maybe support encoded cameras

encode.ts

@@ -0,0 +1,41 @@
+const KEY_TABLE = new Uint8Array([
+  0x7c, 0x9c, 0xe8, 0x4a, 0x13, 0xde, 0xdc, 0xb2, 0x2f, 0x21, 0x23, 0xe4, 0x30, 0x7b, 0x3d, 0x8c, 0xbc, 0x0b, 0x27,
+  0x0c, 0x3c, 0xf7, 0x9a, 0xe7, 0x08, 0x71, 0x96, 0x00, 0x97, 0x85, 0xef, 0xc1, 0x1f, 0xc4, 0xdb, 0xa1, 0xc2, 0xeb,
+  0xd9, 0x01, 0xfa, 0xba, 0x3b, 0x05, 0xb8, 0x15, 0x87, 0x83, 0x28, 0x72, 0xd1, 0x8b, 0x5a, 0xd6, 0xda, 0x93, 0x58,
+  0xfe, 0xaa, 0xcc, 0x6e, 0x1b, 0xf0, 0xa3, 0x88, 0xab, 0x43, 0xc0, 0x0d, 0xb5, 0x45, 0x38, 0x4f, 0x50, 0x22, 0x66,
+  0x20, 0x7f, 0x07, 0x5b, 0x14, 0x98, 0x1d, 0x9b, 0xa7, 0x2a, 0xb9, 0xa8, 0xcb, 0xf1, 0xfc, 0x49, 0x47, 0x06, 0x3e,
+  0xb1, 0x0e, 0x04, 0x3a, 0x94, 0x5e, 0xee, 0x54, 0x11, 0x34, 0xdd, 0x4d, 0xf9, 0xec, 0xc7, 0xc9, 0xe3, 0x78, 0x1a,
+  0x6f, 0x70, 0x6b, 0xa4, 0xbd, 0xa9, 0x5d, 0xd5, 0xf8, 0xe5, 0xbb, 0x26, 0xaf, 0x42, 0x37, 0xd8, 0xe1, 0x02, 0x0a,
+  0xae, 0x5f, 0x1c, 0xc5, 0x73, 0x09, 0x4e, 0x69, 0x24, 0x90, 0x6d, 0x12, 0xb3, 0x19, 0xad, 0x74, 0x8a, 0x29, 0x40,
+  0xf5, 0x2d, 0xbe, 0xa5, 0x59, 0xe0, 0xf4, 0x79, 0xd2, 0x4b, 0xce, 0x89, 0x82, 0x48, 0x84, 0x25, 0xc6, 0x91, 0x2b,
+  0xa2, 0xfb, 0x8f, 0xe9, 0xa6, 0xb0, 0x9e, 0x3f, 0x65, 0xf6, 0x03, 0x31, 0x2e, 0xac, 0x0f, 0x95, 0x2c, 0x5c, 0xed,
+  0x39, 0xb7, 0x33, 0x6c, 0x56, 0x7e, 0xb4, 0xa0, 0xfd, 0x7a, 0x81, 0x53, 0x51, 0x86, 0x8d, 0x9f, 0x77, 0xff, 0x6a,
+  0x80, 0xdf, 0xe2, 0xbf, 0x10, 0xd7, 0x75, 0x64, 0x57, 0x76, 0xf3, 0x55, 0xcd, 0xd0, 0xc8, 0x18, 0xe6, 0x36, 0x41,
+  0x62, 0xcf, 0x99, 0xf2, 0x32, 0x4c, 0x67, 0x60, 0x61, 0x92, 0xca, 0xd3, 0xea, 0x63, 0x7d, 0x16, 0xb6, 0x8e, 0xd4,
+  0x68, 0x35, 0xc3, 0x52, 0x9d, 0x46, 0x44, 0x1e, 0x17,
+]);
+
+const ENC_KEY = new Uint8Array([0x69, 0x97, 0xcc, 0x19]);
+
+export const decode = (dv: DataView): DataView => {
+  let prevByte = 0;
+  let buf = new Uint8Array(dv.byteLength);
+  for (let i = 0; i < dv.byteLength; i++) {
+    const index = (ENC_KEY[prevByte & 0x03] + prevByte) & 0xff;
+    const origByte = dv.getUint8(i);
+    buf[i] = origByte ^ KEY_TABLE[index];
+    prevByte = origByte;
+  }
+  return new DataView(buf.buffer);
+};
+
+export const encode = (dv: DataView): DataView => {
+  let prevByte = 0;
+  let buf = new Uint8Array(dv.byteLength);
+  for (let i = 0; i < dv.byteLength; i++) {
+    const index = (ENC_KEY[prevByte & 0x03] + prevByte) & 0xff;
+    buf[i] = dv.getUint8(i) ^ KEY_TABLE[index];
+    prevByte = buf[i];
+  }
+  return new DataView(buf.buffer);
+};

handlers.ts

@@ -255,6 +255,7 @@ const deal_with_data = (session: Session, dv: DataView) => {
         // retransmit
         return;
       }
+      if (session.curImage.length == 0) return; // missed the start-of-frame packet
 
       let b = Buffer.from(data.buffer);
 
@@ -269,7 +270,7 @@ const deal_with_data = (session: Session, dv: DataView) => {
           return;
         }
 
-        if (session.curImage.length <= 1) return; // header does not have markers
+        if (session.curImage.length == 1) return; // header does not have markers
 
         let lastFrameSlice = session.curImage[session.curImage.length - 1];
         const lastResetMarker = findAllResetMarkers(lastFrameSlice).pop();

session.ts

@@ -1,6 +1,7 @@
 import { createSocket, RemoteInfo } from "node:dgram";
 import EventEmitter from "node:events";
 
+import { decode, encode } from "./encode.js";
 import { Commands, CommandsByValue } from "./datatypes.js";
 import {
   handle_Close,
@@ -32,6 +33,7 @@ export type Session = {
   frame_is_bad: boolean;
   frame_was_fixed: boolean;
   started: boolean;
+  encoded: boolean;
   close: () => void;
 };
 
@@ -46,7 +48,16 @@ type msgCb = (
 
 const handleIncoming: msgCb = (session, handlers, msg, rinfo) => {
   const ab = new Uint8Array(msg).buffer;
-  const dv = new DataView(ab);
+  let dv = new DataView(ab);
+  let firstByte = dv.readU8();
+  if (firstByte != 0xf1) {
+    dv = decode(dv);
+    firstByte = dv.readU8();
+    if (firstByte == 0xf1) {
+      // decoded into a legal command
+      session.encoded = true;
+    }
+  }
   const raw = dv.readU16();
   const cmd = CommandsByValue[raw];
   logger.log("trace", `<< ${cmd}`);
@@ -128,6 +139,9 @@ export const makeSession = (
         unackedDrw[packet_id] = { sent_ts: Date.now(), data: msg };
       }
       logger.log("trace", `>> ${cmd}`);
+      if (session.encoded) {
+        msg = encode(msg);
+      }
       sock.send(new Uint8Array(msg.buffer), ra.port, session.dst_ip);
     },
     ackDrw: (id: number) => {
@@ -139,6 +153,7 @@ export const makeSession = (
     rcvSeqId: 0,
     frame_is_bad: false,
     frame_was_fixed: false,
+    encoded: false,
     unackedDrw,
     close: () => {
       session.eventEmitter.emit("disconnect");

tests/encode.test.js

@@ -0,0 +1,33 @@
+import assert from "assert";
+import { buildLogger } from "../logger.js";
+
+import { decode, encode } from "../encode.js";
+
+const hstrToU8 = (hs) => new Uint8Array(hs.match(/../g).map((h) => parseInt(h, 16)));
+describe("encode/decode", () => {
+  it("decodes example", () => {
+    buildLogger("trace");
+    const pkt = "2ccb6293bf2321ed0ad7ea318106e0d5a28d800233207369";
+    const expected = "f141001444474f4100000000000e3f854e44424e44000000";
+    const pktbuf = hstrToU8(pkt);
+    const expbuf = hstrToU8(expected);
+
+    assert.deepEqual(decode(new DataView(pktbuf.buffer)), new DataView(expbuf.buffer));
+  });
+  it("encodes example", () => {
+    buildLogger("trace");
+    const pkt = "f141001444474f4100000000000e3f854e44424e44000000";
+    const expected = "2ccb6293bf2321ed0ad7ea318106e0d5a28d800233207369";
+    const pktbuf = hstrToU8(pkt);
+    const expbuf = hstrToU8(expected);
+
+    assert.deepEqual(encode(new DataView(pktbuf.buffer)), new DataView(expbuf.buffer));
+  });
+  it("roundtrips encode/decode", () => {
+    buildLogger("trace");
+    const pkt = "f141001444474f4100000000000e3f854e44424e44000000";
+    const pktbuf = hstrToU8(pkt);
+    const encoded = encode(new DataView(pktbuf.buffer));
+    assert.deepEqual(decode(encoded), new DataView(pktbuf.buffer));
+  });
+});