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Fix math in chunk module

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This commit is contained in:
Ryan 2022-10-18 01:45:26 -07:00
parent d22f1edae1
commit dc46f27d5d
3 changed files with 15 additions and 17 deletions
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8
src/chunk.rs
View file

@ -25,7 +25,7 @@ use crate::protocol::packets::s2c::play::{
BlockUpdate, ChunkDataAndUpdateLight, S2cPlayPacket, UpdateSectionBlocks,
};
use crate::protocol::{Encode, VarInt, VarLong};
use crate::util::log2_ceil;
use crate::util::bits_needed;
mod paletted_container;
@ -556,7 +556,7 @@ impl<C: Config> LoadedChunk<C> {
|b| b.to_raw().into(),
4,
8,
log2_ceil(BlockState::max_raw().into()),
bits_needed(BlockState::max_raw().into()),
)
.unwrap();
@ -566,7 +566,7 @@ impl<C: Config> LoadedChunk<C> {
|b| b.0.into(),
0,
3,
log2_ceil(biome_registry_len),
bits_needed(biome_registry_len - 1),
)
.unwrap();
}
@ -612,7 +612,7 @@ impl<C: Config> LoadedChunk<C> {
debug_assert_eq!(bits.count_ones(), 1);
let idx = i * USIZE_BITS + log2_ceil(bits);
let idx = i * USIZE_BITS + bits.trailing_zeros() as usize;
let block = sect.block_states.get(idx);
let global_x = pos.x * 16 + (idx % 16) as i32;

9
src/chunk/paletted_container.rs
View file

@ -5,7 +5,7 @@ use arrayvec::ArrayVec;
use crate::chunk::{compact_u64s_len, encode_compact_u64s};
use crate::protocol::{Encode, VarInt};
use crate::util::log2_ceil;
use crate::util::bits_needed;
/// `HALF_LEN` must be equal to `ceil(LEN / 2)`.
#[derive(Clone, Debug)]
@ -17,7 +17,8 @@ pub enum PalettedContainer<T, const LEN: usize, const HALF_LEN: usize> {
#[derive(Clone, Debug)]
pub struct Indirect<T, const LEN: usize, const HALF_LEN: usize> {
/// Each element is a unique instance of `T`.
/// Each element is a unique instance of `T`. The length of the palette is
/// always ≥2.
palette: ArrayVec<T, 16>,
/// Each half-byte is an index into `palette`.
indices: [u8; HALF_LEN],
@ -147,7 +148,7 @@ impl<T: Copy + Eq + Default, const LEN: usize, const HALF_LEN: usize>
/// force conversion to the direct representation while encoding.
/// - **`direct_bits`**: The minimum number of bits required to represent
/// all instances of the element type. If `N` is the total number of
/// possible values, then `DIRECT_BITS` is `ceil(log2(N))`.
/// possible values, then `DIRECT_BITS` is `floor(log2(N - 1)) + 1`.
pub fn encode_mc_format<W, F>(
&self,
mut writer: W,
@ -177,7 +178,7 @@ impl<T: Copy + Eq + Default, const LEN: usize, const HALF_LEN: usize>
VarInt(0).encode(&mut writer)?;
}
Self::Indirect(ind) => {
let bits_per_entry = min_indirect_bits.max(log2_ceil(ind.palette.len()));
let bits_per_entry = min_indirect_bits.max(bits_needed(ind.palette.len() - 1));
// Encode as direct if necessary.
if bits_per_entry > max_indirect_bits {

15
src/util.rs
View file

@ -127,15 +127,12 @@ pub fn ray_box_intersect(ro: Vec3<f64>, rd: Vec3<f64>, bb: Aabb<f64>) -> Option<
}
}
/// Calculates the log base 2 rounded up.
pub(crate) const fn log2_ceil(n: usize) -> usize {
debug_assert!(n != 0);
// TODO: replace with `n.wrapping_next_power_of_two().trailing_zeros()`.
match n.checked_next_power_of_two() {
Some(n) => n.trailing_zeros() as usize,
None => 0_u64.trailing_zeros() as usize,
}
/// Calculates the minimum number of bits needed to represent the integer `n`.
/// Also known as `floor(log2(n)) + 1`.
///
/// This returns `0` if `n` is `0`.
pub(crate) const fn bits_needed(n: usize) -> usize {
(usize::BITS - n.leading_zeros()) as _
}
#[cfg(test)]