Add Span from upstream Godot.

include/godot_cpp/templates/local_vector.hpp

@@ -33,6 +33,7 @@
 #include <godot_cpp/core/error_macros.hpp>
 #include <godot_cpp/core/memory.hpp>
 #include <godot_cpp/templates/sort_array.hpp>
+#include <godot_cpp/templates/span.hpp>
 #include <godot_cpp/templates/vector.hpp>
 
 #include <initializer_list>
@@ -50,13 +51,12 @@ class LocalVector {
 	T *data = nullptr;
 
 public:
-	T *ptr() {
-		return data;
-	}
+	_FORCE_INLINE_ T *ptr() { return data; }
+	_FORCE_INLINE_ const T *ptr() const { return data; }
+	_FORCE_INLINE_ U size() const { return count; }
 
-	const T *ptr() const {
-		return data;
-	}
+	_FORCE_INLINE_ Span<T> span() const { return Span(data, count); }
+	_FORCE_INLINE_ operator Span<T>() const { return span(); }
 
 	// Must take a copy instead of a reference (see GH-31736).
 	_FORCE_INLINE_ void push_back(T p_elem) {
@@ -148,7 +148,6 @@ class LocalVector {
 		}
 	}
 
-	_FORCE_INLINE_ U size() const { return count; }
 	void resize(U p_size) {
 		if (p_size < count) {
 			if constexpr (!std::is_trivially_destructible_v<T> && !force_trivial) {

include/godot_cpp/templates/span.hpp

@@ -0,0 +1,249 @@
+/**************************************************************************/
+/*  span.hpp                                                              */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#pragma once
+
+#include <godot_cpp/core/defs.hpp>
+#include <godot_cpp/core/error_macros.hpp>
+
+namespace godot {
+
+template <typename LHS, typename RHS>
+bool are_spans_equal(const LHS *p_lhs, const RHS *p_rhs, size_t p_size) {
+	if constexpr (std::is_same_v<LHS, RHS> && std::is_fundamental_v<LHS>) {
+		// Optimize trivial type comparison.
+		// is_trivially_equality_comparable would help, but it doesn't exist.
+		return memcmp(p_lhs, p_rhs, p_size * sizeof(LHS)) == 0;
+	} else {
+		// Normal case: Need to iterate the array manually.
+		for (size_t j = 0; j < p_size; j++) {
+			if (p_lhs[j] != p_rhs[j]) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+}
+
+// Equivalent of std::span.
+// Represents a view into a contiguous memory space.
+// DISCLAIMER: This data type does not own the underlying buffer. DO NOT STORE IT.
+//  Additionally, for the lifetime of the Span, do not resize the buffer, and do not insert or remove elements from it.
+//  Failure to respect this may lead to crashes or undefined behavior.
+template <typename T>
+class Span {
+	const T *_ptr = nullptr;
+	uint64_t _len = 0;
+
+public:
+	static constexpr bool is_string = std::disjunction_v<
+			std::is_same<T, char>,
+			std::is_same<T, char16_t>,
+			std::is_same<T, char32_t>,
+			std::is_same<T, wchar_t>>;
+
+	_FORCE_INLINE_ constexpr Span() = default;
+
+	_FORCE_INLINE_ Span(const T *p_ptr, uint64_t p_len) :
+			_ptr(p_ptr), _len(p_len) {
+#ifdef DEBUG_ENABLED
+		// TODO In c++20, make this check run only in non-consteval, and make this constructor constexpr.
+		if (_ptr == nullptr && _len > 0) {
+			ERR_PRINT("Internal bug, please report: Span was created from nullptr with size > 0. Recovering by using size = 0.");
+			_len = 0;
+		}
+#endif
+	}
+
+	// Allows creating Span directly from C arrays and string literals.
+	template <size_t N>
+	_FORCE_INLINE_ constexpr Span(const T (&p_array)[N]) :
+			_ptr(p_array), _len(N) {
+		if constexpr (is_string) {
+			// Cut off the \0 terminator implicitly added to string literals.
+			if (N > 0 && p_array[N - 1] == '\0') {
+				_len--;
+			}
+		}
+	}
+
+	_FORCE_INLINE_ constexpr uint64_t size() const { return _len; }
+	_FORCE_INLINE_ constexpr bool is_empty() const { return _len == 0; }
+
+	_FORCE_INLINE_ constexpr const T *ptr() const { return _ptr; }
+
+	// NOTE: Span subscripts sanity check the bounds to avoid undefined behavior.
+	//       This is slower than direct buffer access and can prevent autovectorization.
+	//       If the bounds are known, use ptr() subscript instead.
+	_FORCE_INLINE_ constexpr const T &operator[](uint64_t p_idx) const {
+		CRASH_COND(p_idx >= _len);
+		return _ptr[p_idx];
+	}
+
+	_FORCE_INLINE_ constexpr const T *begin() const { return _ptr; }
+	_FORCE_INLINE_ constexpr const T *end() const { return _ptr + _len; }
+
+	template <typename T1>
+	_FORCE_INLINE_ constexpr Span<T1> reinterpret() const {
+		return Span<T1>(reinterpret_cast<const T1 *>(_ptr), _len * sizeof(T) / sizeof(T1));
+	}
+
+	// Algorithms.
+	constexpr int64_t find(const T &p_val, uint64_t p_from = 0) const;
+	template <typename T1 = T>
+	constexpr int64_t find_sequence(const Span<T1> &p_span, uint64_t p_from = 0) const;
+	constexpr int64_t rfind(const T &p_val, uint64_t p_from) const;
+	_FORCE_INLINE_ constexpr int64_t rfind(const T &p_val) const { return rfind(p_val, size() - 1); }
+	template <typename T1 = T>
+	constexpr int64_t rfind_sequence(const Span<T1> &p_span, uint64_t p_from) const;
+	template <typename T1 = T>
+	_FORCE_INLINE_ constexpr int64_t rfind_sequence(const Span<T1> &p_span) const { return rfind_sequence(p_span, size() - p_span.size()); }
+	constexpr uint64_t count(const T &p_val) const;
+	/// Find the index of the given value using binary search.
+	/// Note: Assumes that elements in the span are sorted. Otherwise, use find() instead.
+	template <typename Comparator = Comparator<T>>
+	constexpr uint64_t bisect(const T &p_value, bool p_before, Comparator compare = Comparator()) const;
+
+	/// The caller is responsible to ensure size() > 0.
+	constexpr T max() const;
+};
+
+template <typename T>
+constexpr int64_t Span<T>::find(const T &p_val, uint64_t p_from) const {
+	for (uint64_t i = p_from; i < size(); i++) {
+		if (ptr()[i] == p_val) {
+			return i;
+		}
+	}
+	return -1;
+}
+
+template <typename T>
+template <typename T1>
+constexpr int64_t Span<T>::find_sequence(const Span<T1> &p_span, uint64_t p_from) const {
+	for (uint64_t i = p_from; i <= size() - p_span.size(); i++) {
+		if (are_spans_equal(ptr() + i, p_span.ptr(), p_span.size())) {
+			return i;
+		}
+	}
+
+	return -1;
+}
+
+template <typename T>
+constexpr int64_t Span<T>::rfind(const T &p_val, uint64_t p_from) const {
+	DEV_ASSERT(p_from < size());
+	for (int64_t i = p_from; i >= 0; i--) {
+		if (ptr()[i] == p_val) {
+			return i;
+		}
+	}
+	return -1;
+}
+
+template <typename T>
+template <typename T1>
+constexpr int64_t Span<T>::rfind_sequence(const Span<T1> &p_span, uint64_t p_from) const {
+	DEV_ASSERT(p_from + p_span.size() <= size());
+	for (int64_t i = p_from; i >= 0; i--) {
+		if (are_spans_equal(ptr() + i, p_span.ptr(), p_span.size())) {
+			return i;
+		}
+	}
+
+	return -1;
+}
+
+template <typename T>
+constexpr uint64_t Span<T>::count(const T &p_val) const {
+	uint64_t amount = 0;
+	for (uint64_t i = 0; i < size(); i++) {
+		if (ptr()[i] == p_val) {
+			amount++;
+		}
+	}
+	return amount;
+}
+
+template <typename T>
+template <typename Comparator>
+constexpr uint64_t Span<T>::bisect(const T &p_value, bool p_before, Comparator compare) const {
+	uint64_t lo = 0;
+	uint64_t hi = size();
+	if (p_before) {
+		while (lo < hi) {
+			const uint64_t mid = (lo + hi) / 2;
+			if (compare(ptr()[mid], p_value)) {
+				lo = mid + 1;
+			} else {
+				hi = mid;
+			}
+		}
+	} else {
+		while (lo < hi) {
+			const uint64_t mid = (lo + hi) / 2;
+			if (compare(p_value, ptr()[mid])) {
+				hi = mid;
+			} else {
+				lo = mid + 1;
+			}
+		}
+	}
+	return lo;
+}
+
+template <typename T>
+constexpr T Span<T>::max() const {
+	DEV_ASSERT(size() > 0);
+	T max_val = _ptr[0];
+	for (size_t i = 1; i < _len; ++i) {
+		if (_ptr[i] > max_val) {
+			max_val = _ptr[i];
+		}
+	}
+	return max_val;
+}
+
+template <typename LHS, typename RHS>
+bool operator==(const Span<LHS> &p_lhs, const Span<RHS> &p_rhs) {
+	return p_lhs.size() == p_rhs.size() && are_spans_equal(p_lhs.ptr(), p_rhs.ptr(), p_lhs.size());
+}
+
+template <typename LHS, typename RHS>
+_FORCE_INLINE_ bool operator!=(const Span<LHS> &p_lhs, const Span<RHS> &p_rhs) {
+	return !(p_lhs == p_rhs);
+}
+
+// Zero-constructing Span initializes _ptr and _len to 0 (and thus empty).
+template <typename T>
+struct is_zero_constructible<Span<T>> : std::true_type {};
+
+} // namespace godot

include/godot_cpp/templates/vector.hpp

@@ -40,6 +40,7 @@
 #include <godot_cpp/templates/cowdata.hpp>
 #include <godot_cpp/templates/search_array.hpp>
 #include <godot_cpp/templates/sort_array.hpp>
+#include <godot_cpp/templates/span.hpp>
 
 #include <climits>
 #include <initializer_list>
@@ -90,6 +91,9 @@ class Vector {
 	_FORCE_INLINE_ void clear() { resize(0); }
 	_FORCE_INLINE_ bool is_empty() const { return _cowdata.is_empty(); }
 
+	_FORCE_INLINE_ operator Span<T>() const { return _cowdata.span(); }
+	_FORCE_INLINE_ Span<T> span() const { return _cowdata.span(); }
+
 	_FORCE_INLINE_ T get(Size p_index) { return _cowdata.get(p_index); }
 	_FORCE_INLINE_ const T &get(Size p_index) const { return _cowdata.get(p_index); }
 	_FORCE_INLINE_ void set(Size p_index, const T &p_elem) { _cowdata.set(p_index, p_elem); }