EAW_str_files_structure_explained

  

This document explains the structure of .str files used in EAW (European Air War)









The header structure

  

The first 8 bytes is @ a header, broken down into 2 x 4 byte sections that is to say the first 4 bytes of that header contain a number that is

the size of the file (records) in bytes

- 8 byte header

= the number









example 1a

  

Example; textmap1.str from EAW1.3stuff02.zip/EAW1.3stuff02/savedata folder is 58,743 bytes

in which the header first bytes contains the number (hexidecimal notation in this explaination will have the 0x prefix) 0xE56F 



which is in decimal the number: 58735

so 58,743

- 58735

 = 8 , the size of the header



TMS-1exx.jpg



  



header nodes section

  

Following the first 4 bytes of the header the next 4 bytes have a number which is the number of records or 'nodes'

in the case of same file above the number is 0x0DED which in decimal is 3565

the file contains 3565 records

these records (you can find in the bottom half of the file with a hex editor) are simply ascii text in this case names of various 



.tpc files, .ter files, .spt files

each text record is followed by a null 00 byte

including the last record. So the last byte in the file EOF byte is also a null 00





  



example 1b

  

in the case of same file above the number is 0x0DED which in decimal is 3565

the file contains 3565 records

these records (you can find in the bottom half of the file with a hex editor) are simply ascii text in this case names of various 



.tpc files, .ter files, .spt files

each text record is followed by a null 00 byte

including the last record. So the last byte in the file EOF byte is also a null 00





  



The node structure

  

after the 8 header bytes (2 x 4 bytes sections, including the header nodes section) as previously described), a series of  4 bytes for records or node pointers are found

each of these individual 4 byte nodes contain a number

the number is the jump location to the text record (always from the beginning of the file after the header)



TMS-ex-nodessectionstart.jpg









example 1c

  

in the case of textmap1.str file example above; the first node contains 0x37B4 which in decimal is 14260

If you set your cursor on the first byte there (B4) and jump 14260 down the file you are at the first text record byte the 

TMS-textrecordssection.jpg   


B(ascii 42) of BNcloud0.ter

Each node thereafter follows this same structure, 

but note that since text length of the text records that they point to can vary

so do will the number 

so in other words; the text records are not ex: a series of same length say; 8 bytes, and the file is not broken up into

ex: a series of  i * 8 bytes

(however each text record is terminated by a 0x '00' or 'null' byte) 

follow along in a hex editor:

next node: 0x37CE (aka decimal# 14286)

if you jump down 14286 (always from the beginning of the file after the 8 header bytes):

you find:  clouds.tpc

next 0x37D9 or 14297 jump down you find gun.spt

next 0x37E1 aka 14305 jump down to HWExplos.spt

- you notice those numbers?

14305

- 14297 = 8 

??? you might think.. yes! gun.spt = 7 bytes + a null 00 byte = 8 bytes..

So now you see the structure

other than the 8 header bytes the node pointers uses this structure

Examining the last node right before the first record text BNcloud0.ter the number is 0xE563 or 58723 jump down (again; 



always from beginning) you get to last record tgf255s.tpc





  





  



nodes section review

  

the nodes aka 'nodes pointer'  structure has been explained, but to be clear;

the entire section of the file (before the text records) contains

a series of nodes of 4 bytes each

there should be a node for each text record it points to









example 1d

  

in the case of the file the nodes header section has a number; 3565

3565 x 4 (4 btyes for each node)

= 14260

as explained in the example above that is where the text records start

so the entire nodes section containing the individual 4 byte nodes in the textmap1.str example is 

14260 bytes

if we jump down from the first node as we did, to the first text record byte the B(ascii 42) of BNcloud0.ter, (which is of course the start of the text records section) and then count the remaining bytes in the file, (that is the entire text record section), in this case is the number we get is 44 44,475 bytes

TMS-countbytes-texttoEOF.jpg  
 
 
  44475

+ 14260

= 58735 bytes

exactly the number as listed in the first header bytes

so in this case the entire nodes section as explained is 14260 bytes

it contains 3565 individual nodes of 4 bytes each

which is exactly the same as the number of text records 

(each text record is as many bytes as it takes to contain the ascii characters code for the letter,etc)

we can confirm this by jumping (as above) to the beginning of the text records then count the number of null (00)

bytes to the EOF which is: 3,565

 TMS-bytesfromtexttoEOF.jpg  






  





  





  



The text records section

  

following the entire node pointers section of individual nodes of 4 bytes each is the text records they point to

These are simple text ascii records you can view in a text editor like notepad, however they are terminated by a 0x '00' or 



'null' byte









example 1e

  

3565 individual text records as indicated by examples above





  





  



The end of the file (EOF) byte

  

following the last text record text (the EOF byte) the file terminated by a 0x '00' or 'null' byte



  TMS-at-EOF.jpg 





example 1f

  

so in the case of the textmap1.str file example above in a hex editor the last (12 bytes) record with EOF looks like this:

74 67 66 32 35 35 73 2E 74 70 63 00    which in the ascii or text section of a hex editor would be

  t    g    f   2   5   5   s   .     t   p    c (null)

in a simple text edior like notepad it looks like this:

tgf255s.tpc (a space would follow since notepad doesn't know how to render a null byte, but that space is not the same as 



the ascii character code for space which is 20)

some other editors might render the null as . or other oddities





  





  



Making .str files

  

You can't use notepad or a simple text editor to make a string file but with the old tools made by Paulo Morais like 



BUILDSTR.EXE and DUMPSTR.EXE you can dump and make .str files from text files.

Tony (MrJelly) West made some tools like like StrEdit128Vxx (various versions) DirSet maker (.set files - as of this writing 



- are just .str files just using the .set extension), OAW for 1.3 tools with PDir and FMdir.set maker.

I may have some tools package made available soon also.





  



Comments

  

That's it, the EAW .str files are explained.

Why these odd files? Has to do with easily using the same system with a program to access .str data records like an array. 



with pointers





  



Author

  

RAF_Roy

3/14/2012

Southern California, USA





  



Version

  

Version 1 - dated 3/15/2012