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INT File Format

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Format files in INT- Fallout

The paper describes the format of INT Files for Fallout and Fallout2. Information about this was obtained by analyzing source compiler scripts for Fallout2. Baseline compiler texts were obtained from the source compiler scripts for the game Klingon Academy. Compilers for the two games overlap by about 80%.

BackgroundEdit

INT files are compiled scripts, designed for animating the world of Fallout. They set the behavior of all objects on the maps, and are used to create dialogues with the characters in the game.

File FormatEdit

INT files consists of the following parts:

  • Script initialization code
  • A table of procedure descriptions
  • A list of the names of procedures and variables
  • A list of text strings
  • Script object initialization code
  • The body of procedures

Note: All numbers are stored in big-endian format (the most significant byte first).

Script Initialization CodeEdit

Script initialization code is for the transfer of control to script object initialization code and providing the correct procedure return addresses(?).

This part of an INT file should have a fixed size of 42 bytes, because that is the offset at which it looks for the table of procedures.


Table 2.1 - script initialization code

Offset Size Value Description
0x0000 2 bytes 0x8002 O_CRITICAL_START Start of 'Critical' code section.

(see 'script object initialization code')

0x0002 2 bytes 0xC001 O_INTOP Return address of 'start' procedure
0x0004 4 bytes 0x00000012 INT (0x00000012)
0x0008 2 bytes 0x800D O_D_TO_A Entry return address of the 'start' procedure in the stack addresses
0x000A 2 bytes 0xC001 O_INTOP Starting address of script object initialization code
0x000C 4 bytes ...
0x0010 2 bytes 0x8004 O_JMP Jump to script object initialization code
0x0012 2 bytes 0x8010 O_EXIT_PROG The specific function of each opcode is not entirely clear.

Apparently they support the correct completion of initialization scripts.

0x0014 2 bytes 0x801A O_POP
0x0016 2 bytes 0x8020 O_POP_FLAGS_RETURN
0x0018 2 bytes 0x801A O_POP
0x001A 2 bytes 0x8021 O_POP_FLAGS_EXIT
0x001C 2 bytes 0x801A O_POP
0x001E 2 bytes 0x8022 O_POP_FLAGS_RETURN_EXTERN
0x0020 2 bytes 0x801A O_POP
0x0022 2 bytes 0x8023 O_POP_FLAGS_EXIT_EXTERN
0x0024 2 bytes 0x8024 O_POP_FLAGS_RETURN_VAL_EXTERN
0x0026 2 bytes 0x8025 O_POP_FLAGS_RETURN_VAL_EXIT
0x0028 2 bytes 0x8026 O_POP_FLAGS_RETURN_VAL_EXIT_EXTERN

Table of proceduresEdit

The table of procedures contains information about all the available procedures in an INT file.

It should be noted that the first procedure in INT files is a procedure named '..............' (14 periods). This procedure does not have a body, and is designed to make indices of procedures start at 1, not 0.


Table 2.2-Table of procedures

Offset Size Description
0x0000 4 bytes The number of procedures in the table
0x0004 4 bytes Entry0 Name procedure (offset in the list of names).
0x0008 4 bytes Set flags according to the type of procedure.
P_TIMED       = 0x01 - Timed (delayed?) procedure
P_CONDITIONAL = 0x02 - Conditional procedure
P_IMPORT      = 0x04 - Imported procedure
P_EXPORT      = 0x08 - Exported procedure
P_CRITICAL    = 0x10 - Critical procedure 

Note:

Creating timed and conditional procedures is not entirely understood. It is also not clear if they are used at all in Fallout.

Because of a bug in the original BIS compiler cannot compile conditional procedures.

0x000C 4 bytes The delay in milliseconds for timed procedures
0x0010 4 bytes The position in the file code expressing conditions for conditional procedures (the offset from the beginning of the file).
0x0014 4 bytes The position in the file of the function body (offset from the beginning of the file).
0x0018 4 bytes The number of arguments of the procedure
... ... ... ...
Note: The offset in the table given from the beginning of the table of procedures, not the start of the file.

List of procedure and variable namesEdit

This part of the INT file contains the names of script variables and procedures. It does not include the names of local variables declared within procedures.

Some information in this section may be redundant, since referring to global variables is done by index, not by name.


Table 2.3. List of names of procedures and variables

Offset Size Value Description
0x0000 4 bytes totalSize Size of the list of names, except the ending, in bytes.
0x0004 2 bytes length0 The length of name 0, including the null (zero) terminator, in bytes.

Note:

Length 'object name' MUST be EVEN. Otherwise, the INT file becomes unexecutable.

0x0006 length0 bytes 'Name 0'

A string of ASCII characters ending with a null (zero) byte. Another null will be added if necessary to make the total length of the string even.

... ... ... ...
totalSize 4 bytes 0xFFFFFFFF Indicates the end of the list.
Note:

The offset in the table are given from the beginning of the list of names, not the start of the file.

The addresses of names/strings are specified using offsets from the beginning of the list and point to the first character of the string, not its length.

List of stringsEdit

This part of the INT file contains all the string constants used in the script. The format is the same as the list of procedure and variables. It is possible for this section to be empty (i.e. no strings are used).

Script object initialization codeEdit

This part of the script is to initialize global script variables, export and initialize variables, export procedures, and moving to the 'start' procedure (or returning to the script initialization code if there isn't one).


Table 2.5. Script object initialization code

Offset Size Value Description
0x0000 2 bytes 0x802C O_SET_GLOBAL The specific meaning of this opcode is not entirely clear.

Possibly for switching to the global script stack.

0x0002 2 bytes 0x9001

0xA001 0xC001

O_STRINGOP

O_FLOATOP O_INTOP

Variable Type Global variable 0
0x0004 4 bytes value0 Value of variable
... ... ... ... ... ...
2 bytes 0x9001 O_STRINGOP Variable name Exports variable named name0
4 bytes name0
2 bytes 0x8016 O_EXPORT_VAR Exports variable
... ... ... ... ... ...
2 bytes 0x9001

0xA001 0xC001

O_STRINGOP

O_FLOATOP O_INTOP

Type of assigned value Assigns the value value0 to the external variable name0
4 bytes value0 Value
2 bytes 0x9001 O_STRINGOP Variable name
4 bytes name0
2 bytes 0x8015 O_STORE_EXTERNAL Assign to external variable
... ... ... ... ... ...
2 bytes 0xC001 O_INTOP The number of arguments for the procedure Export the procedure 'name_p'
4 bytes numArgs
2 bytes 0x9001 O_STRINGOP Procedure name
4 bytes name_p
2 bytes 0x8017 O_EXPORT_PROC Export procedure
... ... ... ... ... ...
2 bytes 0xC001 O_INTOP Variable name The number of arguments for the 'start' procedure.
4 bytes 0 INT (0)
2 bytes 0x8003 O_CRITICAL_DONE End of 'Critical' code section

(see 'script initialization code').

2 bytes 0xC001 O_INTOP Address transition The transition to the procedure 'start', and or return to the script initialization code if there isn't one
4 bytes address off the 'start' procedure

or

0x00000012

2 bytes 0x8004 O_JMP The jump to the 'start' procedure or return to script initialization code

Body of procedure codeEdit

This part of the INT file contains a sequence of opcodes implementing the procedures of the script.

Discussion of the meaning of opcodes and their arguments is beyond the scope of this paper.

Original file taken from TeamX documentation

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