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common: Stop abusing wild animals for bit shifts

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This commit is contained in:
haslersn 2019-08-29 17:55:05 +02:00
parent 2cf52b7093
commit 9844e95e5f
1 changed files with 3 additions and 9 deletions
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12
common/src/volumes/vol_map_2d.rs
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@ -26,19 +26,13 @@ pub struct VolMap2d<V: BaseVol, S: VolSize> {
impl<V: BaseVol, S: VolSize> VolMap2d<V, S> {
#[inline(always)]
pub fn chunk_key<P: Into<Vec2<i32>>>(pos: P) -> Vec2<i32> {
pos.into().map2(S::SIZE.into(), |e, sz: u32| {
// Horrid, but it's faster than a cheetah with a red bull blood transfusion
let log2 = (sz - 1).count_ones();
((((i64::from(e) + (1 << 32)) as u64) >> log2) - (1 << (32 - log2))) as i32
})
pos.into()
.map2(S::SIZE.into(), |e, sz: u32| e >> (sz - 1).count_ones())
}
#[inline(always)]
pub fn chunk_offs(pos: Vec3<i32>) -> Vec3<i32> {
let offs = pos.map2(S::SIZE, |e, sz| {
// Horrid, but it's even faster than the aforementioned cheetah
(((i64::from(e) + (1 << 32)) as u64) & u64::from(sz - 1)) as i32
});
let offs = pos.map2(S::SIZE, |e, sz| e & (sz - 1) as i32);
Vec3::new(offs.x, offs.y, pos.z)
}
}