osmio 0.16.1

Read and write OpenStreetMap data files
Documentation 
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use crate::{Lat, Lon, ObjId};
use std::io::Read;
use std::iter::Iterator;

use std::collections::VecDeque;

use super::*;
use crate::COORD_PRECISION_NANOS;
use protobuf::Message;

/// (node id, (latitude, longitude))
type NodeIdPos = (ObjId, (Lat, Lon));

/// Reads a PBF file and returns just (nodeid, pos). This is a little faster than reading the whole
/// file
///
/// ```ignore
/// let mut reader =
/// osmio::stringpbf::PBFNodePositionReader::from_filename("region-latest.osm.pbf")?;
/// let (nid, (lat, lon)) = reader.next().unwrap();
/// # }
/// ```
pub struct PBFNodePositionReader<R: Read> {
    filereader: FileReader<R>,
    buffer: VecDeque<NodeIdPos>,
}

impl<R: Read> PBFNodePositionReader<R> {
    /// Create a new PBFNodePositionReader from this reader
    fn new(reader: R) -> Self {
        Self {
            filereader: FileReader::new(reader),
            buffer: VecDeque::new(),
        }
    }

    /// Create a new PBFNodePositionReader from this reader
    pub fn from_reader(reader: R) -> Self {
        Self::new(reader)
    }
}

impl PBFNodePositionReader<BufReader<File>> {
    /// Create a new PBFNodePositionReader for this path
    pub fn from_filename(filename: impl AsRef<Path>) -> Result<Self> {
        let filename: &Path = filename.as_ref();
        Ok(Self::new(BufReader::new(File::open(filename)?)))
    }
}

impl<R: Read> Iterator for PBFNodePositionReader<R> {
    type Item = NodeIdPos;

    fn next(&mut self) -> Option<Self::Item> {
        let mut blob_data = Vec::new();
        while self.buffer.is_empty() {
            // get the next file block and fill up our buffer
            // FIXME make this parallel

            // get the next block
            let mut blob = self.filereader.next()?;

            blob_raw_data(&mut blob, &mut blob_data, &(true, false, false));
            let block: osmformat::PrimitiveBlock =
                osmformat::PrimitiveBlock::parse_from_bytes(blob_data.as_slice()).unwrap();

            // Turn a block into OSM objects
            let _num_objects_read = decode_block_to_objs(block, &mut self.buffer);
        }

        self.buffer.pop_front()
    }
}

fn decode_block_to_objs(block: osmformat::PrimitiveBlock, sink: &mut VecDeque<NodeIdPos>) -> usize {
    let granularity = &block.granularity();
    let lat_offset = &block.lat_offset();
    let lon_offset = &block.lon_offset();
    let mut num_objects = 0;

    for primitive_group in block.primitivegroup.iter() {
        if !primitive_group.nodes.is_empty() {
            unimplemented!()
        } else if !primitive_group.ways.is_empty() || !primitive_group.relations.is_empty() {
            continue;
        } else if primitive_group.dense.is_some() {
            let dense = &primitive_group.dense.as_ref().unwrap();
            let ids = &dense.id;
            let lats = &dense.lat;
            let lons = &dense.lon;

            let num_nodes = ids.len();

            // NB it's important that these start at zero, makes the code easier later
            let mut last_id: i64 = 0;
            let mut last_raw_lat: i32 = 0;
            let mut last_raw_lon: i32 = 0;

            for index in 0..num_nodes {
                // last_* start off 0
                let id = ids[index] + last_id;
                last_id = id;

                let raw_lat = i32::try_from(lats[index] + last_raw_lat as i64)
                    .expect("raw_lat was larger than the OSM precision allows");
                last_raw_lat = raw_lat;

                let raw_lon = i32::try_from(lons[index] + last_raw_lon as i64)
                    .expect("raw_lon was larger than OSM precision allows");
                last_raw_lon = raw_lon;

                // granularity is in nanodegrees
                let scale_factor = granularity / COORD_PRECISION_NANOS;
                let mut internal_lat = raw_lat * scale_factor;
                let mut internal_lon = raw_lon * scale_factor;

                // Offsets from pbf are in nanodegrees
                let internal_lat_offset = lat_offset / COORD_PRECISION_NANOS as i64;
                let internal_lon_offset = lon_offset / COORD_PRECISION_NANOS as i64;
                internal_lat += internal_lat_offset as i32;
                internal_lon += internal_lon_offset as i32;

                sink.push_back((id as ObjId, (Lat(internal_lat), Lon(internal_lon))));
                num_objects += 1;
            }
        } else {
            unreachable!();
        }
    }

    num_objects
}