/// Given the decompressed pack delta `d`, decode a size in bytes (either the base object size or the result object size)/// Equivalent to [this canonical git function](https://github.com/git/git/blob/311531c9de557d25ac087c1637818bd2aad6eb3a/delta.h#L89)pub fn decode_header_size(d: &[u8]) -> (u64, usize) {    let mut i = 0;    let mut size = 0u64;    let mut consumed = 0;    for cmd in d.iter() {        consumed += 1;        size |= (*cmd as u64 & 0x7f) << i;        i += 7;        if *cmd & 0x80 == 0 {            break;        }    }    (size, consumed)} pub fn apply(base: &[u8], mut target: &mut [u8], data: &[u8]) {    let mut i = 0;    while let Some(cmd) = data.get(i) {        i += 1;        match cmd {            cmd if cmd & 0b1000_0000 != 0 => {                let (mut ofs, mut size): (u32, u32) = (0, 0);                if cmd & 0b0000_0001 != 0 {                    ofs = data[i] as u32;                    i += 1;                }                if cmd & 0b0000_0010 != 0 {                    ofs |= (data[i] as u32) << 8;                    i += 1;                }                if cmd & 0b0000_0100 != 0 {                    ofs |= (data[i] as u32) << 16;                    i += 1;                }                if cmd & 0b0000_1000 != 0 {                    ofs |= (data[i] as u32) << 24;                    i += 1;                }                if cmd & 0b0001_0000 != 0 {                    size = data[i] as u32;                    i += 1;                }                if cmd & 0b0010_0000 != 0 {                    size |= (data[i] as u32) << 8;                    i += 1;                }                if cmd & 0b0100_0000 != 0 {                    size |= (data[i] as u32) << 16;                    i += 1;                }                if size == 0 {                    size = 0x10000; // 65536                }                let ofs = ofs as usize;                std::io::Write::write(&mut target, &base[ofs..ofs + size as usize])                    .expect("delta copy from base: byte slices must match");            }            0 => panic!("encountered unsupported command code: 0"),            size => {                std::io::Write::write(&mut target, &data[i..i + *size as usize])                    .expect("delta copy data: slice sizes to match up");                i += *size as usize;            }        }    }    assert_eq!(i, data.len());    assert_eq!(target.len(), 0);}