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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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// 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_shift_mask_example.cpp
* An example showing how to write a range-hasing functor.
*/
// For cc_hash_assoc_cntnr.
#include <ext/pb_assoc/assoc_cntnr.hpp>
// For hash-related policies.
#include <ext/pb_assoc/hash_policy.hpp>
// For unary_function and binary_function
#include <functional>
/*
* A simple hash functor.
* std::hash could serve instead of this functor,
* but it is not yet standard everywhere.
*/
struct simple_int_hash : public std::unary_function<
int,
size_t>
{
inline size_t
operator()(int i) const
{
return (i);
}
};
// A range-hashing function which shifts 2 bits right and then masks.
class shift_two_mask_range_hashing : private pb_assoc::direct_mask_range_hashing<>
{
public:
typedef size_t size_type;
public:
/*
* Swaps with a different instant.
*/
void
swap(shift_two_mask_range_hashing& r_other)
{
pb_assoc::direct_mask_range_hashing<>::swap(r_other);
}
/*
* Called by the container when internally resized.
*/
void
notify_resized(size_type size)
{
pb_assoc::direct_mask_range_hashing<>::notify_resized(size);
}
/*
* Given a hash value, returns a number in the range of the
* internal size of the container.
*/
inline size_type
operator()(size_type hash) const
{
return (pb_assoc::direct_mask_range_hashing<>::operator()(
hash >> 2));
}
};
int
main()
{
/*
* A collision-chaining hash table mapping ints to chars.
*/
typedef
pb_assoc::cc_hash_assoc_cntnr<
int,
char,
// Hash function.
simple_int_hash,
std::equal_to<int>,
// Range hashing function.
shift_two_mask_range_hashing>
map_t;
map_t h;
// Use normally.
h[16] = 'a';
h[256] = 'e';
h[4] = 'z';
}
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