;; multi-index format?
Payload := Page*
Page := IdxHeader IdxEntry* Padding*
IdxHeader := [ 00 00 00 ] Severity
Severity := int8
Padding := [ 00 00 00 00 00 00 00 00 ]              --- EntryOffset is never 0
IdxEntry := EntryOffset HeaderLength MessageLength
EntryOffset := uint64                               --- byte offset from start of file
HeaderLength := uint32                              --- bytes in the entry's header, message starts at EntryOffset + HeaderLength
MessageLength := uint32