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