combine_http.rs

extern crate combine;

use combine::*;
use combine::primitives::Error;
use combine::combinator::take_while1;

use std::fs::File;
use std::env;


#[derive(Debug)]
struct Request<'a> {
    method:  &'a [u8],
    uri:     &'a [u8],
    version: &'a [u8],
}

#[derive(Debug)]
struct Header<'a> {
    name:  &'a [u8],
    value: Vec<&'a [u8]>,
}

fn is_token(c: u8) -> bool {
    // roughly follows the order of ascii chars: "\"(),/:;<=>?@[\\]{} \t"
    c < 128 && c > 32 && c != b'\t' && c != b'"' && c != b'(' && c != b')' &&
        c != b',' && c != b'/' && !(c > 57 && c < 65) && !(c > 90 && c < 94) &&
        c != b'{' && c != b'}'
}

fn is_horizontal_space(c: u8) -> bool { c == b' ' || c == b'\t' }
fn is_space(c: u8)            -> bool { c == b' ' }
fn is_not_space(c: u8)        -> bool { c != b' ' }
fn is_http_version(c: u8)     -> bool { c >= b'0' && c <= b'9' || c == b'.' }

fn main() {
    let mut contents: Vec<u8> = Vec::new();

    {
        use std::io::Read;

        let mut file = File::open(env::args().nth(1).expect("File to read")).ok().expect("Failed to open file");

        let _ = file.read_to_end(&mut contents).unwrap();
    }

    // Making a closure, because parser instances cannot be reused
    let end_of_line = || (satisfy(|c| c == b'\r').skip(satisfy(|c| c == b'\n'))).or(satisfy(|c| c == b'\n'));

    // let mut http_version = string(&b"HTTP/"[..])
    let mut http_version = satisfy(|c| c == b'H')
        .with(satisfy(|c| c == b'T'))
        .with(satisfy(|c| c == b'T'))
        .with(satisfy(|c| c == b'P'))
        .with(satisfy(|c| c == b'/'))
        .with(take_while1(is_http_version));

    let request_line = parser(|input| (
        // dereferencing pointers before checking if it is a token
        take_while1(is_token),
        skip_many1(satisfy(|c| is_space(c))),
        take_while1(is_not_space),
        skip_many1(satisfy(|c| is_space(c))),
        &mut http_version,
        ).map(|(method, _, uri, _, version)| Request {
              method:  method,
              uri:     uri,
              version: version,
        })
        .parse_lazy(input)
    );


    let message_header = parser(|input| {
        let message_header_line = (
            skip_many1(satisfy(|c| is_horizontal_space(c))),
            take_while1(|c| c != b'\r' && c != b'\n'),
            end_of_line()
        ).map(|(_, line, _)| line);

        (
            take_while1(is_token),
            satisfy(|c| c == b':'),
            many1(message_header_line)
        ).map(|(name, _, value)| Header {
            name: name,
            value: value,
        })
        .parse_lazy(input)
    });

    let mut request = (
        request_line,
        end_of_line(),
        many(message_header),
        end_of_line()
        ).map(|(request, _, headers, _)| (request, headers));

    let mut i   = 0;
    let mut buf = &contents[..];

    loop {
        // Needed for inferrence for many(message_header)
        let r: Result<((Request, Vec<Header>), _), _> = request.parse(buf);

        match r {
            Ok(((_, _), b)) => {
                i = i + 1;

                buf = b
            },
            Err(e) => {
                if e.errors[0] == Error::end_of_input() {
                    return
                }
                panic!("{:?}", e);
            }
        }

        if buf.is_empty() {
            break;
        }
    }

    println!("num: {}", i);
}