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
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
|
/*
* Copyright (C) 2022 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. AND ITS CONTRIBUTORS ``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 ITS 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 <atomic>
#include <utility>
#include <wtf/HashTraits.h>
#include <wtf/Hasher.h>
#include <wtf/Noncopyable.h>
#include <wtf/ObjectIdentifier.h>
namespace IPC {
// Type for the key in mapping from object identifier references to object state.
template<typename T>
class ObjectIdentifierReference {
public:
ObjectIdentifierReference() = default;
ObjectIdentifierReference(T identifier, uint64_t version)
: m_identifier(identifier)
, m_version(version)
{
}
explicit ObjectIdentifierReference(WTF::HashTableDeletedValueType)
: m_identifier(WTF::HashTableDeletedValue)
{
}
T identifier() const { return m_identifier; }
uint64_t version() const { return m_version; }
static ObjectIdentifierReference<T> generateForAdd() { return { T::generate(), 0 }; }
bool operator==(const ObjectIdentifierReference& other) const
{
return other.m_identifier == m_identifier && other.m_version == m_version;
}
bool isHashTableDeletedValue() const
{
return m_identifier.isHashTableDeletedValue();
}
private:
T m_identifier;
uint64_t m_version { 0 };
};
template<typename T>
struct ObjectIdentifierReadReference {
public:
using Reference = ObjectIdentifierReference<T>;
ObjectIdentifierReadReference(Reference reference)
: m_reference(reference)
{
}
T identifier() const { return m_reference.identifier(); }
uint64_t version() const { return m_reference.version(); }
Reference reference() const { return m_reference; }
private:
Reference m_reference;
};
template<typename T>
class ObjectIdentifierWriteReference {
public:
using Reference = ObjectIdentifierReference<T>;
ObjectIdentifierWriteReference(Reference reference, uint64_t pendingReads)
: m_reference(reference)
, m_pendingReads(pendingReads)
{
}
T identifier() const { return m_reference.identifier(); }
uint64_t version() const { return m_reference.version(); }
uint64_t pendingReads() const { return m_pendingReads; }
Reference reference() const { return m_reference; }
ObjectIdentifierReference<T> retiredReference() const { return { identifier(), version() + 1 }; }
private:
Reference m_reference;
uint64_t m_pendingReads { 0 };
};
// Class to generate read and write references to an ObjectIdentifier.
template<typename T>
class ObjectIdentifierReferenceTracker {
WTF_MAKE_NONCOPYABLE(ObjectIdentifierReferenceTracker);
public:
using ReadReference = ObjectIdentifierReadReference<T>;
using WriteReference = ObjectIdentifierWriteReference<T>;
using Reference = ObjectIdentifierReference<T>;
explicit ObjectIdentifierReferenceTracker(T identifier)
: m_identifier(identifier)
{
}
explicit ObjectIdentifierReferenceTracker(Reference reference)
: m_identifier(reference.identifier())
, m_version(reference.version())
{
}
// Thread safe.
ReadReference read() const
{
m_pendingReads++;
return Reference { m_identifier, m_version };
}
// Not thread safe. Client must coordinate writes and reads anyway.
WriteReference write() const
{
return { { m_identifier, m_version++ }, m_pendingReads.exchange(0) };
}
Reference add() const
{
return { m_identifier, m_version };
}
T identifier() const
{
return m_identifier;
}
private:
const T m_identifier;
mutable std::atomic<uint64_t> m_pendingReads { 0 };
mutable uint64_t m_version { 0 };
};
template<typename T> inline void add(Hasher& hasher, ObjectIdentifierReference<T> reference)
{
add(hasher, reference.identifier());
add(hasher, reference.version());
}
template<typename T>
TextStream& operator<<(TextStream& ts, const IPC::ObjectIdentifierReference<T>& reference)
{
ts << "ObjectIdentifierReference(" << reference.identifier() << ", " << reference.version() << ")";
return ts;
}
template<typename T>
TextStream& operator<<(TextStream& ts, const IPC::ObjectIdentifierReadReference<T>& reference)
{
ts << "ObjectIdentifierReadReference(" << reference.identifier() << ", " << reference.version() << ")";
return ts;
}
template<typename T>
TextStream& operator<<(TextStream& ts, const IPC::ObjectIdentifierWriteReference<T>& reference)
{
ts << "ObjectIdentifierWriteReference(" << reference.identifier() << ", " << reference.version() << ", " << reference.pendingReads() << ")";
return ts;
}
}
namespace WTF {
template<typename T> struct HashTraits<IPC::ObjectIdentifierReference<T>> : SimpleClassHashTraits<IPC::ObjectIdentifierReference<T>> {
static constexpr bool emptyValueIsZero = HashTraits<T>::emptyValueIsZero;
static IPC::ObjectIdentifierReference<T> emptyValue() { return { HashTraits<T>::emptyValue(), 0 }; }
};
template<typename T> struct DefaultHash<IPC::ObjectIdentifierReference<T>> {
static unsigned hash(const IPC::ObjectIdentifierReference<T>& reference)
{
return computeHash(reference);
}
static bool equal(const IPC::ObjectIdentifierReference<T>& a, const IPC::ObjectIdentifierReference<T>& b)
{
return a == b;
}
static constexpr bool safeToCompareToEmptyOrDeleted = DefaultHash<T>::safeToCompareToEmptyOrDeleted;
};
} // namespace IPC
|
