gdbsupport/range-chain.h

   1 /* A range adapter that wraps multiple ranges
   2    Copyright (C) 2022-2024 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 GDBSUPPORT_RANGE_CHAIN_H
  20 #define GDBSUPPORT_RANGE_CHAIN_H
  21
  22 /* A range adapter that presents a number of ranges as if it were a
  23    single range.  That is, iterating over a range_chain will iterate
  24    over each sub-range in order.  */
  25 template<typename Range>
  26 struct range_chain
  27 {
  28   /* The type of the iterator that is created by this range.  */
  29   class iterator
  30   {
  31   public:
  32
  33     iterator (const std::vector<Range> &ranges, size_t idx)
  34       : m_index (idx),
  35         m_ranges (ranges)
  36     {
  37       skip_empty ();
  38     }
  39
  40     bool operator== (const iterator &other) const
  41     {
  42       if (m_index != other.m_index || &m_ranges != &other.m_ranges)
  43         return false;
  44       if (m_current.has_value () != other.m_current.has_value ())
  45         return false;
  46       if (m_current.has_value ())
  47         return *m_current == *other.m_current;
  48       return true;
  49     }
  50
  51     bool operator!= (const iterator &other) const
  52     {
  53       return !(*this == other);
  54     }
  55
  56     iterator &operator++ ()
  57     {
  58       ++*m_current;
  59       if (*m_current == m_ranges[m_index].end ())
  60         {
  61           ++m_index;
  62           skip_empty ();
  63         }
  64       return *this;
  65     }
  66
  67     typename Range::iterator::value_type operator* () const
  68     {
  69       return **m_current;
  70     }
  71
  72   private:
  73     /* Skip empty sub-ranges.  If this finds a valid sub-range,
  74        m_current is updated to point to its start; otherwise,
  75        m_current is reset.  */
  76     void skip_empty ()
  77     {
  78       for (; m_index < m_ranges.size (); ++m_index)
  79         {
  80           m_current = m_ranges[m_index].begin ();
  81           if (*m_current != m_ranges[m_index].end ())
  82             return;
  83         }
  84       m_current.reset ();
  85     }
  86
  87     /* Index into the vector indicating where the current iterator
  88        comes from.  */
  89     size_t m_index;
  90     /* The current iterator into one of the vector ranges.  If no
  91        value then this (outer) iterator is at the end of the overall
  92        range.  */
  93     std::optional<typename Range::iterator> m_current;
  94     /* Vector of ranges.  */
  95     const std::vector<Range> &m_ranges;
  96   };
  97
  98   /* Create a new range_chain.  */
  99   template<typename T>
 100   range_chain (T &&ranges)
 101     : m_ranges (std::forward<T> (ranges))
 102   {
 103   }
 104
 105   iterator begin () const
 106   {
 107     return iterator (m_ranges, 0);
 108   }
 109
 110   iterator end () const
 111   {
 112     return iterator (m_ranges, m_ranges.size ());
 113   }
 114
 115 private:
 116
 117   /* The sub-ranges.  */
 118   std::vector<Range> m_ranges;
 119 };
 120
 121 #endif /* GDBSUPPORT_RANGE_CHAIN_H */