String reader

Zero-allocation string reader. The string reader can be used to parse all kinds of values from strings. It can be used for construction of traditional lexical analyzers for example. It is useful in situation when you need to parse simple formatted strings but regular expressions are too heavy-weight.

Example

Parsing HTTP response header:

use std::num::ParseIntError;

use str_reader::{ParseError, StringReader};

/// Parse the first line of an HTTP response header.
fn parse_http_response_line(line: &str) -> Result<(u16, &str), HttpParseError> {
    let mut reader = StringReader::new(line);

    reader.match_str("HTTP/")?;

    match reader.read_word() {
        "1.0" => (),
        "1.1" => (),
        _ => return Err(HttpParseError),
    }

    let status_code = reader.read_u16()?;

    Ok((status_code, reader.as_str().trim()))
}

#[derive(Debug)]
struct HttpParseError;

impl From<ParseError> for HttpParseError {
    fn from(_: ParseError) -> Self {
        Self
    }
}

impl From<ParseIntError> for HttpParseError {
    fn from(_: ParseIntError) -> Self {
        Self
    }
}

let (status_code, status_msg) = parse_http_response_line("HTTP/1.1 404 Not Found").unwrap();

assert_eq!(status_code, 404);
assert_eq!(status_msg, "Not Found");