fast-mvt

fast-mvt is an integer-only Mapbox Vector Tile reader and writer for Rust. Geometry uses geo-types with i32 coordinates. The crate does not project, scale, round, or handle floating point geometry coordinates; callers provide and receive tile-space integers.

Decoding a tile

use fast_mvt::{MvtReaderRef, MvtResult};

fn read_tile(bytes: &[u8]) -> MvtResult<()> {
    let reader = MvtReaderRef::new(bytes)?;

    for layer in reader.layers() {
        for feature in layer.features() {
            let geometry = feature.geometry()?;
            println!("geo: {geometry:?}");
            let id = feature.id();
            println!("id: {id:?}");

            for property in feature.properties() {
                let (key, value) = property?;
                println!("{key} = {value:?}");
            }
        }
    }

    Ok(())
}

Encoding a tile

use fast_mvt::{MvtGeometry, MvtResult, MvtTileBuilder};

fn write_tile() -> MvtResult<Vec<u8>> {
    let tile = MvtTileBuilder::new();
    let layer = tile.layer("places")?;

    let mut feature = layer.feature(MvtGeometry::Point((1, 2).into()))?;
    feature.id(Some(7));
    feature.tag("name", "Example")?;
    feature.tag("visible", true)?;
    let layer = feature.finish();

    let tile = layer.finish();
    Ok(tile.finish())
}

Opening a layer consumes the tile builder, and opening a feature consumes the layer builder. Finishing returns the parent builder with the child committed, so there is no reachable partially committed layer or tile while a child is in progress. A single-layer tile byte buffer is also a framed layer chunk, so multiple independently built layer buffers can be concatenated to form a tile.

Benchmarks

Decoding

Decoder	Time	Compare
`fast-mvt`	453 ms	-
`tinymvt`	638 ms	41% slower
`mvt-reader`	1165 ms	157% slower

Encoding

Encoder	Time	Compare
`fast-mvt`	987 ms	-
`mvt`	11549 ms	1070% slower

Features

Feature	Purpose
`reader`	MVT tile decoding from bytes.
`writer`	MVT tile encoding into bytes.
`json`	Enable serde JSON support.
`codegen`	Regenerate checked-in protobuf bindings from `src/vector_tile.proto`.
`arbitrary`	Derive `arbitrary::Arbitrary` for generated protobuf types for fuzzing.
`views`	Internal feature, do not use. Must be here due to buffa limitations.

The generated protobuf files are checked in, so normal builds do not require protoc. Run just update-generated to refresh generated code after buffa upgrades.

Development

This project is easier to develop with just, a modern alternative to make. Install it with cargo install just.
To get a list of available commands, run just.
To run tests, use just test.

Credits

The code was inspired by several open source MVT implementations:

Encoding and testing from mvt crate by the Minnesota Department of Transportation.
Decoding and testing from mvt-reader by Paul Lange.

License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT) at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual-licensed as above, without any additional terms or conditions.

fast-mvt 0.3.0