lock_free_spmc_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) 2004-2026 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_spmc_ring_buffer.h"
 
namespace lass
{
namespace stde
{
namespace impl
{
 
// --- lock_free_spmc_ring_buffer_base -------------------------------------------------------------
 
inline lock_free_spmc_ring_buffer_base::lock_free_spmc_ring_buffer_base(size_t capacity):
    head_(tagged_index_t(0, 0)),
    tail_(tagged_index_t(0, 0)),
    ring_size_(static_cast<index_type>(enforce_valid_size(capacity)))
{
    static_assert(std::atomic<tagged_index_t>::is_always_lock_free);
}
 
 
/** Return true if ring buffer is empty
 */
inline bool lock_free_spmc_ring_buffer_base::empty() const
{
    return tagged_index_t::empty(head_.load(std::memory_order_acquire), tail_.load(std::memory_order_acquire));
}
 
 
 
/** Return true if ring buffer is empty
 */
inline bool lock_free_spmc_ring_buffer_base::full() const
{
    return tagged_index_t::full(head_.load(std::memory_order_acquire), tail_.load(std::memory_order_acquire));
}
 
 
 
lock_free_spmc_ring_buffer_base::tagged_index_t
inline lock_free_spmc_ring_buffer_base::next_index(tagged_index_t index) const
{
    const index_type i = ++index.index;
    return i < ring_size_
        ? tagged_index_t(i, index.tag)
        : tagged_index_t(0, index.tag + 1);
}
 
 
 
inline size_t lock_free_spmc_ring_buffer_base::enforce_valid_size(size_t size)
{
    if (size == 0)
    {
        throw std::length_error("ring buffer capacitance cannot be zero");
    }
    if (size > num::NumTraits<index_type>::max)
    {
        throw std::length_error("exceeded maximum ring buffer capacitance");
    }
    return size;
}
 
 
 
// --- lock_free_spmc_value_ring_buffer ------------------------------------------------------------
 
template <typename T>
lock_free_spmc_value_ring_buffer<T>::lock_free_spmc_value_ring_buffer(size_t capacity):
    lock_free_spmc_ring_buffer_base(capacity),
    ring_(capacity)
{
}
 
 
 
/** 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_spmc_value_ring_buffer<T>::try_push(const value_type& x)
{
    const tagged_index_t head = head_.load(std::memory_order_relaxed);
    const tagged_index_t tail = tail_.load(std::memory_order_acquire);
    if (tagged_index_t::full(head, tail))
    {
        LASS_ASSERT(head.tag == tail.tag + 1);
        return false;
    }
    ring_[head.index].store(x, std::memory_order_release);
    head_.store(next_index(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_spmc_value_ring_buffer<T>::try_push(value_type&& x)
{
    const tagged_index_t head = head_.load(std::memory_order_relaxed);
    const tagged_index_t tail = tail_.load(std::memory_order_acquire);
    if (tagged_index_t::full(head, tail))
    {
        LASS_ASSERT(head.tag == tail.tag + 1);
        return false;
    }
    ring_[head.index].store(std::move(x), std::memory_order_release);
    head_.store(next_index(head), std::memory_order_release);
    return true;
}
 
 
 
/** Try to emplace a value on the front.
 *  @return false if buffer was full and value could not be pushed.
 */
template <typename T>
template <class... Args>
bool lock_free_spmc_value_ring_buffer<T>::try_emplace(Args&&... args)
{
    const tagged_index_t head = head_.load(std::memory_order_relaxed);
    const tagged_index_t tail = tail_.load(std::memory_order_acquire);
    if (tagged_index_t::full(head, tail))
    {
        LASS_ASSERT(head.tag == tail.tag + 1);
        return false;
    }
    ring_[head.index].store(value_type(std::forward<Args...>(args...)), std::memory_order_release);
    head_.store(next_index(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_spmc_value_ring_buffer<T>::try_pop(value_type& x)
{
    tagged_index_t tail = tail_.load(std::memory_order_acquire);
    while (true)
    {
        const tagged_index_t head = head_.load(std::memory_order_acquire);
        if (tagged_index_t::empty(head, tail))
        {
            return false;
        }
        x = ring_[tail.index].load(std::memory_order_acquire);
        if (tail_.compare_exchange_weak(tail, next_index(tail)))
        {
            return true;
        }
    }
}
 
 
 
// --- lock_free_spmc_object_ring_buffer ----------------------------------------------------------
 
template <typename T, typename A>
lock_free_spmc_object_ring_buffer<T, A>::lock_free_spmc_object_ring_buffer(size_t capacity):
    lock_free_spmc_ring_buffer_base(capacity),
    value_allocator_(sizeof(T)),
    ring_(capacity)
{
}
 
 
 
template <typename T, typename A>
lock_free_spmc_object_ring_buffer<T, A>::~lock_free_spmc_object_ring_buffer()
{
    const tagged_index_t head = head_.load(std::memory_order_acquire);
    const tagged_index_t tail = tail_.load(std::memory_order_acquire);
    for (tagged_index_t i = tail; !tagged_index_t::empty(i, head); i = next_index(i))
    {
        value_type* p = ring_[i.index].load(std::memory_order_relaxed);
        p->~value_type();
        value_allocator_.deallocate(p);
    }
}
 
 
 
/** Try to push a value x on the front.
 *  @return false if buffer was full and x could not be pushed.
 */
template <typename T, typename A>
bool lock_free_spmc_object_ring_buffer<T, A>::try_push(const value_type& x)
{
    const tagged_index_t head = head_.load(std::memory_order_relaxed);
    const tagged_index_t tail = tail_.load(std::memory_order_acquire);
    if (tagged_index_t::full(head, tail))
    {
        return false;
    }
    void* p = value_allocator_.allocate();
    try
    {
        ring_[head.index] = new (p) value_type(x);
    }
    catch (...)
    {
        value_allocator_.deallocate(p);
        throw;
    }
    head_.store(next_index(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, typename A>
bool lock_free_spmc_object_ring_buffer<T, A>::try_push(value_type&& x)
{
    const tagged_index_t head = head_.load(std::memory_order_relaxed);
    const tagged_index_t tail = tail_.load(std::memory_order_acquire);
    if (tagged_index_t::full(head, tail))
    {
        return false;
    }
    void* p = value_allocator_.allocate();
    try
    {
        ring_[head.index] = new (p) value_type(std::move(x));
    }
    catch (...)
    {
        value_allocator_.deallocate(p);
        throw;
    }
    head_.store(next_index(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, typename A>
template <class... Args>
bool lock_free_spmc_object_ring_buffer<T, A>::try_emplace(Args&&... args)
{
    const tagged_index_t head = head_.load(std::memory_order_relaxed);
    const tagged_index_t tail = tail_.load(std::memory_order_acquire);
    if (tagged_index_t::full(head, tail))
    {
        return false;
    }
    void* p = value_allocator_.allocate();
    try
    {
        ring_[head.index] = new (p) value_type(std::forward<Args...>(args...));
    }
    catch (...)
    {
        value_allocator_.deallocate(p);
        throw;
    }
    head_.store(next_index(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, typename A>
bool lock_free_spmc_object_ring_buffer<T, A>::try_pop(value_type& x)
{
    tagged_index_t tail = tail_.load(std::memory_order_acquire);
    while (true)
    {
        const tagged_index_t head = head_.load(std::memory_order_acquire);
        if (tagged_index_t::empty(head, tail))
        {
            return false;
        }
        value_type* p = ring_[tail.index];
        if (tail_.compare_exchange_weak(tail, next_index(tail)))
        {
            x = std::move(*p);
            p->~value_type();
            value_allocator_.deallocate(p);
            return true;
        }
    }
}
 
 
}
}
}
 
// EOF