Added KISS support

src/kiss.ts

@@ -0,0 +1,79 @@
+// KISS (Keep It Simple Stupid) frame reader/writer for AX.25
+// See: http://www.ax25.net/kiss.aspx
+
+export const KISS_FEND = 0xc0;
+export const KISS_FESC = 0xdb;
+export const KISS_TFEND = 0xdc;
+export const KISS_TFESC = 0xdd;
+
+export type KissFrame = {
+  port: number; // 0-15
+  command: number; // 0 = data, 1 = TX delay, etc.
+  data: Uint8Array;
+};
+
+// Encode a KISS frame (data only, port 0 by default)
+export function encodeKissFrame(data: Uint8Array, port = 0, command = 0): Uint8Array {
+  const out: number[] = [KISS_FEND];
+  // Command byte: upper 4 bits = port, lower 4 bits = command
+  out.push(((port & 0x0f) << 4) | (command & 0x0f));
+  for (const b of data) {
+    if (b === KISS_FEND) {
+      out.push(KISS_FESC, KISS_TFEND);
+    } else if (b === KISS_FESC) {
+      out.push(KISS_FESC, KISS_TFESC);
+    } else {
+      out.push(b);
+    }
+  }
+  out.push(KISS_FEND);
+  return Uint8Array.from(out);
+}
+
+// Decode a KISS frame (returns null if not a valid frame)
+export function decodeKissFrame(buf: Uint8Array): KissFrame | null {
+  if (buf.length < 3 || buf[0] !== KISS_FEND || buf[buf.length - 1] !== KISS_FEND) return null;
+  let i = 1;
+  const cmd = buf[i++];
+  const port = (cmd >> 4) & 0x0f;
+  const command = cmd & 0x0f;
+  const data: number[] = [];
+  while (i < buf.length - 1) {
+    const b = buf[i++];
+    if (b === KISS_FESC) {
+      const next = buf[i++];
+      if (next === KISS_TFEND) data.push(KISS_FEND);
+      else if (next === KISS_TFESC) data.push(KISS_FESC);
+      else return null; // Invalid escape
+    } else {
+      data.push(b);
+    }
+  }
+  return { port, command, data: Uint8Array.from(data) };
+}
+
+// Async generator to extract KISS frames from a stream of bytes
+export async function* kissFrameReader(source: AsyncIterable<Uint8Array>): AsyncGenerator<KissFrame> {
+  let buffer: number[] = [];
+  let inFrame = false;
+  for await (const chunk of source) {
+    for (const b of chunk) {
+      if (b === KISS_FEND) {
+        if (inFrame && buffer.length > 0) {
+          const frame = decodeKissFrame(Uint8Array.from([KISS_FEND, ...buffer, KISS_FEND]));
+          if (frame) yield frame;
+        }
+        buffer = [];
+        inFrame = true;
+      } else if (inFrame) {
+        buffer.push(b);
+      }
+    }
+  }
+}
+
+// Write a KISS frame to a sink (e.g., serial port)
+export async function kissFrameWriter(sink: (data: Uint8Array) => Promise<void>, frame: KissFrame) {
+  const buf = encodeKissFrame(frame.data, frame.port, frame.command);
+  await sink(buf);
+}