Function base64::engine::general_purpose::decode::decode_chunk_precise

fn decode_chunk_precise(
    input: &[u8],
    index_at_start_of_input: usize,
    decode_table: &[u8; 256],
    output: &mut [u8],
) -> Result<(), DecodeError>

Decode an 8-byte chunk, but only write the 6 bytes actually decoded instead of including 2 trailing garbage bytes.