store_hash.cc

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// -*- C++ -*-

// Copyright (C) 2005 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.

// Permission to use, copy, modify, sell, and distribute this software
// is hereby granted without fee, provided that the above copyright
// notice appears in all copies, and that both that copyright notice and
// this permission notice appear in supporting documentation. None of
// the above authors, nor IBM Haifa Research Laboratories, make any
// representation about the suitability of this software for any
// purpose. It is provided "as is" without express or implied warranty.

/**
 * @file hash_mod_example.cpp
 * An example showing how to use cc_ht_map with alternative policies.
 */

// For cc_hash_assoc_cntnr.
#include <ext/pb_assoc/assoc_cntnr.hpp>
// For direct_mask_range_hashing and hash_standard_resize_policy.
#include <ext/pb_assoc/hash_policy.hpp>
// For unary_function, binary_function.
#include <functional>
// For string.
#include <string>

/*
 * A string hash functor
 */
struct string_hash : public std::unary_function<
  std::string,
		     size_t>
{
  inline size_t
  operator()(std::string str) const
  {
    std::string::const_iterator b = str.begin();

    std::string::const_iterator e = str.end();

    size_t hash = 0;

    while (b != e)
      {
	hash *= 5;

	hash += static_cast<size_t>(*b);

	++b;
      }

    return (hash);
  }
};

int
main()
{
  /*
   * A collision-chaining hash table mapping strings to ints.
   */
  typedef
    pb_assoc::cc_hash_assoc_cntnr<
    std::string,
    int,
    // Hash function.
    string_hash,
    // Equivalence function.
    std::equal_to<
    std::string>,
    // Range hashing function.
    pb_assoc::direct_mask_range_hashing<>,
    // Resize policy.
    pb_assoc::hash_standard_resize_policy<>,
    // Store the hash value with each entry.
    true>
    map_t;

  map_t h;

  h["Hello, "] = 0;
  h["world"] = 1;
}