start work on lora ingest app

lora/LoraStream.js

@@ -0,0 +1,60 @@
+import { Transform } from 'stream';
+
+export class LoraStream extends Transform {
+    constructor(options) {
+        super(options);
+        this.byteBuffer = new Uint8Array([]);
+        this.textDecoder = new TextDecoder();
+    }
+
+    _transform(chunk, encoding, callback) {
+        this.byteBuffer = new Uint8Array([
+            ...this.byteBuffer,
+            ...chunk,
+        ]);
+        let processingExhausted = false;
+        while (this.byteBuffer.length !== 0 && !processingExhausted) {
+            const framingIndex = this.byteBuffer.findIndex((byte) => byte === 0x94);
+            const framingByte2 = this.byteBuffer[framingIndex + 1];
+            if (framingByte2 === 0xc3) {
+                if (this.byteBuffer.subarray(0, framingIndex).length) {
+                    this.byteBuffer = this.byteBuffer.subarray(framingIndex);
+                }
+                const msb = this.byteBuffer[2];
+                const lsb = this.byteBuffer[3];
+                if (msb !== undefined && lsb !== undefined && this.byteBuffer.length >= 4 + (msb << 8) + lsb) {
+                    const packet = this.byteBuffer.subarray(4, 4 + (msb << 8) + lsb);
+      
+                    const malformedDetectorIndex = packet.findIndex(
+                      (byte) => byte === 0x94,
+                    );
+                    if (malformedDetectorIndex !== -1 && packet[malformedDetectorIndex + 1] === 0xc3) {
+                        // malformed
+                        this.byteBuffer = this.byteBuffer.subarray(malformedDetectorIndex);
+                    } else {
+                        this.byteBuffer = this.byteBuffer.subarray(3 + (msb << 8) + lsb + 1);
+                        this.push(packet);
+                    }
+                } else {
+                    /** Only partioal message in buffer, wait for the rest */
+                    processingExhausted = true;
+                }
+            } else {
+                /** Message not complete, only 1 byte in buffer */
+                processingExhausted = true;
+            }
+        }
+
+        callback();
+    }
+    _flush(callback) {
+        try {
+          if (this._buffer) {
+            this.push(this._buffer.trim());
+          }
+          callback();
+        } catch (err) {
+          callback(err);
+        }
+    }
+}