1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_THREADING_THREAD_LOCAL_STORAGE_H_ 6 #define BASE_THREADING_THREAD_LOCAL_STORAGE_H_ 7 8 #include "base/base_export.h" 9 #include "base/basictypes.h" 10 11 #if defined(OS_POSIX) 12 #include <pthread.h> 13 #endif 14 15 namespace base { 16 17 // Wrapper for thread local storage. This class doesn't do much except provide 18 // an API for portability. 19 class BASE_EXPORT ThreadLocalStorage { 20 public: 21 22 // Prototype for the TLS destructor function, which can be optionally used to 23 // cleanup thread local storage on thread exit. 'value' is the data that is 24 // stored in thread local storage. 25 typedef void (*TLSDestructorFunc)(void* value); 26 27 // StaticSlot uses its own struct initializer-list style static 28 // initialization, as base's LINKER_INITIALIZED requires a constructor and on 29 // some compilers (notably gcc 4.4) this still ends up needing runtime 30 // initialization. 31 #define TLS_INITIALIZER {0} 32 33 // A key representing one value stored in TLS. 34 // Initialize like 35 // ThreadLocalStorage::StaticSlot my_slot = TLS_INITIALIZER; 36 // If you're not using a static variable, use the convenience class 37 // ThreadLocalStorage::Slot (below) instead. 38 struct BASE_EXPORT StaticSlot { 39 // Set up the TLS slot. Called by the constructor. 40 // 'destructor' is a pointer to a function to perform per-thread cleanup of 41 // this object. If set to NULL, no cleanup is done for this TLS slot. 42 // Returns false on error. 43 bool Initialize(TLSDestructorFunc destructor); 44 45 // Free a previously allocated TLS 'slot'. 46 // If a destructor was set for this slot, removes 47 // the destructor so that remaining threads exiting 48 // will not free data. 49 void Free(); 50 51 // Get the thread-local value stored in slot 'slot'. 52 // Values are guaranteed to initially be zero. 53 void* Get() const; 54 55 // Set the thread-local value stored in slot 'slot' to 56 // value 'value'. 57 void Set(void* value); 58 initializedStaticSlot59 bool initialized() const { return initialized_; } 60 61 // The internals of this struct should be considered private. 62 bool initialized_; 63 #if defined(OS_WIN) 64 int slot_; 65 #elif defined(OS_POSIX) 66 pthread_key_t key_; 67 #endif 68 69 }; 70 71 // A convenience wrapper around StaticSlot with a constructor. Can be used 72 // as a member variable. 73 class BASE_EXPORT Slot : public StaticSlot { 74 public: 75 // Calls StaticSlot::Initialize(). 76 explicit Slot(TLSDestructorFunc destructor = NULL); 77 78 private: 79 using StaticSlot::initialized_; 80 #if defined(OS_WIN) 81 using StaticSlot::slot_; 82 #elif defined(OS_POSIX) 83 using StaticSlot::key_; 84 #endif 85 DISALLOW_COPY_AND_ASSIGN(Slot); 86 }; 87 88 DISALLOW_COPY_AND_ASSIGN(ThreadLocalStorage); 89 }; 90 91 } // namespace base 92 93 #endif // BASE_THREADING_THREAD_LOCAL_STORAGE_H_ 94