arctic-map 0.1.2

Lock-free adaptive radix tree
Documentation 
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//! [`Node256`] provides a **total** mapping of 256 key-edge pairs.
//!
//! This is the simplest node representation, and requires the most memory.
//! It is not linear because it has no header metadata at all.

use core::fmt::Debug;

use crate::raw::node;
use crate::raw::node::KeyIter256;

const CAPACITY: usize = 256;

/// [`Node`] representation that contains exactly 256 key-edge pairs.
pub(super) type Node256 = node::Node<CAPACITY, Header>;

// Note: aligning to 4096 would require a newtype wrapper
// and more boilerplate. Just assume a
// reasonable memory allocator will have a dedicated
// size class for 4KiB.
const_assert_size_align!(Node256, 4096, 64);

#[derive(Clone, Debug, Default)]
pub(super) struct Header;

unsafe impl node::Header for Header {
    const TYPE: node::Type = node::Type::Node256;
    type KeyIter = KeyIter256;

    unsafe fn new_unchecked<const CAPACITY: usize>(
        keys: &[u8],
        edges: &[ribbit::Packed<crate::raw::edge::Raw>],
    ) -> Box<node::Node<CAPACITY, Self>> {
        if_validate!(assert!(crate::raw::is_unique(keys)));
        validate!(keys.len() == edges.len());
        validate!(keys.len() <= CAPACITY);

        let mut node = Box::new(node::Node::default());
        for (index, edge) in core::iter::zip(keys, edges) {
            *node.edges[*index as usize].get_mut_packed() = *edge;
        }
        node
    }

    #[inline]
    unsafe fn initialize_unchecked(&mut self, _keys: &[u8]) {}

    #[inline]
    fn keys<L: node::iter::Lower, U: node::iter::Upper>(
        &self,
        lower: L,
        upper: U,
        iter: &mut Self::KeyIter,
    ) {
        *iter = KeyIter256::new(lower, upper)
    }

    #[inline]
    fn get(&self, key: u8) -> Option<u8> {
        Some(key)
    }

    #[inline]
    fn get_or_insert(&self, key: u8) -> Option<u8> {
        Some(key)
    }

    #[inline]
    fn freeze(&self) -> usize {
        CAPACITY
    }

    #[inline]
    fn min<L: node::Lower>(&self, _lower: L) -> Option<node::KeyIndex> {
        todo!()
        // self.0
        //     .iter()
        //     .enumerate()
        //     .skip(lower.get() as usize)
        //     .find_map(|(index, edge)| {
        //         if edge.load_packed(Ordering::Relaxed).is_null() {
        //             return None;
        //         } else {
        //             Some(iter::KeyIndex {
        //                 index: index as u8,
        //                 key: index as u8,
        //             })
        //         }
        //     })
    }

    #[inline]
    fn max<U: node::Upper>(&self, _upper: U) -> Option<node::KeyIndex> {
        todo!()
        // self.0
        //     .iter()
        //     .enumerate()
        //     .rev()
        //     .skip(upper.get() as usize)
        //     .find_map(|(index, edge)| {
        //         if edge.load_packed(Ordering::Relaxed).is_null() {
        //             return None;
        //         } else {
        //             Some(iter::KeyIndex {
        //                 index: index as u8,
        //                 key: index as u8,
        //             })
        //         }
        //     })
    }

    #[inline]
    fn len(&self) -> usize {
        CAPACITY
    }

    #[inline]
    fn is_frozen(&self) -> bool {
        false
    }
}