pray (thing)

PRAY files are files used by the Creatures Evolution Engine to store agents and other information. The online functionality of Docking Station works via the simple mechanism of transferring PRAY files over TCP/IP.

It replaces the COB file format used in Creatures and Creatures 2.

The game engine is usually used to generate these files via CAOS, although seperate tools are available to generate them (the official PRAYBuilder tool and my own Zeus tool).

PRAY files have many different file extensions, eg .agent for agents, .family/.creature/.creatures for creatures, .blueprint for blueprints and .warp for files sent over the "warp" in Docking Station.

The file format consists of the four-byte id which is "PRAY" in ASCII, followed by a set of blocks. Blocks are comprised of a Block Header followed by Block Data (the format of which is specific to a certain type of block).

The Block Header is made up of:

• a 4-byte block id which defines the type of the block
• an 128-name array of bytes where the name of the block is stored (the last character should be zero, and any other space left in the array should be padded with zeros).
• an "unsigned int" (4-byte) which defines the length (in bytes) of the Block Data for this block
• an "unsigned int" (4-byte) which defines the length (in bytes) of the Block Data after decompression for this block ... the same as the length if not compressed
• an "unsigned int" (4-byte) which contains flags. The only known bit is bit one, which is set if the block is compressed (using zLib). All other bits are unused and should be set to zero

If a program doesn't understand (ie can't handle) a certain type of block, it should just skip it (using the length provided in the block header) and continue.

There are two main types of block: a "standard" PRAY block and a "raw" PRAY block. They have lots of different four-byte block ids, depending on exactly what information is contained inside them.

Some common block ids (in ASCII) which use the "standard" PRAY block format are: AGNT, AUTH, EGGS, EXPC. Another useful block id is FILE, which is a "raw" PRAY block allowing you to embed whole files inside a PRAY file, where the block name is the filename, and the block data is the actual data inside the file.

The "standard" PRAY block consists of a number of pairs of "value names" and actual values (which can be integers or strings), and has a format as follows:

• an "unsigned int" (4-byte) containing the number of integer values in this block.
• the integer values, each one consisting of a CString followed by an "unsigned int" with the actual value.
• an "unsigned int" (4-byte) containing the number of string values in this block.
• the string values, each one consisting of a CString followed by another CString with the actual value.

(A CString is an "unsigned int" (4-byte) with the length of the string, followed by the string itself (non-null-terminated))

The information in this node was reverse-engineered by me a few weeks before the release of Creatures 3 and, while not guaranteed to be correct, has stood the test of time.