If unpack_one : ('a, 'state) unpack, then unpack_one ~state ~buf ~pos ~len must unpack at most one value of type 'a from buf starting at pos, and not using more than len characters. unpack_one must return one the following:

create_bin_prot reader returns an unpack buffer that unpacks the "size-prefixed" bin_prot encoding, in which a value is encoded by first writing the length of the bin_prot data as a 64-bit int, and then writing the bin_prot data itself.

is_empty returns true if all the data fed into t has been unpacked into values; false if t has unconsumed bytes or partially unpacked data. is_empty returns an error if t has encountered an unpacking error.

feed t buf ?pos ?len adds the specified substring of buf to t's buffer. It returns an error if t has encountered an unpacking error.

unpack_into t q unpacks all the values that it can from t and enqueues them in q. If there is an unpacking error, unpack_into returns an error, and subsequent feed and unpack operations on t will return that same error -- i.e. no more data can be fed to or unpacked from t.

unpack_iter t ~f unpacks all the values that it can from t, calling f on each value as it's unpacked. If there is an unpacking error (including if f raises), unpack_iter returns an error, and subsequent feed and unpack operations on t will return that same error -- i.e., no more data can be fed to or unpacked from t.

Behavior is unspecified if f operates on t.

debug controls whether invariants are checked at each call. Setting this to true can make things very slow.