Tag File Specification#

The format for tag files is still in its early stages. While we will try to avoid any breaking changes, don't be too surprised if any major format changes occur.

Tags are the primary way that any game content will be stored.

Tag data will vary wildly based on a class, but the following format details are consistent across all tags. The format is based loosely on the format used by Halo Custom Edition, while taking cues from future versions as well as injecting some of our own DNA to fit our needs better.

Remember: Any sizes that begin with 0x indicate a hexadecimal (base 16) length. Ex: 0x10 is equal to decimal 16.

File Header#

Address range: 0x0 -> 0x8F (size 0x90)

    
    Offset (h)   00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F    Decoded text
    00000000     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    00000010     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    00000020     00 00 00 00 62 69 74 6D 00 00 01 00 00 00 00 00    ....bitm........
    00000030     00 00 00 00 00 00 00 00 00 00 00 00 62 6C 61 6D    ............blam
    00000040     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    00000050     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    00000060     30 30 30 30 36 2E 30 39 2E 33 30 2E 31 39 2E 30    00006.09.30.19.0
    00000070     30 30 31 2E 62 6C 61 6D 69 74 65 00 00 00 00 00    001.blamite.....
    00000080     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

Offset Range	Size	Description	Color
`0x0 -> 0x23`	`0x24`	Empty padding	Silver/Gray
`0x24 -> 0x27`	`0x4`	Tag class (short name)	Red
`0x28 -> 0x29`	`0x2`	Empty padding	Gray
`0x2A`	`0x1`	Will be `01` in the case of a Blamite tag, legacy blam! tags will be something else (usually `00`)	Lime
`0x2B -> 0x3B`	`0x11`	Empty padding	Gray
`0x3C -> 0x3F`	`0x4`	Will always contain `blam`	Green
`0x40 -> 0x43`	`0x4`	An integer representing the plugin revision that was used to compile the tag. Will be used for backwards compatibility.	Yellow
`0x44 -> 0x47`	`0x4`	An integer representing the tag fieldset version that was used to compile the tag. Used for backwards compatibility.	Light Blue
`0x48 -> 0x5F`	`0x18`	Empty padding	Silver
`0x60 -> 0x7F`	`0x20`	Engine version the tag was designed for, will be used in the future for backwards compatibility. Must end with `0x00` (null byte).	Salmon
`0x80 -> 0x8F`	`0x10`	Empty padding	Gray

Tag Data#

Address range: 0x90 -> End of File

Tag data will vary drastically for each tag class. Below, you can find information on how various tag fields are stored.

Tag Fields#

Below you can find details about all possible tag fields and how they are stored.

Be aware: Modern systems perform something known as "clamping" to ensure that variables are located at even addresses. If you encounter an exception relating to a tag using Int8 or Boolean fields, keep this in mind if addresses are seemingly "offset" by 1.

Field Name	Description/Purpose	Data Type	Size
ASCII	Plain text storage directly within tag data.	`char[32]`	32 (`0x20`) Bytes
Int32	A 32-bit integer.	`int`	4 Bytes
Int16	A 16-bit integer.	`short`	2 Bytes
Int8	An 8-bit integer.	`byte` (`unsigned char`)	1 Byte
Boolean	A single `true` or `false` value, represented as `01` or `00`.	`bool`	1 Byte
Color	Easy storage of color information. Color values are stored as 4 bytes in RGBA order.	`BlamColor`	4 bytes
Enum	A single selection of a series of potential options.	`enum`	4 Bytes
Bitfield8	A series of 8 true or false flags grouped together. Should be used instead of Boolean fields wherever possible.	`bool[8]`	8 Bytes
Bitfield16	A series of 16 true or false flags grouped together. Should be used instead of Boolean fields wherever possible.	`bool[16]`	16 (`0x10`) Bytes
Bitfield32	A series of 32 true or false flags grouped together. Should be used instead of Boolean fields wherever possible.	`bool[32]`	32 (`0x20`) Bytes

Tag Blocks#

Blocks are the most complex type of tag in the engine. They are used to group together many related fields, as well as provide support for "entries". A block's entries all share the same data structure, but can have unique values per-entry. These allow for more flexibility when defining new tags and see usage all over the place.

Memory Structure#

Below is the memory structure of tag blocks, as they are stored within normal field data. Entry data is stored in a separate location entirely - only the information about the tag block is stored within the normal field list. All offsets listed in the Offset Range column are relative to the start of the tag block data.

Address range: 0x0 -> 0x1F (size 0x20)

    
    Offset (h)   00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F    Decoded text
    00000000     74 62 66 64 00 00 00 00 14 00 00 00 00 00 00 00    tbfd............
    00000010     F8 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00    ø...............

Offset Range	Size	Description	Color
`0x0 -> 0x7`	`0x8`	Block identifier, will always contain `tbfd` (Tag Block ForwarD) followed by 4 null bytes.	Light Blue
`0x8 -> 0xB`	`0x4`	Size of each entry	Red
`0xC -> 0xF`	`0x4`	Reserved/Empty padding	Silver
`0x10 -> 0x17`	`0x8`	The 64-bit address in memory (when a tag is loaded in-engine), or the file offset to the block entry data	Magenta
`0x18 -> 0x1B`	`0x4`	The number of entries in the block	Green
`0x1C -> 0x1F`	`0x4`	Reserved/Empty padding	Gray

Tag References (tagrefs)#

Tag References allow for tags to reference other tags within them. This can be used in cases where specific tags need to depend on another, such as a weapon referencing a model tag, or a shader referencing a bitmap.

Address range: 0x0 -> 0x1B (size 0x1C)

    
    Offset (h)   00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F    Decoded text
    00000000     74 72 66 64 00 00 00 00 62 69 74 6D 00 00 FF FF    trfd....bitm..ÿÿ
    00000010     FF FF FF FF FF FF 00 00 00 02 00 00                ÿÿÿÿÿÿ......

Offset Range	Size	Description	Color
`0x0 -> 0x7`	`0x8`	Tagref identifier, will always contain `trfd` (Tag Reference ForwarD) followed by 4 null bytes.	Light Blue
`0x8 -> 0xB`	`0x4`	Name of the tag's class.	Red
`0xC -> 0xD`	`0x2`	Reserved/Empty padding	Silver
`0xE -> 0x15`	`0x8`	The 64-bit address pointing to either the referenced tag data, or pointing to a string containing the tag's path. When stored on disk, this will always be a file offset pointing to the tag's path.	Magenta
`0x16`	`0x1`	The type of data that the address points to. When set to `00`, it indicates that the address points to a tag path. When set to `01`, it points to the referenced tag data.	Green
`0x17`	`0x1`	Reserved/Empty padding	Gray
`0x18 -> 0x1B`	`0x4`	The size of either the tag path, or the size of the referenced tag data.	Salmon

Data References (datarefs)#

Data References allow for tags to store arbitrary, variable-sized data. This data can be used for virtually anything - as it simply stores an address and a size.

Address range: 0x0 -> 0x13 (size 0x14)

    
    Offset (h)   00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F    Decoded text
    00000000     64 72 66 64 00 00 00 00 FF FF FF FF FF FF FF FF    drfd....ÿÿÿÿÿÿÿÿ
    00000010     00 00 00 00                ....

Offset Range	Size	Description	Color
`0x0 -> 0x7`	`0x8`	Dataref identifier, will always contain `drfd` (Data Reference ForwarD) followed by 4 null bytes.	Light Blue
`0x8 -> 0xF`	`0x8`	The 64-bit address pointing to the referenced data. When stored in a file on disk, this will be the file offset instead of a memory address.	Magenta
`0x10 -> 0x13`	`0x4`	The size of the referenced data.	Green