michael@0: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: #ifndef BASE_THREADING_THREAD_LOCAL_STORAGE_H_
michael@0: #define BASE_THREADING_THREAD_LOCAL_STORAGE_H_
michael@0: 
michael@0: #include "base/base_export.h"
michael@0: #include "base/basictypes.h"
michael@0: 
michael@0: #if defined(OS_POSIX)
michael@0: #include <pthread.h>
michael@0: #endif
michael@0: 
michael@0: namespace base {
michael@0: 
michael@0: // Wrapper for thread local storage.  This class doesn't do much except provide
michael@0: // an API for portability.
michael@0: class BASE_EXPORT ThreadLocalStorage {
michael@0:  public:
michael@0: 
michael@0:   // Prototype for the TLS destructor function, which can be optionally used to
michael@0:   // cleanup thread local storage on thread exit.  'value' is the data that is
michael@0:   // stored in thread local storage.
michael@0:   typedef void (*TLSDestructorFunc)(void* value);
michael@0: 
michael@0:   // StaticSlot uses its own struct initializer-list style static
michael@0:   // initialization, as base's LINKER_INITIALIZED requires a constructor and on
michael@0:   // some compilers (notably gcc 4.4) this still ends up needing runtime
michael@0:   // initialization.
michael@0:   #define TLS_INITIALIZER {0}
michael@0: 
michael@0:   // A key representing one value stored in TLS.
michael@0:   // Initialize like
michael@0:   //   ThreadLocalStorage::StaticSlot my_slot = TLS_INITIALIZER;
michael@0:   // If you're not using a static variable, use the convenience class
michael@0:   // ThreadLocalStorage::Slot (below) instead.
michael@0:   struct BASE_EXPORT StaticSlot {
michael@0:     // Set up the TLS slot.  Called by the constructor.
michael@0:     // 'destructor' is a pointer to a function to perform per-thread cleanup of
michael@0:     // this object.  If set to NULL, no cleanup is done for this TLS slot.
michael@0:     // Returns false on error.
michael@0:     bool Initialize(TLSDestructorFunc destructor);
michael@0: 
michael@0:     // Free a previously allocated TLS 'slot'.
michael@0:     // If a destructor was set for this slot, removes
michael@0:     // the destructor so that remaining threads exiting
michael@0:     // will not free data.
michael@0:     void Free();
michael@0: 
michael@0:     // Get the thread-local value stored in slot 'slot'.
michael@0:     // Values are guaranteed to initially be zero.
michael@0:     void* Get() const;
michael@0: 
michael@0:     // Set the thread-local value stored in slot 'slot' to
michael@0:     // value 'value'.
michael@0:     void Set(void* value);
michael@0: 
michael@0:     bool initialized() const { return initialized_; }
michael@0: 
michael@0:     // The internals of this struct should be considered private.
michael@0:     bool initialized_;
michael@0: #if defined(OS_WIN)
michael@0:     int slot_;
michael@0: #elif defined(OS_POSIX)
michael@0:     pthread_key_t key_;
michael@0: #endif
michael@0: 
michael@0:   };
michael@0: 
michael@0:   // A convenience wrapper around StaticSlot with a constructor. Can be used
michael@0:   // as a member variable.
michael@0:   class BASE_EXPORT Slot : public StaticSlot {
michael@0:    public:
michael@0:     // Calls StaticSlot::Initialize().
michael@0:     explicit Slot(TLSDestructorFunc destructor = NULL);
michael@0: 
michael@0:    private:
michael@0:     using StaticSlot::initialized_;
michael@0: #if defined(OS_WIN)
michael@0:     using StaticSlot::slot_;
michael@0: #elif defined(OS_POSIX)
michael@0:     using StaticSlot::key_;
michael@0: #endif
michael@0:     DISALLOW_COPY_AND_ASSIGN(Slot);
michael@0:   };
michael@0: 
michael@0:   DISALLOW_COPY_AND_ASSIGN(ThreadLocalStorage);
michael@0: };
michael@0: 
michael@0: }  // namespace base
michael@0: 
michael@0: #endif  // BASE_THREADING_THREAD_LOCAL_STORAGE_H_