About

Zero-dependency Rust crate for encoding and decoding Google's polyline format.

Compared to the georust/polyline crate, the polyline-iter decodes polyline into an iterator over points instead of vector, which is benefitial when only a single iteration over the polyline is needed. And in such cases it performs twice as fast as the georust/polyline crate (check cargo bench for exact numbers) and has no hidden allocations.

Usage

Add this to your Cargo.toml:

[dependencies]
polyline-iter = "0.3"

Example

let iter = polyline_iter::decode(6, "avs_iB}xlxWissBw|zEu``AsxgCyoaAm_z@");
assert_eq!(
    iter.collect::<Vec<_>>(),
    vec![
        (55.585137, 12.999583),
        (55.644854, 13.112187),
        (55.678161, 13.182229),
        (55.712222, 13.212444),
    ]
);

// Count points without collecting them
assert_eq!(polyline_iter::decode(5, "avs_iB}xlxWissBw|zEu``AsxgCyoaAm_z@").count(), 4);

// Iterator approach allows to transcode polyline to another precision without intermediate allocations.
let polyline5 = polyline_iter::encode(5, polyline_iter::decode(6, "avs_iB}xlxWissBw|zEu``AsxgCyoaAm_z@"));
assert_eq!(polyline5, "cngrIk~inAgtJw~TeoEwtL{sE{{D");
assert_eq!(
    polyline_iter::decode(5, &polyline5).collect::<Vec<_>>(),
    vec![
        (55.58514, 12.99958),
        (55.64486, 13.11218),
        (55.67817, 13.18222),
        (55.71223, 13.21244)
    ],
);

// Keeping all the power of working with slices
let points = vec![
    (55.58513, 12.99958),
    (55.61461, 13.04627),
    (55.64485, 13.11219),
    (55.67816, 13.18223),
    (55.71840, 13.22343),
];
assert_eq!(polyline_iter::encode(5, points[1..3].iter().copied()), "ifmrIebsnA_|D_{K");

// This crate also provides encoding/decoding into binary format where URL-compatibility is not required
let polyline = polyline_iter::encode(5, points);
let binary = polyline_iter::encode_binary(5, points);
// Binary format is often 20-30% smaller than polyline format
assert!(binary.len() < polyline.len());

// Binary format is lossless if the same precision is used
let transcoded = polyline_iter::encode(5, polyline_iter::decode_binary(5, &binary));
assert_eq!(transcoded, polyline);

License

All code in this project is dual-licensed under either:

• MIT license (LICENSE-MIT)
• Apache License, Version 2.0 (LICENSE-APACHE)

at your option.