2 * Copyright (C) 2008 Apple Inc. All rights reserved.
3 * Copyright (C) 2009 Jian Li <jianli@chromium.org>
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
15 * its contributors may be used to endorse or promote products derived
16 * from this software without specific prior written permission.
18 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
25 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 /* Thread local storage is implemented by using either pthread API or Windows
31 * native API. There is subtle semantic discrepancy for the cleanup function
32 * implementation as noted below:
33 * @ In pthread implementation, the destructor function will be called
34 * repeatedly if there is still non-NULL value associated with the function.
35 * @ In Windows native implementation, the destructor function will be called
37 * This semantic discrepancy does not impose any problem because nowhere in
38 * WebKit the repeated call bahavior is utilized.
41 #ifndef WTF_ThreadSpecific_h
42 #define WTF_ThreadSpecific_h
44 #include <wtf/Noncopyable.h>
45 #include <wtf/StdLibExtras.h>
56 // ThreadSpecificThreadExit should be called each time when a thread is detached.
57 // This is done automatically for threads created with WTF::createThread.
58 void ThreadSpecificThreadExit();
61 template<typename T> class ThreadSpecific {
62 WTF_MAKE_NONCOPYABLE(ThreadSpecific);
65 bool isSet(); // Useful as a fast check to see if this thread has set this value.
72 friend void ThreadSpecificThreadExit();
75 // Not implemented. It's technically possible to destroy a thread specific key, but one would need
76 // to make sure that all values have been destroyed already (usually, that all threads that used it
77 // have exited). It's unlikely that any user of this call will be in that situation - and having
78 // a destructor defined can be confusing, given that it has such strong pre-requisites to work correctly.
83 void static destroy(void* ptr);
86 WTF_MAKE_NONCOPYABLE(Data);
88 Data(T* value, ThreadSpecific<T>* owner) : value(value), owner(owner) {}
91 ThreadSpecific<T>* owner;
93 void (*destructor)(void*);
106 inline ThreadSpecific<T>::ThreadSpecific()
108 int error = pthread_key_create(&m_key, destroy);
114 inline T* ThreadSpecific<T>::get()
116 Data* data = static_cast<Data*>(pthread_getspecific(m_key));
117 return data ? data->value : 0;
121 inline void ThreadSpecific<T>::set(T* ptr)
124 pthread_setspecific(m_key, new Data(ptr, this));
129 // TLS_OUT_OF_INDEXES is not defined on WinCE.
130 #ifndef TLS_OUT_OF_INDEXES
131 #define TLS_OUT_OF_INDEXES 0xffffffff
134 // The maximum number of TLS keys that can be created. For simplification, we assume that:
135 // 1) Once the instance of ThreadSpecific<> is created, it will not be destructed until the program dies.
136 // 2) We do not need to hold many instances of ThreadSpecific<> data. This fixed number should be far enough.
137 const int kMaxTlsKeySize = 256;
139 WTF_EXPORT_PRIVATE long& tlsKeyCount();
140 WTF_EXPORT_PRIVATE DWORD* tlsKeys();
143 inline ThreadSpecific<T>::ThreadSpecific()
146 DWORD tlsKey = TlsAlloc();
147 if (tlsKey == TLS_OUT_OF_INDEXES)
150 m_index = InterlockedIncrement(&tlsKeyCount()) - 1;
151 if (m_index >= kMaxTlsKeySize)
153 tlsKeys()[m_index] = tlsKey;
157 inline ThreadSpecific<T>::~ThreadSpecific()
159 // Does not invoke destructor functions. They will be called from ThreadSpecificThreadExit when the thread is detached.
160 TlsFree(tlsKeys()[m_index]);
164 inline T* ThreadSpecific<T>::get()
166 Data* data = static_cast<Data*>(TlsGetValue(tlsKeys()[m_index]));
167 return data ? data->value : 0;
171 inline void ThreadSpecific<T>::set(T* ptr)
174 Data* data = new Data(ptr, this);
175 data->destructor = &ThreadSpecific<T>::destroy;
176 TlsSetValue(tlsKeys()[m_index], data);
180 #error ThreadSpecific is not implemented for this platform.
184 inline void ThreadSpecific<T>::destroy(void* ptr)
186 Data* data = static_cast<Data*>(ptr);
189 // We want get() to keep working while data destructor works, because it can be called indirectly by the destructor.
190 // Some pthreads implementations zero out the pointer before calling destroy(), so we temporarily reset it.
191 pthread_setspecific(data->owner->m_key, ptr);
195 fastFree(data->value);
198 pthread_setspecific(data->owner->m_key, 0);
200 TlsSetValue(tlsKeys()[data->owner->m_index], 0);
202 #error ThreadSpecific is not implemented for this platform.
209 inline bool ThreadSpecific<T>::isSet()
215 inline ThreadSpecific<T>::operator T*()
217 T* ptr = static_cast<T*>(get());
219 // Set up thread-specific value's memory pointer before invoking constructor, in case any function it calls
220 // needs to access the value, to avoid recursion.
221 ptr = static_cast<T*>(fastZeroedMalloc(sizeof(T)));
223 new (NotNull, ptr) T;
229 inline T* ThreadSpecific<T>::operator->()
231 return operator T*();
235 inline T& ThreadSpecific<T>::operator*()
237 return *operator T*();
242 #endif // WTF_ThreadSpecific_h