119 lines
3.1 KiB
Go
119 lines
3.1 KiB
Go
package world
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import (
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"bytes"
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"fmt"
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// "io"
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"github.com/Tnze/go-mc/data"
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pk "github.com/Tnze/go-mc/net/packet"
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)
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// DecodeChunkColumn decode the chunk data structure.
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// If decoding went error, successful decoded data will be returned.
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func DecodeChunkColumn(mask int32, data []byte) (*Chunk, error) {
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var c Chunk
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r := bytes.NewReader(data)
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for sectionY := 0; sectionY < 16; sectionY++ {
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// If the section's bit set in the mask
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if (mask & (1 << uint(sectionY))) != 0 {
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// read section
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sec, err := readSection(r)
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if err != nil {
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return &c, fmt.Errorf("read section[%d] error: %w", sectionY, err)
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}
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c.sections[sectionY] = sec
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}
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}
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return &c, nil
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}
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func perBits(BitsPerBlock byte) uint32 {
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switch {
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case BitsPerBlock <= 4:
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return 4
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case BitsPerBlock < 9:
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return uint32(BitsPerBlock)
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default:
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return uint32(data.BitsPerBlock) // DefaultBitsPerBlock
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}
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}
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func readSection(data pk.DecodeReader) (s Section, err error) {
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var BlockCount pk.Short
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if err := BlockCount.Decode(data); err != nil {
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return nil, fmt.Errorf("read block count error: %w", err)
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}
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var bpb pk.UnsignedByte
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if err := bpb.Decode(data); err != nil {
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return nil, fmt.Errorf("read bits per block error: %w", err)
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}
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// If bpb values greater than or equal to 9, use directSection.
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// Otherwise use paletteSection.
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var palettes []uint32
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if bpb < 9 {
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// read palettes
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var length pk.VarInt
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if err := length.Decode(data); err != nil {
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return nil, fmt.Errorf("read palettes length error: %w", err)
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}
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palettes = make([]uint32, length)
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for i := 0; i < int(length); i++ {
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var v pk.VarInt
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if err := v.Decode(data); err != nil {
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return nil, fmt.Errorf("read palettes[%d] error: %w", i, err)
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}
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palettes[i] = uint32(v)
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}
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}
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// read data array
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var dataLen pk.VarInt
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if err := dataLen.Decode(data); err != nil {
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return nil, fmt.Errorf("read data array length error: %w", err)
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}
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dataArray := make([]int64, dataLen)
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for i := 0; i < int(dataLen); i++ {
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var v pk.Long
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if err := v.Decode(data); err != nil {
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return nil, fmt.Errorf("read dataArray[%d] error: %w", i, err)
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}
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dataArray[i] = int64(v)
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}
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sec := directSection{bpb: perBits(byte(bpb)), data: dataArray}
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if bpb < 9 {
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return &paletteSection{palette: palettes, directSection: sec}, nil
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} else {
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return &sec, nil
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}
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}
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type directSection struct {
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bpb uint32
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data []int64
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}
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func (d *directSection) GetBlock(x, y, z int) (blockID uint32) {
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// According to wiki.vg: Data Array is given for each block with increasing x coordinates,
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// within rows of increasing z coordinates, within layers of increasing y coordinates.
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// So offset equals to ( x*16^0 + z*16^1 + y*16^2 )*(bits per block).
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offset := uint32(x+z*16+y*16*16) * d.bpb
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block := uint32(d.data[offset/64])
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block >>= offset % 64
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if offset%64 > 64-d.bpb {
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l := 64 - offset%64
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block |= uint32(d.data[offset/64+1] << l)
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}
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return block & (1<<d.bpb - 1) // mask
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}
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type paletteSection struct {
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palette []uint32
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directSection
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}
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func (p *paletteSection) GetBlock(x, y, z int) (blockID uint32) {
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v := p.directSection.GetBlock(x, y, z)
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return p.palette[v]
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}
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