Cheat Engine

[dlpb]

Now, I can easily program this to load the entire file into memory. That's all well and good for small files. But with large files... they have to be loaded and written in chunks with a buffer.

The issue then is the boundaries between buffers.

Let's say we are searching for ABCD.

And our string is

XXXXXABCD

But, in this simplified buffer, let's say only 8 chars (remember, chars are equivalent to bytes) are loaded at a time.

XXXXXABC

Now, D is placed in the next buffer update. And my search will not find ABCD anymore. I've had a look around online, and there seems to be a lot of confusion about how best to tackle this issue.

So, any recommendations?

[Dark Byte]

Read a buffer from the file
Then scan it
When done decrease the read pointer by 7 and read another buffer (that will deal with the overlap)
Repeat till the end of the file is reached

Also, i recommend you look into filemapping

[dlpb]

I thought about doing that before, but wouldn't there be some issues if:

The change made, let's say, is AA to AAB...

Then...

when it goes back 7 places, the overlap may end up going over this change again, and replacing AAB (which it now is) with AABB. In other words, going back over the same part introduces another issue?

[Dark Byte]

The file you're reading from should not be the same file as you're writing to. So you are reading the unmodified file

But since your intent is to have the ability to change the filesize (I really hope it's not binary as that often will mess things up) then make a list of locations to change, and when done scanning write the file with the modifications at the proper locations. (you can only have a file open for either writing or reading anyhow)

[dlpb]

Yeah, I'm just giving people the freedom to edit any file. I will have 2 main functions... if the search and replace lengths are the same, it can be handled much easier. And of course, a file like an executable would always be equal length replacements.

I'll to use fmcreate when filesize changes.

There are times when you do want to change an exe length... like once, when I wanted to single out only bytes that Ascii text uses... but generally, no one will have any use for that.

I like doing things completely...

Anyway, cheers for that. Adding change indexes may just do it.

[dlpb]

Ok, rather than open a new thread, I am wondering if there is an easy way to do the following:

convert 4 chars to hex. Therefore

ÿÿÿÿ

would equal 4294967295

Because ÿ ansi value is 255.

Would I have to process each char (which I have done already in my own function), or is there a nifty delphi trick?

[justa_dude]

[Dark Byte]

Just use a pointer of a specific type like a pdword

You can also typecast on the fly from an incompatible type like a char array
E.g.

[dlpb]

you know, Dark Byte, I REALLY need to start paying attention to pointers... I guess it's easy to forgo their use for most things, and then forget how valuable they can be (Delphi does a lot of it for you so).

Thanks again