1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
|
/*
* Copyright (C) 2017-2024 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <wtf/Atomics.h>
#include <wtf/Noncopyable.h>
#include <wtf/StdLibExtras.h>
namespace WTF {
// This a simple single consumer, multiple producer Bag data structure.
template<typename T>
class LocklessBag final {
WTF_MAKE_FAST_ALLOCATED;
WTF_MAKE_NONCOPYABLE(LocklessBag);
public:
struct Node {
WTF_MAKE_FAST_ALLOCATED;
public:
T data;
Node* next;
};
LocklessBag()
: m_head(nullptr)
{
}
enum PushResult { Empty, NonEmpty };
PushResult add(T&& element)
{
Node* newNode = new Node();
newNode->data = std::forward<T>(element);
Node* oldHead;
m_head.transaction([&] (Node*& head) {
oldHead = head;
newNode->next = head;
head = newNode;
return true;
});
return oldHead == nullptr ? Empty : NonEmpty;
}
// CONSUMER FUNCTIONS: Everything below here is only safe to call from the consumer thread.
// This function is actually safe to call from more than one thread, but ONLY if no thread can call consumeAll.
void iterate(NOESCAPE const Invocable<void(const T&)> auto& func)
{
Node* node = m_head.load();
while (node) {
func(node->data);
node = node->next;
}
}
void consumeAll(NOESCAPE const Invocable<void(T&&)> auto& func)
{
consumeAllWithNode([&] (T&& data, Node* node) {
func(WTFMove(data));
delete node;
});
}
void consumeAllWithNode(NOESCAPE const Invocable<void(T&&, Node*)> auto& func)
{
Node* node = m_head.exchange(nullptr);
while (node) {
Node* oldNode = node;
node = node->next;
func(WTFMove(oldNode->data), oldNode);
}
}
~LocklessBag()
{
consumeAll([] (T&&) { });
}
private:
Atomic<Node*> m_head;
};
} // namespace WTF
|
