Macro combine::decode_futures_03

macro_rules! decode_futures_03 {
    ($decoder: expr, $read: expr, $parser: expr) => { ... };
    ($decoder: expr, $read: expr, $parser: expr, $input_stream: expr $(,)?) => { ... };
    ($decoder: expr, $read: expr, $parser: expr, $input_stream: expr, $post_decode: expr $(,)?) => { ... };
}

This is supported on crate feature futures-io-03 only.

Parses an instance of futures::io::AsyncRead as a &[u8] without reading the entire file into memory.

This is defined as a macro to work around the lack of Higher Ranked Types. See the example for how to pass a parser to the macro (constructing parts of the parser outside of the decode! call is unlikely to work.

use futures::pin_mut;
use async_std::{
    fs::File,
    task,
};

use combine::{decode_futures_03, satisfy, skip_many1, many1, sep_end_by, Parser, stream::Decoder};

fn main() {
    task::block_on(main_());
}

async fn main_() {
    let mut read = File::open("README.md").await.unwrap();
    let mut decoder = Decoder::new();
    let is_whitespace = |b: u8| b == b' ' || b == b'\r' || b == b'\n';
    assert_eq!(
        decode_futures_03!(
            decoder,
            read,
            {
                let word = many1(satisfy(|b| !is_whitespace(b)));
                sep_end_by(word, skip_many1(satisfy(is_whitespace))).map(|words: Vec<Vec<u8>>| words.len())
            },
            |input, _position| combine::easy::Stream::from(input),
        ).map_err(combine::easy::Errors::<u8, &[u8], _>::from),
        Ok(819),
    );
}