gdbsupport/filtered-iterator.h

   1 /* A forward filtered iterator for GDB, the GNU debugger.
   2    Copyright (C) 2018-2024 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 #include <type_traits>
  23
  24 /* A filtered iterator.  This wraps BaseIterator and automatically
  25    skips elements that FilterFunc filters out.  Requires that
  26    default-constructing a BaseIterator creates a valid one-past-end
  27    iterator.  */
  28
  29 template<typename BaseIterator, typename FilterFunc>
  30 class filtered_iterator
  31 {
  32 public:
  33   typedef filtered_iterator self_type;
  34   typedef typename BaseIterator::value_type value_type;
  35   typedef typename BaseIterator::reference reference;
  36   typedef typename BaseIterator::pointer pointer;
  37   typedef typename BaseIterator::iterator_category iterator_category;
  38   typedef typename BaseIterator::difference_type difference_type;
  39
  40   /* Construct by forwarding all arguments to the underlying
  41      iterator.  */
  42   template<typename... Args>
  43   explicit filtered_iterator (Args &&...args)
  44     : m_it (std::forward<Args> (args)...)
  45   { skip_filtered (); }
  46
  47   /* Create a one-past-end iterator.  */
  48   filtered_iterator () = default;
  49
  50   /* Need these as the variadic constructor would be a better match
  51      otherwise.  */
  52   filtered_iterator (filtered_iterator &) = default;
  53   filtered_iterator (const filtered_iterator &) = default;
  54   filtered_iterator (filtered_iterator &&) = default;
  55   filtered_iterator (const filtered_iterator &&other)
  56     : filtered_iterator (static_cast<const filtered_iterator &> (other))
  57   {}
  58
  59   typename std::invoke_result<decltype(&BaseIterator::operator*),
  60                               BaseIterator>::type
  61     operator* () const
  62   { return *m_it; }
  63
  64   self_type &operator++ ()
  65   {
  66     ++m_it;
  67     skip_filtered ();
  68     return *this;
  69   }
  70
  71   bool operator== (const self_type &other) const
  72   { return m_it == other.m_it; }
  73
  74   bool operator!= (const self_type &other) const
  75   { return m_it != other.m_it; }
  76
  77 private:
  78
  79   void skip_filtered ()
  80   {
  81     for (; m_it != m_end; ++m_it)
  82       if (m_filter (*m_it))
  83         break;
  84   }
  85
  86 private:
  87   FilterFunc m_filter {};
  88   BaseIterator m_it {};
  89   BaseIterator m_end {};
  90 };
  91
  92 #endif /* COMMON_FILTERED_ITERATOR_H */