Added thirdparty: boost library

thirdparty/include/boost/histogram/detail/iterator_adaptor.hpp

@@ -0,0 +1,175 @@
+// Copyright 2019 Hans Dembinski
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// Uses code segments from boost/iterator/iterator_adaptor.hpp
+// and boost/iterator/iterator_fascade.hpp
+
+#ifndef BOOST_HISTOGRAM_DETAIL_ITERATOR_ADAPTOR_HPP
+#define BOOST_HISTOGRAM_DETAIL_ITERATOR_ADAPTOR_HPP
+
+#include <cstddef>
+#include <iterator>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+namespace boost {
+namespace histogram {
+namespace detail {
+
+// operator->() needs special support for input iterators to strictly meet the
+// standard's requirements. If *i is not a reference type, we must still
+// produce an lvalue to which a pointer can be formed.  We do that by
+// returning a proxy object containing an instance of the reference object.
+template <class Reference>
+struct operator_arrow_dispatch_t {
+  struct pointer {
+    explicit pointer(Reference const& x) noexcept : m_ref(x) {}
+    Reference* operator->() noexcept { return std::addressof(m_ref); }
+    Reference m_ref;
+  };
+
+  using result_type = pointer;
+  static result_type apply(Reference const& x) noexcept { return pointer(x); }
+};
+
+// specialization for "real" references
+template <class T>
+struct operator_arrow_dispatch_t<T&> {
+  using result_type = T*;
+  static result_type apply(T& x) noexcept { return std::addressof(x); }
+};
+
+// it is ok if void_t is already defined in another header
+template <class...>
+using void_t = void;
+
+template <class T, class = void>
+struct get_difference_type_impl : std::make_signed<T> {};
+
+template <class T>
+struct get_difference_type_impl<
+    T, void_t<typename std::iterator_traits<T>::difference_type>> {
+  using type = typename std::iterator_traits<T>::difference_type;
+};
+
+template <class T>
+using get_difference_type = typename get_difference_type_impl<T>::type;
+
+// adaptor supports only random access Base
+// Base: underlying base type of the iterator; can be iterator, pointer, integer
+// Reference: type returned when pointer is dereferenced
+template <class Derived, class Base, class Reference = std::remove_pointer_t<Base>&,
+          class Value = std::decay_t<Reference>>
+class iterator_adaptor {
+  using operator_arrow_dispatch = operator_arrow_dispatch_t<Reference>;
+
+public:
+  using base_type = Base;
+
+  using reference = Reference;
+  using value_type = Value;
+  using pointer = typename operator_arrow_dispatch::result_type;
+  using difference_type = get_difference_type<base_type>;
+  using iterator_category = std::random_access_iterator_tag;
+
+  iterator_adaptor() = default;
+
+  explicit iterator_adaptor(base_type const& iter) : iter_(iter) {}
+
+  // you can override this in derived
+  decltype(auto) operator*() const noexcept { return *iter_; }
+
+  // you can override this in derived
+  Derived& operator+=(difference_type n) {
+    iter_ += n;
+    return this->derived();
+  }
+
+  // you should override this in derived if there is an override for operator+=
+  template <class... Ts>
+  difference_type operator-(const iterator_adaptor<Ts...>& x) const noexcept {
+    return iter_ - x.iter_;
+  }
+
+  // you can override this in derived
+  template <class... Ts>
+  bool operator==(const iterator_adaptor<Ts...>& x) const noexcept {
+    return iter_ == x.iter_;
+  }
+
+  reference operator[](difference_type n) const { return *(this->derived() + n); }
+  pointer operator->() const noexcept {
+    return operator_arrow_dispatch::apply(this->derived().operator*());
+  }
+
+  Derived& operator-=(difference_type n) { return this->derived().operator+=(-n); }
+  Derived& operator++() { return this->derived().operator+=(1); }
+  Derived& operator--() { return this->derived().operator+=(-1); }
+
+  Derived operator++(int) {
+    Derived tmp(this->derived());
+    operator++();
+    return tmp;
+  }
+
+  Derived operator--(int) {
+    Derived tmp(this->derived());
+    operator--();
+    return tmp;
+  }
+
+  Derived operator+(difference_type n) const { return Derived(this->derived()) += n; }
+  Derived operator-(difference_type n) const { return Derived(this->derived()) -= n; }
+
+  template <class... Ts>
+  bool operator!=(const iterator_adaptor<Ts...>& x) const noexcept {
+    return !this->derived().operator==(x);
+  }
+
+  template <class... Ts>
+  bool operator<(const iterator_adaptor<Ts...>& x) const noexcept {
+    return iter_ < x.iter_;
+  }
+
+  template <class... Ts>
+  bool operator>=(const iterator_adaptor<Ts...>& x) const noexcept {
+    return iter_ >= x.iter_;
+  }
+
+  template <class... Ts>
+  bool operator>(const iterator_adaptor<Ts...>& x) const noexcept {
+    return iter_ > x.iter_;
+  }
+
+  template <class... Ts>
+  bool operator<=(const iterator_adaptor<Ts...>& x) const noexcept {
+    return iter_ <= x.iter_;
+  }
+
+  friend Derived operator+(difference_type n, const Derived& x) { return x + n; }
+
+  Base const& base() const noexcept { return iter_; }
+
+protected:
+  // for convenience: refer to base class in derived class
+  using iterator_adaptor_ = iterator_adaptor;
+
+private:
+  Derived& derived() noexcept { return *static_cast<Derived*>(this); }
+  const Derived& derived() const noexcept { return *static_cast<Derived const*>(this); }
+
+  base_type iter_;
+
+  template <class, class, class, class>
+  friend class iterator_adaptor;
+};
+
+} // namespace detail
+} // namespace histogram
+} // namespace boost
+
+#endif