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220 lines
7.4 KiB
C++
220 lines
7.4 KiB
C++
/**************************************************************************/
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/* span.h */
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/**************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* https://godotengine.org */
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/**************************************************************************/
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/**************************************************************************/
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#pragma once
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#include "core/error_macros.h"
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#include "core/typedefs.h"
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// Equivalent of std::span.
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// Represents a view into a contiguous memory space.
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// DISCLAIMER: This data type does not own the underlying buffer. DO NOT STORE IT.
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// Additionally, for the lifetime of the Span, do not resize the buffer, and do not insert or remove elements from it.
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// Failure to respect this may lead to crashes or undefined behavior.
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template <typename T, class U = uint32_t>
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class Span {
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const T *_ptr = nullptr;
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U _len = 0;
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public:
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static constexpr bool is_string = std::disjunction_v<
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std::is_same<T, char>,
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std::is_same<T, char16_t>,
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std::is_same<T, char32_t>,
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std::is_same<T, wchar_t>>;
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_FORCE_INLINE_ constexpr Span() = default;
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_FORCE_INLINE_ Span(const T *p_ptr, U p_len) :
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_ptr(p_ptr), _len(p_len) {
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#ifdef DEBUG_ENABLED
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// TODO In c++20, make this check run only in non-consteval, and make this constructor constexpr.
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if (_ptr == nullptr && _len > 0) {
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ERR_PRINT("Internal bug, please report: Span was created from nullptr with size > 0. Recovering by using size = 0.");
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_len = 0;
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}
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#endif
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}
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// Allows creating Span directly from C arrays and string literals.
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template <size_t N>
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_FORCE_INLINE_ constexpr Span(const T (&p_array)[N]) :
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_ptr(p_array), _len(N) {
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if constexpr (is_string) {
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// Cut off the \0 terminator implicitly added to string literals.
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if (N > 0 && p_array[N - 1] == '\0') {
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_len--;
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}
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}
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}
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_FORCE_INLINE_ constexpr U size() const { return _len; }
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_FORCE_INLINE_ constexpr bool is_empty() const { return _len == 0; }
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_FORCE_INLINE_ constexpr const T *ptr() const { return _ptr; }
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// NOTE: Span subscripts sanity check the bounds to avoid undefined behavior.
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// This is slower than direct buffer access and can prevent autovectorization.
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// If the bounds are known, use ptr() subscript instead.
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_FORCE_INLINE_ constexpr const T &operator[](U p_idx) const {
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CRASH_COND(p_idx >= _len);
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return _ptr[p_idx];
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}
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_FORCE_INLINE_ constexpr const T *begin() const { return _ptr; }
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_FORCE_INLINE_ constexpr const T *end() const { return _ptr + _len; }
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template <typename T1>
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_FORCE_INLINE_ constexpr Span<T1> reinterpret() const {
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return Span<T1>(reinterpret_cast<const T1 *>(_ptr), _len * sizeof(T) / sizeof(T1));
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}
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// Algorithms.
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constexpr int64_t find(const T &p_val, U p_from = 0) const;
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constexpr int64_t find_sequence(const Span<T> &p_span, U p_from = 0) const;
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constexpr int64_t rfind(const T &p_val, U p_from) const;
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_FORCE_INLINE_ constexpr int64_t rfind(const T &p_val) const { return rfind(p_val, size() - 1); }
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constexpr int64_t rfind_sequence(const Span<T> &p_span, U p_from) const;
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_FORCE_INLINE_ constexpr int64_t rfind_sequence(const Span<T> &p_span) const { return rfind_sequence(p_span, size() - p_span.size()); }
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constexpr U count(const T &p_val) const;
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/// Find the index of the given value using binary search.
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/// Note: Assumes that elements in the span are sorted. Otherwise, use find() instead.
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template <typename Comparator = Comparator<T>>
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constexpr U bisect(const T &p_value, bool p_before, Comparator compare = Comparator()) const;
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/// The caller is responsible to ensure size() > 0.
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constexpr T max() const;
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};
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template <typename T, class U>
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constexpr int64_t Span<T, U>::find(const T &p_val, U p_from) const {
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for (U i = p_from; i < size(); i++) {
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if (ptr()[i] == p_val) {
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return i;
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}
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}
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return -1;
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}
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template <typename T, class U>
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constexpr int64_t Span<T, U>::find_sequence(const Span<T> &p_span, U p_from) const {
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for (U i = p_from; i <= size() - p_span.size(); i++) {
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bool found = true;
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for (U j = 0; j < p_span.size(); j++) {
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if (ptr()[i + j] != p_span.ptr()[j]) {
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found = false;
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break;
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}
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}
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if (found) {
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return i;
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}
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}
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return -1;
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}
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template <typename T, class U>
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constexpr int64_t Span<T, U>::rfind(const T &p_val, U p_from) const {
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for (int64_t i = p_from; i >= 0; i--) {
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if (ptr()[i] == p_val) {
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return i;
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}
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}
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return -1;
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}
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template <typename T, class U>
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constexpr int64_t Span<T, U>::rfind_sequence(const Span<T> &p_span, U p_from) const {
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for (int64_t i = p_from; i >= 0; i--) {
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bool found = true;
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for (U j = 0; j < p_span.size(); j++) {
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if (ptr()[i + j] != p_span.ptr()[j]) {
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found = false;
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break;
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}
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}
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if (found) {
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return i;
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}
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}
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return -1;
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}
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template <typename T, class U>
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constexpr U Span<T, U>::count(const T &p_val) const {
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U amount = 0;
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for (U i = 0; i < size(); i++) {
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if (ptr()[i] == p_val) {
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amount++;
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}
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}
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return amount;
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}
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template <typename T, class U>
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template <typename Comparator>
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constexpr U Span<T, U>::bisect(const T &p_value, bool p_before, Comparator compare) const {
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U lo = 0;
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U hi = size();
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if (p_before) {
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while (lo < hi) {
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const U mid = (lo + hi) / 2;
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if (compare(ptr()[mid], p_value)) {
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lo = mid + 1;
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} else {
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hi = mid;
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}
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}
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} else {
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while (lo < hi) {
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const U mid = (lo + hi) / 2;
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if (compare(p_value, ptr()[mid])) {
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hi = mid;
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} else {
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lo = mid + 1;
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}
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}
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}
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return lo;
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}
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template <typename T, class U>
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constexpr T Span<T, U>::max() const {
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DEV_ASSERT(size() > 0);
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T max_val = _ptr[0];
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for (U i = 1; i < _len; ++i) {
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if (_ptr[i] > max_val) {
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max_val = _ptr[i];
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}
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}
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return max_val;
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}
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