Function grin_util::read_write::read_exact

pub fn read_exact(
    stream: &mut dyn Read, 
    buf: &mut [u8], 
    timeout: Duration, 
    block_on_empty: bool
) -> Result<()>

The default implementation of read_exact is useless with an async stream (TcpStream) as it will return as soon as something has been read, regardless of whether the buffer has been filled (and then errors). This implementation will block until it has read exactly len bytes and returns them as a vec<u8>. Except for a timeout, this implementation will never return a partially filled buffer.

The timeout in milliseconds aborts the read when it's met. Note that the time is not guaranteed to be exact. To support cases where we want to poll instead of blocking, a block_on_empty boolean, when false, ensures read_exact returns early with a io::ErrorKind::WouldBlock if nothing has been read from the socket.