From 83a05ddf63cc5920ad04b0a6936fb8f5625daa07 Mon Sep 17 00:00:00 2001
From: "deanm@google.com"
 <deanm@google.com@0039d316-1c4b-4281-b951-d872f2087c98>
Date: Wed, 3 Sep 2008 16:47:37 +0000
Subject: Add ThreadLocalPointer and ThreadLocalBoolean abstractions, that will
 deprecate the old ThreadLocalStorage / TLSSlot APIs.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@1678 0039d316-1c4b-4281-b951-d872f2087c98
---
 base/thread_local.h | 121 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 base/thread_local.h

(limited to 'base/thread_local.h')

diff --git a/base/thread_local.h b/base/thread_local.h
new file mode 100644
index 0000000..7b3c3da
--- /dev/null
+++ b/base/thread_local.h
@@ -0,0 +1,121 @@
+// 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) {
+    tlp_.Set(reinterpret_cast<void*>(val ? 1 : 0));
+  }
+
+ private:
+  ThreadLocalPointer<void> tlp_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadLocalBoolean);
+};
+
+}  // namespace base
+
+#endif  // BASE_THREAD_LOCAL_H_
-- 
cgit v1.1