Function base64::encode::add_padding

pub(crate) fn add_padding(
    unpadded_output_len: usize,
    output: &mut [u8],
) -> usize

Write padding characters. unpadded_output_len is the size of the unpadded but base64 encoded data. output is the slice where padding should be written, of length at least 2.

Returns the number of padding bytes written.