lock_free_spsc_ring_buffer.inl

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/** @file
 *  @author Bram de Greve (bram@cocamware.com)
 *  @author Tom De Muer (tom@cocamware.com)
 *
 *  *** BEGIN LICENSE INFORMATION ***
 *  
 *  The contents of this file are subject to the Common Public Attribution License 
 *  Version 1.0 (the "License"); you may not use this file except in compliance with 
 *  the License. You may obtain a copy of the License at 
 *  http://lass.sourceforge.net/cpal-license. The License is based on the 
 *  Mozilla Public License Version 1.1 but Sections 14 and 15 have been added to cover 
 *  use of software over a computer network and provide for limited attribution for 
 *  the Original Developer. In addition, Exhibit A has been modified to be consistent 
 *  with Exhibit B.
 *  
 *  Software distributed under the License is distributed on an "AS IS" basis, WITHOUT 
 *  WARRANTY OF ANY KIND, either express or implied. See the License for the specific 
 *  language governing rights and limitations under the License.
 *  
 *  The Original Code is LASS - Library of Assembled Shared Sources.
 *  
 *  The Initial Developer of the Original Code is Bram de Greve and Tom De Muer.
 *  The Original Developer is the Initial Developer.
 *  
 *  All portions of the code written by the Initial Developer are:
 *  Copyright (C) 2004-2021 the Initial Developer.
 *  All Rights Reserved.
 *  
 *  Contributor(s):
 *
 *  Alternatively, the contents of this file may be used under the terms of the 
 *  GNU General Public License Version 2 or later (the GPL), in which case the 
 *  provisions of GPL are applicable instead of those above.  If you wish to allow use
 *  of your version of this file only under the terms of the GPL and not to allow 
 *  others to use your version of this file under the CPAL, indicate your decision by 
 *  deleting the provisions above and replace them with the notice and other 
 *  provisions required by the GPL License. If you do not delete the provisions above,
 *  a recipient may use your version of this file under either the CPAL or the GPL.
 *  
 *  *** END LICENSE INFORMATION ***
 */
 
#include "lock_free_spsc_ring_buffer.h"
 
namespace lass
{
namespace stde
{
 
// --- public --------------------------------------------------------------------------------------
 
template <typename T>
lock_free_spsc_ring_buffer<T>::lock_free_spsc_ring_buffer(size_t capacity):
    head_(0),
    tail_(0),
    ring_(capacity + 1),
    ring_size_(capacity + 1)
{
#if defined(__cpp_lib_atomic_is_always_lock_free)
    static_assert(std::atomic<size_t>::is_always_lock_free);
#else
    LASS_ENFORCE(head_.is_lock_free());
    LASS_ENFORCE(tail_.is_lock_free());
#endif
}
 
 
 
template <typename T>
lock_free_spsc_ring_buffer<T>::~lock_free_spsc_ring_buffer()
{
}
 
 
 
/** Try to push a value x on the front.
 *  @return false if buffer was full and x could not be pushed.
 */
template <typename T>
bool lock_free_spsc_ring_buffer<T>::try_push(const value_type& x)
{
    const size_t head = head_.load(std::memory_order_relaxed);
    const size_t tail = tail_.load(std::memory_order_acquire);
    const size_t new_head = next_index(head);
    if (new_head == tail)
    {
        return false;
    }
    ring_[head] = x;
    head_.store(new_head, std::memory_order_release);
    return true;
}
 
 
 
/** Try to push a value x on the front.
 *  @return false if buffer was full and x could not be pushed.
 */
template <typename T>
bool lock_free_spsc_ring_buffer<T>::try_push(value_type&& x)
{
    const size_t head = head_.load(std::memory_order_relaxed);
    const size_t tail = tail_.load(std::memory_order_acquire);
    const size_t new_head = next_index(head);
    if (new_head == tail)
    {
        return false;
    }
    ring_[head] = std::move(x);
    head_.store(new_head, std::memory_order_release);
    return true;
}
 
 
 
/** Try to push a value x on the front.
 *  @return false if buffer was full and x could not be pushed.
 */
template <typename T>
template <typename... Args>
bool lock_free_spsc_ring_buffer<T>::try_emplace(Args&&... args)
{
    const size_t head = head_.load(std::memory_order_relaxed);
    const size_t tail = tail_.load(std::memory_order_acquire);
    const size_t new_head = next_index(head);
    if (new_head == tail)
    {
        return false;
    }
    ring_[head] = value_type(std::forward<Args...>(args...));
    head_.store(new_head, std::memory_order_release);
    return true;
}
 
 
 
/** Try to pop a value from the back and store it in x.
 *  @return false if buffer was empty and no element could be popped.
 */
template <typename T>
bool lock_free_spsc_ring_buffer<T>::try_pop(value_type& x)
{
    const size_t head = head_.load(std::memory_order_acquire);
    const size_t tail = tail_.load(std::memory_order_relaxed);
    if (tail == head)
    {
        return false;
    }
    x = std::move(ring_[tail]);
    tail_.store(next_index(tail), std::memory_order_release);
    return true;
}
 
 
 
/** Return true if ring buffer is empty
 */
template <typename T>
bool lock_free_spsc_ring_buffer<T>::empty() const
{
    const size_t head = head_.load(std::memory_order_acquire);
    const size_t tail = tail_.load(std::memory_order_acquire);
    return head == tail;
}
 
 
 
/** Return true if ring buffer is empty
 */
template <typename T>
bool lock_free_spsc_ring_buffer<T>::full() const
{
    const size_t head = head_.load(std::memory_order_acquire);
    const size_t tail = tail_.load(std::memory_order_acquire);
    return next_index(head) == tail;
}
 
 
// --- private -------------------------------------------------------------------------------------
 
template <typename T>
size_t lock_free_spsc_ring_buffer<T>::next_index(size_t index) const
{
    ++index;
    return index < ring_size_ ? index : 0;
}
 
 
}
 
}
 
// EOF