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Data in Persister format does not mark itself to indicate their types, the types are assumed by the deserialization code. That is, a Portal being read in knows when to expect a boolean, a string, and an integer, for example. Without knowing what a Portal wants to read, it is not possible to determine where the next item begins.
During reading or writing, WorldsPlayer maintains 3 tables: Object table, Class table, Cookie table (for versions). These serve as a caching mechanism, so that objects can be reused and class names do not need to be repeated.
# Primitive data types
Worlds generally uses the format described by [Java's DataInput](https://docs.oracle.com/javase/7/docs/api/java/io/DataInput.html).
* String: Starts with a byte, where 0x01 means the string is null (and the next byte is for the next item) and 0x00 means non-null. If non-null, next 2 bytes are the length in number of bytes (big-endian). Following is the actual string data, in modified UTF-8. (The bytes after the non-null indicator are merely read by DataInput).
* Boolean: 1 byte, 0x00 for false 0x01 for true.
* Byte, Double, Long, Int, Float, Short: Self-explanatory
* Arrays, vectors, maybenulls: Explained below
* Versions (not applicable to Persister version): Either an integer or non-existent (already interned/cached). When WorldsPlayer tries to retrieve a version, it uses a "cookie", usually but not necessarily corresponding to a class. If that cookie has been used to retrieve a version before, the next time a version corresponding to that cookie is read, it will always be the same version. That is, if the first Room was read as version 3 (hypothetically), the next Room will also be version 3, without another indication directly in the file.
# Header and footer
* Persister files begin with the String "PERSISTER Worlds, Inc." (remember the 3 bytes at beginning), followed by an integer representing persister format version (7 seems to be latest), followed by an object.
* Persister files end with the String "END PERSISTER"
# Objects
Assuming empty class and object table, an object consists of an object ID (integer), a class ID (integer), class name (String), and then data as determined by the specific class.
## Example from GroundZero
| "PERSISTER Worlds, Inc." | Persister version | Object ID | Class ID | Class name |
| ------------------------ | ----------------- | --------- | -------- | ---------- |
| 0x00 0x00 0x16 "PERSISTER Worlds, Inc." | 0x00 0x00 0x00 0x07 | 0x00 0x00 0x03 0x67 | 0x00 0x00 0x02 0xE6 | 0x00 0x00 0x16 "NET.worlds.scape.World" |
|