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comparison: mfbt/ThreadLocal.h
mfbt/ThreadLocal.h
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| 1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ | |
| 2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */ | |
| 3 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 4 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 6 | |
| 7 /* Cross-platform lightweight thread local data wrappers. */ | |
| 8 | |
| 9 #ifndef mozilla_ThreadLocal_h | |
| 10 #define mozilla_ThreadLocal_h | |
| 11 | |
| 12 #if defined(XP_WIN) | |
| 13 // This file will get included in any file that wants to add a profiler mark. | |
| 14 // In order to not bring <windows.h> together we could include windef.h and | |
| 15 // winbase.h which are sufficient to get the prototypes for the Tls* functions. | |
| 16 // # include <windef.h> | |
| 17 // # include <winbase.h> | |
| 18 // Unfortunately, even including these headers causes us to add a bunch of ugly | |
| 19 // stuff to our namespace e.g #define CreateEvent CreateEventW | |
| 20 extern "C" { | |
| 21 __declspec(dllimport) void* __stdcall TlsGetValue(unsigned long); | |
| 22 __declspec(dllimport) int __stdcall TlsSetValue(unsigned long, void*); | |
| 23 __declspec(dllimport) unsigned long __stdcall TlsAlloc(); | |
| 24 } | |
| 25 #else | |
| 26 # include <pthread.h> | |
| 27 # include <signal.h> | |
| 28 #endif | |
| 29 | |
| 30 #include "mozilla/Assertions.h" | |
| 31 #include "mozilla/Attributes.h" | |
| 32 #include "mozilla/NullPtr.h" | |
| 33 | |
| 34 namespace mozilla { | |
| 35 | |
| 36 // sig_safe_t denotes an atomic type which can be read or stored in a single | |
| 37 // instruction. This means that data of this type is safe to be manipulated | |
| 38 // from a signal handler, or other similar asynchronous execution contexts. | |
| 39 #if defined(XP_WIN) | |
| 40 typedef unsigned long sig_safe_t; | |
| 41 #else | |
| 42 typedef sig_atomic_t sig_safe_t; | |
| 43 #endif | |
| 44 | |
| 45 /* | |
| 46 * Thread Local Storage helpers. | |
| 47 * | |
| 48 * Usage: | |
| 49 * | |
| 50 * Only static-storage-duration (e.g. global variables, or static class members) | |
| 51 * objects of this class should be instantiated. This class relies on | |
| 52 * zero-initialization, which is implicit for static-storage-duration objects. | |
| 53 * It doesn't have a custom default constructor, to avoid static initializers. | |
| 54 * | |
| 55 * API usage: | |
| 56 * | |
| 57 * // Create a TLS item. | |
| 58 * // | |
| 59 * // Note that init() should be invoked exactly once, before any usage of set() | |
| 60 * // or get(). | |
| 61 * mozilla::ThreadLocal<int> tlsKey; | |
| 62 * if (!tlsKey.init()) { | |
| 63 * // deal with the error | |
| 64 * } | |
| 65 * | |
| 66 * // Set the TLS value | |
| 67 * tlsKey.set(123); | |
| 68 * | |
| 69 * // Get the TLS value | |
| 70 * int value = tlsKey.get(); | |
| 71 */ | |
| 72 template<typename T> | |
| 73 class ThreadLocal | |
| 74 { | |
| 75 #if defined(XP_WIN) | |
| 76 typedef unsigned long key_t; | |
| 77 #else | |
| 78 typedef pthread_key_t key_t; | |
| 79 #endif | |
| 80 | |
| 81 union Helper { | |
| 82 void* ptr; | |
| 83 T value; | |
| 84 }; | |
| 85 | |
| 86 public: | |
| 87 MOZ_WARN_UNUSED_RESULT inline bool init(); | |
| 88 | |
| 89 inline T get() const; | |
| 90 | |
| 91 inline void set(const T value); | |
| 92 | |
| 93 bool initialized() const { | |
| 94 return inited; | |
| 95 } | |
| 96 | |
| 97 private: | |
| 98 key_t key; | |
| 99 bool inited; | |
| 100 }; | |
| 101 | |
| 102 template<typename T> | |
| 103 inline bool | |
| 104 ThreadLocal<T>::init() | |
| 105 { | |
| 106 static_assert(sizeof(T) <= sizeof(void*), | |
| 107 "mozilla::ThreadLocal can't be used for types larger than " | |
| 108 "a pointer"); | |
| 109 MOZ_ASSERT(!initialized()); | |
| 110 #ifdef XP_WIN | |
| 111 key = TlsAlloc(); | |
| 112 inited = key != 0xFFFFFFFFUL; // TLS_OUT_OF_INDEXES | |
| 113 #else | |
| 114 inited = !pthread_key_create(&key, nullptr); | |
| 115 #endif | |
| 116 return inited; | |
| 117 } | |
| 118 | |
| 119 template<typename T> | |
| 120 inline T | |
| 121 ThreadLocal<T>::get() const | |
| 122 { | |
| 123 MOZ_ASSERT(initialized()); | |
| 124 Helper h; | |
| 125 #ifdef XP_WIN | |
| 126 h.ptr = TlsGetValue(key); | |
| 127 #else | |
| 128 h.ptr = pthread_getspecific(key); | |
| 129 #endif | |
| 130 return h.value; | |
| 131 } | |
| 132 | |
| 133 template<typename T> | |
| 134 inline void | |
| 135 ThreadLocal<T>::set(const T value) | |
| 136 { | |
| 137 MOZ_ASSERT(initialized()); | |
| 138 Helper h; | |
| 139 h.value = value; | |
| 140 bool succeeded; | |
| 141 #ifdef XP_WIN | |
| 142 succeeded = TlsSetValue(key, h.ptr); | |
| 143 #else | |
| 144 succeeded = !pthread_setspecific(key, h.ptr); | |
| 145 #endif | |
| 146 if (!succeeded) | |
| 147 MOZ_CRASH(); | |
| 148 } | |
| 149 | |
| 150 } // namespace mozilla | |
| 151 | |
| 152 #endif /* mozilla_ThreadLocal_h */ |
