Payload's sub-header

Described below is the format of the 32-byte-long payload sub-header. This format is unique to v1.

Field	Type	Size (bytes)	Description
stored_size	uint	8	Compressed size, in bytes, of the records. If records are not compressed, stored_size is equal to plain_size.
plain_size	uint	8	Uncompressed size, in bytes, of records.
checksum	blob	8	Checksum of records, computed using XXH3_64bits.
num_records	uint	4	Number of records contained in the payload.
version	uint	2	Version of the payload data format. Unused.
record_kind	uint	1	Kind of records that the payload contains.
compression	uint	1	Compression algorithm used for the records.

record_kind

record_kind is an enum. The following table lists all possible values:

Value	Name
1	Meta
2	Content
3	Layout
4	Index
5	Attributes

compression

Value	Name
1	Uncompressed
2	Zstd