jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
3 * Copyright (c) 2022, the SerenityOS developers.
4 *
5 * SPDX-License-Identifier: BSD-2-Clause
6 */
7
8#pragma once
9
10#include <AK/Error.h>
11#include <AK/Iterator.h>
12#include <AK/Span.h>
13#include <AK/kmalloc.h>
14#include <initializer_list>
15
16namespace AK {
17
18// FixedArray is an Array with a size only known at run-time.
19// It guarantees to only allocate when being constructed, and to only deallocate when being destructed.
20template<typename T>
21class FixedArray {
22public:
23 FixedArray() = default;
24
25 static ErrorOr<FixedArray<T>> create(std::initializer_list<T> initializer)
26 {
27 auto array = TRY(create(initializer.size()));
28 auto it = initializer.begin();
29 for (size_t i = 0; i < array.size(); ++i) {
30 array[i] = move(*it);
31 ++it;
32 }
33 return array;
34 }
35
36 static ErrorOr<FixedArray<T>> create(size_t size)
37 {
38 if (size == 0)
39 return FixedArray<T>();
40 auto* new_storage = static_cast<Storage*>(kmalloc(storage_allocation_size(size)));
41 if (!new_storage)
42 return Error::from_errno(ENOMEM);
43 new_storage->size = size;
44 for (size_t i = 0; i < size; ++i)
45 new (&new_storage->elements[i]) T();
46 return FixedArray<T>(new_storage);
47 }
48
49 static FixedArray<T> must_create_but_fixme_should_propagate_errors(size_t size)
50 {
51 return MUST(create(size));
52 }
53
54 template<size_t N>
55 static ErrorOr<FixedArray<T>> create(T (&&array)[N])
56 {
57 return create(Span(array, N));
58 }
59
60 template<typename U>
61 static ErrorOr<FixedArray<T>> create(Span<U> span)
62 {
63 if (span.size() == 0)
64 return FixedArray<T>();
65 auto* new_storage = static_cast<Storage*>(kmalloc(storage_allocation_size(span.size())));
66 if (!new_storage)
67 return Error::from_errno(ENOMEM);
68 new_storage->size = span.size();
69 for (size_t i = 0; i < span.size(); ++i)
70 new (&new_storage->elements[i]) T(span[i]);
71 return FixedArray<T>(new_storage);
72 }
73
74 ErrorOr<FixedArray<T>> clone() const
75 {
76 return create(span());
77 }
78
79 static size_t storage_allocation_size(size_t size)
80 {
81 return sizeof(Storage) + size * sizeof(T);
82 }
83
84 // Nobody can ever use these functions, since it would be impossible to make them OOM-safe due to their signatures. We just explicitly delete them.
85 FixedArray(FixedArray<T> const&) = delete;
86 FixedArray<T>& operator=(FixedArray<T> const&) = delete;
87
88 FixedArray(FixedArray<T>&& other)
89 : m_storage(exchange(other.m_storage, nullptr))
90 {
91 }
92 // This function would violate the contract, as it would need to deallocate this FixedArray. As it also has no use case, we delete it.
93 FixedArray<T>& operator=(FixedArray<T>&&) = delete;
94
95 ~FixedArray()
96 {
97 if (!m_storage)
98 return;
99 for (size_t i = 0; i < m_storage->size; ++i)
100 m_storage->elements[i].~T();
101 kfree_sized(m_storage, storage_allocation_size(m_storage->size));
102 m_storage = nullptr;
103 }
104
105 size_t size() const { return m_storage ? m_storage->size : 0; }
106 bool is_empty() const { return size() == 0; }
107 T* data() { return m_storage ? m_storage->elements : nullptr; }
108 T const* data() const { return m_storage ? m_storage->elements : nullptr; }
109
110 T& at(size_t index)
111 {
112 VERIFY(index < m_storage->size);
113 return m_storage->elements[index];
114 }
115
116 T const& at(size_t index) const
117 {
118 VERIFY(index < m_storage->size);
119 return m_storage->elements[index];
120 }
121
122 T& operator[](size_t index)
123 {
124 return at(index);
125 }
126
127 T const& operator[](size_t index) const
128 {
129 return at(index);
130 }
131
132 bool contains_slow(T const& value) const
133 {
134 if (!m_storage)
135 return false;
136 for (size_t i = 0; i < m_storage->size; ++i) {
137 if (m_storage->elements[i] == value)
138 return true;
139 }
140 return false;
141 }
142
143 void swap(FixedArray<T>& other)
144 {
145 ::swap(m_storage, other.m_storage);
146 }
147
148 void fill_with(T const& value)
149 {
150 if (!m_storage)
151 return;
152 for (size_t i = 0; i < m_storage->size; ++i)
153 m_storage->elements[i] = value;
154 }
155
156 using Iterator = SimpleIterator<FixedArray, T>;
157 using ConstIterator = SimpleIterator<FixedArray const, T const>;
158
159 Iterator begin() { return Iterator::begin(*this); }
160 ConstIterator begin() const { return ConstIterator::begin(*this); }
161
162 Iterator end() { return Iterator::end(*this); }
163 ConstIterator end() const { return ConstIterator::end(*this); }
164
165 Span<T> span() { return { data(), size() }; }
166 ReadonlySpan<T> span() const { return { data(), size() }; }
167
168private:
169 struct Storage {
170 size_t size { 0 };
171 T elements[0];
172 };
173
174 FixedArray(Storage* storage)
175 : m_storage(storage)
176 {
177 }
178
179 Storage* m_storage { nullptr };
180};
181
182}
183
184#if USING_AK_GLOBALLY
185using AK::FixedArray;
186#endif