Decoding NWN memory - Part 1 - Basics

[isilweo]

In last half year i've done some research on nwn scturctures in memory. I'll post my findings here cause they're useful and

if i get sucked by time hole (which happens sometimes) someone can make something out of them.

In the first part of my decoding memory series i'll focus on basics and describe most basic structures used by nwn. First of

all some most basic types that i'll used later

byte (or "b") - 1byte :) 1 cell of memory
int - 4b. integer. i'll asume it is unsigned
pointer - int (4b) - it holds address to something else (points for it)

and now simple structures. the structure notation i'll use is diffrent than in c++ but it's easier to imagine how data is

placed in memory.

SNWString - most (or all) strings in memory have this structure

//structure presented in my way
SNWString:
int ValuePointer;
int size;


struct SNWString //c-like
{
char * stringValue;
int stringSize;
};

this structure in memory looks like this:
36 08 00 07 05 00 00 00
it means that first int is pointer to string. It points to address 0x07000836. the second int is string size.
Note that the thing which is where valuePointer points is array of chars BUT it's is not said it's null-terminated string.

Sometimes it'll have \0 on the end and sometimes not (resrefs's don't have 0 and ie Names have). Note also that \0 is counted

in size if it's there and it's not counted if it's not there.



Arrays
Before all arrays there is always a simple structure

SArrayPointer:
int PointerToFirstElement
int NumberOfElements

you probably noticed that SNWString is exactly array of type char.
Array elements are placed one after another without any spacer bytes.

array of pointers - basicly array of ints. in memory it looks like this

Offset: 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

07808080: 90 80 80 07 05 00 00 00 //this is array pointer structure

07808090: A0 80 80 07 D0 90 30 07 20 34 32 08 48 0C 10 06
078080A0: Cc 84 40 07


in example above we have array of 5 pointers.
SArrayPointer's elements are:
pointer to first element - 07 80 80 90
number of array elements - 5

and then in 07808090 are 5 pointers.



Lists
List are a bit more complicated structures but are really simple (after you spend many hours looking at them in memory, where they're in complete disorder hehe)
List are used by nwn to store something that BW calls CExoLocString - that are names and descriptions in language sensitive string.

Before all lists we have simple structure with number of items and pointer to something i call PreList so:

SListPointer:
int pointerToSPreList
int NumberOfListElements

now if we follow our pointerToSPreList we'll have SPreList

SPreList:
int pointerToFirstElement
int pointerToLastElement
int NumberOfListElements

in above we have possibility to choose way we're going to loop through list (from begining or from end), and we have number of elements again. All elements of list have SListElement structure that is:

SListElement:
int pointerToPriorElement
int pointerToNextElement
int pointerToElementValue

Note that in first element pointerToPriorElement will be null (that is 00 00 00 00) and also in the last element pointerToNextElement will be null that's how you will know that you're at end (or begining). Before example just one more little structure

SLanguageString:
int LanguageId
sNWString LanguageString

i hope you remember (if not look at top of this post) that SNWString has to elements pointer and element count


To present example of list i'll use one more struct and it'll be important one

CExoLocString:
SListPointer PointerToList
int StrRef

if StrRef is FF FF FF FF it means that we'll have to look into PointerToList to search for string. If StrRef != FF FF FF FF we must lookup TLK files (dialog.tlk and user tlks if there are) to find string. And also if we look for string in TLK our SListPointer has 0 elements (but it always points somewhere).

Example of Lists on CExoLocString

[dragonsong]

Great stuff, please keep it coming.
_________________
- dragonsong