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+// Copyright 2017 Elias Kosunen
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// This file is a part of scnlib:
+// https://github.com/eliaskosunen/scnlib
+
+#ifndef SCN_DETAIL_RANGE_H
+#define SCN_DETAIL_RANGE_H
+
+#include "../ranges/ranges.h"
+#include "../util/algorithm.h"
+#include "../util/memory.h"
+#include "error.h"
+#include "vectored.h"
+
+namespace scn {
+ SCN_BEGIN_NAMESPACE
+
+ namespace detail {
+ namespace _reset_begin_iterator {
+ struct fn {
+ private:
+ template <typename Iterator>
+ static auto impl(Iterator& it, priority_tag<1>) noexcept(
+ noexcept(it.reset_begin_iterator()))
+ -> decltype(it.reset_begin_iterator())
+ {
+ return it.reset_begin_iterator();
+ }
+
+ template <typename Iterator>
+ static void impl(Iterator&, size_t, priority_tag<0>) noexcept
+ {
+ }
+
+ public:
+ template <typename Iterator>
+ auto operator()(Iterator& it) const
+ noexcept(noexcept(fn::impl(it, priority_tag<1>{})))
+ -> decltype(fn::impl(it, priority_tag<1>{}))
+ {
+ return fn::impl(it, priority_tag<1>{});
+ }
+ };
+ } // namespace _reset_begin_iterator
+ namespace {
+ static constexpr auto& reset_begin_iterator =
+ static_const<detail::_reset_begin_iterator::fn>::value;
+ }
+
+ template <typename Iterator, typename = void>
+ struct extract_char_type;
+ template <typename Iterator>
+ struct extract_char_type<
+ Iterator,
+ typename std::enable_if<std::is_integral<
+ polyfill_2a::iter_value_t<Iterator>>::value>::type> {
+ using type = polyfill_2a::iter_value_t<Iterator>;
+ };
+ template <typename Iterator>
+ struct extract_char_type<
+ Iterator,
+ void_t<
+ typename std::enable_if<!std::is_integral<
+ polyfill_2a::iter_value_t<Iterator>>::value>::type,
+ typename polyfill_2a::iter_value_t<Iterator>::success_type>> {
+ using type =
+ typename polyfill_2a::iter_value_t<Iterator>::success_type;
+ };
+
+ template <typename Range, typename = void>
+ struct is_direct_impl
+ : std::is_integral<ranges::range_value_t<const Range>> {
+ };
+
+ template <typename Range>
+ struct reconstruct_tag {
+ };
+
+ template <
+ typename Range,
+ typename Iterator,
+ typename Sentinel,
+ typename = typename std::enable_if<
+ std::is_constructible<Range, Iterator, Sentinel>::value>::type>
+ Range reconstruct(reconstruct_tag<Range>, Iterator begin, Sentinel end)
+ {
+ return {begin, end};
+ }
+#if SCN_HAS_STRING_VIEW
+ // std::string_view is not reconstructible pre-C++20
+ template <typename CharT,
+ typename Traits,
+ typename Iterator,
+ typename Sentinel>
+ std::basic_string_view<CharT, Traits> reconstruct(
+ reconstruct_tag<std::basic_string_view<CharT, Traits>>,
+ Iterator begin,
+ Sentinel end)
+ {
+ // On MSVC, string_view can't even be constructed from its
+ // iterators!
+ return {::scn::detail::to_address(begin),
+ static_cast<size_t>(ranges::distance(begin, end))};
+ }
+#endif // SCN_HAS_STRING_VIEW
+
+ template <typename T, bool>
+ struct range_wrapper_storage;
+ template <typename T>
+ struct range_wrapper_storage<T, true> {
+ using type = remove_cvref_t<T>;
+ using range_type = const type&;
+
+ const type* value{nullptr};
+
+ range_wrapper_storage() = default;
+ range_wrapper_storage(const type& v, dummy_type)
+ : value(std::addressof(v))
+ {
+ }
+
+ const type& get() const& noexcept
+ {
+ return *value;
+ }
+ type&& get() && noexcept
+ {
+ return *value;
+ }
+ };
+ template <typename T>
+ struct range_wrapper_storage<T, false> {
+ using range_type = T;
+
+ T value{};
+
+ range_wrapper_storage() = default;
+ template <typename U>
+ range_wrapper_storage(U&& v, dummy_type) : value(SCN_FWD(v))
+ {
+ }
+
+ const T& get() const& noexcept
+ {
+ return value;
+ }
+ T&& get() && noexcept
+ {
+ return value;
+ }
+ };
+
+ template <typename T>
+ using _range_wrapper_marker = typename T::range_wrapper_marker;
+
+ template <typename T>
+ struct _has_range_wrapper_marker
+ : custom_ranges::detail::exists<_range_wrapper_marker, T> {
+ };
+
+ /**
+ * Wraps a source range for more consistent behavior
+ */
+ template <typename Range>
+ class range_wrapper {
+ public:
+ using range_type = Range;
+ using range_nocvref_type = remove_cvref_t<Range>;
+ using iterator = ranges::iterator_t<const range_nocvref_type>;
+ using sentinel = ranges::sentinel_t<const range_nocvref_type>;
+ using char_type = typename extract_char_type<iterator>::type;
+ using difference_type =
+ ranges::range_difference_t<const range_nocvref_type>;
+ using storage_type =
+ range_wrapper_storage<Range, std::is_reference<Range>::value>;
+ using storage_range_type = typename storage_type::range_type;
+
+ using range_wrapper_marker = void;
+
+ template <
+ typename R,
+ typename = typename std::enable_if<
+ !_has_range_wrapper_marker<remove_cvref_t<R>>::value>::type>
+ range_wrapper(R&& r)
+ : m_range(SCN_FWD(r), dummy_type{}),
+ m_begin(ranges::cbegin(m_range.get()))
+ {
+ }
+
+ range_wrapper(const range_wrapper& o) : m_range(o.m_range)
+ {
+ const auto n =
+ ranges::distance(o.begin_underlying(), o.m_begin);
+ m_begin = ranges::cbegin(m_range.get());
+ ranges::advance(m_begin, n);
+ m_read = o.m_read;
+ }
+ range_wrapper& operator=(const range_wrapper& o)
+ {
+ const auto n =
+ ranges::distance(o.begin_underlying(), o.m_begin);
+ m_range = o.m_range;
+ m_begin = ranges::cbegin(m_range.get());
+ ranges::advance(m_begin, n);
+ m_read = o.m_read;
+ return *this;
+ }
+
+ range_wrapper(range_wrapper&& o) noexcept
+ {
+ const auto n =
+ ranges::distance(o.begin_underlying(), o.m_begin);
+ m_range = SCN_MOVE(o.m_range);
+ m_begin = ranges::cbegin(m_range.get());
+ ranges::advance(m_begin, n);
+ m_read = exchange(o.m_read, 0);
+ }
+ range_wrapper& operator=(range_wrapper&& o) noexcept
+ {
+ reset_to_rollback_point();
+
+ const auto n =
+ ranges::distance(o.begin_underlying(), o.m_begin);
+ m_range = SCN_MOVE(o.m_range);
+ m_begin = ranges::cbegin(m_range.get());
+ ranges::advance(m_begin, n);
+ m_read = exchange(o.m_read, 0);
+ return *this;
+ }
+
+ ~range_wrapper() = default;
+
+ iterator begin() const noexcept
+ {
+ return m_begin;
+ }
+ SCN_GCC_PUSH
+ SCN_GCC_IGNORE("-Wnoexcept")
+ sentinel end() const noexcept(
+ noexcept(ranges::end(SCN_DECLVAL(const storage_type&).get())))
+ {
+ return ranges::end(m_range.get());
+ }
+ SCN_GCC_POP
+
+ struct dummy {
+ };
+
+ /**
+ * Returns `true` if `begin() == end()`.
+ */
+ bool empty() const
+ {
+ return begin() == end();
+ }
+
+ /**
+ * Advance the begin iterator by `n` characters.
+ */
+ iterator advance(difference_type n = 1) noexcept
+ {
+ SCN_EXPECT(_advance_check(
+ n, std::integral_constant<bool, is_contiguous>{}));
+ m_read += n;
+ ranges::advance(m_begin, n);
+ return m_begin;
+ }
+
+ /// @{
+ /**
+ * Advance the begin iterator, until it's equal to `it`.
+ * Assumes that `it` is reachable by repeatedly incrementing begin,
+ * will hang otherwise.
+ */
+ template <typename R = range_nocvref_type,
+ typename std::enable_if<SCN_CHECK_CONCEPT(
+ ranges::sized_range<R>)>::type* = nullptr>
+ void advance_to(iterator it) noexcept
+ {
+ const auto diff = ranges::distance(m_begin, it);
+ m_read += diff;
+ m_begin = it;
+ }
+ template <typename R = range_nocvref_type,
+ typename std::enable_if<SCN_CHECK_CONCEPT(
+ !ranges::sized_range<R>)>::type* = nullptr>
+ void advance_to(iterator it) noexcept
+ {
+ while (m_begin != it) {
+ ++m_read;
+ ++m_begin;
+ }
+ }
+ /// @}
+
+ /**
+ * Returns the begin iterator of the underlying source range, is not
+ * necessarily equal to `begin()`.
+ */
+ iterator begin_underlying() const noexcept(noexcept(
+ ranges::cbegin(SCN_DECLVAL(const range_nocvref_type&))))
+ {
+ return ranges::cbegin(m_range.get());
+ }
+
+ /**
+ * Returns the underlying source range.
+ * Note that `range_underlying().begin()` may not be equal to
+ * `begin()`.
+ */
+ const range_type& range_underlying() const noexcept
+ {
+ return m_range.get();
+ }
+
+ /**
+ * Returns a pointer to the beginning of the range.
+ * `*this` must be contiguous.
+ */
+ template <typename R = range_nocvref_type,
+ typename std::enable_if<SCN_CHECK_CONCEPT(
+ ranges::contiguous_range<R>)>::type* = nullptr>
+ auto data() const
+ noexcept(noexcept(*SCN_DECLVAL(ranges::iterator_t<const R>)))
+ -> decltype(std::addressof(
+ *SCN_DECLVAL(ranges::iterator_t<const R>)))
+ {
+ return std::addressof(*m_begin);
+ }
+ SCN_GCC_PUSH
+ SCN_GCC_IGNORE("-Wnoexcept")
+ /**
+ * Returns `end() - begin()`.
+ * `*this` must be sized.
+ */
+ template <typename R = range_nocvref_type,
+ typename std::enable_if<SCN_CHECK_CONCEPT(
+ ranges::sized_range<R>)>::type* = nullptr>
+ auto size() const noexcept(noexcept(
+ ranges::distance(SCN_DECLVAL(ranges::iterator_t<const R>),
+ SCN_DECLVAL(ranges::sentinel_t<const R>))))
+ -> decltype(ranges::distance(
+ SCN_DECLVAL(ranges::iterator_t<const R>),
+ SCN_DECLVAL(ranges::sentinel_t<const R>)))
+ {
+ return ranges::distance(m_begin, end());
+ }
+ SCN_GCC_POP
+ struct dummy2 {
+ };
+
+ template <typename R = range_nocvref_type,
+ typename std::enable_if<provides_buffer_access_impl<
+ R>::value>::type* = nullptr>
+ span<const char_type> get_buffer_and_advance(
+ size_t max_size = std::numeric_limits<size_t>::max())
+ {
+ auto buf = get_buffer(m_range.get(), begin(), max_size);
+ if (buf.size() == 0) {
+ return buf;
+ }
+ advance(buf.ssize());
+ return buf;
+ }
+
+ /**
+ * Reset `begin()` to the rollback point, as if by repeatedly
+ * calling `operator--()` on the begin iterator.
+ *
+ * Returns `error::unrecoverable_source_error` on failure.
+ *
+ * \see set_rollback_point()
+ */
+ error reset_to_rollback_point()
+ {
+ for (; m_read != 0; --m_read) {
+ --m_begin;
+ if (m_begin == end()) {
+ return {error::unrecoverable_source_error,
+ "Putback failed"};
+ }
+ }
+ return {};
+ }
+ /**
+ * Sets the rollback point equal to the current `begin()` iterator.
+ *
+ * \see reset_to_rollback_point()
+ */
+ void set_rollback_point()
+ {
+ m_read = 0;
+ }
+
+ void reset_begin_iterator()
+ {
+ detail::reset_begin_iterator(m_begin);
+ }
+
+ /**
+ * Construct a new source range from `begin()` and `end()`, and wrap
+ * it in a new `range_wrapper`.
+ */
+ template <typename R>
+ auto reconstruct_and_rewrap() && -> range_wrapper<R>
+ {
+ auto reconstructed =
+ reconstruct(reconstruct_tag<R>{}, begin(), end());
+ return {SCN_MOVE(reconstructed)};
+ }
+
+ /**
+ * `true` if `value_type` is a character type (`char` or `wchar_t`)
+ * `false` if it's an `expected` containing a character
+ */
+ static constexpr bool is_direct =
+ is_direct_impl<range_nocvref_type>::value;
+ // can call .data() and memcpy
+ /**
+ * `true` if `this->data()` can be called, and `memcpy` can be
+ * performed on it.
+ */
+ static constexpr bool is_contiguous =
+ SCN_CHECK_CONCEPT(ranges::contiguous_range<range_nocvref_type>);
+ /**
+ * `true` if the range provides a way to access a contiguous buffer
+ * on it (`detail::get_buffer()`), which may not provide the entire
+ * source data, e.g. a `span` of `span`s (vectored I/O).
+ */
+ static constexpr bool provides_buffer_access =
+ provides_buffer_access_impl<range_nocvref_type>::value;
+
+ private:
+ template <typename R = Range>
+ bool _advance_check(std::ptrdiff_t n, std::true_type)
+ {
+ SCN_CLANG_PUSH
+ SCN_CLANG_IGNORE("-Wzero-as-null-pointer-constant")
+ return m_begin + n <= end();
+ SCN_CLANG_POP
+ }
+ template <typename R = Range>
+ bool _advance_check(std::ptrdiff_t, std::false_type)
+ {
+ return true;
+ }
+
+ storage_type m_range;
+ iterator m_begin;
+ mutable difference_type m_read{0};
+ };
+
+ namespace _wrap {
+ struct fn {
+ private:
+ template <typename Range>
+ static range_wrapper<Range> impl(const range_wrapper<Range>& r,
+ priority_tag<4>) noexcept
+ {
+ return r;
+ }
+ template <typename Range>
+ static range_wrapper<Range> impl(range_wrapper<Range>&& r,
+ priority_tag<4>) noexcept
+ {
+ return SCN_MOVE(r);
+ }
+
+ template <typename Range>
+ static auto impl(Range&& r, priority_tag<3>) noexcept(
+ noexcept(SCN_FWD(r).wrap())) -> decltype(SCN_FWD(r).wrap())
+ {
+ return SCN_FWD(r).wrap();
+ }
+
+ template <typename CharT, std::size_t N>
+ static auto impl(CharT (&str)[N], priority_tag<2>) noexcept
+ -> range_wrapper<
+ basic_string_view<typename std::remove_cv<CharT>::type>>
+ {
+ return {
+ basic_string_view<typename std::remove_cv<CharT>::type>(
+ str, str + N - 1)};
+ }
+
+ template <typename CharT, typename Allocator>
+ static auto impl(
+ const std::basic_string<CharT,
+ std::char_traits<CharT>,
+ Allocator>& str,
+ priority_tag<2>) noexcept
+ -> range_wrapper<basic_string_view<CharT>>
+ {
+ return {basic_string_view<CharT>{str.data(), str.size()}};
+ }
+ template <typename CharT, typename Allocator>
+ static auto impl(
+ std::basic_string<CharT,
+ std::char_traits<CharT>,
+ Allocator>&& str,
+ priority_tag<2>) noexcept(std::
+ is_nothrow_move_constructible<
+ decltype(str)>::value)
+ -> range_wrapper<std::basic_string<CharT,
+ std::char_traits<CharT>,
+ Allocator>>
+ {
+ return {SCN_MOVE(str)};
+ }
+
+#if SCN_HAS_STRING_VIEW
+ template <typename CharT>
+ static auto impl(const std::basic_string_view<CharT>& str,
+ priority_tag<1>) noexcept
+ -> range_wrapper<basic_string_view<CharT>>
+ {
+ return {basic_string_view<CharT>{str.data(), str.size()}};
+ }
+#endif
+ template <typename T,
+ typename CharT = typename std::remove_const<T>::type>
+ static auto impl(span<T> s, priority_tag<2>) noexcept
+ -> range_wrapper<basic_string_view<CharT>>
+ {
+ return {basic_string_view<CharT>{s.data(), s.size()}};
+ }
+
+ template <typename Range,
+ typename = typename std::enable_if<
+ SCN_CHECK_CONCEPT(ranges::view<Range>)>::type>
+ static auto impl(Range r, priority_tag<1>) noexcept
+ -> range_wrapper<Range>
+ {
+ return {r};
+ }
+
+ template <typename Range>
+ static auto impl(const Range& r, priority_tag<0>) noexcept
+ -> range_wrapper<Range&>
+ {
+ static_assert(SCN_CHECK_CONCEPT(ranges::range<Range>),
+ "Input needs to be a Range");
+ return {r};
+ }
+ template <typename Range,
+ typename = typename std::enable_if<
+ !std::is_reference<Range>::value>::type>
+ static auto impl(Range&& r, priority_tag<0>) noexcept
+ -> range_wrapper<Range>
+ {
+ static_assert(SCN_CHECK_CONCEPT(ranges::range<Range>),
+ "Input needs to be a Range");
+ return {SCN_MOVE(r)};
+ }
+
+ public:
+ template <typename Range>
+ auto operator()(Range&& r) const
+ noexcept(noexcept(fn::impl(SCN_FWD(r), priority_tag<4>{})))
+ -> decltype(fn::impl(SCN_FWD(r), priority_tag<4>{}))
+ {
+ return fn::impl(SCN_FWD(r), priority_tag<4>{});
+ }
+ };
+ } // namespace _wrap
+ } // namespace detail
+
+ namespace {
+ /**
+ * Create a `range_wrapper` for any supported source range.
+ */
+ static constexpr auto& wrap =
+ detail::static_const<detail::_wrap::fn>::value;
+ } // namespace
+
+ template <typename Range>
+ struct range_wrapper_for {
+ using type = decltype(wrap(SCN_DECLVAL(Range)));
+ };
+ template <typename Range>
+ using range_wrapper_for_t = typename range_wrapper_for<Range>::type;
+
+ SCN_END_NAMESPACE
+} // namespace scn
+
+#endif // SCN_DETAIL_RANGE_H
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