Port SMPP definitions: constants, errors, encodings and wire types

src/defs/encodings.ts

@@ -0,0 +1,124 @@
+export type EncodingName = 'ASCII' | 'FLASH' | 'LATIN1' | 'UCS2';
+
+export type Encoding = {
+	decode: (buffer: Uint8Array) => string;
+	encode: (value: string) => Buffer;
+	match: (value: string) => boolean;
+};
+
+const gsmChars =
+	'@£$¥èéùìòÇ\nØø\rÅåΔ_ΦΓΛΩΠΨΣΘΞ\x1BÆæßÉ !"#¤%&\'()*+,-./0123456789:;<=>?¡ABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÑܧ¿abcdefghijklmnopqrstuvwxyzäöñüà';
+
+const gsmRegex =
+	/^[@£$¥èéùìòÇ\nØø\rÅåΔ_ΦΓΛΩΠΨΣΘΞ\x1BÆæßÉ !"#¤%&'()*+,\-./0-9:;<=>?¡A-ZÄÖÑܧ¿a-zäöñüà\f^{}\\[~\]|€]*$/;
+
+const gsmExtended = /[\f^{}\\[~\]|€]/g;
+const gsmEscaped = /\x1B([\nΛ()/<=>¡e])/g;
+
+const gsmCharCodes = new Map<string, number>();
+const gsmExtChars = new Map<string, string>();
+
+for (let i = 0; i < gsmChars.length; i++) {
+	gsmCharCodes.set(gsmChars[i], i);
+}
+
+{
+	const from = '\f^{}\\[~]|€';
+	const to = '\nΛ()/<=>¡e';
+
+	for (let i = 0; i < from.length; i++) {
+		gsmExtChars.set(from[i], to[i]);
+		gsmExtChars.set(to[i], from[i]);
+	}
+}
+
+const ascii: Encoding = {
+	decode(buffer) {
+		let result = '';
+
+		for (const byte of buffer) {
+			result += gsmChars[byte] ?? ' ';
+		}
+
+		return result.replace(gsmEscaped, (match, escaped: string) => gsmExtChars.get(escaped) ?? match);
+	},
+
+	encode(value) {
+		const escaped = value.replace(gsmExtended, match => `\x1B${gsmExtChars.get(match) ?? ''}`);
+		const result: number[] = [];
+
+		for (const char of escaped) {
+			result.push(gsmCharCodes.get(char) ?? 0x20);
+		}
+
+		return Buffer.from(result);
+	},
+
+	match(value) {
+		return gsmRegex.test(value);
+	},
+};
+
+const latin1: Encoding = {
+	decode(buffer) {
+		return Buffer.from(buffer).toString('latin1');
+	},
+
+	encode(value) {
+		return Buffer.from(value, 'latin1');
+	},
+
+	// Deliberately never selected by detect(); Latin-1 is decoded when a peer asks for it, never
+	// chosen for outgoing messages.
+	match() {
+		return false;
+	},
+};
+
+const ucs2: Encoding = {
+	decode(buffer) {
+		return Buffer.from(buffer).swap16().toString('utf16le');
+	},
+
+	encode(value) {
+		return Buffer.from(value, 'utf16le').swap16();
+	},
+
+	match() {
+		return true;
+	},
+};
+
+export const encodings: Record<EncodingName, Encoding> = {
+	ASCII: ascii,
+	FLASH: ascii,
+	LATIN1: latin1,
+	UCS2: ucs2,
+};
+
+export function detect(value: string): EncodingName {
+	if (encodings.ASCII.match(value)) return 'ASCII';
+	if (encodings.LATIN1.match(value)) return 'LATIN1';
+
+	return 'UCS2';
+}
+
+/**
+ * SMPP data_coding is a flat table for 0x00-0x0E, but the 0x1X and 0xFX ranges carry a GSM message
+ * class and encode the alphabet in bits 3-2 (or bit 2) instead — which is how a flash UCS2 message
+ * arrives as 0x18. Alphabets with no codec here fall back to ASCII.
+ */
+export function encodingByDataCoding(dataCoding: number): EncodingName {
+	if ((dataCoding & 0xF0) === 0x10) {
+		return ((dataCoding >> 2) & 0x03) === 0x02 ? 'UCS2' : 'ASCII';
+	}
+
+	if ((dataCoding & 0xF0) === 0xF0) {
+		return 'ASCII';
+	}
+
+	if (dataCoding === 0x03) return 'LATIN1';
+	if (dataCoding === 0x08) return 'UCS2';
+
+	return 'ASCII';
+}