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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// WARNING: Thread local storage is a bit tricky to get right. Please make
+// sure that this is really the proper solution for what you're trying to
+// achieve. Don't prematurely optimize, most likely you can just use a Lock.
+//
+// These classes implement a warpper around the platform's TLS storage
+// mechanism. On construction, they will allocate a TLS slot, and free the
+// TLS slot on destruction. No memory management (creation or destruction) is
+// handled. This means for uses of ThreadLocalPointer, you must correctly
+// manage the memory yourself, these classes will not destroy the pointer for
+// you. There are no at-thread-exit actions taken by these classes.
+//
+// ThreadLocalPointer<Type> wraps a Type*. It performs no creation or
+// destruction, so memory management must be handled elsewhere. The first call
+// to Get() on a thread will return NULL. You can update the pointer with a
+// call to Set().
+//
+// ThreadLocalBoolean wraps a bool. It will default to false if it has never
+// been set otherwise with Set().
+//
+// Thread Safety: An instance of ThreadLocalStorage is completely thread safe
+// once it has been created. If you want to dynamically create an instance,
+// you must of course properly deal with safety and race conditions. This
+// means a function-level static initializer is generally inappropiate.
+//
+// Example usage:
+// // My class is logically attached to a single thread. We cache a pointer
+// // on the thread it was created on, so we can implement current().
+// MyClass::MyClass() {
+// DCHECK(Singleton<ThreadLocalPointer<MyClass> >::get()->Get() == NULL);
+// Singleton<ThreadLocalPointer<MyClass> >::get()->Set(this);
+// }
+//
+// MyClass::~MyClass() {
+// DCHECK(Singleton<ThreadLocalPointer<MyClass> >::get()->Get() != NULL);
+// Singleton<ThreadLocalPointer<MyClass> >::get()->Set(NULL);
+// }
+//
+// // Return the current MyClass associated with the calling thread, can be
+// // NULL if there isn't a MyClass associated.
+// MyClass* MyClass::current() {
+// return Singleton<ThreadLocalPointer<MyClass> >::get()->Get();
+// }
+
+#ifndef BASE_THREAD_LOCAL_H_
+#define BASE_THREAD_LOCAL_H_
+
+#include "base/basictypes.h"
+
+#if defined(OS_POSIX)
+#include <pthread.h>
+#endif
+
+namespace base {
+
+// Helper functions that abstract the cross-platform APIs. Do not use directly.
+struct ThreadLocalPlatform {
+#if defined(OS_WIN)
+ typedef int SlotType;
+#elif defined(OS_POSIX)
+ typedef pthread_key_t SlotType;
+#endif
+
+ static void AllocateSlot(SlotType& slot);
+ static void FreeSlot(SlotType& slot);
+ static void* GetValueFromSlot(SlotType& slot);
+ static void SetValueInSlot(SlotType& slot, void* value);
+};
+
+template <typename Type>
+class ThreadLocalPointer {
+ public:
+ ThreadLocalPointer() : slot_() {
+ ThreadLocalPlatform::AllocateSlot(slot_);
+ }
+
+ ~ThreadLocalPointer() {
+ ThreadLocalPlatform::FreeSlot(slot_);
+ }
+
+ Type* Get() {
+ return static_cast<Type*>(ThreadLocalPlatform::GetValueFromSlot(slot_));
+ }
+
+ void Set(Type* ptr) {
+ ThreadLocalPlatform::SetValueInSlot(slot_, ptr);
+ }
+
+ private:
+ typedef ThreadLocalPlatform::SlotType SlotType;
+
+ SlotType slot_;
+
+ DISALLOW_COPY_AND_ASSIGN(ThreadLocalPointer<Type>);
+};
+
+class ThreadLocalBoolean {
+ public:
+ ThreadLocalBoolean() { }
+ ~ThreadLocalBoolean() { }
+
+ bool Get() {
+ return tlp_.Get() != NULL;
+ }
+
+ void Set(bool val) {
+ uintptr_t intVal = val ? 1 : 0;
+ tlp_.Set(reinterpret_cast<void*>(intVal));
+ }
+
+ private:
+ ThreadLocalPointer<void> tlp_;
+
+ DISALLOW_COPY_AND_ASSIGN(ThreadLocalBoolean);
+};
+
+} // namespace base
+
+#endif // BASE_THREAD_LOCAL_H_