Guess the character set of a base64-encoded byte buffer: sniffs a byte-order mark, then falls back to ASCII / UTF-8 validation and a UTF-16 NUL-pattern heuristic. Returns a best-effort charset with a confidence label — a low-confidence guess is still a successful 200.

Break a string into its Unicode code points, each with its U+ notation, decimal value and UTF-8 / UTF-16 byte layout, plus total byte lengths.

Apply a Unicode normalisation form (NFC, NFD, NFKC or NFKD) to a string. Reports whether the text changed and its length in UTF-16 code units and code points.

Decode a base64 byte buffer from one character set and re-encode it into another (utf-8, utf-16le, utf-16be, latin1, ascii). Characters that the target set cannot represent, or bytes invalid for the source set, are clean 400s.