mirror of
https://github.com/mozilla/gecko-dev.git
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152 lines
3.6 KiB
C++
152 lines
3.6 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* Cross-platform lightweight thread local data wrappers. */
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#ifndef mozilla_ThreadLocal_h
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#define mozilla_ThreadLocal_h
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#if defined(XP_WIN)
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// This file will get included in any file that wants to add a profiler mark.
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// In order to not bring <windows.h> together we could include windef.h and
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// winbase.h which are sufficient to get the prototypes for the Tls* functions.
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// # include <windef.h>
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// # include <winbase.h>
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// Unfortunately, even including these headers causes us to add a bunch of ugly
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// stuff to our namespace e.g #define CreateEvent CreateEventW
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extern "C" {
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__declspec(dllimport) void* __stdcall TlsGetValue(unsigned long);
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__declspec(dllimport) int __stdcall TlsSetValue(unsigned long, void*);
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__declspec(dllimport) unsigned long __stdcall TlsAlloc();
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}
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#else
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# include <pthread.h>
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# include <signal.h>
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#endif
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#include "mozilla/Assertions.h"
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#include "mozilla/Attributes.h"
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#include "mozilla/NullPtr.h"
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namespace mozilla {
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// sig_safe_t denotes an atomic type which can be read or stored in a single
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// instruction. This means that data of this type is safe to be manipulated
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// from a signal handler, or other similar asynchronous execution contexts.
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#if defined(XP_WIN)
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typedef unsigned long sig_safe_t;
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#else
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typedef sig_atomic_t sig_safe_t;
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#endif
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/*
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* Thread Local Storage helpers.
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*
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* Usage:
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*
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* Only static-storage-duration (e.g. global variables, or static class members)
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* objects of this class should be instantiated. This class relies on
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* zero-initialization, which is implicit for static-storage-duration objects.
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* It doesn't have a custom default constructor, to avoid static initializers.
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*
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* API usage:
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*
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* // Create a TLS item.
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* //
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* // Note that init() should be invoked exactly once, before any usage of set()
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* // or get().
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* mozilla::ThreadLocal<int> tlsKey;
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* if (!tlsKey.init()) {
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* // deal with the error
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* }
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*
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* // Set the TLS value
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* tlsKey.set(123);
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*
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* // Get the TLS value
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* int value = tlsKey.get();
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*/
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template<typename T>
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class ThreadLocal
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{
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#if defined(XP_WIN)
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typedef unsigned long key_t;
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#else
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typedef pthread_key_t key_t;
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#endif
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union Helper
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{
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void* mPtr;
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T mValue;
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};
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public:
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MOZ_WARN_UNUSED_RESULT inline bool init();
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inline T get() const;
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inline void set(const T aValue);
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bool initialized() const { return mInited; }
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private:
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key_t mKey;
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bool mInited;
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};
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template<typename T>
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inline bool
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ThreadLocal<T>::init()
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{
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static_assert(sizeof(T) <= sizeof(void*),
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"mozilla::ThreadLocal can't be used for types larger than "
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"a pointer");
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MOZ_ASSERT(!initialized());
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#ifdef XP_WIN
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mKey = TlsAlloc();
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mInited = mKey != 0xFFFFFFFFUL; // TLS_OUT_OF_INDEXES
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#else
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mInited = !pthread_key_create(&mKey, nullptr);
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#endif
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return mInited;
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}
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template<typename T>
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inline T
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ThreadLocal<T>::get() const
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{
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MOZ_ASSERT(initialized());
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Helper h;
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#ifdef XP_WIN
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h.mPtr = TlsGetValue(mKey);
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#else
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h.mPtr = pthread_getspecific(mKey);
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#endif
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return h.mValue;
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}
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template<typename T>
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inline void
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ThreadLocal<T>::set(const T aValue)
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{
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MOZ_ASSERT(initialized());
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Helper h;
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h.mValue = aValue;
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#ifdef XP_WIN
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bool succeeded = TlsSetValue(mKey, h.mPtr);
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#else
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bool succeeded = !pthread_setspecific(mKey, h.mPtr);
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#endif
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if (!succeeded) {
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MOZ_CRASH();
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}
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}
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} // namespace mozilla
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#endif /* mozilla_ThreadLocal_h */
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