Minecraft NBT (Named Binary Tag): Go parsing library

A structured binary format native to Minecraft for saving game data and transferring it over the network (in multiplayer), such as player data (<player>.dat; contains e.g. player's inventory and location), saved worlds (level.dat and Chunk format), list of saved multiplayer servers (servers.dat) and so on - see https://minecraft.gamepedia.com/NBT_format#Uses.

The entire file should be gzip-compressed (in accordance with the original specification NBT.txt by Notch), but can also be compressed with zlib or uncompressed.

This spec can only handle uncompressed NBT data, so be sure to first detect what type of data you are dealing with. You can use the Unix file command to do this (file-5.20 or later is required; older versions do not recognize zlib-compressed data and return application/octet-stream instead):

file --brief --mime-type input-unknown.nbt

If it says:

  • application/x-gzip or application/gzip (since file-5.37), you can decompress it by
    • gunzip -c input-gzip.nbt > output.nbt or
    • python3 -c "import sys, gzip; sys.stdout.buffer.write( gzip.decompress(sys.stdin.buffer.read()) )" < input-gzip.nbt > output.nbt
  • application/zlib, you can use
    • openssl zlib -d -in input-zlib.nbt -out output.nbt (does not work on most systems)
    • python3 -c "import sys, zlib; sys.stdout.buffer.write( zlib.decompress(sys.stdin.buffer.read()) )" < input-zlib.nbt > output.nbt
  • something else (especially image/x-pcx and application/octet-stream), it is most likely already uncompressed.

The file output.nbt generated by one of the above commands can already be processed with this Kaitai Struct specification.

This spec only implements the Java edition format. There is also a Bedrock edition NBT format, which uses little-endian encoding and has a few other differences, but it isn't as popular as the Java edition format.

Implementation note: strings in TAG_String are incorrectly decoded with standard UTF-8, while they are encoded in Modified UTF-8 (MUTF-8). That's because MUTF-8 is not supported natively by most target languages, and thus one must use external libraries to achieve a fully-compliant decoder. But decoding in standard UTF-8 is still better than nothing, and it usually works fine.

All Unicode code points with incompatible representations in MUTF-8 and UTF-8 are U+0000 (NUL), U+D800-U+DFFF (High and Low Surrogates) and U+10000-U+10FFFF (all Supplementary Planes; includes e.g. emoticons, pictograms). A MUTF-8-encoded string containing these code points cannot be successfully decoded as UTF-8. The behavior in this case depends on the target language - usually an exception is thrown, or the bytes that are not valid UTF-8 are replaced or ignored.

Sample files:

Application

Minecraft

File extension

["nbt", "dat", "schematic", "schem"]

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of Minecraft NBT (Named Binary Tag) using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Go source code to parse Minecraft NBT (Named Binary Tag)

minecraft_nbt.go

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

import (
	"github.com/kaitai-io/kaitai_struct_go_runtime/kaitai"
	"io"
)


/**
 * A structured binary format native to Minecraft for saving game data and transferring
 * it over the network (in multiplayer), such as player data
 * ([`<player>.dat`](https://minecraft.gamepedia.com/Player.dat_format); contains
 * e.g. player's inventory and location), saved worlds
 * ([`level.dat`](
 *   https://minecraft.gamepedia.com/Java_Edition_level_format#level.dat_format
 * ) and [Chunk format](https://minecraft.gamepedia.com/Chunk_format#NBT_structure)),
 * list of saved multiplayer servers
 * ([`servers.dat`](https://minecraft.gamepedia.com/Servers.dat_format)) and so on -
 * see <https://minecraft.gamepedia.com/NBT_format#Uses>.
 * 
 * The entire file should be _gzip_-compressed (in accordance with the original
 * specification [NBT.txt](
 *   https://web.archive.org/web/20110723210920/https://www.minecraft.net/docs/NBT.txt
 * ) by Notch), but can also be compressed with _zlib_ or uncompressed.
 * 
 * This spec can only handle uncompressed NBT data, so be sure to first detect
 * what type of data you are dealing with. You can use the Unix `file` command
 * to do this (`file-5.20` or later is required; older versions do not recognize
 * _zlib_-compressed data and return `application/octet-stream` instead):
 * 
 * ```shell
 * file --brief --mime-type input-unknown.nbt
 * ```
 * 
 * If it says:
 * 
 *   * `application/x-gzip` or `application/gzip` (since `file-5.37`), you can decompress it by
 *     * `gunzip -c input-gzip.nbt > output.nbt` or
 *     * `python3 -c "import sys, gzip; sys.stdout.buffer.write(
 *       gzip.decompress(sys.stdin.buffer.read()) )" < input-gzip.nbt > output.nbt`
 *   * `application/zlib`, you can use
 *     * `openssl zlib -d -in input-zlib.nbt -out output.nbt` (does not work on most systems)
 *     * `python3 -c "import sys, zlib; sys.stdout.buffer.write(
 *       zlib.decompress(sys.stdin.buffer.read()) )" < input-zlib.nbt > output.nbt`
 *   * something else (especially `image/x-pcx` and `application/octet-stream`),
 *     it is most likely already uncompressed.
 * 
 * The file `output.nbt` generated by one of the above commands can already be
 * processed with this Kaitai Struct specification.
 * 
 * This spec **only** implements the Java edition format. There is also
 * a [Bedrock edition](https://wiki.vg/NBT#Bedrock_edition) NBT format,
 * which uses little-endian encoding and has a few other differences, but it isn't
 * as popular as the Java edition format.
 * 
 * **Implementation note:** strings in `TAG_String` are incorrectly decoded with
 * standard UTF-8, while they are encoded in [**Modified UTF-8**](
 *   https://docs.oracle.com/javase/8/docs/api/java/io/DataInput.html#modified-utf-8
 * ) (MUTF-8). That's because MUTF-8 is not supported natively by most target
 * languages, and thus one must use external libraries to achieve a fully-compliant
 * decoder. But decoding in standard UTF-8 is still better than nothing, and
 * it usually works fine.
 * 
 * All Unicode code points with incompatible representations in MUTF-8 and UTF-8 are
 * U+0000 (_NUL_), U+D800-U+DFFF (_High_ and _Low Surrogates_) and U+10000-U+10FFFF
 * (all _Supplementary_ Planes; includes e.g. emoticons, pictograms).
 * A _MUTF-8_-encoded string containing these code points cannot be successfully
 * decoded as UTF-8. The behavior in this case depends on the target language -
 * usually an exception is thrown, or the bytes that are not valid UTF-8
 * are replaced or ignored.
 * 
 * **Sample files:**
 * 
 *   * <https://wiki.vg/NBT#Download>
 *   * <https://github.com/twoolie/NBT/blob/f9e892e/tests/world_test/data/scoreboard.dat>
 *   * <https://github.com/chmod222/cNBT/tree/3f74b69/testdata>
 *   * <https://github.com/PistonDevelopers/hematite_nbt/tree/0b85f89/tests>
 * @see <a href="https://wiki.vg/NBT">Source</a>
 * @see <a href="https://web.archive.org/web/20110723210920/https://www.minecraft.net/docs/NBT.txt">Source</a>
 * @see <a href="https://minecraft.gamepedia.com/NBT_format">Source</a>
 */

type MinecraftNbt_Tag int
const (
	MinecraftNbt_Tag__End MinecraftNbt_Tag = 0
	MinecraftNbt_Tag__Byte MinecraftNbt_Tag = 1
	MinecraftNbt_Tag__Short MinecraftNbt_Tag = 2
	MinecraftNbt_Tag__Int MinecraftNbt_Tag = 3
	MinecraftNbt_Tag__Long MinecraftNbt_Tag = 4
	MinecraftNbt_Tag__Float MinecraftNbt_Tag = 5
	MinecraftNbt_Tag__Double MinecraftNbt_Tag = 6
	MinecraftNbt_Tag__ByteArray MinecraftNbt_Tag = 7
	MinecraftNbt_Tag__String MinecraftNbt_Tag = 8
	MinecraftNbt_Tag__List MinecraftNbt_Tag = 9
	MinecraftNbt_Tag__Compound MinecraftNbt_Tag = 10
	MinecraftNbt_Tag__IntArray MinecraftNbt_Tag = 11
	MinecraftNbt_Tag__LongArray MinecraftNbt_Tag = 12
)
type MinecraftNbt struct {
	RootCheck []byte
	Root *MinecraftNbt_NamedTag
	_io *kaitai.Stream
	_root *MinecraftNbt
	_parent interface{}
	_f_rootType bool
	rootType MinecraftNbt_Tag
}
func NewMinecraftNbt() *MinecraftNbt {
	return &MinecraftNbt{
	}
}

func (this *MinecraftNbt) Read(io *kaitai.Stream, parent interface{}, root *MinecraftNbt) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp1, err := this.RootType()
	if err != nil {
		return err
	}
	if ( ((tmp1 == MinecraftNbt_Tag__End) && (false)) ) {
		tmp2, err := this._io.ReadBytes(int(0))
		if err != nil {
			return err
		}
		tmp2 = tmp2
		this.RootCheck = tmp2
	}
	tmp3 := NewMinecraftNbt_NamedTag()
	err = tmp3.Read(this._io, this, this._root)
	if err != nil {
		return err
	}
	this.Root = tmp3
	return err
}
func (this *MinecraftNbt) RootType() (v MinecraftNbt_Tag, err error) {
	if (this._f_rootType) {
		return this.rootType, nil
	}
	_pos, err := this._io.Pos()
	if err != nil {
		return nil, err
	}
	_, err = this._io.Seek(int64(0), io.SeekStart)
	if err != nil {
		return nil, err
	}
	tmp4, err := this._io.ReadU1()
	if err != nil {
		return nil, err
	}
	this.rootType = MinecraftNbt_Tag(tmp4)
	_, err = this._io.Seek(_pos, io.SeekStart)
	if err != nil {
		return nil, err
	}
	this._f_rootType = true
	tmp5, err := this.RootType()
	if err != nil {
		return nil, err
	}
	tmp6, err := this.RootType()
	if err != nil {
		return nil, err
	}
	if !(tmp6 == MinecraftNbt_Tag__Compound) {
		return nil, kaitai.NewValidationNotEqualError(MinecraftNbt_Tag__Compound, tmp5, this._io, "/instances/root_type")
	}
	this._f_rootType = true
	return this.rootType, nil
}
type MinecraftNbt_TagLongArray struct {
	NumTags int32
	Tags []int64
	_io *kaitai.Stream
	_root *MinecraftNbt
	_parent interface{}
	_f_tagsType bool
	tagsType MinecraftNbt_Tag
}
func NewMinecraftNbt_TagLongArray() *MinecraftNbt_TagLongArray {
	return &MinecraftNbt_TagLongArray{
	}
}

func (this *MinecraftNbt_TagLongArray) Read(io *kaitai.Stream, parent interface{}, root *MinecraftNbt) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp7, err := this._io.ReadS4be()
	if err != nil {
		return err
	}
	this.NumTags = int32(tmp7)
	this.Tags = make([]int64, this.NumTags)
	for i := range this.Tags {
		tmp8, err := this._io.ReadS8be()
		if err != nil {
			return err
		}
		this.Tags[i] = tmp8
	}
	return err
}
func (this *MinecraftNbt_TagLongArray) TagsType() (v MinecraftNbt_Tag, err error) {
	if (this._f_tagsType) {
		return this.tagsType, nil
	}
	this.tagsType = MinecraftNbt_Tag(MinecraftNbt_Tag__Long)
	this._f_tagsType = true
	return this.tagsType, nil
}
type MinecraftNbt_TagByteArray struct {
	LenData int32
	Data []byte
	_io *kaitai.Stream
	_root *MinecraftNbt
	_parent interface{}
}
func NewMinecraftNbt_TagByteArray() *MinecraftNbt_TagByteArray {
	return &MinecraftNbt_TagByteArray{
	}
}

func (this *MinecraftNbt_TagByteArray) Read(io *kaitai.Stream, parent interface{}, root *MinecraftNbt) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp9, err := this._io.ReadS4be()
	if err != nil {
		return err
	}
	this.LenData = int32(tmp9)
	tmp10, err := this._io.ReadBytes(int(this.LenData))
	if err != nil {
		return err
	}
	tmp10 = tmp10
	this.Data = tmp10
	return err
}
type MinecraftNbt_TagIntArray struct {
	NumTags int32
	Tags []int32
	_io *kaitai.Stream
	_root *MinecraftNbt
	_parent interface{}
	_f_tagsType bool
	tagsType MinecraftNbt_Tag
}
func NewMinecraftNbt_TagIntArray() *MinecraftNbt_TagIntArray {
	return &MinecraftNbt_TagIntArray{
	}
}

func (this *MinecraftNbt_TagIntArray) Read(io *kaitai.Stream, parent interface{}, root *MinecraftNbt) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp11, err := this._io.ReadS4be()
	if err != nil {
		return err
	}
	this.NumTags = int32(tmp11)
	this.Tags = make([]int32, this.NumTags)
	for i := range this.Tags {
		tmp12, err := this._io.ReadS4be()
		if err != nil {
			return err
		}
		this.Tags[i] = tmp12
	}
	return err
}
func (this *MinecraftNbt_TagIntArray) TagsType() (v MinecraftNbt_Tag, err error) {
	if (this._f_tagsType) {
		return this.tagsType, nil
	}
	this.tagsType = MinecraftNbt_Tag(MinecraftNbt_Tag__Int)
	this._f_tagsType = true
	return this.tagsType, nil
}
type MinecraftNbt_TagList struct {
	TagsType MinecraftNbt_Tag
	NumTags int32
	Tags []interface{}
	_io *kaitai.Stream
	_root *MinecraftNbt
	_parent interface{}
}
func NewMinecraftNbt_TagList() *MinecraftNbt_TagList {
	return &MinecraftNbt_TagList{
	}
}

func (this *MinecraftNbt_TagList) Read(io *kaitai.Stream, parent interface{}, root *MinecraftNbt) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp13, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.TagsType = MinecraftNbt_Tag(tmp13)
	tmp14, err := this._io.ReadS4be()
	if err != nil {
		return err
	}
	this.NumTags = int32(tmp14)
	this.Tags = make([]interface{}, this.NumTags)
	for i := range this.Tags {
		switch (this.TagsType) {
		case MinecraftNbt_Tag__LongArray:
			tmp15 := NewMinecraftNbt_TagLongArray()
			err = tmp15.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Tags[i] = tmp15
		case MinecraftNbt_Tag__Compound:
			tmp16 := NewMinecraftNbt_TagCompound()
			err = tmp16.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Tags[i] = tmp16
		case MinecraftNbt_Tag__Double:
			tmp17, err := this._io.ReadF8be()
			if err != nil {
				return err
			}
			this.Tags[i] = tmp17
		case MinecraftNbt_Tag__List:
			tmp18 := NewMinecraftNbt_TagList()
			err = tmp18.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Tags[i] = tmp18
		case MinecraftNbt_Tag__Float:
			tmp19, err := this._io.ReadF4be()
			if err != nil {
				return err
			}
			this.Tags[i] = tmp19
		case MinecraftNbt_Tag__Short:
			tmp20, err := this._io.ReadS2be()
			if err != nil {
				return err
			}
			this.Tags[i] = tmp20
		case MinecraftNbt_Tag__Int:
			tmp21, err := this._io.ReadS4be()
			if err != nil {
				return err
			}
			this.Tags[i] = tmp21
		case MinecraftNbt_Tag__ByteArray:
			tmp22 := NewMinecraftNbt_TagByteArray()
			err = tmp22.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Tags[i] = tmp22
		case MinecraftNbt_Tag__Byte:
			tmp23, err := this._io.ReadS1()
			if err != nil {
				return err
			}
			this.Tags[i] = tmp23
		case MinecraftNbt_Tag__IntArray:
			tmp24 := NewMinecraftNbt_TagIntArray()
			err = tmp24.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Tags[i] = tmp24
		case MinecraftNbt_Tag__String:
			tmp25 := NewMinecraftNbt_TagString()
			err = tmp25.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Tags[i] = tmp25
		case MinecraftNbt_Tag__Long:
			tmp26, err := this._io.ReadS8be()
			if err != nil {
				return err
			}
			this.Tags[i] = tmp26
		}
	}
	return err
}
type MinecraftNbt_TagString struct {
	LenData uint16
	Data string
	_io *kaitai.Stream
	_root *MinecraftNbt
	_parent interface{}
}
func NewMinecraftNbt_TagString() *MinecraftNbt_TagString {
	return &MinecraftNbt_TagString{
	}
}

func (this *MinecraftNbt_TagString) Read(io *kaitai.Stream, parent interface{}, root *MinecraftNbt) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp27, err := this._io.ReadU2be()
	if err != nil {
		return err
	}
	this.LenData = uint16(tmp27)
	tmp28, err := this._io.ReadBytes(int(this.LenData))
	if err != nil {
		return err
	}
	tmp28 = tmp28
	this.Data = string(tmp28)
	return err
}

/**
 * unsigned according to https://wiki.vg/NBT#Specification
 */
type MinecraftNbt_TagCompound struct {
	Tags []*MinecraftNbt_NamedTag
	_io *kaitai.Stream
	_root *MinecraftNbt
	_parent interface{}
	_f_dumpNumTags bool
	dumpNumTags int
}
func NewMinecraftNbt_TagCompound() *MinecraftNbt_TagCompound {
	return &MinecraftNbt_TagCompound{
	}
}

func (this *MinecraftNbt_TagCompound) Read(io *kaitai.Stream, parent interface{}, root *MinecraftNbt) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	for i := 1;; i++ {
		tmp29 := NewMinecraftNbt_NamedTag()
		err = tmp29.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		_it := tmp29
		this.Tags = append(this.Tags, _it)
		tmp30, err := _it.IsTagEnd()
		if err != nil {
			return err
		}
		if tmp30 {
			break
		}
	}
	return err
}
func (this *MinecraftNbt_TagCompound) DumpNumTags() (v int, err error) {
	if (this._f_dumpNumTags) {
		return this.dumpNumTags, nil
	}
	var tmp31 int8;
	tmp32 := this.Tags
	tmp33, err := tmp32[len(tmp32) - 1].IsTagEnd()
	if err != nil {
		return 0, err
	}
	if ( ((len(this.Tags) >= 1) && (tmp33)) ) {
		tmp31 = 1
	} else {
		tmp31 = 0
	}
	this.dumpNumTags = int((len(this.Tags) - tmp31))
	this._f_dumpNumTags = true
	return this.dumpNumTags, nil
}
type MinecraftNbt_NamedTag struct {
	Type MinecraftNbt_Tag
	Name *MinecraftNbt_TagString
	Payload interface{}
	_io *kaitai.Stream
	_root *MinecraftNbt
	_parent interface{}
	_f_isTagEnd bool
	isTagEnd bool
}
func NewMinecraftNbt_NamedTag() *MinecraftNbt_NamedTag {
	return &MinecraftNbt_NamedTag{
	}
}

func (this *MinecraftNbt_NamedTag) Read(io *kaitai.Stream, parent interface{}, root *MinecraftNbt) (err error) {
	this._io = io
	this._parent = parent
	this._root = root

	tmp34, err := this._io.ReadU1()
	if err != nil {
		return err
	}
	this.Type = MinecraftNbt_Tag(tmp34)
	tmp35, err := this.IsTagEnd()
	if err != nil {
		return err
	}
	if (!(tmp35)) {
		tmp36 := NewMinecraftNbt_TagString()
		err = tmp36.Read(this._io, this, this._root)
		if err != nil {
			return err
		}
		this.Name = tmp36
	}
	tmp37, err := this.IsTagEnd()
	if err != nil {
		return err
	}
	if (!(tmp37)) {
		switch (this.Type) {
		case MinecraftNbt_Tag__LongArray:
			tmp38 := NewMinecraftNbt_TagLongArray()
			err = tmp38.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Payload = tmp38
		case MinecraftNbt_Tag__Compound:
			tmp39 := NewMinecraftNbt_TagCompound()
			err = tmp39.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Payload = tmp39
		case MinecraftNbt_Tag__Double:
			tmp40, err := this._io.ReadF8be()
			if err != nil {
				return err
			}
			this.Payload = tmp40
		case MinecraftNbt_Tag__List:
			tmp41 := NewMinecraftNbt_TagList()
			err = tmp41.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Payload = tmp41
		case MinecraftNbt_Tag__Float:
			tmp42, err := this._io.ReadF4be()
			if err != nil {
				return err
			}
			this.Payload = tmp42
		case MinecraftNbt_Tag__Short:
			tmp43, err := this._io.ReadS2be()
			if err != nil {
				return err
			}
			this.Payload = tmp43
		case MinecraftNbt_Tag__Int:
			tmp44, err := this._io.ReadS4be()
			if err != nil {
				return err
			}
			this.Payload = tmp44
		case MinecraftNbt_Tag__ByteArray:
			tmp45 := NewMinecraftNbt_TagByteArray()
			err = tmp45.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Payload = tmp45
		case MinecraftNbt_Tag__Byte:
			tmp46, err := this._io.ReadS1()
			if err != nil {
				return err
			}
			this.Payload = tmp46
		case MinecraftNbt_Tag__IntArray:
			tmp47 := NewMinecraftNbt_TagIntArray()
			err = tmp47.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Payload = tmp47
		case MinecraftNbt_Tag__String:
			tmp48 := NewMinecraftNbt_TagString()
			err = tmp48.Read(this._io, this, this._root)
			if err != nil {
				return err
			}
			this.Payload = tmp48
		case MinecraftNbt_Tag__Long:
			tmp49, err := this._io.ReadS8be()
			if err != nil {
				return err
			}
			this.Payload = tmp49
		}
	}
	return err
}
func (this *MinecraftNbt_NamedTag) IsTagEnd() (v bool, err error) {
	if (this._f_isTagEnd) {
		return this.isTagEnd, nil
	}
	this.isTagEnd = bool(this.Type == MinecraftNbt_Tag__End)
	this._f_isTagEnd = true
	return this.isTagEnd, nil
}