use data_encoding::{DecodeError, DecodeKind, Encoding, BASE32_NOPAD};

fn main() {
    println!("{:?}", decode(b"77777777"));
    println!("{:?}", decode(b"777777777"));
    println!("{:?}", decode(b"7777777777"));
}

fn decode(bytes: &[u8]) -> Result<Vec<u8>, DecodeError> {
    let mut spec = BASE32_NOPAD.specification();
    spec.check_trailing_bits = false;
    truncate_decode(&spec.encoding().unwrap(), bytes)
}

fn truncate_decode(encoding: &Encoding, input: &[u8]) -> Result<Vec<u8>, DecodeError> {
    match encoding.decode(input) {
        Err(DecodeError {
            position,
            kind: DecodeKind::Length,
        }) => encoding.decode(&input[..position]),
        output => output,
    }
}