# osmpbf-parser

parse open street map protobuf files and scan for records with explicit file offsets

This crate differs from [osmpbf][] mainly in that you get explicit u64 file offsets for jumping and
scanning and can bring your own concurrency strategy by creating many file handles and parser
instances for the same file to fan out operations in parallel.

[osmpbf]: https://crates.io/crates/osmpbf

This example loops over all the blobs in an osmpbf file and prints diagnostic info such as the
element type (node, way, or relation), the file offset and byte length of each blob, the number of
items, and the range of ids.

```rust,no_run
use std::fs::File;
use osmpbf_parser::{Parser,Element};

type Error = Box<dyn std::error::Error+Send+Sync+'static>;

fn main() -> Result<(),Error> {
  let args = std::env::args().collect::<Vec<String>>();
  let h = File::open(&args[1])?;
  let file_len = h.metadata()?.len();
  let mut opd = Parser::new(Box::new(h));
  let mut offset = 0;
  while offset < file_len {
    let (byte_len,items) = opd.read(offset)?;
    let mut etype = "";
    let mut min_id = i64::MAX;
    let mut max_id = i64::MIN;
    for item in items.iter() {
      match item {
        Element::Node(node) => {
          etype = "node";
          min_id = node.id.min(min_id);
          max_id = node.id.max(max_id);
        },
        Element::Way(way) => {
          etype = "way";
          min_id = way.id.min(min_id);
          max_id = way.id.max(max_id);
        },
        Element::Relation(relation) => {
          etype = "relation";
          min_id = relation.id.min(min_id);
          max_id = relation.id.max(max_id);
        },
      }
    }
    if !items.is_empty() {
      println!["{}: offset={} byte_len={} items.len()={} id range {}..{}",
        etype, offset, byte_len, items.len(), min_id, max_id];
    }
    offset += byte_len;
  }
  Ok(())
}
```

There are more explicit routines to read the file block, blob header, and blob without decoding.