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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
/* Cross-platform lightweight thread local data wrappers. */
#ifndef mozilla_ThreadLocal_h_
#define mozilla_ThreadLocal_h_
#if defined(XP_WIN)
// This file will get included in any file that wants to add a profiler mark.
// In order to not bring <windows.h> together we could include windef.h and
// winbase.h which are sufficient to get the prototypes for the Tls* functions.
// # include <windef.h>
// # include <winbase.h>
// Unfortunately, even including these headers causes us to add a bunch of ugly
// stuff to our namespace e.g #define CreateEvent CreateEventW
extern "C" {
__declspec(dllimport) void* __stdcall TlsGetValue(unsigned long);
__declspec(dllimport) int __stdcall TlsSetValue(unsigned long, void*);
__declspec(dllimport) unsigned long __stdcall TlsAlloc();
}
#else
# include <pthread.h>
# include <signal.h>
#endif
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
namespace mozilla {
// sig_safe_t denotes an atomic type which can be read or stored in a single
// instruction. This means that data of this type is safe to be manipulated
// from a signal handler, or other similar asynchronous execution contexts.
#if defined(XP_WIN)
typedef unsigned long sig_safe_t;
#else
typedef sig_atomic_t sig_safe_t;
#endif
/*
* Thread Local Storage helpers.
*
* Usage:
*
* Only static-storage-duration (e.g. global variables, or static class members)
* objects of this class should be instantiated. This class relies on
* zero-initialization, which is implicit for static-storage-duration objects.
* It doesn't have a custom default constructor, to avoid static initializers.
*
* API usage:
*
* // Create a TLS item
* mozilla::ThreadLocal<int> tlsKey;
* if (!tlsKey.init()) {
* // deal with the error
* }
*
* // Set the TLS value
* tlsKey.set(123);
*
* // Get the TLS value
* int value = tlsKey.get();
*/
template<typename T>
class ThreadLocal
{
#if defined(XP_WIN)
typedef unsigned long key_t;
#else
typedef pthread_key_t key_t;
#endif
union Helper {
void* ptr;
T value;
};
public:
MOZ_WARN_UNUSED_RESULT inline bool init();
inline T get() const;
inline void set(const T value);
bool initialized() const {
return inited;
}
private:
key_t key;
bool inited;
};
template<typename T>
inline bool
ThreadLocal<T>::init()
{
MOZ_STATIC_ASSERT(sizeof(T) <= sizeof(void*),
"mozilla::ThreadLocal can't be used for types larger than "
"a pointer");
MOZ_ASSERT(!initialized());
#ifdef XP_WIN
key = TlsAlloc();
inited = key != 0xFFFFFFFFUL; // TLS_OUT_OF_INDEXES
#else
inited = !pthread_key_create(&key, NULL);
#endif
return inited;
}
template<typename T>
inline T
ThreadLocal<T>::get() const
{
MOZ_ASSERT(initialized());
Helper h;
#ifdef XP_WIN
h.ptr = TlsGetValue(key);
#else
h.ptr = pthread_getspecific(key);
#endif
return h.value;
}
template<typename T>
inline void
ThreadLocal<T>::set(const T value)
{
MOZ_ASSERT(initialized());
Helper h;
h.value = value;
bool succeeded;
#ifdef XP_WIN
succeeded = TlsSetValue(key, h.ptr);
#else
succeeded = !pthread_setspecific(key, h.ptr);
#endif
if (!succeeded)
MOZ_CRASH();
}
} // namespace mozilla
#endif // mozilla_ThreadLocal_h_
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