/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* Cross-platform lightweight thread local data wrappers. */

#ifndef mozilla_ThreadLocal_h

#define mozilla_ThreadLocal_h

#if !defined(XP_WIN)

#include <pthread.h>

#endif

#include "mozilla/Assertions.h"

#include "mozilla/Attributes.h"

#include "mozilla/TypeTraits.h"

namespace mozilla {

namespace detail {

#ifdef XP_MACOSX

#if defined(__has_feature)

#if __has_feature(cxx_thread_local)

#define MACOSX_HAS_THREAD_LOCAL

#endif

#endif

#endif

/*

 * Thread Local Storage helpers.

 *

 * Usage:

 *

 * Do not directly instantiate this class.  Instead, use the

 * MOZ_THREAD_LOCAL macro to declare or define instances.  The macro

 * takes a type name as its argument.

 *

 * Declare like this:

 * extern MOZ_THREAD_LOCAL(int) tlsInt;

 * Define like this:

 * MOZ_THREAD_LOCAL(int) tlsInt;

 * or:

 * static MOZ_THREAD_LOCAL(int) tlsInt;

 *

 * Only static-storage-duration (e.g. global variables, or static class members)

 * objects of this class should be instantiated. This class relies on

 * zero-initialization, which is implicit for static-storage-duration objects.

 * It doesn't have a custom default constructor, to avoid static initializers.

 *

 * API usage:

 *

 * // Create a TLS item.

 * //

 * // Note that init() should be invoked before the first use of set()

 * // or get().  It is ok to call it multiple times.  This must be

 * // called in a way that avoids possible races with other threads.

 * MOZ_THREAD_LOCAL(int) tlsKey;

 * if (!tlsKey.init()) {

 *   // deal with the error

 * }

 *

 * // Set the TLS value

 * tlsKey.set(123);

 *

 * // Get the TLS value

 * int value = tlsKey.get();

 */

// Integral types narrower than void* must be extended to avoid

// warnings from valgrind on some platforms.  This helper type

// achieves that without penalizing the common case of ThreadLocals

// instantiated using a pointer type.

template <typename S>

struct Helper {

  typedef uintptr_t Type;

};

template <typename S>

struct Helper<S*> {

  typedef S* Type;

};

#if defined(XP_WIN)

/*

 * ThreadLocalKeyStorage uses Thread Local APIs that are declared in

 * processthreadsapi.h. To use this class on Windows, include that file

 * (or windows.h) before including ThreadLocal.h.

 *

 * TLS_OUT_OF_INDEXES is a #define that is used to detect whether

 * an appropriate header has been included prior to this file

 */

#if defined(TLS_OUT_OF_INDEXES)

/* Despite not being used for MOZ_THREAD_LOCAL, we expose an implementation for

 * Windows for cases where it's not desirable to use thread_local */

template <typename T>

class ThreadLocalKeyStorage {

 public:

  ThreadLocalKeyStorage() : mKey(TLS_OUT_OF_INDEXES) {}

  inline bool initialized() const { return mKey != TLS_OUT_OF_INDEXES; }

  inline void init() { mKey = TlsAlloc(); }

  inline T get() const {

    void* h = TlsGetValue(mKey);

    return static_cast<T>(reinterpret_cast<typename Helper<T>::Type>(h));

  }

  inline bool set(const T aValue) {

    void* h =

        reinterpret_cast<void*>(static_cast<typename Helper<T>::Type>(aValue));

    return TlsSetValue(mKey, h);

  }

 private:

  unsigned long mKey;

};

#endif

#else

template <typename T>

class ThreadLocalKeyStorage {

 public:

  constexpr ThreadLocalKeyStorage() : mKey(0), mInited(false) {}

  inline bool initialized() const { return mInited; }

  inline void init() { mInited = !pthread_key_create(&mKey, nullptr); }

  inline T get() const {

    void* h = pthread_getspecific(mKey);

    return static_cast<T>(reinterpret_cast<typename Helper<T>::Type>(h));

  }

  inline bool set(const T aValue) {

    void* h =

        reinterpret_cast<void*>(static_cast<typename Helper<T>::Type>(aValue));

    return !pthread_setspecific(mKey, h);

  }

 private:

  pthread_key_t mKey;

  bool mInited;

};

#endif

template <typename T>

class ThreadLocalNativeStorage {

 public:

  // __thread does not allow non-trivial constructors, but we can

  // instead rely on zero-initialization.

  inline bool initialized() const { return true; }

  inline void init() {}

  inline T get() const { return mValue; }

  inline bool set(const T aValue) {

    mValue = aValue;

    return true;

  }

 private:

  T mValue;

};

template <typename T, template <typename U> class Storage>

class ThreadLocal : public Storage<T> {

 public:

  MOZ_MUST_USE inline bool init();

  void infallibleInit() {

    MOZ_RELEASE_ASSERT(init(), "Infallible TLS initialization failed");

  }

  inline T get() const;

  inline void set(const T aValue);

};

template <typename T, template <typename U> class Storage>

inline bool ThreadLocal<T, Storage>::init() {

  static_assert(mozilla::IsPointer<T>::value || mozilla::IsIntegral<T>::value,

                "mozilla::ThreadLocal must be used with a pointer or "

                "integral type");

  static_assert(sizeof(T) <= sizeof(void*),

                "mozilla::ThreadLocal can't be used for types larger than "

                "a pointer");

  if (!Storage<T>::initialized()) {

    Storage<T>::init();

  }

  return Storage<T>::initialized();

}

template <typename T, template <typename U> class Storage>

inline T ThreadLocal<T, Storage>::get() const {

  MOZ_ASSERT(Storage<T>::initialized());

  return Storage<T>::get();

}

template <typename T, template <typename U> class Storage>

inline void ThreadLocal<T, Storage>::set(const T aValue) {

  MOZ_ASSERT(Storage<T>::initialized());

  bool succeeded = Storage<T>::set(aValue);

  if (!succeeded) {

    MOZ_CRASH();

  }

}

#if (defined(XP_WIN) || defined(MACOSX_HAS_THREAD_LOCAL)) && \

    !defined(__MINGW32__)

#define MOZ_THREAD_LOCAL(TYPE)               \

  thread_local mozilla::detail::ThreadLocal< \

      TYPE, mozilla::detail::ThreadLocalNativeStorage>

#elif defined(HAVE_THREAD_TLS_KEYWORD)

#define MOZ_THREAD_LOCAL(TYPE)           \

  __thread mozilla::detail::ThreadLocal< \

      TYPE, mozilla::detail::ThreadLocalNativeStorage>

#else

#define MOZ_THREAD_LOCAL(TYPE) \

  mozilla::detail::ThreadLocal<TYPE, mozilla::detail::ThreadLocalKeyStorage>

#endif

}  // namespace detail

}  // namespace mozilla

#endif /* mozilla_ThreadLocal_h */