Repo created

TMessagesProj/jni/voip/webrtc/base/threading/thread_local.h

@@ -0,0 +1,136 @@
+// Copyright (c) 2011 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 ThreadLocalStorage::Slot. 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.
+//
+// In Android, the system TLS is limited.
+//
+// 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_THREADING_THREAD_LOCAL_H_
+#define BASE_THREADING_THREAD_LOCAL_H_
+
+#include <memory>
+
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/threading/thread_local_internal.h"
+#include "base/threading/thread_local_storage.h"
+
+namespace base {
+
+template <typename T>
+class ThreadLocalPointer {
+ public:
+  ThreadLocalPointer() = default;
+  ~ThreadLocalPointer() = default;
+
+  T* Get() const { return static_cast<T*>(slot_.Get()); }
+
+  void Set(T* ptr) {
+    slot_.Set(const_cast<void*>(static_cast<const void*>(ptr)));
+  }
+
+ private:
+  ThreadLocalStorage::Slot slot_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadLocalPointer<T>);
+};
+
+// A ThreadLocalOwnedPointer<T> is like a ThreadLocalPointer<T> except that
+// pointers handed to it are owned and automatically deleted during their
+// associated thread's exit phase (or when replaced if Set() is invoked multiple
+// times on the same thread).
+// The ThreadLocalOwnedPointer instance itself can only be destroyed when no
+// threads, other than the one it is destroyed on, have remaining state set in
+// it. Typically this means that ThreadLocalOwnedPointer instances are held in
+// static storage or at the very least only recycled in the single-threaded
+// phase between tests in the same process.
+#if DCHECK_IS_ON()
+template <typename T>
+using ThreadLocalOwnedPointer = internal::CheckedThreadLocalOwnedPointer<T>;
+#else   // DCHECK_IS_ON()
+template <typename T>
+class ThreadLocalOwnedPointer {
+ public:
+  ThreadLocalOwnedPointer() = default;
+
+  ~ThreadLocalOwnedPointer() {
+    // Assume that this thread is the only one with potential state left. This
+    // is verified in ~CheckedThreadLocalOwnedPointer().
+    Set(nullptr);
+  }
+
+  T* Get() const { return static_cast<T*>(slot_.Get()); }
+
+  void Set(std::unique_ptr<T> ptr) {
+    delete Get();
+    slot_.Set(const_cast<void*>(static_cast<const void*>(ptr.release())));
+  }
+
+ private:
+  static void DeleteTlsPtr(void* ptr) { delete static_cast<T*>(ptr); }
+
+  ThreadLocalStorage::Slot slot_{&DeleteTlsPtr};
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadLocalOwnedPointer<T>);
+};
+#endif  // DCHECK_IS_ON()
+
+class ThreadLocalBoolean {
+ public:
+  ThreadLocalBoolean() = default;
+  ~ThreadLocalBoolean() = default;
+
+  bool Get() const { return tlp_.Get() != nullptr; }
+
+  void Set(bool val) { tlp_.Set(val ? this : nullptr); }
+
+ private:
+  ThreadLocalPointer<void> tlp_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadLocalBoolean);
+};
+
+}  // namespace base
+
+#endif  // BASE_THREADING_THREAD_LOCAL_H_