SCUMM/Technical Reference/Index File

From ScummVM :: Wiki
< SCUMM‎ | Technical Reference
Revision as of 12:46, 16 April 2007 by Sullivan (talk | contribs) (More information about V3/4 Index with examples)
Jump to navigation Jump to search

SCUMM Technical ReferenceSCUMM 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:


filenameSCUMM version
00.lfl / 000.lflV3/4
.000V5/6
.LA0V7/8


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

tbd.

Scumm 6

tbd.

Scumm 7

tbd.

Scumm 8

tbd.