278 lines
7.8 KiB
C++
278 lines
7.8 KiB
C++
/*
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* Copyright Andrey Semashev 2007 - 2013.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*/
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/*!
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* \file threadsafe_queue.hpp
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* \author Andrey Semashev
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* \date 05.11.2010
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*
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* \brief This header is the Boost.Log library implementation, see the library documentation
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* at http://www.boost.org/doc/libs/release/libs/log/doc/html/index.html.
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*/
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#ifndef BOOST_LOG_DETAIL_THREADSAFE_QUEUE_HPP_INCLUDED_
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#define BOOST_LOG_DETAIL_THREADSAFE_QUEUE_HPP_INCLUDED_
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#include <boost/log/detail/config.hpp>
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#ifdef BOOST_HAS_PRAGMA_ONCE
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#pragma once
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#endif
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#ifndef BOOST_LOG_NO_THREADS
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#include <new>
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#include <memory>
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#include <cstddef>
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#include <boost/aligned_storage.hpp>
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#include <boost/move/core.hpp>
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#include <boost/move/utility.hpp>
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#include <boost/type_traits/alignment_of.hpp>
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#include <boost/type_traits/type_with_alignment.hpp>
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#include <boost/log/detail/header.hpp>
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namespace boost {
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BOOST_LOG_OPEN_NAMESPACE
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namespace aux {
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//! Base class for the thread-safe queue implementation
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struct threadsafe_queue_impl
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{
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struct
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#if defined(__GNUC__)
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// Explicitly mark the type so that it may alias other types
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__attribute__ ((__may_alias__))
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#endif
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pointer_storage
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{
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union
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{
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void* data[2];
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type_with_alignment< 2 * sizeof(void*) >::type alignment;
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};
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};
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struct node_base
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{
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pointer_storage next;
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};
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static BOOST_LOG_API threadsafe_queue_impl* create(node_base* first_node);
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static BOOST_LOG_API void* operator new (std::size_t size);
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static BOOST_LOG_API void operator delete (void* p, std::size_t);
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virtual ~threadsafe_queue_impl() {}
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virtual node_base* reset_last_node() = 0;
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virtual bool unsafe_empty() = 0;
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virtual void push(node_base* p) = 0;
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virtual bool try_pop(node_base*& node_to_free, node_base*& node_with_value) = 0;
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};
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//! A helper class to compose some of the types used by the queue
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template< typename T, typename AllocatorT >
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struct threadsafe_queue_types
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{
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struct node :
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public threadsafe_queue_impl::node_base
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{
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typedef typename aligned_storage< sizeof(T), alignment_of< T >::value >::type storage_type;
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storage_type storage;
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node() {}
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explicit node(T const& val) { new (storage.address()) T(val); }
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T& value() { return *static_cast< T* >(storage.address()); }
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void destroy() { static_cast< T* >(storage.address())->~T(); }
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};
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typedef typename AllocatorT::BOOST_NESTED_TEMPLATE rebind< node >::other allocator_type;
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};
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/*!
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* \brief An unbounded thread-safe queue
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*
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* The implementation is based on algorithms published in the "Simple, Fast,
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* and Practical Non-Blocking and Blocking Concurrent Queue Algorithms" article
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* in PODC96 by Maged M. Michael and Michael L. Scott. Pseudocode is available here:
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* http://www.cs.rochester.edu/research/synchronization/pseudocode/queues.html
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*
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* The implementation provides thread-safe \c push and \c try_pop operations, as well as
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* a thread-unsafe \c empty operation. The queue imposes the following requirements
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* on the element type:
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*
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* \li Default constructible, the default constructor must not throw.
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* \li Copy constructible.
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* \li Movable (i.e. there should be an efficient move assignment for this type).
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*
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* The last requirement is not mandatory but is crucial for decent performance.
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*/
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template< typename T, typename AllocatorT = std::allocator< void > >
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class threadsafe_queue :
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private threadsafe_queue_types< T, AllocatorT >::allocator_type
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{
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private:
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typedef typename threadsafe_queue_types< T, AllocatorT >::allocator_type base_type;
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typedef typename threadsafe_queue_types< T, AllocatorT >::node node;
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//! A simple scope guard to automate memory reclaiming
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struct auto_deallocate;
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friend struct auto_deallocate;
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struct auto_deallocate
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{
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auto_deallocate(base_type* alloc, node* dealloc, node* destr) :
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m_pAllocator(alloc),
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m_pDeallocate(dealloc),
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m_pDestroy(destr)
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{
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}
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~auto_deallocate()
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{
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m_pAllocator->deallocate(m_pDeallocate, 1);
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m_pDestroy->destroy();
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}
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private:
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base_type* m_pAllocator;
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node* m_pDeallocate;
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node* m_pDestroy;
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};
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public:
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typedef T value_type;
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typedef T& reference;
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typedef T const& const_reference;
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typedef T* pointer;
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typedef T const* const_pointer;
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typedef std::ptrdiff_t difference_type;
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typedef std::size_t size_type;
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typedef AllocatorT allocator_type;
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public:
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/*!
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* Default constructor, creates an empty queue. Unlike most containers,
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* the constructor requires memory allocation.
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*
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* \throw std::bad_alloc if there is not sufficient memory
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*/
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threadsafe_queue(base_type const& alloc = base_type()) :
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base_type(alloc)
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{
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node* p = base_type::allocate(1);
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if (p)
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{
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try
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{
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new (p) node();
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try
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{
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m_pImpl = threadsafe_queue_impl::create(p);
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}
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catch (...)
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{
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p->~node();
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throw;
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}
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}
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catch (...)
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{
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base_type::deallocate(p, 1);
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throw;
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}
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}
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else
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throw std::bad_alloc();
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}
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/*!
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* Destructor
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*/
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~threadsafe_queue()
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{
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// Clear the queue
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if (!unsafe_empty())
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{
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value_type value;
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while (try_pop(value));
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}
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// Remove the last dummy node
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node* p = static_cast< node* >(m_pImpl->reset_last_node());
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p->~node();
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base_type::deallocate(p, 1);
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delete m_pImpl;
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}
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/*!
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* Checks if the queue is empty. Not thread-safe, the returned result may not be actual.
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*/
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bool unsafe_empty() const { return m_pImpl->unsafe_empty(); }
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/*!
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* Puts a new element to the end of the queue. Thread-safe, can be called
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* concurrently by several threads, and concurrently with the \c pop operation.
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*/
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void push(const_reference value)
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{
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node* p = base_type::allocate(1);
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if (p)
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{
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try
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{
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new (p) node(value);
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}
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catch (...)
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{
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base_type::deallocate(p, 1);
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throw;
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}
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m_pImpl->push(p);
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}
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else
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throw std::bad_alloc();
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}
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/*!
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* Attempts to pop an element from the beginning of the queue. Thread-safe, can
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* be called concurrently with the \c push operation. Should not be called by
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* several threads concurrently.
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*/
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bool try_pop(reference value)
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{
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threadsafe_queue_impl::node_base *dealloc, *destr;
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if (m_pImpl->try_pop(dealloc, destr))
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{
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register node* p = static_cast< node* >(destr);
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auto_deallocate guard(static_cast< base_type* >(this), static_cast< node* >(dealloc), p);
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value = boost::move(p->value());
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return true;
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}
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else
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return false;
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}
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// Copying and assignment is prohibited
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BOOST_DELETED_FUNCTION(threadsafe_queue(threadsafe_queue const&))
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BOOST_DELETED_FUNCTION(threadsafe_queue& operator= (threadsafe_queue const&))
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private:
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//! Pointer to the implementation
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threadsafe_queue_impl* m_pImpl;
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};
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} // namespace aux
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BOOST_LOG_CLOSE_NAMESPACE // namespace log
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} // namespace boost
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#include <boost/log/detail/footer.hpp>
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#endif // BOOST_LOG_NO_THREADS
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#endif // BOOST_LOG_DETAIL_THREADSAFE_QUEUE_HPP_INCLUDED_
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