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
|
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// WARNING: Thread local storage is a bit tricky to get right. Please make sure
// that this is really the proper solution for what you're trying to achieve.
// Don't prematurely optimize, most likely you can just use a Lock.
//
// These classes implement a wrapper around ThreadLocalStorage::Slot. On
// construction, they will allocate a TLS slot, and free the TLS slot on
// destruction. No memory management (creation or destruction) is handled. This
// means for uses of ThreadLocalPointer, you must correctly manage the memory
// yourself, these classes will not destroy the pointer for you. There are no
// at-thread-exit actions taken by these classes.
//
// ThreadLocalPointer<Type> wraps a Type*. It performs no creation or
// destruction, so memory management must be handled elsewhere. The first call
// to Get() on a thread will return NULL. You can update the pointer with a call
// to Set().
//
// ThreadLocalBoolean wraps a bool. It will default to false if it has never
// been set otherwise with Set().
//
// Thread Safety: An instance of ThreadLocalStorage is completely thread safe
// once it has been created. If you want to dynamically create an instance, you
// must of course properly deal with safety and race conditions.
//
// In Android, the system TLS is limited.
//
// Example usage:
// // My class is logically attached to a single thread. We cache a pointer
// // on the thread it was created on, so we can implement current().
// MyClass::MyClass() {
// DCHECK(Singleton<ThreadLocalPointer<MyClass> >::get()->Get() == NULL);
// Singleton<ThreadLocalPointer<MyClass> >::get()->Set(this);
// }
//
// MyClass::~MyClass() {
// DCHECK(Singleton<ThreadLocalPointer<MyClass> >::get()->Get() != NULL);
// Singleton<ThreadLocalPointer<MyClass> >::get()->Set(NULL);
// }
//
// // Return the current MyClass associated with the calling thread, can be
// // NULL if there isn't a MyClass associated.
// MyClass* MyClass::current() {
// return Singleton<ThreadLocalPointer<MyClass> >::get()->Get();
// }
#ifndef BASE_THREADING_THREAD_LOCAL_H_
#define BASE_THREADING_THREAD_LOCAL_H_
#include <memory>
#include "base/check_op.h"
#include "base/macros.h"
#include "base/threading/thread_local_internal.h"
#include "base/threading/thread_local_storage.h"
namespace base {
template <typename T>
class ThreadLocalPointer {
public:
ThreadLocalPointer() = default;
~ThreadLocalPointer() = default;
T* Get() const { return static_cast<T*>(slot_.Get()); }
void Set(T* ptr) {
slot_.Set(const_cast<void*>(static_cast<const void*>(ptr)));
}
private:
ThreadLocalStorage::Slot slot_;
DISALLOW_COPY_AND_ASSIGN(ThreadLocalPointer<T>);
};
// A ThreadLocalOwnedPointer<T> is like a ThreadLocalPointer<T> except that
// pointers handed to it are owned and automatically deleted during their
// associated thread's exit phase (or when replaced if Set() is invoked multiple
// times on the same thread).
// The ThreadLocalOwnedPointer instance itself can only be destroyed when no
// threads, other than the one it is destroyed on, have remaining state set in
// it. Typically this means that ThreadLocalOwnedPointer instances are held in
// static storage or at the very least only recycled in the single-threaded
// phase between tests in the same process.
#if DCHECK_IS_ON()
template <typename T>
using ThreadLocalOwnedPointer = internal::CheckedThreadLocalOwnedPointer<T>;
#else // DCHECK_IS_ON()
template <typename T>
class ThreadLocalOwnedPointer {
public:
ThreadLocalOwnedPointer() = default;
~ThreadLocalOwnedPointer() {
// Assume that this thread is the only one with potential state left. This
// is verified in ~CheckedThreadLocalOwnedPointer().
Set(nullptr);
}
T* Get() const { return static_cast<T*>(slot_.Get()); }
void Set(std::unique_ptr<T> ptr) {
delete Get();
slot_.Set(const_cast<void*>(static_cast<const void*>(ptr.release())));
}
private:
static void DeleteTlsPtr(void* ptr) { delete static_cast<T*>(ptr); }
ThreadLocalStorage::Slot slot_{&DeleteTlsPtr};
DISALLOW_COPY_AND_ASSIGN(ThreadLocalOwnedPointer<T>);
};
#endif // DCHECK_IS_ON()
class ThreadLocalBoolean {
public:
ThreadLocalBoolean() = default;
~ThreadLocalBoolean() = default;
bool Get() const { return tlp_.Get() != nullptr; }
void Set(bool val) { tlp_.Set(val ? this : nullptr); }
private:
ThreadLocalPointer<void> tlp_;
DISALLOW_COPY_AND_ASSIGN(ThreadLocalBoolean);
};
} // namespace base
#endif // BASE_THREADING_THREAD_LOCAL_H_
|
