hash_eq_fn.hpp

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// -*- C++ -*-

// Copyright (C) 2005-2019 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
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// version.

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// General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
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// 3.1, as published by the Free Software Foundation.

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// 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
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/**
 * @file hash_eq_fn.hpp
 * Contains 2 eqivalence functions, one employing a hash value,
 * and one ignoring it.
 */

#ifndef PB_DS_HASH_EQ_FN_HPP
#define PB_DS_HASH_EQ_FN_HPP

#include <utility>
#include <debug/debug.h>

namespace __gnu_pbds
{
  namespace detail
  {
    /// Primary template.
    template<typename Key, typename Eq_Fn, typename _Alloc, bool Store_Hash>
      struct hash_eq_fn;

    /// Specialization 1 - The client requests that hash values not be stored.
    template<typename Key, typename Eq_Fn, typename _Alloc>
    struct hash_eq_fn<Key, Eq_Fn, _Alloc, false> : public Eq_Fn
    {
      typedef Eq_Fn                                        eq_fn_base;
      typedef typename _Alloc::template rebind<Key>::other key_allocator;
      typedef typename key_allocator::const_reference      key_const_reference;

      hash_eq_fn() { }

      hash_eq_fn(const Eq_Fn& r_eq_fn) : Eq_Fn(r_eq_fn) { }

      bool
      operator()(key_const_reference r_lhs_key, 
                 key_const_reference r_rhs_key) const
      { return eq_fn_base::operator()(r_lhs_key, r_rhs_key); }

      void
      swap(const hash_eq_fn& other)
      { std::swap((Eq_Fn&)(*this), (Eq_Fn&)other); }
    };


    /// Specialization 2 - The client requests that hash values be stored.
    template<typename Key, class Eq_Fn, class _Alloc>
    struct hash_eq_fn<Key, Eq_Fn, _Alloc, true> : public Eq_Fn
    {
      typedef typename _Alloc::size_type                   size_type;
      typedef Eq_Fn                                        eq_fn_base;
      typedef typename _Alloc::template rebind<Key>::other key_allocator;
      typedef typename key_allocator::const_reference      key_const_reference;

      hash_eq_fn() { }

      hash_eq_fn(const Eq_Fn& r_eq_fn) : Eq_Fn(r_eq_fn) { }

      bool
      operator()(key_const_reference r_lhs_key, size_type lhs_hash, 
                 key_const_reference r_rhs_key, size_type rhs_hash) const
      {
        _GLIBCXX_DEBUG_ASSERT(!eq_fn_base::operator()(r_lhs_key, r_rhs_key) 
                              || lhs_hash == rhs_hash);

        return (lhs_hash == rhs_hash && 
                eq_fn_base::operator()(r_lhs_key, r_rhs_key));
      }

      void
      swap(const hash_eq_fn& other)
      { std::swap((Eq_Fn&)(*this), (Eq_Fn&)(other)); }
    };
  } // namespace detail
} // namespace __gnu_pbds

#endif