Extensible ChunkStorage

Co-authored-by: sdwhw <191973436+sdwhw@users.noreply.github.com>

1 files changed, 305 insertions, 0 deletions

diff --git a/azalea-world/src/chunk/mod.rs b/azalea-world/src/chunk/mod.rs
new file mode 100644
index 00000000..cd52026a
--- /dev/null
+++ b/azalea-world/src/chunk/mod.rs
@@ -0,0 +1,305 @@
+pub mod partial;
+pub mod storage;
+
+use std::{
+    collections::HashMap,
+    fmt::Debug,
+    io,
+    io::{Cursor, Write},
+};
+
+use azalea_block::block_state::{BlockState, BlockStateIntegerRepr};
+use azalea_buf::{AzBuf, BufReadError};
+use azalea_core::{
+    heightmap_kind::HeightmapKind,
+    position::{ChunkBiomePos, ChunkBlockPos, ChunkSectionBiomePos, ChunkSectionBlockPos},
+};
+use azalea_registry::data::Biome;
+use tracing::warn;
+
+use crate::{heightmap::Heightmap, palette::PalettedContainer};
+
+const SECTION_HEIGHT: u32 = 16;
+
+/// A single chunk in a world (16*?*16 blocks).
+///
+/// This only contains blocks and biomes. You can derive the height of the chunk
+/// from the number of sections, but you need a [`ChunkStorage`] to get the
+/// minimum Y coordinate.
+#[derive(Debug)]
+pub struct Chunk {
+    pub sections: Box<[Section]>,
+    /// Heightmaps are used for identifying the surface blocks in a chunk.
+    /// Usually for clients only `WorldSurface` and `MotionBlocking` are
+    /// present.
+    pub heightmaps: HashMap<HeightmapKind, Heightmap>,
+}
+
+/// A section of a chunk, i.e. a 16*16*16 block area.
+#[derive(Clone, Debug, Default, PartialEq)]
+pub struct Section {
+    /// The number of non-empty blocks in the section, which is initialized
+    /// based on a value sent to us by the server.
+    ///
+    /// This may be updated every time [`Self::get_and_set_block_state`] is
+    /// called.
+    pub block_count: u16,
+    pub states: PalettedContainer<BlockState>,
+    pub biomes: PalettedContainer<Biome>,
+}
+
+/// Get the actual stored view distance for the selected view distance.
+///
+/// For some reason, Minecraft stores an extra 3 chunks.
+pub fn calculate_chunk_storage_range(view_distance: u32) -> u32 {
+    u32::max(view_distance, 2) + 3
+}
+
+impl Default for Chunk {
+    fn default() -> Self {
+        Chunk {
+            sections: vec![Section::default(); (384 / 16) as usize].into(),
+            heightmaps: HashMap::new(),
+        }
+    }
+}
+
+impl Chunk {
+    pub fn read_with_dimension_height(
+        buf: &mut Cursor<&[u8]>,
+        dimension_height: u32,
+        min_y: i32,
+        heightmaps_data: &[(HeightmapKind, Box<[u64]>)],
+    ) -> Result<Self, BufReadError> {
+        let section_count = dimension_height / SECTION_HEIGHT;
+        let mut sections = Vec::with_capacity(section_count as usize);
+        for _ in 0..section_count {
+            let section = Section::azalea_read(buf)?;
+            sections.push(section);
+        }
+        let sections = sections.into_boxed_slice();
+
+        let mut heightmaps = HashMap::new();
+        for (kind, data) in heightmaps_data {
+            let data = data.clone();
+            let heightmap = Heightmap::new(*kind, dimension_height, min_y, data);
+            heightmaps.insert(*kind, heightmap);
+        }
+
+        Ok(Chunk {
+            sections,
+            heightmaps,
+        })
+    }
+
+    pub fn get_block_state(&self, pos: &ChunkBlockPos, min_y: i32) -> Option<BlockState> {
+        get_block_state_from_sections(&self.sections, pos, min_y)
+    }
+
+    #[must_use = "Use Chunk::set_block_state instead if you don't need the previous state"]
+    pub fn get_and_set_block_state(
+        &mut self,
+        pos: &ChunkBlockPos,
+        state: BlockState,
+        min_y: i32,
+    ) -> BlockState {
+        let section_index = section_index(pos.y, min_y);
+        let Some(section) = self.sections.get_mut(section_index as usize) else {
+            warn!(
+                "Tried to get and set block state {state:?} at out-of-bounds relative chunk position {pos:?}",
+            );
+            return BlockState::AIR;
+        };
+        let chunk_section_pos = ChunkSectionBlockPos::from(pos);
+        let previous_state = section.get_and_set_block_state(chunk_section_pos, state);
+
+        for heightmap in self.heightmaps.values_mut() {
+            heightmap.update(pos, state, &self.sections);
+        }
+
+        previous_state
+    }
+
+    pub fn set_block_state(&mut self, pos: &ChunkBlockPos, state: BlockState, min_y: i32) {
+        let section_index = section_index(pos.y, min_y);
+        let Some(section) = self.sections.get_mut(section_index as usize) else {
+            warn!(
+                "Tried to set block state {state:?} at out-of-bounds relative chunk position {pos:?}",
+            );
+            return;
+        };
+        let chunk_section_pos = ChunkSectionBlockPos::from(pos);
+        section.get_and_set_block_state(chunk_section_pos, state);
+
+        for heightmap in self.heightmaps.values_mut() {
+            heightmap.update(pos, state, &self.sections);
+        }
+    }
+
+    /// Get the biome at the given position, or `None` if it's out of bounds.
+    pub fn get_biome(&self, pos: ChunkBiomePos, min_y: i32) -> Option<Biome> {
+        if pos.y < min_y {
+            // y position is out of bounds
+            return None;
+        }
+        let section_index = section_index(pos.y, min_y);
+        let Some(section) = self.sections.get(section_index as usize) else {
+            warn!("Tried to get biome at out-of-bounds relative chunk position {pos:?}",);
+            return None;
+        };
+        let chunk_section_pos = ChunkSectionBiomePos::from(pos);
+        Some(section.get_biome(chunk_section_pos))
+    }
+}
+
+/// Get the block state at the given position from a list of sections. Returns
+/// `None` if the position is out of bounds.
+#[inline]
+pub fn get_block_state_from_sections(
+    sections: &[Section],
+    pos: &ChunkBlockPos,
+    min_y: i32,
+) -> Option<BlockState> {
+    if pos.y < min_y {
+        // y position is out of bounds
+        return None;
+    }
+    let section_index = section_index(pos.y, min_y) as usize;
+    if section_index >= sections.len() {
+        // y position is out of bounds
+        return None;
+    };
+    let section = &sections[section_index];
+
+    let chunk_section_pos = ChunkSectionBlockPos::from(pos);
+    Some(section.get_block_state(chunk_section_pos))
+}
+
+impl AzBuf for Section {
+    fn azalea_read(buf: &mut Cursor<&[u8]>) -> Result<Self, BufReadError> {
+        let block_count = u16::azalea_read(buf)?;
+
+        // this is commented out because the vanilla server is wrong
+        // TODO: ^ this comment was written ages ago. needs more investigation.
+        // assert!(
+        //     block_count <= 16 * 16 * 16,
+        //     "A section has more blocks than what should be possible. This is a bug!"
+        // );
+
+        let states = PalettedContainer::<BlockState>::read(buf)?;
+
+        for i in 0..states.storage.size() {
+            if !BlockState::is_valid_state(states.storage.get(i) as BlockStateIntegerRepr) {
+                return Err(BufReadError::Custom(format!(
+                    "Invalid block state {} (index {i}) found in section.",
+                    states.storage.get(i)
+                )));
+            }
+        }
+
+        let biomes = PalettedContainer::<Biome>::read(buf)?;
+        Ok(Section {
+            block_count,
+            states,
+            biomes,
+        })
+    }
+    fn azalea_write(&self, buf: &mut impl Write) -> io::Result<()> {
+        self.block_count.azalea_write(buf)?;
+        self.states.write(buf)?;
+        self.biomes.write(buf)?;
+        Ok(())
+    }
+}
+
+impl Section {
+    pub fn get_block_state(&self, pos: ChunkSectionBlockPos) -> BlockState {
+        self.states.get(pos)
+    }
+    pub fn get_and_set_block_state(
+        &mut self,
+        pos: ChunkSectionBlockPos,
+        state: BlockState,
+    ) -> BlockState {
+        let previous_state = self.states.get_and_set(pos, state);
+
+        if previous_state.is_air() && !state.is_air() {
+            self.block_count += 1;
+        } else if !previous_state.is_air() && state.is_air() {
+            self.block_count -= 1;
+        }
+
+        previous_state
+    }
+
+    pub fn get_biome(&self, pos: ChunkSectionBiomePos) -> Biome {
+        self.biomes.get(pos)
+    }
+    pub fn set_biome(&mut self, pos: ChunkSectionBiomePos, biome: Biome) {
+        self.biomes.set(pos, biome);
+    }
+    pub fn get_and_set_biome(&mut self, pos: ChunkSectionBiomePos, biome: Biome) -> Biome {
+        self.biomes.get_and_set(pos, biome)
+    }
+}
+
+/// Get the index of where a section is in a chunk based on its y coordinate
+/// and the minimum y coordinate of the world.
+#[inline]
+pub fn section_index(y: i32, min_y: i32) -> u32 {
+    if y < min_y {
+        #[cfg(debug_assertions)]
+        tracing::warn!("y ({y}) must be at least {min_y}");
+        #[cfg(not(debug_assertions))]
+        tracing::trace!("y ({y}) must be at least {min_y}")
+    };
+    let min_section_index = min_y >> 4;
+    ((y >> 4) - min_section_index) as u32
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::palette::SectionPos;
+
+    #[test]
+    fn test_section_index() {
+        assert_eq!(section_index(0, 0), 0);
+        assert_eq!(section_index(128, 0), 8);
+        assert_eq!(section_index(127, 0), 7);
+        assert_eq!(section_index(0, -64), 4);
+        assert_eq!(section_index(-64, -64), 0);
+        assert_eq!(section_index(-49, -64), 0);
+        assert_eq!(section_index(-48, -64), 1);
+        assert_eq!(section_index(128, -64), 12);
+    }
+
+    #[test]
+    fn serialize_and_deserialize_section() {
+        let mut states = PalettedContainer::new();
+
+        states.set(
+            SectionPos::new(1, 2, 3),
+            BlockState::try_from(BlockState::MAX_STATE).unwrap(),
+        );
+        states.set(
+            SectionPos::new(4, 5, 6),
+            BlockState::try_from(BlockState::MAX_STATE).unwrap(),
+        );
+        let biomes = PalettedContainer::new();
+        let section = Section {
+            block_count: 2,
+            states,
+            biomes,
+        };
+
+        let mut buf = Vec::new();
+        section.azalea_write(&mut buf).unwrap();
+
+        let mut cur = Cursor::new(buf.as_slice());
+        let deserialized_section = Section::azalea_read(&mut cur).unwrap();
+        assert_eq!(cur.position(), buf.len() as u64);
+
+        assert_eq!(section, deserialized_section);
+    }
+}