  48 /**
  49  * This example shows the case where a hash-based container object is
  50  * resized to a value which it cannot accomodate at runtime. Illegal
  51  * runtime resizes cause an exception.
  52  */
  53
  54 #include <ext/pb_ds/assoc_container.hpp>
  55 #include <ext/pb_ds/hash_policy.hpp>
  56 #include <ext/pb_ds/exception.hpp>
  57 #include <cassert>
  58
  59 using namespace std;
  60 using namespace __gnu_pbds;
  61
  62 // A simple hash functor.
  63 // hash could serve instead of this functor, but it is not yet
  64 // standard everywhere.
  65 struct int_hash : public unary_function<int, size_t>
  66 {
  67   inline size_t
  68   operator()(const int& r_i) const
  69   { return r_i; }
  70 };
  71
  72
  73 int main()
  74 {
  75   // A probing hash table mapping ints to chars.
  76   typedef
  77     gp_hash_table<
  78     int,
  79     int,
  80     int_hash,
  81     equal_to<
  82     int>,
  83     // Combining function.
  84     direct_mod_range_hashing<>,
  85     // Probe function.
  86     quadratic_probe_fn<>,
  87     // Resize policy.
  88     hash_standard_resize_policy<
  89     hash_prime_size_policy,
  90     hash_load_check_resize_trigger<>,
  91     /* Allow external access to size.
  92      *     Without setting this to true, external resizing
  93      *     is not possible.
  94      */
  95     true> >
  96     map_t;
  97
  98   map_t g;
  99
 100   // Insert some elements.
 101   int i;
 102
 103   for (i = 0; i < 1000; ++i)
 104     g[i] = 2*  i;
 105
 106   // Check all ok.
 107   assert(g.size() == 1000);
 108   for (i = 0; i < 1000; ++i)
 109     assert(g.find(i) != g.end()&&  g.find(i)->second == 2*  i);
 110
 111   // Now attempt to resize the table to 200 (impossible).
 112   bool ex_thrown = false;
 113
 114   try
 115     {
 116       g.resize(200);
 117     }
 118   catch(__gnu_pbds::resize_error& )
 119     {
 120       ex_thrown = true;
 121     }
 122
 123   // Assert an exception was thrown. A probing table cannot contain
 124   // 1000 entries in less than 1000 places.
 125   assert(ex_thrown);
 126
 127   // Irrespective of the fact that the resize was not successful, the
 128   // container object should still be in a valid state; the following
 129   // checks this.
 130   // Check all ok.
 131   assert(g.size() == 1000);
 132   for (i = 0; i < 1000; ++i)
 133     assert(g.find(i) != g.end()&&  g.find(i)->second == 2*  i);
 134
 135   return 0;
 136 }
 137