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Serenity Operating System
1/*
2 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright notice, this
9 * list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
18 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
21 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
22 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
23 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#pragma once
28
29#include <AK/OwnPtr.h>
30#include <AK/SinglyLinkedList.h>
31#include <AK/Vector.h>
32
33namespace AK {
34
35template<typename T, int segment_size = 1000>
36class Queue {
37public:
38 Queue() { }
39 ~Queue() { }
40
41 size_t size() const { return m_size; }
42 bool is_empty() const { return m_size == 0; }
43
44 void enqueue(T&& value)
45 {
46 if (m_segments.is_empty() || m_segments.last()->size() >= segment_size)
47 m_segments.append(make<Vector<T, segment_size>>());
48 m_segments.last()->append(move(value));
49 ++m_size;
50 }
51
52 void enqueue(const T& value)
53 {
54 enqueue(T(value));
55 }
56
57 T dequeue()
58 {
59 ASSERT(!is_empty());
60 auto value = move((*m_segments.first())[m_index_into_first++]);
61 if (m_index_into_first == segment_size) {
62 m_segments.take_first();
63 m_index_into_first = 0;
64 }
65 --m_size;
66 return value;
67 }
68
69 const T& head() const
70 {
71 ASSERT(!is_empty());
72 return (*m_segments.first())[m_index_into_first];
73 }
74
75 void clear()
76 {
77 m_segments.clear();
78 m_index_into_first = 0;
79 m_size = 0;
80 }
81
82private:
83 SinglyLinkedList<OwnPtr<Vector<T, segment_size>>> m_segments;
84 size_t m_index_into_first { 0 };
85 size_t m_size { 0 };
86};
87
88}
89
90using AK::Queue;
91