Implement ranges::fill and ranges::fill_n

microsoft · Jun 26, 2020 · ad0055a · ad0055a
1 parent 4deaf6c
commit ad0055a
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Showing 7 changed files with 420 additions and 133 deletions.
diff --git a/stl/inc/algorithm b/stl/inc/algorithm
@@ -2841,6 +2841,85 @@ _FwdIt2 replace_copy_if(_ExPo&&, _FwdIt1 _First, _FwdIt1 _Last, _FwdIt2 _Dest, _
 }
 #endif // _HAS_CXX17
 
+#ifdef __cpp_lib_concepts
+namespace ranges {
+    // VARIABLE ranges::fill
+    class _Fill_fn : private _Not_quite_object {
+    public:
+        using _Not_quite_object::_Not_quite_object;
+
+        template <class _Ty, output_iterator<const _Ty&> _It, sentinel_for<_It> _Se>
+        constexpr _It operator()(_It _First, _Se _Last, const _Ty& _Value) const {
+            _Adl_verify_range(_First, _Last);
+            auto _UFirst      = _Get_unwrapped(_STD move(_First));
+            const auto _ULast = _Get_unwrapped(_STD move(_Last));
+            if constexpr (_Fill_memset_is_safe<decltype(_UFirst), _Ty>) {
+#ifdef __cpp_lib_is_constant_evaluated
+                if (!_STD is_constant_evaluated())
+#endif // __cpp_lib_is_constant_evaluated
+                {
+                    const int distance = static_cast<size_t>(_ULast - _UFirst);
+                    _CSTD memset(_UFirst, static_cast<unsigned char>(_Value), distance);
+                    _UFirst += distance;
+                    _Seek_wrapped(_First, _UFirst);
+                    return _First;
+                }
+            }
+
+            for (; _UFirst != _ULast; ++_UFirst) {
+                *_UFirst = _Value;
+            }
+
+            _Seek_wrapped(_First, _STD move(_UFirst));
+            return _First;
+        }
+
+        template <class _Ty, output_range<const _Ty&> _Rng>
+        constexpr borrowed_iterator_t<_Rng> operator()(_Rng&& _Range, const _Ty& _Value) const {
+            auto _First = _RANGES begin(_Range);
+            _Seek_wrapped(_First, (*this)(_Get_unwrapped(_STD move(_First)), _Uend(_Range), _Value));
+            return _First;
+        }
+    };
+
+    inline constexpr _Fill_fn fill{_Not_quite_object::_Construct_tag{}};
+
+    // VARIABLE ranges::fill_n
+    class _Fill_n_fn : private _Not_quite_object {
+    public:
+        using _Not_quite_object::_Not_quite_object;
+
+        template <class _Ty, output_iterator<const _Ty&> _It>
+        constexpr _It operator()(_It _First, iter_difference_t<_It> _Count, const _Ty& _Value) const {
+            if (_Count >= 0) {
+                auto _UFirst = _Get_unwrapped_n(_STD move(_First), _Count);
+                if constexpr (_Fill_memset_is_safe<decltype(_UFirst), _Ty>) {
+#ifdef __cpp_lib_is_constant_evaluated
+                    if (!_STD is_constant_evaluated())
+#endif // __cpp_lib_is_constant_evaluated
+                    {
+                        _CSTD memset(_UFirst, static_cast<unsigned char>(_Value), static_cast<size_t>(_Count));
+                        _UFirst += _Count;
+                        _Seek_wrapped(_First, _UFirst);
+                        return _First;
+                    }
+                }
+
+                for (; _Count > 0; ++_UFirst, (void) --_Count) {
+                    *_UFirst = _Value;
+                }
+
+                _Seek_wrapped(_First, _STD move(_UFirst));
+            }
+
+            return _First;
+        }
+    };
+
+    inline constexpr _Fill_n_fn fill_n{_Not_quite_object::_Construct_tag{}};
+} // namespace ranges
+#endif // __cpp_lib_concepts
+
 // FUNCTION TEMPLATE generate
 template <class _FwdIt, class _Fn>
 _CONSTEXPR20 void generate(_FwdIt _First, _FwdIt _Last, _Fn _Func) { // replace [_First, _Last) with _Func()