gdbsupport/filtered-iterator.h

   1 /* A forward filtered iterator for GDB, the GNU debugger.
   2    Copyright (C) 2018-2020 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef COMMON_FILTERED_ITERATOR_H
  20 #define COMMON_FILTERED_ITERATOR_H
  21
  22 /* A filtered iterator.  This wraps BaseIterator and automatically
  23    skips elements that FilterFunc filters out.  Requires that
  24    default-constructing a BaseIterator creates a valid one-past-end
  25    iterator.  */
  26
  27 template<typename BaseIterator, typename FilterFunc>
  28 class filtered_iterator
  29 {
  30 public:
  31   typedef filtered_iterator self_type;
  32   typedef typename BaseIterator::value_type value_type;
  33   typedef typename BaseIterator::reference reference;
  34   typedef typename BaseIterator::pointer pointer;
  35   typedef typename BaseIterator::iterator_category iterator_category;
  36   typedef typename BaseIterator::difference_type difference_type;
  37
  38   /* Construct by forwarding all arguments to the underlying
  39      iterator.  */
  40   template<typename... Args>
  41   explicit filtered_iterator (Args &&...args)
  42     : m_it (std::forward<Args> (args)...)
  43   { skip_filtered (); }
  44
  45   /* Create a one-past-end iterator.  */
  46   filtered_iterator () = default;
  47
  48   /* Need these as the variadic constructor would be a better match
  49      otherwise.  */
  50   filtered_iterator (filtered_iterator &) = default;
  51   filtered_iterator (const filtered_iterator &) = default;
  52   filtered_iterator (filtered_iterator &&) = default;
  53   filtered_iterator (const filtered_iterator &&other)
  54     : filtered_iterator (static_cast<const filtered_iterator &> (other))
  55   {}
  56
  57   value_type operator* () const { return *m_it; }
  58
  59   self_type &operator++ ()
  60   {
  61     ++m_it;
  62     skip_filtered ();
  63     return *this;
  64   }
  65
  66   bool operator== (const self_type &other) const
  67   { return m_it == other.m_it; }
  68
  69   bool operator!= (const self_type &other) const
  70   { return m_it != other.m_it; }
  71
  72 private:
  73
  74   void skip_filtered ()
  75   {
  76     for (; m_it != m_end; ++m_it)
  77       if (m_filter (*m_it))
  78         break;
  79   }
  80
  81 private:
  82   FilterFunc m_filter {};
  83   BaseIterator m_it {};
  84   BaseIterator m_end {};
  85 };
  86
  87 #endif /* COMMON_FILTERED_ITERATOR_H */