Function carmack_decompress

src/cache.rs:472–523

See: https://moddingwiki.shikadi.net/wiki/Carmack_compression

(compressed_data: &[u8])

/// See: https://moddingwiki.shikadi.net/wiki/Carmack_compression
fn carmack_decompress(compressed_data: &[u8]) -> Vec<u8> {
    const NEAR_POINTER: u8 = 0xA7;
    const FAR_POINTER: u8 = 0xA8;
    let mut output = Vec::new();
    let mut word_i = 0;
    let mut n_shifts = 0;
    let mut offset = 0;

    while offset < compressed_data.len() - 2 {
        match &compressed_data[offset..(offset + 2)] {
            [0x00, NEAR_POINTER] | [0x00, FAR_POINTER] => {
                // ignore 0x00 and invert the following word
                output.push(compressed_data[offset + 2]);
                output.push(compressed_data[offset + 1]);
                n_shifts += 1;
            }
            [count, NEAR_POINTER] => {
                let distance = usize::from(compressed_data[offset + 2]);
                let segment_start = output.len() - distance * 2;
                let segment_end = segment_start + usize::from(*count) * 2;
                let segment_to_repeat = output[segment_start..segment_end].to_vec();
                output.extend_from_slice(&segment_to_repeat);
                n_shifts += 1;
            }
            [count, FAR_POINTER] => {
                let distance = u16::from_le_bytes(
                    compressed_data[(offset + 2)..(offset + 4)]
                        .try_into()
                        .unwrap(),
                );
                let segment_start = (usize::from(distance) + 1) * 2;
                let segment_end = segment_start + usize::from(*count) * 2;
                let segment_to_repeat = output[segment_start..segment_end].to_vec();
                output.extend_from_slice(&segment_to_repeat);
                word_i += 1;
            }
            word_bytes => {
                output.extend_from_slice(word_bytes);
            }
        }

        word_i += 1;
        offset = word_i * 2 + n_shifts;
    }

    if offset < compressed_data.len() {
        let remainder = &compressed_data[offset..];
        output.extend_from_slice(remainder);
    }

    output
}

fn get_plane(data: &[u8], offset: i32, length: u16, magic_rlew_word: &[u8; 2]) -> [[u16; 64]; 64] {
    let plane_start = offset as usize;