Function pack_bytes

src/pack.rs:90–109

Packs multiple bytes into single bytes and writes them to `out`. This only works if `max - min < 16`, otherwise this just copies `bytes` to `out`. These particular tradeoffs were selected so input bytes don't span multiple output bytes to avoid confusing bytewise compression algorithms (e.g. Deflate). Mutates `bytes` to avoid copying them. The remaining `bytes` should be considered garbage.

(bytes: &mut [T], out: &mut Vec<u8>)

///
/// Mutates `bytes` to avoid copying them. The remaining `bytes` should be considered garbage.
pub fn pack_bytes<T: Byte>(bytes: &mut [T], out: &mut Vec<u8>) {
    if skip_packing(bytes.len()) {
        out.extend_from_slice(bytemuck::must_cast_slice(bytes));
        return;
    }
    let (min, max) = crate::pack_ints::minmax(bytes);

    // i8 packs as u8 if positive.
    let basic_packing = if min >= T::default() {
        Packing::new(bytemuck::must_cast(max))
    } else {
        Packing::_256 // Any negative i8 as u8 is > 15 and can't be packed without offset_packing.
    };

    // u8::wrapping_sub == i8::wrapping_sub, so we can use u8s from here onward.
    let min: u8 = bytemuck::must_cast(min);
    let max: u8 = bytemuck::must_cast(max);
    let bytes: &mut [u8] = bytemuck::must_cast_slice_mut(bytes);
    pack_bytes_unsigned(bytes, out, basic_packing, min, max);
}

/// [`pack_bytes`] but after i8s have been cast to u8s.
fn pack_bytes_unsigned(