Crate zdex

Zdex is for evaluating z-order indexes (morton encoding) for types, iterators, and tuples of BitCollections.

Z-order indexing is a database range-querying technique to optimise scanning performance, and Zdex aims to be prescriptive in providing that functionality.

Examples

Basic example using built-in FromU8 BitCollection:

use zdex::*;

fn main() -> Result<(), std::io::Error> {
  let v1: FromU8 = 0b0011.into();
  let v2: FromU8 = 0b1111.into();

  // Prints "Vob[01011111]".
  println!("{:?}", (v1, v2).z_index()?);

  Ok(())
}

Example with custom BitCollection and high dimensionality:

use bit_collection::*;
use zdex::*;

#[bit(BitU8, mask = "!0", retr = "0")]
#[derive(BitCollection, Clone, Copy, Debug)]
pub struct BigVal(u128);

fn main() -> Result<(), std::io::Error> {
    let vals: Vec<BigVal> = [BigVal(1u128 << 90)]
        .into_iter()
        .cycle()
        .take(10)
        .map(|r| r.to_owned())
        .collect();

    let z_index = vals.z_index()?;

    // Prints out a large vob, followed by the numbers 10 and 900.
    println!(
        "{:?}\n  {}\n  {}",
        z_index,
        z_index.iter_set_bits(..).count(),
        z_index.iter_unset_bits(..).count()
    );

    Ok(())
}

Practical example: querying over a (lon, lat) z-index:

use bit_collection::*;
use std::collections::BTreeMap;
use zdex::*;

#[bit(BitU8, mask = "!0", retr = "0")]
#[derive(BitCollection, Clone, Copy, Debug)]
pub struct LonLatVal(i32);

fn lonlat_val(lonlat: (f32, f32)) -> (LonLatVal, LonLatVal) {
    (LonLatVal(lonlat.0 as i32), LonLatVal(lonlat.1 as i32))
}

fn main() -> Result<(), std::io::Error> {
    let database = vec![
        ((  -0.127758,  51.507351), "London"),
        ((   2.352222,  48.856613), "Paris"),
        ((  10.752245,  59.913868), "Oslo"),
        (( -74.005974,  40.712776), "New York"),
        ((-118.243683,  34.052235), "Los Angeles"),
        (( -46.633308, -23.550520), "Sao Paolo"),
        (( 151.209290, -33.868820), "Sydney"),
    ].into_iter()
    .map(|(lonlat, loc)| (
        lonlat_val(lonlat),
        loc
    )).map(|(lonlat, loc)| (
        lonlat
            .z_index()
            .map(|v| v.iter_storage().next().expect("empty vob"))
            .expect("failed to produce z-index"),
            loc
    )).collect::<BTreeMap<_, _>>();

    let usa_query = (
        lonlat_val((-200.0, 20.0))
            .z_index()?
            .iter_storage()
            .next()
            .expect("empty vob")
    )..(
        lonlat_val((-50.0, 50.0))
            .z_index()?
            .iter_storage()
            .next()
            .expect("empty vob")
    );

    // Prints `["New York", "Los Angeles"]`.
    println!(
        "{:?}",
        database.range(usa_query).map(|(_k, v)| v).collect::<Vec<_>>()
    );

    Ok(())
}

Structs

• BitU8
  The BitCollection::Item-type prescribed by Zdex for use in Zdexed-compatible BitCollections. Custom BitCollections specified for use with Zdex must therefore specify #[bit(BitU8, ...].
• FromU8
  A built-in Zdex-compatible BitCollection for u8.
• FromU16
  A built-in Zdex-compatible BitCollection for u16.
• FromU32
  A built-in Zdex-compatible BitCollection for u32.
• FromU64
  A built-in Zdex-compatible BitCollection for u64.
• FromU128
  A built-in Zdex-compatible BitCollection for u128.

Traits

• Zdexed
  Trait for implementing z_index() for BitCollections. A blanket implementation is provided for BitCollection<Item=BitU8>.
• ZdexedIter
  A trait for implementing Zdexed over iterables. A blanket implementation is provided for IntoIter<T: Zdexed>.
• ZdexedTup
  A trait for implementing Zdexed over tuples. A blanket implementation is provided for homogeneous 2-, 3-, and 4- tuples.