Using FlatCityBuf with Rust

Table of contents

1. Adding to your project
2. Basic reading and spatial queries
3. HTTP streaming

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For maximum performance and control, you can use FlatCityBuf directly in Rust applications.

Adding to your project

Initialise a new Rust project:

cargo new fcb_demo
cd fcb_demo

Add FlatCityBuf to your Cargo.toml:

[dependencies]
fcb_core = "0.5.0"

# For HTTP support
fcb_core = { version = "0.5.0", features = ["http"] }

Basic reading and spatial queries

Use bounding box queries with the packed R-tree index:

use fcb_core::{FcbReader, packed_rtree::Query};
use std::fs::File;
use std::io::BufReader;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let input_file = File::open("../delft.fcb")?;
    let input_reader = BufReader::new(input_file);

    // Define bounding box
    let minx = 84227.77;
    let miny = 445377.33;
    let maxx = 85323.23;
    let maxy = 446334.69;

    let mut reader = FcbReader::open(input_reader)?.select_query(
        Query::BBox(minx, miny, maxx, maxy),
        None,
        None,
    )?;

    let mut count = 0;
    while let Some(feature_buf) = reader.next()? {
        let cj_feature = feature_buf.cur_cj_feature()?;
        println!("Feature in bbox: {}", cj_feature.id);
        count += 1;
    }

    println!("Found {} features in bounding box", count);

    Ok(())
}

then run it with:

cargo run

HTTP streaming

For cloud-based FCB files, use the async HTTP reader: Don’t forget to add tokio to your Cargo.toml:

[dependencies]
tokio = { version = "1.48.0", features = ["rt-multi-thread", "macros"] }

use fcb_core::{FcbReader, HttpFcbReader, packed_rtree::Query};
use std::fs::File;
use std::io::BufReader;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let http_reader =
        HttpFcbReader::open("https://storage.googleapis.com/flatcitybuf/3dbag_all_index.fcb")
            .await?;

    // Get header information
    let header = http_reader.header();
    println!("Features: {}", header.features_count());

    // Spatial query over HTTP
    let minx = 84227.77;
    let miny = 445377.33;
    let maxx = 85323.23;
    let maxy = 446334.69;

    let mut iter = http_reader
        .select_query(Query::BBox(minx, miny, maxx, maxy))
        .await?;

    while let Some(feature) = iter.next().await? {
        let cj_feature = feature.cj_feature()?;
        println!("Feature: {}", cj_feature.id);
    }

    Ok(())
}