NBTFile is a low-level library for reading and writing NBT-format files, as used by the popular game Minecraft.
The official (if somewhat confusing) specification for the NBT file format may be found at www.minecraft.net/docs/NBT.txt
The NBT data model has ten different data types:
- 8-bit signed integers (Tag_Byte) - 16-bit signed integers (Tag_Short) - 32-bit signed integers (Tag_Int) - 64-bit signed integers (Tag_Long) - 32-bit floating-point numbers (Tag_Float) - 64-bit floating-point numbers (Tag_Double) - UTF-8 strings (Tag_String) - raw byte strings (Tag_Byte_Array) - homogenous lists (Tag_List) - compound structures (Tag_Compound)
Compound structures (Tag_Compound) are unordered collections where each item (“tag”) has a name associated with it. Compound structures are heterogenous; the elements of a compound structure may be any mixture of types.
Lists (Tag_List) are ordered collections of unnamed items. Lists are homogenous; every element of a particular list must have the same type. Note that all lists have the same type (Tag_List) regardless of the type of their elements.
Items of an eleventh “type” (Tag_End) serve to terminate compound structures and lists (of any type). The wording of the official specification could permit lists of Tag_End, but this is not supported in practice.
The top level of an NBT file must be a single-element compound structure.
NBT files are gzip-compressed; the structure of the uncompressed data can be described by the following ABNF (see RFC 5234).
nbt-data = tag-compound tag-compound = TAG-COMPOUND name compound-body compound-body = *tag TAG-END tag = TAG-BYTE name byte / TAG-SHORT name short / TAG-INT name int / TAG-LONG name long / TAG-FLOAT name float / TAG-DOUBLE name double / TAG-STRING name string / TAG-BYTE-ARRAY name byte-array / TAG-LIST name list / tag-compound name = string list = TAG-BYTE list-length *byte / TAG-SHORT list-length *short / TAG-INT list-length *int / TAG-LONG list-length *long / TAG-FLOAT list-length *float / TAG-DOUBLE list-length *double / TAG-STRING list-length *string / TAG-BYTE-ARRAY list-length *byte-array / TAG-LIST list-length *list / TAG-COMPOUND list-length *compound-body list-length = int ; see RFC 3629 for definition of UTF8-octets string = string-length UTF8-octets string-length = short byte-array = byte-array-length *byte byte-array-length = int byte = OCTET ; 8-bit signed integer short = 2OCTET ; 16-bit signed integer, big-endian int = 4OCTET ; 32-bit signed integer, big-endian long = 8OCTET ; 64-bit signed integer, big-endian float = 4OCTET ; 32-bit float, big-endian, IEEE 754-2008 double = 8OCTET ; 64-bit float, big-endian, IEEE 754-2008 TAG-END = %x00 TAG-BYTE = %x01 TAG-SHORT = %x02 TAG-INT = %x03 TAG-LONG = %x04 TAG-FLOAT = %x05 TAG-DOUBLE = %x06 TAG-BYTE-ARRAY = %x07 TAG-STRING = %x08 TAG-LIST = %x09 TAG-COMPOUND = %x0a
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