DAT (Ever17)

Used in the following game(s):

• Ever17 (PC)

Structure

Header
Size	Content	Description
4Bytes	Magic/ID
4Bytes	File Count
8Bytes	Padding	0x00
Index
Size	Content	Description
4Bytes	Offset	Starts from zero.
4Bytes	File Size	Stored value is double the actual size
24Bytes	File name	Unused space will be padding (0x00).

Notes

The files inside saver.dat, sysvoice.dat, and wallpaper.dat for Ever17 have had a small chunk data obfuscated. From offset 0x1100 to 0x1200 (256 bytes), data has been modified which breaks/corrupts the file. To undo this modification requires generating numbers to subtract from each byte in the affected area.

To generate these numbers, start off by adding each character in the file name of the file in question together, byte-by-byte. For example: 'test' 0x74 0x65 0x73 0x74 = 0x1C0 and then truncate the number down to 1 byte so 0xC0. This would be the first difference number out of the 256. The rest of the numbers are generated by using the previous number in a series of calculations.

• 1.) temp = previousNum + (previousNum * 2)
• 2.) temp = temp + (temp * 8)
• 3.) nextNum = previousNum + (temp * 4) + 1243

Note: This can probably be optimized to one statement to make it more readable.

y = x + (((x + (x * 2)) + (x + (x * 2) * 8))* 4) + 1243

y = 81x + 1243

nextNum = (81 * previousNum) + 1243;

A C++ representation.

unsigned char diff_array[256];

void diff_gen(std::string &incoming_filename)
{
	char firstValue = 0;
	for (int i = 0; i < incoming_filename.size(); i++) //Better be 14 bytes... Though adding 0x00 shouldn't affect output.
	{
		firstValue += incoming_filename[i];
	}

	diff_array[0] = firstValue;

	for (int i = 1; i < 255; i++)
	{
                diff_array[i] = diff_array[i - 1] * 81 + 1243;
	}
}

Tools

-n/a-