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datafile.md

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Introduction

The Teeworlds datafile format is the format which Teeworlds uses to save its game maps. Despite having been used for quite some time, it has not yet been formally described. The format enables one to store fixed-size "items" along with variable-sized "data items".

The format is designed in a way that makes it easy to directly load most parts into the memory (i. e. in version 4 everything except for the data block, as the data block is stored compressed in the file). In this document the versions 3 and 4 of Teeworlds datafiles will be explained.

Terminology

The following is an abstract description of the data contained in a Teeworlds datafile. It does not specify how they are laid out in the file.

Items

An item consists of a 16-bit unsigned integer type_id, a 16-bit unsigned integer id and an array of 32-bit signed integers data. The combination of type_id and id is unique amongst all items. The length of data is usually the same for all items of a given type_id.

Examples of types in actual Teeworlds maps include metadata for layers, layer groups, images (external or not), etc. Since only the metadata and not the actual contents are stored, the items can remain fixed-size.

Data items

A data item is an array of bytes (8-bit unsigned integers) data. id is unique amongst all data items, the only possible IDs are from 0 (incl.) to the number of data items (excl.). These data items are indexed via unsigned integers, counting sequentially in the order they are laid out in the file.

In actual Teeworlds maps, data items are used e.g. for the tiles of a tile layer or the image data of an embedded image. They are referred to in the metadata items by their index.

Format

Datafile

The format of datafiles looks like follows, all parts are explained later:

datafile:
    [  8] version_header
    [ 28] header
    [*12] item_types
    [* 4] item_offsets
    [* 4] data_offsets
    [* 4] _data_sizes
    [   ] items
    [   ] data

The _data_sizes part is only present in version 4 of Teeworlds datafiles.

The header contains size information for the rest of the file:

  • item_types has the length of header.num_item_types item types.
  • item_offsets has the length of header.num_items 32-bit integers.
  • data_offsets has the length of header.num_data 32-bit integers.
  • _data_sizes is only present in version 4 of Teeworlds datafiles, it has the length of header.num_data 32-bit integers.
  • items has the length of header.item_size bytes which must be divisible by four.
  • data has the length of header.data_size bytes.

Version header

The version header consists of a magic byte sequence, identifying the file as a Teeworlds datafile and a version number.

version_header:
    [4] magic
    [4] version

The magic must exactly be the ASCII representations of the four characters, 'D', 'A', 'T', 'A'.

NOTE: Readers of Teeworlds datafiles should be able to read datafiles which start with a reversed magic too, that is 'A', 'T', 'A', 'D'. A bug in the reference implementation caused big-endian machines to save the reversed magic bytes.

The version is a little-endian signed 32-bit integer, for version 3 or 4 of Teeworlds datafiles, it must be 3 or 4, respectively.

Header

The header specific to version 3 and 4 consists of seven 32-bit signed integers.

header:
    [4] size
    [4] swaplen
    [4] num_item_types
    [4] num_items
    [4] num_data
    [4] item_size
    [4] data_size

The size is a little-endian integer and must be the size of the complete datafile without the version_header and both size and swaplen.

NOTE: The reference implementation does not read this value.

The swaplen is a little-endian integer and must specify the number of bytes containing integers following the size and swaplen fields, up until the data of the data items. It can therefore be used to reverse the endian on big-endian machines.

NOTE: The reference implementation does not read datafiles correctly on little-endian machines, because it interprets swaplen as starting after the header.

NOTE: All further integers can be assumed to be already converted to machine-native endian, if an endian swap was performed using the swaplen field.

The num_item_types integer specifies the number of item types in the datafile.item_types field.

The num_items integer specifies the number of items in the datafile.items field.

The num_data integer specifies the number of raw data blocks in the datafile.data field.

The item_size integer specifies the total size in bytes of the datafile.items field.

The data_size integer specifies the total size in bytes of the datafile.data field.

Item types

The item types are an array of item types. The number of item types in that array is num_item_types, each item type is identified by its unique type_id (explained below). Each item type is of the following form:

item_type:
    [4] type_id
    [4] start
    [4] num

The type_id 32-bit signed integer must be unique amongst all other item_type.type_ids. Its value must fit into an unsigned 16-bit integer.

The start signed integer is the index of the first item in the items with the type type_id.

The num signed integer must be the number of items with the the type type_id.

NOTE: Since all items of the same type must be sequential in the items array, exactly the items with the index start (incl.) to start + num (excl.) are of the type type_id.

Item offsets, data offsets and data sizes

The item offsets, the data offsets and the data sizes are 32-bit signed integers.

Each item offset is the offset of the item with the corresponding index, relative to the first item's position in the file.

Each data offset is an offset of the data with the corresponding index, relative to the position of the first data item in the file. The data item's size can then be calculated from the next data item's offset or the size of the data section.

Each data size is the size of the uncompressed data of the data with the corresponding index. Note that this field is only present in datafile version 4.

Items

This is an array of items. Each is of the following form:

item:
    [4] type_id__id
    [4] size
    [ ] item_data

The type_id__id integer consists of 16 bit type_id of the type the item belongs to and 16 bit id that uniquely identifies the item among all others of the same type, in that order, i.e. the upper 16 bit of type_id__id specify the type_id and the lower 16 bit specify id.

The size signed 32-bit integer is the size of the item_data field, in bytes, which must be divisible by four.

NOTE: Neither the type_id nor the size are interpreted by the reference implementation.

Data

This section contains the data items. The order of the data items implicitly defines their ID.

In version 3, this section solely consists of the concatenated data. In version 4, however, it stores the data compressed by zlib's compress function.