level

level/packet.go

@@ -0,0 +1,147 @@
+package level
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"math"
+
+	"github.com/admin-else/strom/proto_base"
+)
+
+const (
+	BlocksPerChunkSection = 4096
+	BiomesPerChunkSection = 64
+)
+
+func UnpackArrayPalette(r io.Reader, bitsPerEntry uint8, numberOfEntries int) (data []int32, err error) {
+	var palletLen proto_base.VarInt
+	palletLen, err = palletLen.Decode(r)
+	if err != nil {
+		return
+	}
+	var pallet []int32 // remember we can't use make because this is user-controlled data
+	for range palletLen {
+		var entry proto_base.VarInt
+		entry, err = proto_base.VarInt(0).Decode(r)
+		if err != nil {
+			return
+		}
+		pallet = append(pallet, int32(entry))
+	}
+	data, err = UnpackLongData(r, bitsPerEntry, numberOfEntries)
+	for i, b := range data {
+		data[i] = pallet[b] // maybe check bounds?
+	}
+
+	return
+}
+
+func UnpackLongData(r io.Reader, bitsPerEntry uint8, numberOfEntries int) (data []int32, err error) {
+	entriesPerLong := int(64 / bitsPerEntry)
+	numberOfLongs := int(math.Ceil(float64(numberOfEntries) / float64(entriesPerLong)))
+	var dataL []uint64
+	for range numberOfLongs {
+		var entry uint64
+		err = binary.Read(r, binary.BigEndian, &entry)
+		if err != nil {
+			return
+		}
+		dataL = append(dataL, entry)
+	}
+
+	data = LongsToData(dataL, int32(numberOfEntries), int32(bitsPerEntry))
+	return
+}
+
+func UnpackSingleValuePalette(r io.Reader, numberOfEntries int) (data []int32, err error) {
+	entry, err := proto_base.VarInt(0).Decode(r)
+	if err != nil {
+		return
+	}
+	data = make([]int32, numberOfEntries)
+	for i := range data {
+		data[i] = int32(entry)
+	}
+	return
+}
+
+func LongsToData(data []uint64, n, bpe int32) (ret []int32) {
+	mask := (uint64(1) << uint32(bpe)) - 1
+	elementsPerLong := 64 / bpe
+
+	ret = make([]int32, n)
+	for i := range n {
+		ret[i] = int32((data[i/elementsPerLong] >> ((i % elementsPerLong) * bpe)) & mask)
+	}
+	return
+}
+
+func UnpackBlockData(r io.Reader) (blocks [BlocksPerChunkSection]int32, err error) {
+	var bitsPerEntry uint8
+	err = binary.Read(r, binary.BigEndian, &bitsPerEntry)
+	if err != nil {
+		return
+	}
+	var blocksSlice []int32
+	fmt.Println("blocks bpe", bitsPerEntry)
+	switch bitsPerEntry {
+	case 0:
+		blocksSlice, err = UnpackSingleValuePalette(r, BlocksPerChunkSection)
+	case 1, 2, 3, 4:
+		blocksSlice, err = UnpackArrayPalette(r, bitsPerEntry, BlocksPerChunkSection)
+	case 5, 6, 7, 8:
+		panic("unimplemented")
+	default:
+		blocksSlice, err = UnpackLongData(r, bitsPerEntry, BlocksPerChunkSection)
+	}
+	blocks = [BlocksPerChunkSection]int32(blocksSlice)
+	return
+}
+
+func UnpackBiomeData(r io.Reader) (biomes [BiomesPerChunkSection]int32, err error) {
+	// net.minecraft.world.chunk.PaletteProvider#forBiomes
+	var bitsPerEntry uint8
+	err = binary.Read(r, binary.BigEndian, &bitsPerEntry)
+	if err != nil {
+		return
+	}
+	var biomesSlice []int32
+	fmt.Println("biome bpe", bitsPerEntry)
+	switch bitsPerEntry {
+	case 0:
+		biomesSlice, err = UnpackSingleValuePalette(r, BiomesPerChunkSection)
+	case 1, 2, 3:
+		biomesSlice, err = UnpackArrayPalette(r, bitsPerEntry, BiomesPerChunkSection)
+	default:
+		biomesSlice, err = UnpackLongData(r, bitsPerEntry, BiomesPerChunkSection)
+	}
+	if err != nil {
+		return
+	}
+	biomes = [BiomesPerChunkSection]int32(biomesSlice)
+	return
+}
+
+type ChunkSection struct {
+	BlockData [BlocksPerChunkSection]int32
+	BiomeData [BiomesPerChunkSection]int32
+}
+
+func UnpackSection(r io.Reader) (s ChunkSection, err error) {
+	var blockCount int16
+	err = binary.Read(r, binary.BigEndian, &blockCount)
+	if err != nil {
+		return
+	}
+	s.BlockData, err = UnpackBlockData(r)
+	if err != nil {
+		return
+	}
+	s.BiomeData, err = UnpackBiomeData(r)
+	if err != nil {
+		return
+	}
+
+	return
+}