/*
* Copyright (C) 2008 Apple Inc. All rights reserved.
* Copyright (C) 2009 Jian Li <jianli@chromium.org>
* Copyright (C) 2012 Patrick Gansterer <paroga@paroga.com>
*
* 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.
* 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE 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 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.
*/
/* Thread local storage is implemented by using either pthread API or Windows
* native API. There is subtle semantic discrepancy for the cleanup function
* implementation as noted below:
* @ In pthread implementation, the destructor function will be called
* repeatedly if there is still non-NULL value associated with the function.
* @ In Windows native implementation, the destructor function will be called
* only once.
* This semantic discrepancy does not impose any problem because nowhere in
* WebKit the repeated call bahavior is utilized.
*/
#ifndef WTF_ThreadSpecific_h
#define WTF_ThreadSpecific_h
#include "wtf/Noncopyable.h"
#include "wtf/StdLibExtras.h"
#include "wtf/WTF.h"
#include "wtf/WTFExport.h"
#if USE(PTHREADS)
#include <pthread.h>
#elif OS(WIN)
#include <windows.h>
#endif
namespace WTF {
#if OS(WIN)
// ThreadSpecificThreadExit should be called each time when a thread is detached.
// This is done automatically for threads created with WTF::createThread.
WTF_EXPORT void ThreadSpecificThreadExit();
#endif
template<typename T> class ThreadSpecific {
WTF_MAKE_NONCOPYABLE(ThreadSpecific);
public:
ThreadSpecific();
bool isSet(); // Useful as a fast check to see if this thread has set this value.
T* operator->();
operator T*();
T& operator*();
private:
#if OS(WIN)
WTF_EXPORT friend void ThreadSpecificThreadExit();
#endif
// Not implemented. It's technically possible to destroy a thread specific key, but one would need
// to make sure that all values have been destroyed already (usually, that all threads that used it
// have exited). It's unlikely that any user of this call will be in that situation - and having
// a destructor defined can be confusing, given that it has such strong pre-requisites to work correctly.
~ThreadSpecific();
T* get();
void set(T*);
void static destroy(void* ptr);
struct Data {
WTF_MAKE_NONCOPYABLE(Data);
public:
Data(T* value, ThreadSpecific<T>* owner) : value(value), owner(owner) {}
T* value;
ThreadSpecific<T>* owner;
#if OS(WIN)
void (*destructor)(void*);
#endif
};
#if USE(PTHREADS)
pthread_key_t m_key;
#elif OS(WIN)
int m_index;
#endif
};
#if USE(PTHREADS)
typedef pthread_key_t ThreadSpecificKey;
inline void threadSpecificKeyCreate(ThreadSpecificKey* key, void (*destructor)(void *))
{
int error = pthread_key_create(key, destructor);
if (error)
CRASH();
}
inline void threadSpecificKeyDelete(ThreadSpecificKey key)
{
int error = pthread_key_delete(key);
if (error)
CRASH();
}
inline void threadSpecificSet(ThreadSpecificKey key, void* value)
{
pthread_setspecific(key, value);
}
inline void* threadSpecificGet(ThreadSpecificKey key)
{
return pthread_getspecific(key);
}
template<typename T>
inline ThreadSpecific<T>::ThreadSpecific()
{
int error = pthread_key_create(&m_key, destroy);
if (error)
CRASH();
}
template<typename T>
inline T* ThreadSpecific<T>::get()
{
Data* data = static_cast<Data*>(pthread_getspecific(m_key));
return data ? data->value : 0;
}
template<typename T>
inline void ThreadSpecific<T>::set(T* ptr)
{
ASSERT(!get());
pthread_setspecific(m_key, new Data(ptr, this));
}
#elif OS(WIN)
// TLS_OUT_OF_INDEXES is not defined on WinCE.
#ifndef TLS_OUT_OF_INDEXES
#define TLS_OUT_OF_INDEXES 0xffffffff
#endif
// The maximum number of TLS keys that can be created. For simplification, we assume that:
// 1) Once the instance of ThreadSpecific<> is created, it will not be destructed until the program dies.
// 2) We do not need to hold many instances of ThreadSpecific<> data. This fixed number should be far enough.
const int kMaxTlsKeySize = 256;
WTF_EXPORT long& tlsKeyCount();
WTF_EXPORT DWORD* tlsKeys();
class PlatformThreadSpecificKey;
typedef PlatformThreadSpecificKey* ThreadSpecificKey;
WTF_EXPORT void threadSpecificKeyCreate(ThreadSpecificKey*, void (*)(void *));
WTF_EXPORT void threadSpecificKeyDelete(ThreadSpecificKey);
WTF_EXPORT void threadSpecificSet(ThreadSpecificKey, void*);
WTF_EXPORT void* threadSpecificGet(ThreadSpecificKey);
template<typename T>
inline ThreadSpecific<T>::ThreadSpecific()
: m_index(-1)
{
DWORD tlsKey = TlsAlloc();
if (tlsKey == TLS_OUT_OF_INDEXES)
CRASH();
m_index = InterlockedIncrement(&tlsKeyCount()) - 1;
if (m_index >= kMaxTlsKeySize)
CRASH();
tlsKeys()[m_index] = tlsKey;
}
template<typename T>
inline ThreadSpecific<T>::~ThreadSpecific()
{
// Does not invoke destructor functions. They will be called from ThreadSpecificThreadExit when the thread is detached.
TlsFree(tlsKeys()[m_index]);
}
template<typename T>
inline T* ThreadSpecific<T>::get()
{
Data* data = static_cast<Data*>(TlsGetValue(tlsKeys()[m_index]));
return data ? data->value : 0;
}
template<typename T>
inline void ThreadSpecific<T>::set(T* ptr)
{
ASSERT(!get());
Data* data = new Data(ptr, this);
data->destructor = &ThreadSpecific<T>::destroy;
TlsSetValue(tlsKeys()[m_index], data);
}
#else
#error ThreadSpecific is not implemented for this platform.
#endif
template<typename T>
inline void ThreadSpecific<T>::destroy(void* ptr)
{
if (isShutdown())
return;
Data* data = static_cast<Data*>(ptr);
#if USE(PTHREADS)
// We want get() to keep working while data destructor works, because it can be called indirectly by the destructor.
// Some pthreads implementations zero out the pointer before calling destroy(), so we temporarily reset it.
pthread_setspecific(data->owner->m_key, ptr);
#endif
data->value->~T();
fastFree(data->value);
#if USE(PTHREADS)
pthread_setspecific(data->owner->m_key, 0);
#elif OS(WIN)
TlsSetValue(tlsKeys()[data->owner->m_index], 0);
#else
#error ThreadSpecific is not implemented for this platform.
#endif
delete data;
}
template<typename T>
inline bool ThreadSpecific<T>::isSet()
{
return !!get();
}
template<typename T>
inline ThreadSpecific<T>::operator T*()
{
T* ptr = static_cast<T*>(get());
if (!ptr) {
// Set up thread-specific value's memory pointer before invoking constructor, in case any function it calls
// needs to access the value, to avoid recursion.
ptr = static_cast<T*>(fastZeroedMalloc(sizeof(T)));
set(ptr);
new (NotNull, ptr) T;
}
return ptr;
}
template<typename T>
inline T* ThreadSpecific<T>::operator->()
{
return operator T*();
}
template<typename T>
inline T& ThreadSpecific<T>::operator*()
{
return *operator T*();
}
} // namespace WTF
using WTF::ThreadSpecific;
#endif // WTF_ThreadSpecific_h