An accessor designates a valid readable area in one of the pack files.

Accessors are meant to be used from within the Irmin_pack_unix implementation. Their validity is only checked at creation time, so they are not meant to be kept for a long time. (e.g. if kept over a GC finalisation, an accessor could no longer point to a valid area because the GC changes the domain of valid readable areas)

create_accessor_exn returns an accessor if off and len designate a readable area of the pack files, otherwise it raises one of Errors.Pack_error `Read_out_of_bounds, Errors.Pack_error (`Invalid_prefix_read _) and Errors.Pack_error (`Invalid_read_of_gced_object _).

create_accessor_from_maxlen_exn is similar to create_accessor_exn except that the precise length of the span will be decided during the call.

shrink_accessor_exn a ~new_len is a where the length is smaller than in a.

create_sequential_accessor_seq ~min_header_len ~max_header_len ~read_len returns a sequence of accessors, which simulates iterating sequentially trough the entries of a pack file. min_header_len & max_header_len represents the minimum & maximum lengths required to read the header of an entry. read_len will then be called with a buffer containing the header of the entry and should return the total length of the entry (the length of he header plus the length of the payload)

read_exn either reads in the prefix or the suffix file, depending on accessor.

end_offset is the end offsets of the pack entries, counting that the prefix doesn't start at 0. It counts the entries not yet flushed from the prefix.

offset_of_suffix_poff t suffix_off converts a suffix offset into a (global) offset.

Simlar to read_exn but if off + len is greater than the end of the prefix, it will read the remaining in the prefix.

create_accessor_to_prefix_exn mapping ~off ~len returns an accessor for the prefix file associated with mapping.