mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-02 12:32:04 +00:00
145 lines
3.2 KiB
C++
145 lines
3.2 KiB
C++
//
|
|
// ThreadLocal.h
|
|
//
|
|
// Library: Foundation
|
|
// Package: Threading
|
|
// Module: Thread
|
|
//
|
|
// Definition of the ThreadLocal template and related classes.
|
|
//
|
|
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
|
|
// and Contributors.
|
|
//
|
|
// SPDX-License-Identifier: BSL-1.0
|
|
//
|
|
|
|
|
|
#ifndef Foundation_ThreadLocal_INCLUDED
|
|
#define Foundation_ThreadLocal_INCLUDED
|
|
|
|
|
|
#include <map>
|
|
#include "Poco/Foundation.h"
|
|
|
|
|
|
namespace Poco
|
|
{
|
|
|
|
|
|
class Foundation_API TLSAbstractSlot
|
|
/// This is the base class for all objects
|
|
/// that the ThreadLocalStorage class manages.
|
|
{
|
|
public:
|
|
TLSAbstractSlot();
|
|
virtual ~TLSAbstractSlot();
|
|
};
|
|
|
|
|
|
template <class C>
|
|
class TLSSlot : public TLSAbstractSlot
|
|
/// The Slot template wraps another class
|
|
/// so that it can be stored in a ThreadLocalStorage
|
|
/// object. This class is used internally, and you
|
|
/// must not create instances of it yourself.
|
|
{
|
|
public:
|
|
TLSSlot() : _value() { }
|
|
|
|
~TLSSlot() { }
|
|
|
|
C & value() { return _value; }
|
|
|
|
private:
|
|
TLSSlot(const TLSSlot &);
|
|
TLSSlot & operator=(const TLSSlot &);
|
|
|
|
C _value;
|
|
};
|
|
|
|
|
|
class Foundation_API ThreadLocalStorage
|
|
/// This class manages the local storage for each thread.
|
|
/// Never use this class directly, always use the
|
|
/// ThreadLocal template for managing thread local storage.
|
|
{
|
|
public:
|
|
ThreadLocalStorage();
|
|
/// Creates the TLS.
|
|
|
|
~ThreadLocalStorage();
|
|
/// Deletes the TLS.
|
|
|
|
TLSAbstractSlot *& get(const void * key);
|
|
/// Returns the slot for the given key.
|
|
|
|
static ThreadLocalStorage & current();
|
|
/// Returns the TLS object for the current thread
|
|
/// (which may also be the main thread).
|
|
|
|
static void clear();
|
|
/// Clears the current thread's TLS object.
|
|
/// Does nothing in the main thread.
|
|
|
|
private:
|
|
typedef std::map<const void *, TLSAbstractSlot *> TLSMap;
|
|
|
|
TLSMap _map;
|
|
|
|
friend class Thread;
|
|
};
|
|
|
|
|
|
template <class C>
|
|
class ThreadLocal
|
|
/// This template is used to declare type safe thread
|
|
/// local variables. It can basically be used like
|
|
/// a smart pointer class with the special feature
|
|
/// that it references a different object
|
|
/// in every thread. The underlying object will
|
|
/// be created when it is referenced for the first
|
|
/// time.
|
|
/// See the NestedDiagnosticContext class for an
|
|
/// example how to use this template.
|
|
/// Every thread only has access to its own
|
|
/// thread local data. There is no way for a thread
|
|
/// to access another thread's local data.
|
|
{
|
|
typedef TLSSlot<C> Slot;
|
|
|
|
public:
|
|
ThreadLocal() { }
|
|
|
|
~ThreadLocal() { }
|
|
|
|
C * operator->() { return &get(); }
|
|
|
|
C & operator*()
|
|
/// "Dereferences" the smart pointer and returns a reference
|
|
/// to the underlying data object. The reference can be used
|
|
/// to modify the object.
|
|
{
|
|
return get();
|
|
}
|
|
|
|
C & get()
|
|
/// Returns a reference to the underlying data object.
|
|
/// The reference can be used to modify the object.
|
|
{
|
|
TLSAbstractSlot *& p = ThreadLocalStorage::current().get(this);
|
|
if (!p)
|
|
p = new Slot;
|
|
return static_cast<Slot *>(p)->value();
|
|
}
|
|
|
|
private:
|
|
ThreadLocal(const ThreadLocal &);
|
|
ThreadLocal & operator=(const ThreadLocal &);
|
|
};
|
|
|
|
|
|
} // namespace Poco
|
|
|
|
|
|
#endif // Foundation_ThreadLocal_INCLUDED
|