read_capnp_frame.rs

struct WordWrapper(Vec<capnp::Word>);

impl AsMut<[u8]> for WordWrapper {
    fn as_mut(&mut self) -> &mut [u8] {
        capnp::Word::words_to_bytes_mut(&mut self.0)
    }
}

fn read_capnp_frame<T: io::Read>(stream: T, mut segment_sizes: Vec<u8>, mut segment_data: Vec<capnp::Word>) -> impl Future<Item=(T, Vec<u8>, Vec<capnp::Word>), Error=io::Error> {
    tokio::io::read_exact(stream, [0; 4]).and_then(move |(stream, segment_count)| {
        segment_sizes.resize(LittleEndian::read_u32(&segment_count) as usize * 4, 0);
        tokio::io::read_exact(stream, segment_sizes).and_then(move |(stream, segment_sizes)| {
            let mut len = 0;
            for i in 0..segment_sizes.len()/4 {
                len += LittleEndian::read_u32(&segment_sizes[i*4..i*4+4]) as usize;
            }
            segment_data.resize(len, capnp_word!(0, 0, 0, 0, 0, 0, 0, 0));
            tokio::io::read_exact(stream, WordWrapper(segment_data)).map(move |(stream, segment_data)| (stream, segment_sizes, segment_data.0))
        })
    })
}