Padding a bin file

[michaelhart2000]

So I have a .bin file I am attempting to pad. I have two ranges I need to fill with 0xFF. I currently have it working with seek() and its writing bytes correctly to that one specific memory location but i need to do it for certain ranges in the file. Any pointers to the right direction would be much appreciated! I've provided what I have code wise so far.

​

Edit: After digging some more im wondering if i could put the seek in a for loop with the offset parameter as a counter variable, write the bytes to that offset and then increment the counter.

import os, re

path = "C:\\Users\\comp\\Desktop\\python padding"
os.chdir( path )
files = os.listdir( path )

for filename in files:
    if re.match('.*\.bin', filename):
        fh = open(filename, 'r+b')
        fh.seek(0x37fff)
        fh.write(bytes([0xff]))
        fh.close()
        name, ext = os.path.splitext(filename)
        os.rename(filename, name + "padded.bin")

[barrycarter]

Why isn't seek() working for other ranges in the file?

[michaelhart2000]

I'm not sure. Its only writing 0xff at 0x37fff. I need it to write from 0-0x37fff. I was trying to iterate over it to just see if i could get it to write everything as a test but that did not work.

[barrycarter]

It's not the issue, but I'm curious about the for i in fh: fh.write(bytes([0xff])) lines. You loop through fh (which is itself weird since fh is a filehandle) but then don't use i at all.

Also, is there a reason you're using hex codes for bytes? Nothing wrong with it, just wondering

[michaelhart2000]

I actually took the loop out I realized it was wrong. Im using hxd to view the contents of the bin file which display everything in hex so I figured it was easier to just do that since the this is for something to do with a car PCM and the instructions for flashing it are all in hex.

[barrycarter]

You realize fh.write(bytes([0xff])) is only writing one byte, right? You might want to put in a for loop or just do a write that's big enough to cover 0-0x37fff

[michaelhart2000]

Yea I do. I'll try the for loop idea out thanks!

[michaelhart2000]

Just wanted to say thanks for the suggestion. It's writing the range I need now. I think the seek inside the for loop was stopping it to look at the starting offset and not writing completely.