feat: RangeFor

Author: vinniefalco

include/mrdox/Support/RangeFor.hpp

@@ -0,0 +1,165 @@
+//
+// This is a derivative work. originally part of the LLVM Project.
+// Licensed under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// Copyright (c) 2023 Vinnie Falco ([email protected])
+//
+// Official repository: https://github.com/cppalliance/mrdox
+//
+
+#ifndef MRDOX_SUPPORT_RANGEFOR_HPP
+#define MRDOX_SUPPORT_RANGEFOR_HPP
+
+#include <mrdox/Platform.hpp>
+
+namespace clang {
+namespace mrdox {
+
+/** Range to help range-for loops identify first and last.
+*/
+template<class Container>
+class RangeFor
+{
+    Container const& C_;
+
+public:
+    struct value_type;
+    using size_type = std::size_t;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type*;
+    using reference = value_type&;
+    using const_pointer = value_type const*;
+    using const_reference = value_type const&;
+
+    class iterator;
+
+    explicit
+    RangeFor(Container const& C) noexcept
+        : C_(C)
+    {
+    }
+
+    iterator begin() const noexcept;
+    iterator end() const noexcept;
+};
+
+//------------------------------------------------
+
+template<class Container>
+struct RangeFor<Container>::value_type
+{
+    typename Container::value_type const& value;
+    bool const first;
+    bool const last;
+
+    value_type const* operator->() const noexcept
+    {
+        return this;
+    }
+};
+
+//------------------------------------------------
+
+template<class Container>
+class RangeFor<Container>::iterator
+{
+    using const_iterator =
+        typename Container::const_iterator;
+
+    const_iterator it_{};
+    const_iterator begin_;
+    const_iterator last_;
+    const_iterator end_;
+
+    friend class RangeFor;
+    friend struct value_type;
+
+    iterator(
+        Container const& C,
+        const_iterator it) noexcept
+        : it_(it)
+        , begin_(C.begin())
+        , last_(C.begin() != C.end() ?
+            std::prev(C.end()) : C.end())
+        , end_(C.end())
+    {
+    }
+
+public:
+    using value_type = typename RangeFor<Container>::value_type;
+    using pointer    = void;
+    using reference  = value_type;
+    using size_type  = std::size_t;
+    using iterator_category = typename
+        std::iterator_traits<typename Container::iterator>::iterator_category;
+
+    iterator() = default;
+    iterator(iterator const&) = default;
+    iterator& operator=(
+        iterator const&) = default;
+
+    iterator& operator++() noexcept
+    {
+        ++it_;
+        return *this;
+    }
+
+    iterator operator++(int) noexcept
+    {
+        auto temp = *this;
+        ++temp;
+        return temp;
+    }
+
+    reference operator->() const noexcept
+    {
+        return value_type{
+            *it_,
+            it_ == begin_,
+            it_ == last_ };
+    }
+
+    reference operator*() const noexcept
+    {
+        return value_type{
+            *it_,
+            it_ == begin_,
+            it_ == last_ };
+    }
+
+    bool operator==(iterator const& it) const noexcept
+    {
+        return it_ == it.it_;
+    }
+
+    bool operator!=(iterator const& it) const noexcept
+    {
+        return it_ != it.it_;
+    }
+};
+
+//------------------------------------------------
+
+template<class Container>
+RangeFor(Container const&) -> RangeFor<Container>;
+
+template<class Container>
+auto RangeFor<Container>::begin() const noexcept ->
+    iterator
+{
+    return iterator(C_, C_.begin());
+}
+
+template<class Container>
+auto RangeFor<Container>::end() const noexcept ->
+    iterator
+{
+    return iterator(C_, C_.end());
+}
+
+} // mrdox
+} // clang
+
+#endif