Segmented (.sd0/.si0)

To download content as needed from the server while playing the game, LEGO introduced a custom segmented file format. The actual files lived in Segmented Data (.sd0) files, while the compression process also generated Segmented Index (.si0) files to be used when creating the Catalog (.pki).

Segmented Data (.sd0)


There is a decompressor available, see the Tools section.

[L:5] - header, ‘s’-‘d’-‘0’-01-ff
[L:4] - length of compressed chunk
a chunk usually consists of 1024*256 uncompressed bytes
[L:V] - compressed (zlib) chunk

Segmented Index (.si0)

The first line is a header of the following form:


with the following data:

1) the file extension si0
2) the magic bytes 0x01 0xff as x01xff
3) the total size of the input
4) the MD5 hash of the input
5) the chunk size

The rest of the file is one line for every compressed block, in the following form:


with the following data:

1) start of the block in the raw file
2) size of the block
3) Adler32 of the raw bytes modulo 0xFFFFFFFF, as hex, with the first two and last letters removed
4) MD5 hash of the raw bytes
5) number of bytes already written to compressed file (without magic bytes)
6) number of compressed bytes
7) MD5 hash of compressed bytes