Function cookie_factory::position

pub fn position<'a, F>(
    f: F
) -> impl Fn(&'a mut [u8]) -> Result<(&'a mut [u8], &'a mut [u8]), GenError> where
    F: SerializeFn<&'a mut [u8]>, 

applies a serializer then returns a tuple containing what was written and the remaining output buffer

use cookie_factory::{position, string};

let mut buf = [0u8; 100];

let (written, remaining) = position(string("abcd"))(&mut buf[..]).unwrap();

assert_eq!(remaining.len(), 96);
assert_eq!(written, &b"abcd"[..]);