ceph/src/boost/libs/stl_interfaces/example/repeated_chars_iterator.cpp

   1 // Copyright (C) 2019 T. Zachary Laine
   2 //
   3 // Distributed under the Boost Software License, Version 1.0. (See
   4 // accompanying file LICENSE_1_0.txt or copy at
   5 // http://www.boost.org/LICENSE_1_0.txt)
   6 #include <boost/stl_interfaces/iterator_interface.hpp>
   7
   8 #include <string>
   9
  10 #include <cassert>
  11
  12
  13 //[ repeated_chars_iterator
  14 struct repeated_chars_iterator : boost::stl_interfaces::iterator_interface<
  15                                      repeated_chars_iterator,
  16                                      std::random_access_iterator_tag,
  17                                      char,
  18                                      char>
  19 {
  20     constexpr repeated_chars_iterator() noexcept :
  21         first_(nullptr),
  22         size_(0),
  23         n_(0)
  24     {}
  25     constexpr repeated_chars_iterator(
  26         char const * first, difference_type size, difference_type n) noexcept :
  27         first_(first),
  28         size_(size),
  29         n_(n)
  30     {}
  31
  32     constexpr char operator*() const noexcept { return first_[n_ % size_]; }
  33     constexpr repeated_chars_iterator & operator+=(std::ptrdiff_t i) noexcept
  34     {
  35         n_ += i;
  36         return *this;
  37     }
  38     constexpr auto operator-(repeated_chars_iterator other) const noexcept
  39     {
  40         return n_ - other.n_;
  41     }
  42
  43 private:
  44     char const * first_;
  45     difference_type size_;
  46     difference_type n_;
  47 };
  48 //]
  49
  50
  51 int main()
  52 {
  53     //[ repeated_chars_iterator_usage
  54     repeated_chars_iterator first("foo", 3, 0); // 3 is the length of "foo", 0 is this iterator's position.
  55     repeated_chars_iterator last("foo", 3, 7);  // Same as above, but now the iterator's position is 7.
  56     std::string result;
  57     std::copy(first, last, std::back_inserter(result));
  58     assert(result == "foofoof");
  59     //]
  60 }