Mojo: re-org public/utility and public/environment

mojo/public/utility/thread_local.h

-// Copyright 2013 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 wrapper 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 MOJO_PUBLIC_UTILITY_THREAD_LOCAL_H_
-#define MOJO_PUBLIC_UTILITY_THREAD_LOCAL_H_
-
-#ifndef _WIN32
-#include <pthread.h>
-#endif
-
-#include "mojo/public/system/macros.h"
-
-namespace mojo {
-namespace internal {
-
-// Helper functions that abstract the cross-platform APIs.  Do not use directly.
-struct ThreadLocalPlatform {
-#ifdef _WIN32
-  typedef unsigned long SlotType;
-#else
-  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);
-};
-
-}  // namespace internal
-
-template <typename Type>
-class ThreadLocalPointer {
- public:
-  ThreadLocalPointer() : slot_() {
-    internal::ThreadLocalPlatform::AllocateSlot(&slot_);
-  }
-
-  ~ThreadLocalPointer() {
-    internal::ThreadLocalPlatform::FreeSlot(slot_);
-  }
-
-  Type* Get() {
-    return static_cast<Type*>(
-        internal::ThreadLocalPlatform::GetValueFromSlot(slot_));
-  }
-
-  void Set(Type* ptr) {
-    internal::ThreadLocalPlatform::SetValueInSlot(
-        slot_, const_cast<void*>(static_cast<const void*>(ptr)));
-  }
-
- private:
-  typedef internal::ThreadLocalPlatform::SlotType SlotType;
-
-  SlotType slot_;
-
-  MOJO_DISALLOW_COPY_AND_ASSIGN(ThreadLocalPointer<Type>);
-};
-
-class ThreadLocalBoolean {
- public:
-  ThreadLocalBoolean() {}
-  ~ThreadLocalBoolean() {}
-
-  bool Get() {
-    return tlp_.Get() != NULL;
-  }
-
-  void Set(bool val) {
-    tlp_.Set(val ? this : NULL);
-  }
-
- private:
-  ThreadLocalPointer<void> tlp_;
-
-  MOJO_DISALLOW_COPY_AND_ASSIGN(ThreadLocalBoolean);
-};
-
-}  // namespace mojo
-
-#endif  // MOJO_PUBLIC_UTILITY_THREAD_LOCAL_H_