con-art-rust 0.2.0

A Rust implementation of ART-OLC concurrent adaptive radix tree.
Documentation 
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use std::alloc;

use crate::{
    base_node::{BaseNode, Node, NodeType},
    child_ptr::NodePtr,
};

#[repr(C)]
pub(crate) struct Node4 {
    base: BaseNode,

    keys: [u8; 4],
    children: [NodePtr; 4],
}

impl Node for Node4 {
    fn new(prefix: &[u8]) -> Box<Node4> {
        let layout = alloc::Layout::from_size_align(
            std::mem::size_of::<Node4>(),
            std::mem::align_of::<Node4>(),
        )
        .unwrap();
        unsafe {
            let mem = alloc::alloc_zeroed(layout) as *mut BaseNode;
            let base = BaseNode::new(NodeType::N4, prefix);
            mem.write(base);
            Box::from_raw(mem as *mut Node4)
        }
    }

    fn get_type() -> NodeType {
        NodeType::N4
    }

    fn remove(&mut self, k: u8) {
        for i in 0..self.base.count {
            if self.keys[i as usize] == k {
                unsafe {
                    std::ptr::copy(
                        self.keys.as_ptr().add(i as usize + 1),
                        self.keys.as_mut_ptr().add(i as usize),
                        (self.base.count - i - 1) as usize,
                    );

                    std::ptr::copy(
                        self.children.as_ptr().add(i as usize + 1),
                        self.children.as_mut_ptr().add(i as usize),
                        (self.base.count - i - 1) as usize,
                    )
                }
                self.base.count -= 1;
                return;
            }
        }
    }

    fn get_children(&self, start: u8, end: u8) -> Vec<(u8, NodePtr)> {
        let mut out_children = Vec::with_capacity(4);

        for i in 0..self.base.count as usize {
            if self.keys[i] >= start && self.keys[i] <= end {
                out_children.push((self.keys[i], self.children[i]));
            }
        }

        out_children
    }

    fn copy_to<N: Node>(&self, dst: &mut N) {
        for i in 0..self.base.count {
            dst.insert(self.keys[i as usize], self.children[i as usize]);
        }
    }

    fn base(&self) -> &BaseNode {
        &self.base
    }

    fn base_mut(&mut self) -> &mut BaseNode {
        &mut self.base
    }

    fn is_full(&self) -> bool {
        self.base.count == 4
    }

    fn is_under_full(&self) -> bool {
        false
    }

    fn insert(&mut self, key: u8, node: NodePtr) {
        let mut pos: usize = 0;

        while (pos as u16) < self.base.count {
            if self.keys[pos] < key {
                pos += 1;
                continue;
            } else {
                break;
            }
        }

        unsafe {
            std::ptr::copy(
                self.keys.as_ptr().add(pos),
                self.keys.as_mut_ptr().add(pos + 1),
                self.base.count as usize - pos,
            );

            std::ptr::copy(
                self.children.as_ptr().add(pos),
                self.children.as_mut_ptr().add(pos + 1),
                self.base.count as usize - pos,
            );
        }

        self.keys[pos] = key;
        self.children[pos] = node;
        self.base.count += 1;
    }

    fn change(&mut self, key: u8, val: NodePtr) {
        for i in 0..self.base.count {
            if self.keys[i as usize] == key {
                self.children[i as usize] = val;
            }
        }
    }

    fn get_child(&self, key: u8) -> Option<NodePtr> {
        for i in 0..self.base.count {
            if self.keys[i as usize] == key {
                return Some(self.children[i as usize]);
            }
        }
        None
    }
}