hayro-syntax 0.4.0

A low-level crate for reading PDF files.
Documentation 
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use crate::reader::Reader;
use log::warn;

pub(crate) fn decode(data: &[u8]) -> Option<Vec<u8>> {
    let mut reader = Reader::new(data);
    let mut decoded = vec![];

    if decode_inner(&mut reader, &mut decoded).is_none() {
        warn!("run-length decode stream ended prematurely");
    }

    Some(decoded)
}

fn decode_inner(reader: &mut Reader, decoded: &mut Vec<u8>) -> Option<()> {
    loop {
        let length = reader.read_byte()?;

        match length {
            128 => return Some(()),
            0..=127 => decoded.extend(reader.read_bytes(length as usize + 1)?),
            _ => {
                let length = 257 - length as usize;
                decoded.extend([reader.read_byte()?].repeat(length))
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::filter::run_length::decode;

    #[test]
    fn run_length() {
        let input = vec![4, 10, 11, 12, 13, 14, 253, 3, 128];
        assert_eq!(
            decode(&input).unwrap(),
            vec![10, 11, 12, 13, 14, 3, 3, 3, 3]
        );
    }
}