636 lines
20 KiB
C++
636 lines
20 KiB
C++
/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Copyright 2010-2018 Danny Robson <danny@nerdcruft.net>
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*/
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#ifndef CRUFT_UTIL_ITERATOR_HPP
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#define CRUFT_UTIL_ITERATOR_HPP
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#include "types/traits.hpp"
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#include "variadic.hpp"
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#include "view.hpp"
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#include <iterator>
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template <typename Base>
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class referencing_iterator {
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protected:
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typedef typename std::enable_if<
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is_dereferencable<
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typename Base::value_type
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>::value,
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typename Base::value_type
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>::type base_value_type;
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public:
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typedef typename dereferenced_type<base_value_type>::type value_type ;
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typedef typename Base::difference_type difference_type ;
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typedef value_type& reference ;
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typedef value_type* pointer;
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typedef typename Base::iterator_category iterator_category;
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protected:
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Base m_base;
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public:
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explicit referencing_iterator (Base _base):
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m_base (_base)
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{ ; }
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referencing_iterator& operator++() { ++m_base; return *this; }
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referencing_iterator operator++(int) { auto val = *this; ++m_base; return val; }
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bool operator== (const referencing_iterator<Base> &rhs) { return m_base == rhs.m_base; }
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bool operator!= (const referencing_iterator<Base> &rhs) { return m_base != rhs.m_base; }
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bool operator>= (const referencing_iterator<Base> &rhs) { return m_base >= rhs.m_base; }
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bool operator<= (const referencing_iterator<Base> &rhs) { return m_base <= rhs.m_base; }
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bool operator> (const referencing_iterator<Base> &rhs) { return m_base > rhs.m_base; }
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bool operator< (const referencing_iterator<Base> &rhs) { return m_base < rhs.m_base; }
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const value_type& operator*() const
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{ return **m_base; }
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reference operator*()
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{ return **m_base; }
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difference_type operator-(const referencing_iterator<Base>& rhs) const { return m_base - rhs.m_base; }
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referencing_iterator<Base> operator-(int rhs) const { return referencing_iterator (m_base - rhs); }
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referencing_iterator<Base> operator+(int rhs) const { return referencing_iterator (m_base + rhs); }
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};
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namespace util {
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///////////////////////////////////////////////////////////////////////////
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/// an output iterator that inserts a delimiter between successive
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/// assignments
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///
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/// very useful for outputting comma seperated lists to an ostream, eg:
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///
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/// std::copy (
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/// std::cbegin (container),
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/// std::cend (container),
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/// util::infix_iterator<value_type> (os, ", ")
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/// );
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template <
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typename T,
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class CharT = char,
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class Traits = std::char_traits<CharT>
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>
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class infix_iterator : public std::iterator<std::output_iterator_tag, void, void, void, void> {
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public:
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using char_type = CharT;
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using traits_type = Traits;
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using ostream_type = std::basic_ostream<char_type, traits_type>;
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infix_iterator (ostream_type& _output, const CharT *_delimiter):
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m_output (_output),
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m_delimiter (_delimiter)
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{ ; }
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infix_iterator&
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operator= (const T &value)
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{
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if (!m_first)
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m_output << m_delimiter;
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m_output << value;
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m_first = false;
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return *this;
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}
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infix_iterator& operator* (void) { return *this; }
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infix_iterator& operator++ (void) { return *this; }
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infix_iterator& operator++ (int) { return *this; }
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private:
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bool m_first = true;
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ostream_type &m_output;
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const CharT *m_delimiter;
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};
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namespace detail {
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template <typename ContainerT, typename CharT>
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struct infix_t {
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const ContainerT &_container;
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const CharT *_delimiter;
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};
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template <typename ContainerT, typename CharT>
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std::ostream&
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operator<< (std::ostream &os, const infix_t<ContainerT,CharT> &val)
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{
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std::copy (std::cbegin (val._container),
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std::cend (val._container),
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infix_iterator<typename ContainerT::value_type> (os, val._delimiter));
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return os;
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}
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};
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/// a helper function that returns an object that will use a
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/// util::infix_iterator to output a container's values to an ostream with
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/// the given delimiter.
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///
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/// reduces boilerplate code required to output lists of things
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///
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/// std::cout << util::make_infix (container) << '\n';
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template <typename ContainerT, typename CharT = char>
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auto
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make_infix (const ContainerT &_container, const CharT *_delimiter = ", ")
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{
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return detail::infix_t<ContainerT,CharT> { _container, _delimiter };
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}
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template <typename ValueT, size_t CountV>
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auto
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make_infix (const ValueT (&val)[CountV])
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{
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return make_infix (util::view {val});
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}
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///////////////////////////////////////////////////////////////////////////
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//
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template <typename IteratorT>
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struct numeric_iterator : public std::iterator<
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typename std::iterator_traits<IteratorT>::iterator_category,
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decltype (+std::declval<typename std::iterator_traits<IteratorT>::value_type> ()),
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typename std::iterator_traits<IteratorT>::difference_type,
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typename std::iterator_traits<IteratorT>::pointer,
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typename std::iterator_traits<IteratorT>::reference
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> {
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static_assert (std::is_arithmetic_v<typename std::iterator_traits<numeric_iterator>::value_type>);
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explicit numeric_iterator (IteratorT _inner):
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m_inner (_inner)
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{ ; }
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auto operator++ (void) { ++m_inner; return *this; }
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auto
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operator- (const numeric_iterator &rhs) const
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{
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return typename std::iterator_traits<IteratorT>::difference_type { m_inner - rhs.m_inner };
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}
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auto
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operator* (void) const
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{
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return +*m_inner;
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}
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auto operator== (const numeric_iterator &rhs) const { return m_inner == rhs.m_inner; }
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auto operator!= (const numeric_iterator &rhs) const { return m_inner != rhs.m_inner; }
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private:
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IteratorT m_inner;
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};
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//-------------------------------------------------------------------------
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// convenience function that constructs a view of numeric_iterators for a
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// provided container
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template <typename ContainerT>
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auto
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numeric_view (ContainerT &data)
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{
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return util::view {
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numeric_iterator (std::begin (data)),
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numeric_iterator (std::end (data))
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};
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}
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//-------------------------------------------------------------------------
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template <typename ContainerT>
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auto
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numeric_view (const ContainerT &data)
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{
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return util::view {
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numeric_iterator (std::begin (data)),
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numeric_iterator (std::end (data))
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};
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}
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///////////////////////////////////////////////////////////////////////////
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/// a trait that stores a type suitable for indexing a container
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template <typename, typename = std::void_t<>>
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struct index_type { using type = std::size_t; };
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//-------------------------------------------------------------------------
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template <typename ContainerT>
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struct index_type<
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ContainerT,
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std::void_t<
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typename ContainerT::index_t
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>
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> {
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using type = typename ContainerT::index_t;
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};
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///////////////////////////////////////////////////////////////////////////
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template <typename ContainerT>
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class indices {
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public:
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using value_type = typename index_type<ContainerT>::type;
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indices (const ContainerT &_container):
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m_container (_container)
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{ ; }
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class iterator {
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public:
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using iterator_category = std::forward_iterator_tag;
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iterator (value_type _index):
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m_index (_index)
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{ ; }
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bool
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operator!= (const iterator &rhs) const
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{
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return m_index != rhs.m_index;
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}
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bool
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operator== (const iterator &rhs) const
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{
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return m_index == rhs.m_index;
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}
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iterator&
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operator++ (void) &
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{
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++m_index;
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return *this;
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};
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const value_type&
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operator* (void) const&
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{
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return m_index;
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}
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private:
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value_type m_index;
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};
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iterator begin (void) const { return iterator { value_type {0} }; }
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iterator end (void) const { return iterator { value_type (m_container.size ()) }; }
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private:
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const ContainerT &m_container;
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};
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//-------------------------------------------------------------------------
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template <typename T>
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indices<T>
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make_indices (const T &_t)
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{
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return indices<T> (_t);
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}
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///////////////////////////////////////////////////////////////////////////
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namespace detail::zip {
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template <
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typename IteratorT,
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typename = std::make_index_sequence<std::tuple_size_v<IteratorT>>
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>
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struct iterator;
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template <typename IteratorT, std::size_t ...Indices>
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struct iterator<IteratorT, std::index_sequence<Indices...>> {
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public:
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// we cannot be a forward iterator because we don't want to supply
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// references to a value type as that would necessitate storing
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// said value types within the iterator.
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using iterator_category = std::input_iterator_tag;
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using difference_type = std::ptrdiff_t;
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iterator (IteratorT _iterators):
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m_iterators (_iterators)
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{ ; }
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iterator&
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operator++ (void)
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{
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std::tuple (++std::get<Indices> (m_iterators)...);
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return *this;
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}
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iterator operator++ (int);
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auto
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operator* (void)
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{
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return std::forward_as_tuple (*std::get<Indices> (m_iterators)...);
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}
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bool
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operator== (const iterator &rhs) const
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{
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return m_iterators == rhs.m_iterators;
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}
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bool
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operator!= (const iterator &rhs) const
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{
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return !(*this == rhs);
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}
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private:
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IteratorT m_iterators;
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};
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// holds a tuple of iterators for begin and end, and returns an
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// iterator that transforms these iterators into tuples of value_types.
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//
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// this must be expressed in terms of iterators, rather than containers,
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// because it dramatically simplifies iterating over raw arrays.
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//
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// we have to store begin and end iterators because we might not have
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// enough information to determine the correct types from StoreT;
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// eg, in the case of arrays that have decayed to pointers we can't
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// find the end.
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//
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// BeginT: a tuple of begin iterators across all containers
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//
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// EndT: a tuple of end iterators across all containers
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//
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// StoreT: a tuple of containers we might own. used when we were
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// provided with an rval at zip time. allows us to destroy the
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// data when we're actually done iterating.
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template <
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typename StoreT,
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typename BeginT,
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typename EndT,
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typename I = std::make_index_sequence<std::tuple_size_v<StoreT>>
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>
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class collection;
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//---------------------------------------------------------------------
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template <
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typename StoreT,
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typename BeginT,
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typename EndT,
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std::size_t ...I
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>
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class collection<
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StoreT,
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BeginT,
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EndT,
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std::index_sequence<I...>
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> {
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public:
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collection (StoreT _store, BeginT _begin, EndT _end):
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m_store { std::move (_store) },
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m_begin (std::move (_begin)),
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m_end (std::move (_end))
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{ ; }
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auto begin (void)& { return iterator<BeginT> { m_begin }; }
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auto end (void)& { return iterator<EndT> { m_end }; }
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private:
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StoreT m_store;
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BeginT m_begin;
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EndT m_end;
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};
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}
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///------------------------------------------------------------------------
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/// takes a variable number of container arguments and returns an interable
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/// object with a value_type of tuple of the argument's value_types.
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///
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/// the returned iterator value_type is suitable for using in range-for
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/// and structured bindings (and really, that's the entire point here).
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///
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/// eg, util::zip ({1,2,3}, {4,5,6}) ~= {{1,4},{2,5},{3,6}}
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template <typename ...ContainerT>
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auto
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zip (ContainerT&&... data)
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{
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return detail::zip::collection<
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decltype (std::forward_as_tuple (data...)),
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decltype (std::make_tuple (std::begin (data)...)),
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decltype (std::make_tuple (std::end (data)...)),
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std::make_index_sequence<sizeof...(ContainerT)>
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> (
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std::forward_as_tuple (data...),
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std::make_tuple (std::begin (data)...),
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std::make_tuple (std::end (data)...)
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);
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};
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///------------------------------------------------------------------------
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/// takes a variable number of containers and returns a zipped iterable
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/// object where the first of the iterator's value_types is the index of
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/// that iterator. ie, it combines container offsets with value_types.
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///
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/// eg, util::izip ("abc") ~= {{0,'a'},{1,'b'},{2,'c'}}
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template <typename ...ContainerT>
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auto
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izip (ContainerT&&... data)
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{
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return zip (
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::util::make_indices (::util::variadic::get<0> (data...)),
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std::forward<ContainerT> (data)...
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);
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}
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///////////////////////////////////////////////////////////////////////////
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/// an output iterator that always discards any parameters on assignment.
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///
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/// sometimes useful to pass to algorithms that generate useful results as
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/// a return value, while not caring about the implicit OutputIterator
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/// results.
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struct discard_iterator : public std::iterator<std::output_iterator_tag, discard_iterator> {
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template <typename T>
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void operator= (const T&) { ; }
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discard_iterator& operator++ ( ) { return *this; }
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discard_iterator operator++ (int) { return *this; }
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discard_iterator& operator* ( ) { return *this; }
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};
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///////////////////////////////////////////////////////////////////////////
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/// an iterator that can be infinitely incremented but never assigned.
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///
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/// useful for iterator ranges where the begin iterator is an output
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/// iterator and hence never reaches an end point (and where we don't want
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/// to engineer the client code to account for this).
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template <
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typename ValueT,
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typename CategoryT,
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typename DistanceT,
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typename PointerT,
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typename ReferenceT
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>
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struct unequal_iterator {
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using value_type = ValueT;
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using iterator_category = CategoryT;
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using difference_type = DistanceT;
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using pointer = PointerT;
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using reference = ReferenceT;
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unequal_iterator& operator++ ( ) { return *this; }
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unequal_iterator operator++ (int) { return *this; }
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};
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//-------------------------------------------------------------------------
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template <typename ContainerT>
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auto
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make_unequal_iterator (const ContainerT&)
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{
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using t = typename std::iterator_traits<typename ContainerT::iterator>;
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return unequal_iterator<
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typename t::value_type,
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typename t::iterator_category,
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typename t::difference_type,
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typename t::pointer,
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typename t::reference
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> {};
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};
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//-------------------------------------------------------------------------
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template <
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typename OtherT,
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typename ValueT,
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typename CategoryT,
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typename DistanceT,
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typename PointerT,
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typename ReferenceT>
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constexpr bool
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operator== (
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const unequal_iterator<ValueT,CategoryT,DistanceT,PointerT,ReferenceT>&,
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const OtherT&
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) {
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return false;
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}
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//-------------------------------------------------------------------------
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template <
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typename OtherT,
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typename ValueT,
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typename CategoryT,
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typename DistanceT,
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typename PointerT,
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typename ReferenceT>
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constexpr bool
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operator== (
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const OtherT&,
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const unequal_iterator<ValueT,CategoryT,DistanceT,PointerT,ReferenceT>&
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) {
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return false;
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}
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///////////////////////////////////////////////////////////////////////////
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template <typename OutputIt, typename FunctionT>
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OutputIt
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_transform_by_block (
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const util::view<OutputIt> &,
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OutputIt cursor,
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FunctionT &&
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) {
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return cursor;
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}
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//-------------------------------------------------------------------------
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template <typename OutputIt, typename FunctionT, typename InputT, typename ...TailT>
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OutputIt
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_transform_by_block (
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const util::view<OutputIt> &dst,
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OutputIt cursor,
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FunctionT &&func,
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const InputT &_src,
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TailT &&...tail
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) {
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auto remain = _src;
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if (cursor != dst.begin ()) {
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auto infill = std::distance (cursor, dst.end ());
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if (remain.size () < static_cast<size_t> (infill)) {
|
|
return _transform_by_block (
|
|
dst,
|
|
std::copy_n (remain.begin (), remain.size (), cursor),
|
|
std::forward<FunctionT> (func),
|
|
std::forward<TailT> (tail)...
|
|
);
|
|
}
|
|
|
|
std::copy_n (remain.begin (), infill, cursor);
|
|
func (dst);
|
|
cursor = dst.begin ();
|
|
remain = { remain.begin () + infill, remain.end () };
|
|
}
|
|
|
|
while (remain.size () >= dst.size ()) {
|
|
std::copy_n (remain.begin (), dst.size (), dst.begin ());
|
|
func (dst);
|
|
remain = { remain.begin () + dst.size (), remain.end () };
|
|
}
|
|
|
|
return _transform_by_block (
|
|
dst,
|
|
std::copy (remain.begin (), remain.end (), cursor),
|
|
std::forward<FunctionT> (func),
|
|
std::forward<TailT> (tail)...
|
|
);
|
|
}
|
|
|
|
|
|
//-------------------------------------------------------------------------
|
|
template <typename OutputIt, typename FunctionT, typename ...Args>
|
|
OutputIt
|
|
transform_by_block (const util::view<OutputIt> &dst, FunctionT &&func, Args &&...src)
|
|
{
|
|
return _transform_by_block (
|
|
dst,
|
|
dst.begin (),
|
|
std::forward<FunctionT> (func),
|
|
std::forward<Args> (src)...
|
|
);
|
|
}
|
|
};
|
|
|
|
#endif
|