1 // Copyright 2017 The Chromium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "base/threading/sequence_local_storage_map.h"
6
7 #include <ostream>
8 #include <utility>
9
10 #include "base/check_op.h"
11 #include "third_party/abseil-cpp/absl/base/attributes.h"
12
13 namespace base {
14 namespace internal {
15
16 namespace {
17
18 ABSL_CONST_INIT thread_local SequenceLocalStorageMap*
19 current_sequence_local_storage = nullptr;
20
21 } // namespace
22
23 SequenceLocalStorageMap::SequenceLocalStorageMap() = default;
24
25 SequenceLocalStorageMap::~SequenceLocalStorageMap() = default;
26
27 // static
GetForCurrentThread()28 SequenceLocalStorageMap& SequenceLocalStorageMap::GetForCurrentThread() {
29 DCHECK(IsSetForCurrentThread())
30 << "SequenceLocalStorageSlot cannot be used because no "
31 "SequenceLocalStorageMap was stored in TLS. Use "
32 "ScopedSetSequenceLocalStorageMapForCurrentThread to store a "
33 "SequenceLocalStorageMap object in TLS.";
34
35 return *current_sequence_local_storage;
36 }
37
38 // static
IsSetForCurrentThread()39 bool SequenceLocalStorageMap::IsSetForCurrentThread() {
40 return current_sequence_local_storage != nullptr;
41 }
42
Has(int slot_id) const43 bool SequenceLocalStorageMap::Has(int slot_id) const {
44 return const_cast<SequenceLocalStorageMap*>(this)->Get(slot_id) != nullptr;
45 }
46
Reset(int slot_id)47 void SequenceLocalStorageMap::Reset(int slot_id) {
48 sls_map_.erase(slot_id);
49 }
50
Get(int slot_id)51 SequenceLocalStorageMap::Value* SequenceLocalStorageMap::Get(int slot_id) {
52 auto it = sls_map_.find(slot_id);
53 if (it != sls_map_.end()) {
54 return it->second.get();
55 }
56 return nullptr;
57 }
58
Set(int slot_id,SequenceLocalStorageMap::ValueDestructorPair value_destructor_pair)59 SequenceLocalStorageMap::Value* SequenceLocalStorageMap::Set(
60 int slot_id,
61 SequenceLocalStorageMap::ValueDestructorPair value_destructor_pair) {
62 auto it = sls_map_.find(slot_id);
63
64 if (it == sls_map_.end())
65 it = sls_map_.emplace(slot_id, std::move(value_destructor_pair)).first;
66 else
67 it->second = std::move(value_destructor_pair);
68
69 // The maximum number of entries in the map is 256. This can be adjusted, but
70 // will require reviewing the choice of data structure for the map.
71 DCHECK_LE(sls_map_.size(), 256U);
72 return it->second.get();
73 }
74
ValueDestructorPair()75 SequenceLocalStorageMap::ValueDestructorPair::ValueDestructorPair()
76 : destructor_(nullptr) {}
77
ValueDestructorPair(ExternalValue value,DestructorFunc * destructor)78 SequenceLocalStorageMap::ValueDestructorPair::ValueDestructorPair(
79 ExternalValue value,
80 DestructorFunc* destructor)
81 : value_{.external_value = std::move(value)}, destructor_(destructor) {}
82
ValueDestructorPair(InlineValue value,DestructorFunc * destructor)83 SequenceLocalStorageMap::ValueDestructorPair::ValueDestructorPair(
84 InlineValue value,
85 DestructorFunc* destructor)
86 : value_{.inline_value = std::move(value)}, destructor_(destructor) {}
87
~ValueDestructorPair()88 SequenceLocalStorageMap::ValueDestructorPair::~ValueDestructorPair() {
89 if (destructor_) {
90 destructor_(&value_);
91 }
92 }
93
ValueDestructorPair(ValueDestructorPair && value_destructor_pair)94 SequenceLocalStorageMap::ValueDestructorPair::ValueDestructorPair(
95 ValueDestructorPair&& value_destructor_pair)
96 : value_(value_destructor_pair.value_),
97 destructor_(value_destructor_pair.destructor_) {
98 value_destructor_pair.destructor_ = nullptr;
99 }
100
101 SequenceLocalStorageMap::ValueDestructorPair&
operator =(ValueDestructorPair && value_destructor_pair)102 SequenceLocalStorageMap::ValueDestructorPair::operator=(
103 ValueDestructorPair&& value_destructor_pair) {
104 if (this == &value_destructor_pair) {
105 return *this;
106 }
107 // Destroy |value_| before overwriting it with a new value.
108 if (destructor_) {
109 destructor_(&value_);
110 }
111 value_ = value_destructor_pair.value_;
112 destructor_ = std::exchange(value_destructor_pair.destructor_, nullptr);
113
114 return *this;
115 }
116
operator bool() const117 SequenceLocalStorageMap::ValueDestructorPair::operator bool() const {
118 return destructor_ != nullptr;
119 }
120
121 ScopedSetSequenceLocalStorageMapForCurrentThread::
ScopedSetSequenceLocalStorageMapForCurrentThread(SequenceLocalStorageMap * sequence_local_storage)122 ScopedSetSequenceLocalStorageMapForCurrentThread(
123 SequenceLocalStorageMap* sequence_local_storage)
124 : resetter_(¤t_sequence_local_storage,
125 sequence_local_storage,
126 nullptr) {}
127
128 ScopedSetSequenceLocalStorageMapForCurrentThread::
129 ~ScopedSetSequenceLocalStorageMapForCurrentThread() = default;
130
131 } // namespace internal
132 } // namespace base
133