Save file format

This page describes the save format used by Arx Fatalis as well as Arx Libertatis extensions. All integers are encoded in little-endian byte order. Types are the same as in platform/Platform.h - s (signed integer) / u (unsigned integer) / f (float), followed by the number of bits.

Arx save file container (.sav)

Save files are stored in a generic container that maps names (arbitrary strings) to chunks of data. Arx Libertatis adds two extensions to the vanilla Arx Fatalis .sav format.

Header

The file header starts at byte position 0 - there is no magic number.

Type	Description
u32	File table offset

The file table offset is the location of the file table (in bytes) relative to the first byte after the header. Add 4 bytes to get the offset relative to the start of the file.

File table

The file table starts with a file table header:

File table header

Type	Description
u32	Format version
u32	Number of file entries

Currently, the following version numbers are defined.

Name	Value	Description
SAV_VERSION_LEGACY	0x00010000	Legacy version
SAV_VERSION_RELEASE	0x00010001	Current Arx Fatalis version
SAV_VERSION_DEFLATE	0x00020000	Added support for different compression algorithms (Arx Libertatis extension)
SAV_VERSION_NOEXT	0x00020001	Removed ".sav" suffix from internal filenames (Arx Libertatis extension)

The file table is followed by the specified number of file entries. For save files with version SAV_VERSION_LEGACY the first file entry should be ignored.

File table entry

Type	Description
null-terminated string	File name

Each file table entry is preceded by a null-terminated string - the file name. Versions older than SAV_VERSION_NOEXT store file names case-insensitively and append ".sav". When loading such versions, the filename should be converted to lowercase and the ".sav" extension removed.

For versions older than SAV_VERSION_DEFLATE:

Type	Description
u32	Stored (compressed) file size - This can be ignored and calculated from chunk sizes.
u32	Number of chunks - 0 means 1!
u32	Useless data. This can be safely ignored

For SAV_VERSION_DEFLATE and newer:

Type	Description
u32	Uncompressed file size
u32	Number of chunks
u32	Compression algorithm

Currently, the following version numbers are defined.

Value	Name	Description
0	Stored	No compression. Data is stored as-is.
1	ImplodeCrypt	Data is compressed using the PKWARE implode library. The result is bitwise negated.
2	Deflate	Data is compressed using the ZLIB deflate format.

Code to decompress PKWARE implode-encoded data can be found in blast.c in the contrib directory of the zlib tarball.

Versions older than SAV_VERSION_DEFLATE always use the ImplodeCrypt algorithm. To allow changing save files without not decompressing all data, the value 0xffffffff may be used to indicate that the uncompressed size is not known if (and only if) the compression algorithm is ImplodeCrypt.

The rest of the file entry is a list of as many chunk offsets as specified. For versions older than SAV_VERSION_DEFLATE, the actual number of chunks is always 1 or more, even if the file entry says 0. The concatenation of the chunks referenced by these offsets makes up the compressed file data.

Chunk offsets

Type	Description
u32	Chunk size
u32	Chunk offset

The chunk offset is the location of the chunk data (in bytes) relative to the first byte after the header. Add 4 bytes to get the offset relative to the start of the file. The chunk size is given in bytes. There is no guarantee that all parts of the .sav file are used in chunks or the file table.

Saved structures

TODO