forked from OSchip/llvm-project
[libc++] Simplify std::ranges::subrange
Instead of using a base class to store the members and the optional size, use [[no_unique_address]] to achieve the same thing without needing a base class. Also, as a fly-by: - Change subrange from struct to class (per the standard) - Improve the diagnostic for when one doesn't provide a size to the ctor of a sized subrange - Replace this->member by just member since it's not in a dependent base anymore This change would be an ABI break due to [[no_unique_address]], but we haven't shipped ranges anywhere yet, so this shouldn't affect anyone. Differential Revision: https://reviews.llvm.org/D110370
This commit is contained in:
Louis Dionne
parent
952f030fe6
commit
86df5a2fa8
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@ -67,62 +67,41 @@ namespace ranges {
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enum class _LIBCPP_ENUM_VIS subrange_kind : bool { unsized, sized };
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template<class _Iter, class _Sent, bool>
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struct __subrange_base {
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static constexpr bool __store_size = false;
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_Iter __begin_ = _Iter();
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_Sent __end_ = _Sent();
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_LIBCPP_HIDE_FROM_ABI
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constexpr __subrange_base() = default;
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_LIBCPP_HIDE_FROM_ABI
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constexpr __subrange_base(_Iter __iter, _Sent __sent, make_unsigned_t<iter_difference_t<_Iter>> = 0)
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: __begin_(_VSTD::move(__iter)), __end_(__sent) { }
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};
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template<class _Iter, class _Sent>
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struct __subrange_base<_Iter, _Sent, true> {
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static constexpr bool __store_size = true;
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_Iter __begin_ = _Iter();
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_Sent __end_ = _Sent();
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make_unsigned_t<iter_difference_t<_Iter>> __size_ = 0;
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_LIBCPP_HIDE_FROM_ABI
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constexpr __subrange_base() = default;
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_LIBCPP_HIDE_FROM_ABI
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constexpr __subrange_base(_Iter __iter, _Sent __sent, decltype(__size_) __size)
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: __begin_(_VSTD::move(__iter)), __end_(__sent), __size_(__size) { }
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};
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template<input_or_output_iterator _Iter, sentinel_for<_Iter> _Sent = _Iter,
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subrange_kind _Kind = sized_sentinel_for<_Sent, _Iter>
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? subrange_kind::sized
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: subrange_kind::unsized>
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requires (_Kind == subrange_kind::sized || !sized_sentinel_for<_Sent, _Iter>)
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struct _LIBCPP_TEMPLATE_VIS subrange
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: public view_interface<subrange<_Iter, _Sent, _Kind>>,
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private __subrange_base<_Iter, _Sent, _Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _Iter>> {
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using _Base = __subrange_base<_Iter, _Sent, _Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _Iter>>;
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class _LIBCPP_TEMPLATE_VIS subrange
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: public view_interface<subrange<_Iter, _Sent, _Kind>>
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{
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private:
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static constexpr bool _StoreSize = (_Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _Iter>);
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static constexpr bool _MustProvideSizeAtConstruction = !_StoreSize; // just to improve compiler diagnostics
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struct _Empty { constexpr _Empty(auto) noexcept { } };
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using _Size = conditional_t<_StoreSize, make_unsigned_t<iter_difference_t<_Iter>>, _Empty>;
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[[no_unique_address]] _Iter __begin_ = _Iter();
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[[no_unique_address]] _Sent __end_ = _Sent();
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[[no_unique_address]] _Size __size_ = 0;
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public:
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_LIBCPP_HIDE_FROM_ABI
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subrange() requires default_initializable<_Iter> = default;
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_LIBCPP_HIDE_FROM_ABI
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constexpr subrange(__convertible_to_non_slicing<_Iter> auto __iter, _Sent __sent)
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requires (!_Base::__store_size)
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: _Base(_VSTD::move(__iter), __sent) {}
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requires _MustProvideSizeAtConstruction
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: __begin_(_VSTD::move(__iter)), __end_(std::move(__sent))
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{ }
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_LIBCPP_HIDE_FROM_ABI
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constexpr subrange(__convertible_to_non_slicing<_Iter> auto __iter, _Sent __sent,
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make_unsigned_t<iter_difference_t<_Iter>> __n)
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requires (_Kind == subrange_kind::sized)
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: _Base(_VSTD::move(__iter), __sent, __n)
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: __begin_(_VSTD::move(__iter)), __end_(std::move(__sent)), __size_(__n)
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{
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if constexpr (sized_sentinel_for<_Sent, _Iter>)
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_LIBCPP_ASSERT((this->__end_ - this->__begin_) == static_cast<iter_difference_t<_Iter>>(__n),
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_LIBCPP_ASSERT((__end_ - __begin_) == static_cast<iter_difference_t<_Iter>>(__n),
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"std::ranges::subrange was passed an invalid size hint");
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}
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@ -132,8 +111,9 @@ namespace ranges {
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convertible_to<sentinel_t<_Range>, _Sent>
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_LIBCPP_HIDE_FROM_ABI
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constexpr subrange(_Range&& __range)
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requires (!_Base::__store_size)
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: subrange(ranges::begin(__range), ranges::end(__range)) { }
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requires (!_StoreSize)
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: subrange(ranges::begin(__range), ranges::end(__range))
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{ }
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template<__different_from<subrange> _Range>
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requires borrowed_range<_Range> &&
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@ -141,9 +121,9 @@ namespace ranges {
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convertible_to<sentinel_t<_Range>, _Sent>
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_LIBCPP_HIDE_FROM_ABI
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constexpr subrange(_Range&& __range)
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requires _Base::__store_size && sized_range<_Range>
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: subrange(__range, ranges::size(__range)) { }
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requires _StoreSize && sized_range<_Range>
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: subrange(__range, ranges::size(__range))
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{ }
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template<borrowed_range _Range>
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requires __convertible_to_non_slicing<iterator_t<_Range>, _Iter> &&
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@ -151,39 +131,47 @@ namespace ranges {
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_LIBCPP_HIDE_FROM_ABI
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constexpr subrange(_Range&& __range, make_unsigned_t<iter_difference_t<_Iter>> __n)
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requires (_Kind == subrange_kind::sized)
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: subrange(ranges::begin(__range), ranges::end(__range), __n) { }
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: subrange(ranges::begin(__range), ranges::end(__range), __n)
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{ }
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template<__different_from<subrange> _Pair>
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requires __pair_like_convertible_from<_Pair, const _Iter&, const _Sent&>
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_LIBCPP_HIDE_FROM_ABI
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constexpr operator _Pair() const { return _Pair(this->__begin_, this->__end_); }
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constexpr operator _Pair() const {
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return _Pair(__begin_, __end_);
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr _Iter begin() const requires copyable<_Iter> {
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return this->__begin_;
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return __begin_;
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}
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Iter begin() requires (!copyable<_Iter>) {
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return _VSTD::move(this->__begin_);
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return _VSTD::move(__begin_);
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr _Sent end() const { return this->__end_; }
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constexpr _Sent end() const {
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return __end_;
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}
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const { return this->__begin_ == this->__end_; }
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const {
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return __begin_ == __end_;
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr make_unsigned_t<iter_difference_t<_Iter>> size() const
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requires (_Kind == subrange_kind::sized)
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{
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if constexpr (_Base::__store_size)
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return this->__size_;
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if constexpr (_StoreSize)
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return __size_;
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else
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return __to_unsigned_like(this->__end_ - this->__begin_);
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return _VSTD::__to_unsigned_like(__end_ - __begin_);
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}
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr subrange next(iter_difference_t<_Iter> __n = 1) const&
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requires forward_iterator<_Iter> {
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requires forward_iterator<_Iter>
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{
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auto __tmp = *this;
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__tmp.advance(__n);
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return __tmp;
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@ -195,7 +183,8 @@ namespace ranges {
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}
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr subrange prev(iter_difference_t<_Iter> __n = 1) const
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requires bidirectional_iterator<_Iter> {
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requires bidirectional_iterator<_Iter>
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{
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auto __tmp = *this;
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__tmp.advance(-__n);
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return __tmp;
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@ -205,16 +194,16 @@ namespace ranges {
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constexpr subrange& advance(iter_difference_t<_Iter> __n) {
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if constexpr (bidirectional_iterator<_Iter>) {
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if (__n < 0) {
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ranges::advance(this->__begin_, __n);
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if constexpr (_Base::__store_size)
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this->__size_ += _VSTD::__to_unsigned_like(-__n);
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ranges::advance(__begin_, __n);
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if constexpr (_StoreSize)
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__size_ += _VSTD::__to_unsigned_like(-__n);
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return *this;
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}
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}
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auto __d = __n - ranges::advance(this->__begin_, __n, this->__end_);
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if constexpr (_Base::__store_size)
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this->__size_ -= _VSTD::__to_unsigned_like(__d);
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auto __d = __n - ranges::advance(__begin_, __n, __end_);
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if constexpr (_StoreSize)
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__size_ -= _VSTD::__to_unsigned_like(__d);
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return *this;
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}
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};
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@ -0,0 +1,69 @@
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03, c++11, c++14, c++17
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// UNSUPPORTED: libcpp-no-concepts
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// UNSUPPORTED: libcpp-has-no-incomplete-ranges
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// constexpr subrange() requires default_initializable<I>;
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#include <ranges>
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#include <cassert>
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#include <cstddef>
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#include "test_iterators.h"
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// An input_or_output_iterator that is not default constructible so we can test
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// the `requires` on subrange's default constructor.
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struct NoDefaultIterator {
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using difference_type = std::ptrdiff_t;
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NoDefaultIterator() = delete;
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NoDefaultIterator& operator++();
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void operator++(int);
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int& operator*() const;
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friend bool operator==(NoDefaultIterator const&, NoDefaultIterator const&);
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};
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static_assert(std::input_or_output_iterator<NoDefaultIterator>);
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// A sentinel type for the above iterator
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struct Sentinel {
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friend bool operator==(NoDefaultIterator const&, Sentinel const&);
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friend bool operator==(Sentinel const&, NoDefaultIterator const&);
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friend bool operator!=(NoDefaultIterator const&, Sentinel const&);
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friend bool operator!=(Sentinel const&, NoDefaultIterator const&);
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};
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constexpr bool test() {
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{
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static_assert(!std::is_default_constructible_v<std::ranges::subrange<NoDefaultIterator, Sentinel, std::ranges::subrange_kind::sized>>);
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static_assert(!std::is_default_constructible_v<std::ranges::subrange<NoDefaultIterator, Sentinel, std::ranges::subrange_kind::unsized>>);
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}
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{
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using Iter = forward_iterator<int*>;
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std::ranges::subrange<Iter, Iter, std::ranges::subrange_kind::sized> subrange;
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assert(subrange.begin() == Iter());
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assert(subrange.end() == Iter());
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}
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{
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using Iter = forward_iterator<int*>;
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std::ranges::subrange<Iter, Iter, std::ranges::subrange_kind::unsized> subrange;
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assert(subrange.begin() == Iter());
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assert(subrange.end() == Iter());
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}
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return true;
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}
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int main(int, char**) {
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test();
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static_assert(test());
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return 0;
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}
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