Also fix MIME header parsing in JavaScript, read issue #1403

dev/Mime/Encoding.js

@@ -0,0 +1,35 @@
+const
+	QPDecodeParams = [/=([0-9A-F]{2})/g, (...args) => String.fromCharCode(parseInt(args[1], 16))];
+
+export const
+	// https://datatracker.ietf.org/doc/html/rfc2045#section-6.8
+	BDecode = atob,
+
+	// unescape(encodeURIComponent()) makes the UTF-16 DOMString to an UTF-8 string
+	BEncode = data => btoa(unescape(encodeURIComponent(data))),
+/* 	// Without deprecated 'unescape':
+	BEncode = data => btoa(encodeURIComponent(data).replace(
+		/%([0-9A-F]{2})/g, (match, p1) => String.fromCharCode('0x' + p1)
+	)),
+*/
+
+	// https://datatracker.ietf.org/doc/html/rfc2045#section-6.7
+	QPDecode = data => data.replace(/=\r?\n/g, '').replace(...QPDecodeParams),
+
+	// https://datatracker.ietf.org/doc/html/rfc2047#section-4.1
+	// https://datatracker.ietf.org/doc/html/rfc2047#section-4.2
+	// encoded-word = "=?" charset "?" encoding "?" encoded-text "?="
+	decodeEncodedWords = data =>
+		data.replace(/=\?([^?]+)\?(B|Q)\?(.+?)\?=/g, (m, charset, encoding, text) =>
+			decodeText(charset, 'B' == encoding ? BDecode(text) : QPDecode(text))
+		)
+	,
+
+	decodeText = (charset, data) => {
+		try {
+			// https://developer.mozilla.org/en-US/docs/Web/API/Encoding_API/Encodings
+			return new TextDecoder(charset).decode(Uint8Array.from(data, c => c.charCodeAt(0)));
+		} catch (e) {
+			console.error({charset:charset,error:e});
+		}
+	};