RAW_LONGS_

The raw 64-bit (Longs) that constitute the representation of the string of 21-bit codepoints. Each long contains up to three codepoints occupying 21 bits each, in little-endian order. Only the last long can be incomplete, and is required to have zeros for the unused elements. The descriptor instances include the field unusedEntriesOfLastLong, which indicates how many (0-2) of the 21-bit subfields of the last long are unused.