Survival-Project-Images-Reader-Writer

A console interface that allows the user to unpack the PAK file of the game Survival Project and pack it back

Survival project's images are packed using two files - image.idx and image.pak.

image.pak contains the data itself while image.idx contains pointers to the data in the pak file.

Usage

-e PATH to extract the PAK file. PATH must contain image.idx and image.pak

-p PATH to pack into a PAK file. PATH needs to be the extracted images folder

image.idx file format

Header

26 bytes - The packer version

4 bytes - The PAK file size in bytes

4 bytes - The IDX file size in bytes

4 bytes - Total number of files

Then a list of files follows.

Each file has the following fields

4 bytes - Checksum of the file name (below).

255 bytes - File name

4 bytes - File size

4 bytes - File offset in the PAK file

image.pak file format

38 bytes - not used

Then a list of files follows. Each file is simply the binary data of the file (the size and offset of each file appears in the image.idx file).

Checksum calculation

In order to repack the image.idx file, one needs to calculate the correct checksum of each file. The checkname is calculated using the file name as follows:

private static uint ComputeChecksum(string fileName)
{
  uint v2 = 0;
  uint v3 = 0;
  
  for (int i = 0; i < fileName.Length; i++)
  {
    var v5 = fileName[i];
    v3 = (v5 | (v3 << 8)) % 0xFFFFFD;
    v2 ^= v5;
  }

  return v3 | (v2 << 24);
}