ReadonlycodeNumeric code page identifier.
ReadonlywebCanonical MIME charset name (C#: Encoding.WebName, lowercase).
Decode bytes; fatal=true throws on invalid input (C#: ExceptionFallback).
Optionalfatal: booleanNumber of replacement-triggering sequences when decoding non-fatally.
Encode text; only utf-8 / us-ascii / iso-8859-1 support this (plan Q3).
Small encoding abstraction used in place of .NET's Encoding type.