Proto-Pack format Version 2.0

Header

name	type	description
magic	byte[16]	"ProtoPack\r\n2.0\n\0"

The header contains both types of new-lines, which is common in file headers to detect corruption caused by automatic new-line conversions. The header is followed by arbitrary number of variable-sized chunks. Chunks can be either object instance or type definition depending on the sign of the size field (encoded as protobuf's variable-length zigzag).

Object instance chunk (size>0)

name	type	description
size	sint32	Total size of the chunk excluding this size field.
parent	sint32	If >= 0: New root object instance. If < 0: Relative index of chunk which is the parent.
type	sint32	If > 0: Type index. The object has no children. If < 0: Negated type index if it may have children. If == 0: Terminates children list of the parent.
data	byte[]	Proto message.

Objects may form a tree. Parent object is specified as back-reference to previous chunk (-1 is the previous chunk). The referenced chunk must also be an object and it must allow addition of children. Values of parent>=0 define a root object. Values of parent>0 may be used in the future to add information to the root object.

Negated type index denotes object which may have children. The children list must be terminated by chunk with type==0. Object with positive type can not have children and does not need terminator.

As an optimization, if size is small enough to cover only the parent field, type field is implicitly set to 0 (i.e. it is list terminator).

Type definition chunk (size<0)

name	type	description
size	sint32	Negated total size of the chunk excluding this size field.
name	string	Fully qualified type name as proto string.
desc	byte[]	Proto descriptor of one message type of the given name.

The format is self-describing. All objects are stored as typed proto messages, where the type must be first described by type definition chunk. Types are assigned indices based on the order in the file (starting with 1).