Documentation

The TXT resource record (RFC 1035 section 3.3.14) — a non-empty list of byte-strings, each at most 255 bytes long. Most TXT-record conventions (SPF, DKIM, DMARC, ...) concatenate the strings on read, but the wire format preserves the boundaries.

The constructor does not enforce the per-string 255-byte limit; encoding fails if any individual string exceeds it. Values decoded from wire form are always within the limit by construction.

The Ord instance compares the strings as DNS character-strings (length-prefixed lexicographic), agreeing with the canonical wire-form ordering of RFC 4034 section 6.2.

The HINFO resource record (RFC 1035 section 3.3.2) — host information: a CPU character-string and an OS character-string describing the named host's hardware and operating system. Rarely used in modern zone data; RFC 8482 reuses the type code as a placeholder answer for ANY queries.

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/                      CPU                      /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/                       OS                      /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

The Ord instance compares both fields as DNS character-strings, giving canonical ordering (RFC 4034 section 6.2).

The NULL resource record (RFC 1035 section 3.3.10) — arbitrary opaque bytes (up to 65535). Rarely seen on the wire; presented using the generic RFC 3597 section 5 syntax (\# n hex).

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/                  <anything>                   /
/                                               /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

Derived Ord is canonical (RFC 4034 section 6.2).