checkpipe

A rust library for computing things about bytes as they flow through pipelines.

The motivating use case is performing a checksum on all bytes passing through a reader or writer.

Example

use checkpipe::{Check, Checker};
use std::io::{Read, Write};
use std::fs::{File, remove_file};

const DATA: [u8; 13] = *b"Hello, world!";
const PATH: &'static str = "foo.txt";

pub fn write_checksummed() -> std::io::Result<()> {
    let outfile = File::create(PATH)?;
    let mut outpipe = Checker::new_default_hasher(outfile);

    outpipe.write_all(DATA.as_slice())?;
    let checksum = outpipe.output();
    outpipe.write(&mut checksum.to_le_bytes()[..])?;
    Ok(())
}

pub fn read_checksummed() -> std::io::Result<()> {
    let infile = File::open(PATH)?;
    let mut inpipe = Checker::new_default_hasher(infile);

    let mut buf = [0u8; DATA.len()];
    inpipe.read(&mut buf)?;
    let checksum = inpipe.output();

    let mut checksum_buf = [0u8; 8];
    inpipe.read(&mut checksum_buf)?;
    assert_eq!(checksum, u64::from_le_bytes(checksum_buf));
    Ok(())
}

pub fn main() -> std::io::Result<()> {
    write_checksummed()?;
    read_checksummed()?;
    remove_file(PATH)
}

Implementing your own checks

Implement the Check trait on a struct, which provides methods for taking a chunk of bytes, and eventually returning the result of its computation. Then wrap that struct and some struct through which bytes pass in a Checker.

Check is already implemented for all types implementing Hasher, and there are some convenience methods in place if you want to use rust's default hasher. If the wrapped type in Checker is Read or Write, so too will the Checker.