cc-queue 0.0.1

Fatourou and Kallimanis's CC Queue, ccqueue, an unbounded, concurrent blocking queue faster than the classic Michael & Scott queue, suitable for use with different memory allocators.
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// This file is part of cc-queue. It is subject to the license terms in the COPYRIGHT file found in the top-level directory of this distribution and at https://raw.githubusercontent.com/lemonrock/cc-queue/master/COPYRIGHT. No part of predicator, including this file, may be copied, modified, propagated, or distributed except according to the terms contained in the COPYRIGHT file.
// Copyright © 2017 The developers of cc-queue. See the COPYRIGHT file in the top-level directory of this distribution and at https://raw.githubusercontent.com/lemonrock/cc-queue/master/COPYRIGHT.


#[derive(Debug)]
#[repr(C)]
struct Node<T>
{
	next: *mut Node<T>, // TODO: CACHE_ALIGNED
	data: NonNull<T>, // except the dummy node's data can be null
}

impl<T> Node<T>
{
	#[inline(always)]
	fn clearing_queue_drop<A: Allocator, FreeData: Fn(NonNull<T>)>(this: NonNull<Self>, allocator: &mut A, free_data: &FreeData)
	{
		let x = unsafe { this.as_ref() };
		
		let next = x.next;
		if next.is_not_null()
		{
			Self::clearing_queue_drop(unsafe { NonNull::new_unchecked(next) }, allocator, free_data);
		}
		
		// dummy_node is created with a dangling data pointer
		let data = x.data;
		if data.as_ptr() != NonNull::dangling().as_ptr()
		{
			free_data(data);
		}
		
		Self::free_after_drop(this, allocator)
	}
	
	#[inline(always)]
	fn free_after_drop<A: Allocator>(this: NonNull<Self>, allocator: &mut A)
	{
		allocator.free_cache_line_size(this)
	}
	
	#[inline(always)]
	unsafe fn dummy_node<A: Allocator>(allocator: &mut A) -> NonNull<Self>
	{
		let mut dummy = allocator.align_malloc_cache_line_size();
		{
			let dummy: &mut Self = dummy.as_mut();
			// This data is believed to be always overwritten...
			write(&mut dummy.data, NonNull::dangling());
			write(&mut dummy.next, null_mut());
		}
		dummy
	}
}