Put save_chunk fn in serialization module

src/world/serialization.rs

@@ -0,0 +1,81 @@
+use std::{
+    fs::OpenOptions,
+    io::{Seek, SeekFrom, Write},
+    path::Path,
+};
+
+use crate::world::{
+    format_reg_file_name, loc_byte_idx, loc_idx, reg_chunk_existence::ExistenceBitset,
+    REGION_BYTES, TILE_BYTES,
+};
+
+use super::{Chunk, ChunkPos};
+
+pub(super) fn save_chunk(pos: &ChunkPos, chk: &Chunk) {
+    let reg_file_name = format_reg_file_name(pos.region());
+    dbg!(&reg_file_name);
+    let reg_file_exists = Path::new(&reg_file_name).exists();
+    if !reg_file_exists {
+        log::warn!("Region file doesn't exist. Going to create one.");
+    }
+    let mut f = OpenOptions::new()
+        .read(true)
+        .write(true)
+        .create(true)
+        .open(&reg_file_name)
+        .unwrap();
+    let mut existence_bitset = if reg_file_exists {
+        ExistenceBitset::read_from_file(&mut f)
+    } else {
+        ExistenceBitset::EMPTY
+    };
+    dbg!(existence_bitset);
+    let _ = dbg!(f.stream_position());
+    let mut region_tile_data = if reg_file_exists {
+        zstd::decode_all(&mut f).unwrap()
+    } else {
+        vec![0; REGION_BYTES]
+    };
+    // Even the zstd decompressed data should be exactly REGION_BYTES size
+    assert_eq!(region_tile_data.len(), REGION_BYTES);
+    let (loc_x, loc_y) = pos.local();
+    dbg!(loc_x, loc_y);
+    let loc_idx = loc_idx(loc_y, loc_x);
+    crate::bitmanip::set_nth_bit(&mut existence_bitset.0, loc_idx as usize, true);
+    let byte_idx = loc_byte_idx(loc_idx);
+    dbg!(byte_idx);
+    for (i, tile) in chk.tiles.iter().enumerate() {
+        let off = byte_idx + (i * TILE_BYTES);
+        region_tile_data[off..off + 2].copy_from_slice(&tile.bg.to_le_bytes());
+        region_tile_data[off + 2..off + 4].copy_from_slice(&tile.mid.to_le_bytes());
+        region_tile_data[off + 4..off + 6].copy_from_slice(&tile.fg.to_le_bytes());
+    }
+    f.seek(SeekFrom::Start(0)).unwrap();
+    f.write_all(&u64::to_le_bytes(existence_bitset.0)[..])
+        .unwrap();
+    assert_eq!(f.stream_position().unwrap(), 8);
+    assert_eq!(region_tile_data.len(), REGION_BYTES);
+    let result = f.write_all(&zstd::encode_all(&region_tile_data[..], COMP_LEVEL).unwrap());
+    log::info!("{result:?}");
+}
+
+const COMP_LEVEL: i32 = 9;
+
+#[test]
+fn test_chunk_seri() {
+    env_logger::builder()
+        .filter_level(log::LevelFilter::Info)
+        .init();
+    let result = std::fs::remove_file("0.0.rgn");
+    log::info!("File del result: {result:?}");
+    let mut chk = Chunk {
+        tiles: super::default_chunk_tiles(),
+    };
+    for t in &mut chk.tiles {
+        t.bg = 1;
+    }
+    save_chunk(&ChunkPos { x: 2, y: 0 }, &chk);
+    save_chunk(&ChunkPos { x: 3, y: 0 }, &chk);
+    let raw = std::fs::read("0.0.rgn").unwrap();
+    zstd::decode_all(&raw[8..]).unwrap();
+}