Constant MAX_COMPACT_DATA 

pub const MAX_COMPACT_DATA: usize = _; // 65_531usize

Bytes a compact dataset’s raw image may occupy.

H5D__compact_construct bounds it by H5O_MESG_MAX_SIZE less the layout message’s own four bytes (version, class, and the 2-byte data length). The constant it subtracts from is 65536, one past what the object header’s 2-byte message size field can express, so the ceiling here is taken from MAX_MESSAGE_SIZE — the largest message that actually encodes — and is one byte below libhdf5’s.