User:SniffleMan

TES4 BSA Layout

File Structure

Name	Type/Size	Info
header	Header
directory entries	Directory Entry[directory count]
files	File Block[directory count]
file names	zstring[file count]	only present if "file strings" is set
data	File Data[file count]

Header

Name	Type/Size	Info
tag	char[4]	"BSA\x00"
version	uint32	103/104/105
header size	uint32	0x24
archive flags	uint32	Bit Description 1 << 0 directory strings 1 << 1 file strings 1 << 2 compressed 1 << 3 retain directory names 1 << 4 retain file names 1 << 5 retain file name offsets 1 << 6 xbox archive 1 << 7 retain strings during startup v104/v105 only 1 << 8 embedded file names 1 << 9 xbox compressed (only works on v104)
directory count	uint32
file count	uint32
directory names length	uint32	includes null terminators
file names length	uint32	includes null terminators
archive type	uint16	Bit Description 1 << 0 meshes 1 << 1 textures 1 << 2 menus 1 << 3 sounds 1 << 4 voices 1 << 5 shaders 1 << 6 trees 1 << 7 fonts 1 << 8 misc
padding	uint16

Directory Entry

Name	Type/Size	Info
hash	Hash
file count	uint32
v105 only padding uint32
file entries offset	uint32	subtract "file names length" to get the absolute offset
v105 only padding uint32

File Block

Name	Type/Size	Info
directory name	bzstring	only present if "directory strings" is set
files	File Entry[...]

File Entry

Name	Type/Size	Info
hash	Hash
size	uint32	bit 1 << 30 indicates the file has the opposite compression of the archive bit 1 << 31 indicates if the file has been checked yet (internal usage)
offset	uint32	bit 1 << 31 is used as a flag

File Data

Name	Type/Size	Info
v104/v105 only name bstring only present if "embedded file names" is set
decompressed size	uint32	only present if the file is compressed
data	uint8[...]

Hash

Name	Type/Size	Info
last	uint8
last2	uint8
length	uint8
first	uint8
crc	uint32

TES4 BSL Layout

File Structure

Name	Type/Size	Info
header	Header	same header, except tag is "BSL\x00"
root directory	dzstring
directory entries	Directory Entry[directory count]
file entries	File Entry[file count]

Directory Entry

Name	Type/Size	Info
file count	uint32
directory name	dzstring

File Entry

Name	Type/Size	Info
size	uint32	bits 1 << 31 and 1 << 30 are reserved for flags see also File Entry -> size
last write time	uint64	see also FILETIME
file name	dzstring

BA2 Layout

Files within BA2s are unsorted.

File Structure

Name	Type/Size	Info
header	Header
chunks	Chunk[file count]
file data	uint8[...]
strings	wstring[file count]

Header

Name	Type/Size	Info
magic	char[4]	"BTDX"
version	uint32	1/2/3/7/8
contents format	char[4]	"GNRL" / "DX10" / "GNMF"
file count	uint32
string table offset	uint64	absolute offset, 0 if not present
v2/v3 only unknown uint64 always set to 1, immediately discarded on load
v3 only compression format uint32 lz4 block format if present and set to 3, else zlib

Chunk

Name	Type/Size	Info
header	Chunk Header
data	Chunk Data[chunk count]

Chunk Header

Name	Type/Size	Info
id	Hash
data file index	uint8
chunk count	uint8
chunk header size	uint16	GNRL: 0x10 DX10: 0x18 GNMF: 0x30
DX10 Only height uint16 width uint16 mip count uint8 format uint8 flags uint8 tile mode uint8
GNMF Only metadata uint32[8] see also GNF

Chunk Data

Name	Type/Size	Info
data file offset	uint64	absolute offset
compressed size	uint32	0 if not compressed
decompressed size	uint32
DX10/GNMF Only mip first uint16 mip last uint16
sentinel	uint32	0xBAADF00D

Hash

Name	Type/Size	Info
file	uint32
extension	uint32
directory	uint32