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@@ -0,0 +1,97 @@
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+//
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+// view.h
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+// stream
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+//
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+// Created by Sam Jaffe on 3/29/23.
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+//
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+
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+#pragma once
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+
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+#include <memory>
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+
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+#include <iterator/sentinel_iterator.h>
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+#include <stream/detail/traits.h>
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+#include <stream/forward.h>
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+
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+namespace stream::ranges {
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+
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+template <typename T> class view_iterator : public facade<view_iterator<T>> {
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+private:
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+ T (*dereference_)(void *){nullptr};
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+ bool (*equal_to_)(void *, void *){nullptr};
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+ void (*increment_)(void *){nullptr};
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+ std::shared_ptr<void> impl_{nullptr};
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+
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+public:
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+ template <typename It>
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+ view_iterator(It impl)
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+ : dereference_([](void * p) -> T { return **((It *)p); }),
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+ equal_to_([](void * l, void * r) { return *((It *)l) == *((It *)r); }),
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+ increment_([](void * p) { ++(*(It *)(p)); }),
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+ impl_(std::make_shared<It>(impl)) {}
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+
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+ T dereference() const { return dereference_(impl_.get()); }
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+
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+ void increment() { increment_(impl_.get()); }
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+
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+ bool equal_to(view_iterator const & other) const {
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+ return impl_ == other.impl_ ||
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+ (impl_ && other.impl_ && equal_to_(impl_.get(), other.impl_.get()));
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+ }
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+};
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+
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+template <typename T> class any_view {
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+private:
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+ template <typename S>
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+ using sentinel_iterator =
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+ iterator::sentinel_iterator<detail::begin_t<S>, detail::end_t<S>>;
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+ template <typename S, typename It>
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+ using iter_cast_t =
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+ std::conditional_t<detail::is_sentinal_v<S>, sentinel_iterator<S>, It>;
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+
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+ using make_iter_t = view_iterator<T> (*)(void *);
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+
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+private:
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+ std::shared_ptr<void> impl_{nullptr};
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+ make_iter_t begin_{nullptr};
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+ make_iter_t end_{nullptr};
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+
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+public:
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+ template <typename S>
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+ any_view(std::shared_ptr<S> impl)
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+ : impl_(impl), begin_(begin_function<S>()), end_(end_function<S>()) {}
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+
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+ template <typename S>
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+ any_view(S & impl) : any_view(std::shared_ptr<S>(&impl, [](void *) {})) {}
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+
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+ template <typename S>
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+ any_view(S const & impl)
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+ : any_view(std::shared_ptr<S const>(&impl, [](void *) {})) {}
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+
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+ template <typename S>
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+ any_view(S && impl) : any_view(std::make_shared<S>(std::forward<S>(impl))) {}
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+
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+ auto begin() const { return begin_(impl_.get()); }
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+ auto end() const { return end_(impl_.get()); }
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+
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+private:
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+ template <typename S> static make_iter_t begin_function() {
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+ return [](void * p) -> view_iterator<T> {
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+ return iter_cast_t<S, detail::begin_t<S>>(static_cast<S *>(p)->begin());
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+ };
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+ }
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+
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+ template <typename S> static make_iter_t end_function() {
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+ return [](void * p) -> view_iterator<T> {
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+ return iter_cast_t<S, detail::end_t<S>>(static_cast<S *>(p)->end());
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+ };
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+ }
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+};
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+
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+template <typename S>
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+any_view(std::shared_ptr<S>) -> any_view<detail::value_type<S>>;
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+template <typename S> any_view(S &) -> any_view<detail::value_type<S>>;
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+template <typename S> any_view(S const &) -> any_view<detail::value_type<S>>;
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+template <typename S> any_view(S &&) -> any_view<detail::value_type<S>>;
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+
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+}
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