blob: 626ba07b915f2bcbc44c87c47b7c7da0e3cbd298 (
plain)
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
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
|
/*
* Copyright (c) 2020, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/Atomic.h>
#include <AK/Noncopyable.h>
#ifdef KERNEL
# include <Kernel/Arch/Processor.h>
# include <Kernel/Locking/SpinlockProtected.h>
# include <Kernel/ScopedCritical.h>
#elif defined(AK_OS_WINDOWS)
// Forward declare to avoid pulling Windows.h into every file in existence.
extern "C" __declspec(dllimport) void __stdcall Sleep(unsigned long);
# ifndef sched_yield
# define sched_yield() Sleep(0)
# endif
#else
# include <sched.h>
#endif
#ifndef AK_OS_SERENITY
# include <new>
#endif
namespace AK {
template<typename T>
struct SingletonInstanceCreator {
static T* create()
{
return new T();
}
};
#ifdef KERNEL
template<typename T, Kernel::LockRank Rank>
struct SingletonInstanceCreator<Kernel::SpinlockProtected<T, Rank>> {
static Kernel::SpinlockProtected<T, Rank>* create()
{
return new Kernel::SpinlockProtected<T, Rank> {};
}
};
#endif
template<typename T, T* (*InitFunction)() = SingletonInstanceCreator<T>::create>
class Singleton {
AK_MAKE_NONCOPYABLE(Singleton);
AK_MAKE_NONMOVABLE(Singleton);
public:
Singleton() = default;
template<bool allow_create = true>
static T* get(Atomic<T*>& obj_var)
{
T* obj = obj_var.load(AK::memory_order_acquire);
if (FlatPtr(obj) <= 0x1) {
// If this is the first time, see if we get to initialize it
#ifdef KERNEL
Kernel::ScopedCritical critical;
#endif
if constexpr (allow_create) {
if (obj == nullptr && obj_var.compare_exchange_strong(obj, (T*)0x1, AK::memory_order_acq_rel)) {
// We're the first one
obj = InitFunction();
obj_var.store(obj, AK::memory_order_release);
return obj;
}
}
// Someone else was faster, wait until they're done
while (obj == (T*)0x1) {
#ifdef KERNEL
Kernel::Processor::wait_check();
#else
sched_yield();
#endif
obj = obj_var.load(AK::memory_order_acquire);
}
if constexpr (allow_create) {
// We should always return an instance if we allow creating one
VERIFY(obj != nullptr);
}
VERIFY(obj != (T*)0x1);
}
return obj;
}
T* ptr() const
{
return get(m_obj);
}
T* operator->() const
{
return ptr();
}
T& operator*() const
{
return *ptr();
}
operator T*() const
{
return ptr();
}
operator T&() const
{
return *ptr();
}
bool is_initialized() const
{
T* obj = m_obj.load(AK::MemoryOrder::memory_order_consume);
return FlatPtr(obj) > 0x1;
}
void ensure_instance()
{
ptr();
}
private:
mutable Atomic<T*> m_obj { nullptr };
};
}
#if USING_AK_GLOBALLY
using AK::Singleton;
#endif
|
