1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/mfbt/ThreadLocal.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,152 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim: set ts=8 sts=2 et sw=2 tw=80: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +/* Cross-platform lightweight thread local data wrappers. */
1.11 +
1.12 +#ifndef mozilla_ThreadLocal_h
1.13 +#define mozilla_ThreadLocal_h
1.14 +
1.15 +#if defined(XP_WIN)
1.16 +// This file will get included in any file that wants to add a profiler mark.
1.17 +// In order to not bring <windows.h> together we could include windef.h and
1.18 +// winbase.h which are sufficient to get the prototypes for the Tls* functions.
1.19 +// # include <windef.h>
1.20 +// # include <winbase.h>
1.21 +// Unfortunately, even including these headers causes us to add a bunch of ugly
1.22 +// stuff to our namespace e.g #define CreateEvent CreateEventW
1.23 +extern "C" {
1.24 +__declspec(dllimport) void* __stdcall TlsGetValue(unsigned long);
1.25 +__declspec(dllimport) int __stdcall TlsSetValue(unsigned long, void*);
1.26 +__declspec(dllimport) unsigned long __stdcall TlsAlloc();
1.27 +}
1.28 +#else
1.29 +# include <pthread.h>
1.30 +# include <signal.h>
1.31 +#endif
1.32 +
1.33 +#include "mozilla/Assertions.h"
1.34 +#include "mozilla/Attributes.h"
1.35 +#include "mozilla/NullPtr.h"
1.36 +
1.37 +namespace mozilla {
1.38 +
1.39 +// sig_safe_t denotes an atomic type which can be read or stored in a single
1.40 +// instruction. This means that data of this type is safe to be manipulated
1.41 +// from a signal handler, or other similar asynchronous execution contexts.
1.42 +#if defined(XP_WIN)
1.43 +typedef unsigned long sig_safe_t;
1.44 +#else
1.45 +typedef sig_atomic_t sig_safe_t;
1.46 +#endif
1.47 +
1.48 +/*
1.49 + * Thread Local Storage helpers.
1.50 + *
1.51 + * Usage:
1.52 + *
1.53 + * Only static-storage-duration (e.g. global variables, or static class members)
1.54 + * objects of this class should be instantiated. This class relies on
1.55 + * zero-initialization, which is implicit for static-storage-duration objects.
1.56 + * It doesn't have a custom default constructor, to avoid static initializers.
1.57 + *
1.58 + * API usage:
1.59 + *
1.60 + * // Create a TLS item.
1.61 + * //
1.62 + * // Note that init() should be invoked exactly once, before any usage of set()
1.63 + * // or get().
1.64 + * mozilla::ThreadLocal<int> tlsKey;
1.65 + * if (!tlsKey.init()) {
1.66 + * // deal with the error
1.67 + * }
1.68 + *
1.69 + * // Set the TLS value
1.70 + * tlsKey.set(123);
1.71 + *
1.72 + * // Get the TLS value
1.73 + * int value = tlsKey.get();
1.74 + */
1.75 +template<typename T>
1.76 +class ThreadLocal
1.77 +{
1.78 +#if defined(XP_WIN)
1.79 + typedef unsigned long key_t;
1.80 +#else
1.81 + typedef pthread_key_t key_t;
1.82 +#endif
1.83 +
1.84 + union Helper {
1.85 + void* ptr;
1.86 + T value;
1.87 + };
1.88 +
1.89 + public:
1.90 + MOZ_WARN_UNUSED_RESULT inline bool init();
1.91 +
1.92 + inline T get() const;
1.93 +
1.94 + inline void set(const T value);
1.95 +
1.96 + bool initialized() const {
1.97 + return inited;
1.98 + }
1.99 +
1.100 + private:
1.101 + key_t key;
1.102 + bool inited;
1.103 +};
1.104 +
1.105 +template<typename T>
1.106 +inline bool
1.107 +ThreadLocal<T>::init()
1.108 +{
1.109 + static_assert(sizeof(T) <= sizeof(void*),
1.110 + "mozilla::ThreadLocal can't be used for types larger than "
1.111 + "a pointer");
1.112 + MOZ_ASSERT(!initialized());
1.113 +#ifdef XP_WIN
1.114 + key = TlsAlloc();
1.115 + inited = key != 0xFFFFFFFFUL; // TLS_OUT_OF_INDEXES
1.116 +#else
1.117 + inited = !pthread_key_create(&key, nullptr);
1.118 +#endif
1.119 + return inited;
1.120 +}
1.121 +
1.122 +template<typename T>
1.123 +inline T
1.124 +ThreadLocal<T>::get() const
1.125 +{
1.126 + MOZ_ASSERT(initialized());
1.127 + Helper h;
1.128 +#ifdef XP_WIN
1.129 + h.ptr = TlsGetValue(key);
1.130 +#else
1.131 + h.ptr = pthread_getspecific(key);
1.132 +#endif
1.133 + return h.value;
1.134 +}
1.135 +
1.136 +template<typename T>
1.137 +inline void
1.138 +ThreadLocal<T>::set(const T value)
1.139 +{
1.140 + MOZ_ASSERT(initialized());
1.141 + Helper h;
1.142 + h.value = value;
1.143 + bool succeeded;
1.144 +#ifdef XP_WIN
1.145 + succeeded = TlsSetValue(key, h.ptr);
1.146 +#else
1.147 + succeeded = !pthread_setspecific(key, h.ptr);
1.148 +#endif
1.149 + if (!succeeded)
1.150 + MOZ_CRASH();
1.151 +}
1.152 +
1.153 +} // namespace mozilla
1.154 +
1.155 +#endif /* mozilla_ThreadLocal_h */
