Merge pull request #104055 from Ivorforce/fixed-vector

Core: Add `FixedVector` template - a collection that can be used completely on the stack.

core/templates/fixed_vector.h

@@ -0,0 +1,163 @@
+/**************************************************************************/
+/*  fixed_vector.h                                                        */
+/**************************************************************************/
+/*                         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
+
+/**
+ * A high performance Vector of fixed capacity.
+ * Especially useful if you need to create an array on the stack, to
+ *  prevent dynamic allocations (especially in bottleneck code).
+ *
+ * Choose CAPACITY such that it is enough for all elements that could be added through all branches.
+ *
+ */
+template <class T, uint32_t CAPACITY>
+class FixedVector {
+	// This declaration allows us to access other FixedVector's private members.
+	template <class T_, uint32_t CAPACITY_>
+	friend class FixedVector;
+
+	uint32_t _size = 0;
+	alignas(T) uint8_t _data[CAPACITY * sizeof(T)];
+
+	constexpr static uint32_t DATA_PADDING = MAX(alignof(T), alignof(uint32_t)) - alignof(uint32_t);
+
+public:
+	_FORCE_INLINE_ constexpr FixedVector() = default;
+	constexpr FixedVector(std::initializer_list<T> p_init) {
+		ERR_FAIL_COND(p_init.size() > CAPACITY);
+		for (const T &element : p_init) {
+			memnew_placement(ptr() + _size++, T(element));
+		}
+	}
+
+	template <uint32_t p_capacity>
+	constexpr FixedVector(const FixedVector<T, p_capacity> &p_from) {
+		ERR_FAIL_COND(p_from.size() > CAPACITY);
+		if constexpr (std::is_trivially_copyable_v<T>) {
+			// Copy size and all provided elements at once.
+			memcpy((void *)&_size, (void *)&p_from._size, sizeof(_size) + DATA_PADDING + p_from.size() * sizeof(T));
+		} else {
+			for (const T &element : p_from) {
+				memnew_placement(ptr() + _size++, T(element));
+			}
+		}
+	}
+
+	template <uint32_t p_capacity>
+	constexpr FixedVector(FixedVector<T, p_capacity> &&p_from) {
+		ERR_FAIL_COND(p_from.size() > CAPACITY);
+		// Copy size and all provided elements at once.
+		// Note: Assumes trivial relocatability.
+		memcpy((void *)&_size, (void *)&p_from._size, sizeof(_size) + DATA_PADDING + p_from.size() * sizeof(T));
+		p_from._size = 0;
+	}
+
+	~FixedVector() {
+		if constexpr (!std::is_trivially_destructible_v<T>) {
+			for (uint32_t i = 0; i < _size; i++) {
+				ptr()[i].~T();
+			}
+		}
+	}
+
+	_FORCE_INLINE_ constexpr T *ptr() { return (T *)(_data); }
+	_FORCE_INLINE_ constexpr const T *ptr() const { return (const T *)(_data); }
+
+	_FORCE_INLINE_ constexpr operator Span<T>() const { return Span<T>(ptr(), size()); }
+	_FORCE_INLINE_ constexpr Span<T> span() const { return operator Span<T>(); }
+
+	_FORCE_INLINE_ constexpr uint32_t size() const { return _size; }
+	_FORCE_INLINE_ constexpr bool is_empty() const { return !_size; }
+	_FORCE_INLINE_ constexpr bool is_full() const { return _size == CAPACITY; }
+	_FORCE_INLINE_ constexpr uint32_t capacity() const { return CAPACITY; }
+
+	_FORCE_INLINE_ constexpr void clear() { resize_initialized(0); }
+
+	/// Changes the size of the vector.
+	/// If p_size > size(), constructs new elements.
+	/// If p_size < size(), destructs new elements.
+	constexpr Error resize_initialized(uint32_t p_size) {
+		if (p_size > _size) {
+			ERR_FAIL_COND_V(p_size > CAPACITY, ERR_OUT_OF_MEMORY);
+			memnew_arr_placement<true>(ptr() + _size, p_size - _size);
+		} else if (p_size < _size) {
+			if constexpr (!std::is_trivially_destructible_v<T>) {
+				for (uint32_t i = p_size; i < _size; i++) {
+					ptr()[i].~T();
+				}
+			}
+		}
+
+		_size = p_size;
+		return OK;
+	}
+
+	/// Changes the size of the vector.
+	/// The initializer of new elements is skipped, making this function faster than resize_initialized.
+	/// The caller is required to initialize the new values.
+	constexpr Error resize_uninitialized(uint32_t p_size) {
+		static_assert(std::is_trivially_destructible_v<T>, "resize_uninitialized is unsafe to call if T is not trivially destructible.");
+		ERR_FAIL_COND_V(p_size > CAPACITY, ERR_OUT_OF_MEMORY);
+		_size = p_size;
+		return OK;
+	}
+
+	constexpr void push_back(const T &p_val) {
+		ERR_FAIL_COND(_size >= CAPACITY);
+		memnew_placement(ptr() + _size, T(p_val));
+		_size++;
+	}
+
+	constexpr void pop_back() {
+		ERR_FAIL_COND(_size == 0);
+		_size--;
+		ptr()[_size].~T();
+	}
+
+	// NOTE: 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.
+	constexpr const T &operator[](uint32_t p_index) const {
+		CRASH_COND(p_index >= _size);
+		return ptr()[p_index];
+	}
+
+	constexpr T &operator[](uint32_t p_index) {
+		CRASH_COND(p_index >= _size);
+		return ptr()[p_index];
+	}
+
+	_FORCE_INLINE_ constexpr T *begin() { return ptr(); }
+	_FORCE_INLINE_ constexpr T *end() { return ptr() + _size; }
+
+	_FORCE_INLINE_ constexpr const T *begin() const { return ptr(); }
+	_FORCE_INLINE_ constexpr const T *end() const { return ptr() + _size; }
+};

tests/core/templates/test_fixed_vector.h

@@ -0,0 +1,107 @@
+/**************************************************************************/
+/*  test_fixed_vector.h                                                   */
+/**************************************************************************/
+/*                         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 "core/templates/fixed_vector.h"
+
+#include "tests/test_macros.h"
+
+namespace TestFixedVector {
+
+TEST_CASE("[FixedVector] Basic Checks") {
+	FixedVector<uint16_t, 1> vector;
+	CHECK_EQ(vector.capacity(), 1);
+
+	CHECK_EQ(vector.size(), 0);
+	CHECK(vector.is_empty());
+	CHECK(!vector.is_full());
+
+	vector.push_back(5);
+	CHECK_EQ(vector.size(), 1);
+	CHECK_EQ(vector[0], 5);
+	CHECK_EQ(vector.ptr()[0], 5);
+	CHECK(!vector.is_empty());
+	CHECK(vector.is_full());
+
+	vector.pop_back();
+	CHECK_EQ(vector.size(), 0);
+	CHECK(vector.is_empty());
+	CHECK(!vector.is_full());
+
+	FixedVector<uint16_t, 2> vector1 = { 1, 2 };
+	CHECK_EQ(vector1.capacity(), 2);
+	CHECK_EQ(vector1.size(), 2);
+	CHECK_EQ(vector1[0], 1);
+	CHECK_EQ(vector1[1], 2);
+
+	FixedVector<uint16_t, 3> vector2(vector1);
+	CHECK_EQ(vector2.capacity(), 3);
+	CHECK_EQ(vector2.size(), 2);
+	CHECK_EQ(vector2[0], 1);
+	CHECK_EQ(vector2[1], 2);
+
+	FixedVector<Variant, 3> vector_variant;
+	CHECK_EQ(vector_variant.size(), 0);
+	CHECK_EQ(vector_variant.capacity(), 3);
+	vector_variant.resize_initialized(3);
+	vector_variant[0] = "Test";
+	vector_variant[1] = 1;
+	CHECK_EQ(vector_variant.capacity(), 3);
+	CHECK_EQ(vector_variant.size(), 3);
+	CHECK_EQ(vector_variant[0], "Test");
+	CHECK_EQ(vector_variant[1], Variant(1));
+	CHECK_EQ(vector_variant[2].get_type(), Variant::NIL);
+}
+
+TEST_CASE("[FixedVector] Alignment Checks") {
+	FixedVector<uint16_t, 4> vector_uint16;
+	vector_uint16.resize_uninitialized(4);
+	CHECK((size_t)&vector_uint16[0] % alignof(uint16_t) == 0);
+	CHECK((size_t)&vector_uint16[1] % alignof(uint16_t) == 0);
+	CHECK((size_t)&vector_uint16[2] % alignof(uint16_t) == 0);
+	CHECK((size_t)&vector_uint16[3] % alignof(uint16_t) == 0);
+
+	FixedVector<uint32_t, 4> vector_uint32;
+	vector_uint32.resize_uninitialized(4);
+	CHECK((size_t)&vector_uint32[0] % alignof(uint32_t) == 0);
+	CHECK((size_t)&vector_uint32[1] % alignof(uint32_t) == 0);
+	CHECK((size_t)&vector_uint32[2] % alignof(uint32_t) == 0);
+	CHECK((size_t)&vector_uint32[3] % alignof(uint32_t) == 0);
+
+	FixedVector<uint64_t, 4> vector_uint64;
+	vector_uint64.resize_uninitialized(4);
+	CHECK((size_t)&vector_uint64[0] % alignof(uint64_t) == 0);
+	CHECK((size_t)&vector_uint64[1] % alignof(uint64_t) == 0);
+	CHECK((size_t)&vector_uint64[2] % alignof(uint64_t) == 0);
+	CHECK((size_t)&vector_uint64[3] % alignof(uint64_t) == 0);
+}
+
+} //namespace TestFixedVector

tests/test_main.cpp

@@ -95,6 +95,7 @@
 #include "tests/core/string/test_translation_server.h"
 #include "tests/core/templates/test_a_hash_map.h"
 #include "tests/core/templates/test_command_queue.h"
+#include "tests/core/templates/test_fixed_vector.h"
 #include "tests/core/templates/test_hash_map.h"
 #include "tests/core/templates/test_hash_set.h"
 #include "tests/core/templates/test_list.h"