SCUMM/Technical Reference/Index File

SCUMM Technical Reference → SCUMM index file

Introduction

Most of the information below are retrieved from the LucasHacks! site and from the Pascal source code of the IndexFileReader 1.2 (written by Ben Gorman (Bgbennyboy, http://quick.mixnmojo.com). In addition, ScummRevisited (written by Jimmi Thøgersen (Serge), http://www.mixnmojo.com/scumm/scummrev) turned out to be very useful in verifying the found offsets.

The SCUMM index file contains special information to allow quick random access to the resources in the other game files. It also includes the room names and some max limits for the game. The following filenames are used:

filename	SCUMM version
00.lfl / 000.lfl	V3/4
.000	V5/6
.LA0	V7/8

Version 1 to 3 use hardcoded offsets and cannot be treated that easily. For the other games, the index file can be used to determine the SCUMM version because there have been slight changes in each version.

• Version 4: the 5th and 6th byte match RN or OR
• Version 5: RNAM xor'ed with 0x69 at the beginning of the file, next 4 byte integer xor'ed with 0x69 is > 9
• Version 6: RNAM xor'ed with 0x69 at the beginning, next 4 byte integer xor'ed with 0x69 is 9 (actually it's the size of the chunk. In V6 games, no room names are stored so the size is 4 bytes (header) + 4 bytes (size) + 1 byte for the termination character).
• Version 7: RNAM at the beginning of the file (not xor'ed this time), next 4 bytes result in BE integer 9. (NOTE: must be verified!)
• Version 8: RNAM at the beginning of the file, next 4 bytes integer is > 9

Conventions

As usual, the endianness (Wikipedia) is important. Unless stated, little endianess (LE) is used. BE is used as abbreviation for big endianness.

A Chunk is a named part of the file, e.g. RNAM. Each chunk has a header that contains at least the chunk name and its size. The following chunks are available:

RNAM Room Names	In V5+
MAXS Maximum Values	In V5+
DROO Directory of Rooms	In V5+
DRSC Direcory of Room Scripts	In V8
DSCR Directory of Scripts	In V5+
DSOU Directory of Sounds	In V5+
DCOS Directory of Costumes	In V5+
DCHR Directory of Charsets	In V5+
DOBJ Directory of Objects	In V5+
AARY List of Arrays	In V6+
ANAM Animation Names?	In V7
RM Room Names	In V3/4
0R Directory Of Rooms	In V3/4
0S Directory Of Scripts?	In V3/4
0N Directory Of Sounds?	In V3/4
0C Directory Of Costumes?	In V3/4
0O Directory Of Objects?	In V3/4

Scumm 3/4

• File's aren't xor'ed
• Block Size does not include the 6 bytes used up by Block Name and Block Size, it's the size of the data that follows.

To read in the data, the following pseudo-code can be used:

Read Number of Items
FROM 1 to "Number of Items" DO
  Read subvalue 1
  Read subvalue 2
END

RN - Room names

Block Size         (4 bytes)
Block Name         (2 bytes)
  #Room No         (1 byte)
  #Room Name       (9 bytes) XOR'ed with FF
Blank (00) byte    (1 byte) Marks end of chunk

0R - Directory of Rooms

Block Size         (4 bytes)
Block Name         (2 bytes)
No of items        (2 bytes)
  File Number      (1 byte)
  Offset           (4 bytes)

File Number is interesting if a game is splitted on multiple disks. 0 means not used.

For Offset only the value 0 seems to be used.

0S - Directory of Scripts

Block Size         (4 bytes)
Block Name         (2 bytes)
No of items        (2 bytes)
  Room Number      (1 byte)
  Offset           (4 bytes)

The global scripts are stored in this directory. The offsets are relative to the room.

0N - Directory of Sounds

Block Size         (4 bytes)
Block Name         (2 bytes)
No of items        (2 bytes)
  Room Number      (1 byte)
  Offset           (4 bytes)

Similar to scripts but holds indexes for sounds.

0C - Directory of Costumes

Block Size         (4 bytes)
Block Name         (2 bytes)
No of items        (2 bytes)
  Room Number      (1 byte)
  Offset           (4 bytes)

Similar to scripts but holds indexes of customes.

0O - Directory of Objects

Block Size         (4 bytes)
Block Name         (2 bytes)
No of items        (2 bytes)
  Owner+state      (1 byte)

The Object owner and state are encoded in one byte. Example:

0xA2      → Owner = 0xA, State = 0x2

The pseudo decode code would be:

Owner   = ( (Owner+state Byte) AND 0xF0) >> 4
State   =   (Owner+state Byte) AND 0x0F

Scumm 5

• The files are xor'ed with 0x69

RNAM - Room Names

Block Name	  (4 bytes)
Block Size	  (4 bytes BE)
 #Room No	  (1 byte)
 #Room Name	  (9 bytes) XOR'ed with FF

Blank (00) byte (1 byte) Marks end of chunk

MAXS

Block Name	   (4 bytes)
Block Size	   (4 bytes BE)
Variables	   (2 bytes)
Unknown	   (2 bytes)
Bit Variables	   (2 bytes)
Local Objects	   (2 bytes)
Unknown	   (2 bytes)
Character Sets	   (2 bytes)
Unknown	   (2 bytes)
Unknown	   (2 bytes)
Inventory Objects (2 bytes)

DROO - Directory of Rooms

Block Name (4 bytes) Block Size (4 bytes BE) No of items (2 bytes)

*Room Number	(1 byte)
*Offset	(4 bytes)

The flow how to read in this kind of information has changed slightly from V3/4.

Read "No of items"
FROM 1 TO "No of items" DO
   Read "Room Number"
END

FROM 1 TO "No of items" DO
   Read "Offset"
END

First read in all room numbers, then read in all room offsets.

DSCR - Directory of Scripts

Block Name	(4 bytes)
Block Size	(4 bytes BE)
No of items	(2 bytes)
 *Room Number	(1 byte)
 *Offset	(4 bytes)

Indexes for global scripts, see pseudo code above on how to read in the data.

DSOU - Directory of Sound

Block Name	(4 bytes)
Block Size	(4 bytes BE)
No of items	(2 bytes)
 *Room Number	(1 byte)
 *Offset	(4 bytes)

Indexes for sound objects.

DCOS - Directory of Costumes

Block Name	(4 bytes)
Block Size	(4 bytes BE)
No of items	(2 bytes)
 *Room Number	(1 byte)
 *Offset	(4 bytes)

Indexes for costumes

DCHR - Director of Charsets

Block Name	(4 bytes)
Block Size	(4 bytes BE)
No of items	(2 bytes)
 *Room Number	(1 byte)
 *Offset	(4 bytes)

Indexes for charsets.

DOBJ - Directory of Objects

Block Name	  (4 bytes)
Block Size	  (4 bytes BE)
No of items	  (2 bytes)
 *Owner+state    (1 byte)

Information about objects. See remarks in V3/4 section how the value should be interpreted.

Scumm 6

tbd.

Scumm 7

tbd.

Scumm 8

tbd.