packed_spatial_index 0.18.1

Packed static spatial index (Hilbert R-tree) for 2D/3D AABBs — SIMD range, kNN, raycast, and spatial-join queries, with zero-copy and streaming serialization.
Documentation 
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use super::SimdIndex2D;
use crate::persistence::{
    ByteWriter, CHUNK_ENTRY_LEN, LoadError, SUPERBLOCK_LEN, TAG_TREE, TREE_DESC_LEN, parse_index,
    plan_container, read_f64_le_unchecked, read_u64_le_unchecked,
};

impl SimdIndex2D {
    /// Serialize into the stable little-endian `PSINDEX` format.
    ///
    /// The output is byte-identical to [`Index2D::to_bytes`](crate::Index2D::to_bytes)
    /// for the same items, so a `SimdIndex2D` and an `Index2D` are interchangeable on
    /// disk: either can load bytes produced by the other.
    pub fn to_bytes(&self) -> Vec<u8> {
        let mut out = Vec::new();
        self.to_bytes_into(&mut out);
        out
    }

    /// Serialize into a caller-provided buffer, reusing its allocation.
    ///
    /// Equivalent to [`to_bytes`](Self::to_bytes) but writes into `out` (cleared first).
    pub fn to_bytes_into(&self, out: &mut Vec<u8>) {
        let num_nodes = self.min_xs.len();
        let tree_len = TREE_DESC_LEN + num_nodes * 32 + num_nodes * 8;
        let (total, off) = plan_container(&[tree_len]).expect("serialized index is too large");
        let mut bytes = ByteWriter::new(out, total);
        bytes.write_superblock(1);
        bytes.write_chunk_entry(&TAG_TREE, true, off[0], tree_len);
        bytes.write_zeros(off[0] - (SUPERBLOCK_LEN + CHUNK_ENTRY_LEN));
        bytes.write_tree_desc(2, 8, false, self.num_items, self.node_size);
        bytes.write_soa_boxes_2d(&self.min_xs, &self.min_ys, &self.max_xs, &self.max_ys);
        bytes.write_usize_slice_as_u64(&self.indices);
        bytes.write_zeros(total - (off[0] + tree_len));
        bytes.finish();
    }

    /// Load a SIMD index from bytes produced by [`to_bytes`](Self::to_bytes) or by
    /// [`Index2D::to_bytes`](crate::Index2D::to_bytes); the AoS box records are
    /// scattered into the structure-of-arrays columns.
    pub fn from_bytes(bytes: &[u8]) -> Result<Self, LoadError> {
        let (parsed, payload) = parse_index(bytes, 2, 8)?;
        // SIMD indexes do not expose payloads; refuse a payload file rather than
        // silently drop the data (SIMD indexes have no payload accessor).
        if payload.is_some() {
            return Err(LoadError::UnsupportedVersion);
        }
        let num_nodes = parsed.num_nodes;
        let level_bounds = parsed.level_bounds;

        let mut min_xs = Vec::with_capacity(num_nodes);
        let mut min_ys = Vec::with_capacity(num_nodes);
        let mut max_xs = Vec::with_capacity(num_nodes);
        let mut max_ys = Vec::with_capacity(num_nodes);
        let mut indices = Vec::with_capacity(num_nodes);
        for i in 0..num_nodes {
            let off = i * 32; // four f64 per 2D box record
            min_xs.push(read_f64_le_unchecked(parsed.entries, off));
            min_ys.push(read_f64_le_unchecked(parsed.entries, off + 8));
            max_xs.push(read_f64_le_unchecked(parsed.entries, off + 16));
            max_ys.push(read_f64_le_unchecked(parsed.entries, off + 24));
            indices.push(read_u64_le_unchecked(parsed.indices, i * 8) as usize);
        }

        Ok(SimdIndex2D {
            node_size: parsed.node_size,
            num_items: parsed.num_items,
            level_bounds,
            min_xs,
            min_ys,
            max_xs,
            max_ys,
            indices,
        })
    }
}