Cheat Engine

Gwinx

How can I read and write a huge file? I need to do it in a fast and efficient way.

HomerSexual · Posted: Sun Apr 01, 2012 10:28 pm Post subject:

You're at the mercy of the HDD basically. Standard file i/o should work fine but it's going to be slow because disk r/w is slow, comparatively

Dark Byte · Posted: Mon Apr 02, 2012 5:19 am Post subject:

Look into filemapping

Windows won't actually load the file into memory until you read a page of memory from the mapped memory that corresponds to the mapped file.

If you ARE going to read every single byte of the file in order (like a movie), you can tell windows it's going to get sequential reads so it'll optimize it (buffer ahead)

Gwinx · Posted: Mon Apr 02, 2012 6:13 pm Post subject:

Okay thanks. I will also have to quickly parse through it.

Dark Byte · Posted: Tue Apr 03, 2012 6:01 am Post subject:

Just noticed the size. If you're in 64-bit(and compile as 64-bit), use filemapping, it's perfect for quick parsing (loads the parts you need and has direct access to all of the file at once)

If you're in 32-bit you'll have to use small views of the map, which kinda breaks the usefulness. In that case I recommend writing a class that emulates this. (on accessing a byte of the virtual file cache in the data from the file and return a pointer to that)

(perhaps a class that does this already exists in the standard library, I don't know)