streamparser — incrementally parse input from a stream

This crate provides adapters to turn a stream of input into a sequence of parsed items, using a simple incremental parsing function. It supports both sync and async input and allows returning items that hold a reference to the input.

Usage

Add the crate to your Cargo.toml:

[dependencies]
streamparser = "0.1"

Example

A complete example parsing whitespace-separated words from a stream:

use std::{convert::Infallible, error::Error, io::Cursor};
use streamparser::{read::ReadSource, utf8::Utf8Adapter, Parse, Parsed, StreamParser, Streaming};

struct SplitWords;

impl<'a> Parse<'a> for SplitWords {
    type Input = &'a str;
    type Output = &'a str;
    type Error = Infallible;

    fn parse(
        &mut self,
        input: Self::Input,
    ) -> Result<Streaming<Parsed<Self::Output>>, Self::Error> {
        let trimmed = input.trim_start();
        let trimmed_count = input.len() - trimmed.len();
        match trimmed.find(' ') {
            Some(end) => Ok(Streaming::Item((
                Some(&trimmed[..end]),
                trimmed_count + end,
            ))),
            None => Ok(Streaming::Incomplete),
        }
    }

    fn parse_eof(
        &mut self,
        input: Self::Input,
    ) -> Result<Parsed<Self::Output>, Self::Error> {
        let trimmed = input.trim();
        if !trimmed.is_empty() {
            Ok((Some(trimmed), input.len()))
        } else {
            Ok((None, input.len()))
        }
    }
}

fn main() -> Result<(), Box<dyn Error>> {
    let mut results = Vec::new();
    let mut parser = StreamParser::new(
        Utf8Adapter::new(SplitWords),
        ReadSource::new(Cursor::new(b"words separated by whitespace"), 6),
    );
    while let Some(streaming) = parser.get()? {
        match streaming {
            Streaming::Item(item) => {
                results.push(item.to_owned());
            }
            Streaming::Incomplete => parser.advance()?,
        }
    }
    assert_eq!(results, vec!["words", "separated", "by", "whitespace",]);
    Ok(())
}

Documentation

Reference documentation

Developing

Releases

• bump the version in Cargo.toml
• for major versions: bump the version in README.md
• tag the commit as v<VERSION>, e.g. v0.1.0