Added AMBE client

Author: rick51231

README.md

@@ -16,6 +16,7 @@ Motorola MotoTRBO DMR protocols research project.
 - IPSCPeer - IPSC peer node, maintains master connection and provides DMR sending/receiving.
 - DMRIPGateway - DMR to UDP/IP gateway. Connects to the IPSCPeer.
 - DMRServices - ARS/LRRP/BMS service. Connects to the DMRIPGateway.
+- AMBEClient - Client for AMBE server for encoding/decoding voice frames ([example](https://github.com/rick51231/ambe-server-docker))
 
 #### Supported encodings/checksums:
 - BPTC 196/96

src/Services/AMBEClient.js

@@ -0,0 +1,75 @@
+const udp = require('dgram');
+
+// Use with md380-emulator server https://github.com/rick51231/ambe-server-docker
+
+// Convert to wav:
+// ffmpeg -f s16le -ar 8000 -ac 1 -i decoded.pcm -af "volume=5" out.wav
+// sox -r 8000 -e signed-integer -L -b 16 -c 1 -v 5 decoded.pcm out.wav
+class AMBEClient {
+    socket;
+    ip;
+    port;
+    timeout; //ms
+    isBusy = false;
+    currentPromise = null;
+    currentTimeout = null;
+
+    constructor(ip, port, timeout = 500) {
+        this.ip = ip;
+        this.port = port;
+        this.timeout = timeout;
+
+        this.socket = udp.createSocket('udp4');
+
+        this.socket.on('message', (msg) => {
+            this.ready(msg);
+        });
+    }
+
+    decode(buffer) {
+        return new Promise( resolve => {
+            if(buffer.length!==7)
+                return resolve(null);
+
+            this.run(buffer, resolve);
+        });
+    }
+
+    encode(buffer) {
+        return new Promise( resolve => {
+            if(buffer.length!==320)
+                return resolve(null);
+
+            this.run(buffer, resolve);
+        });
+    }
+
+    run(buffer, resolve) {
+        if(this.isBusy)
+            return setTimeout(() => {
+                this.run(buffer, resolve);
+            }, 1);
+
+        this.isBusy = true;
+        this.currentPromise = resolve;
+
+        this.currentTimeout = setTimeout(() => {
+            this.ready(null);
+        }, this.timeout);
+
+        this.socket.send(buffer, this.port, this.ip);
+    }
+
+    ready(result) {
+        if(this.currentPromise===null)
+            return;
+
+        this.currentPromise(result);
+        clearTimeout(this.currentTimeout);
+        this.currentTimeout = null;
+        this.currentPromise = null;
+        this.isBusy = false;
+    }
+}
+
+module.exports = AMBEClient;

src/Services/index.js

@@ -1,3 +1,4 @@
+module.exports.AMBEClient = require('./AMBEClient');
 module.exports.DMRIPGateway = require('./DMRIPGateway');
 module.exports.DMRServices = require('./DMRServices');
 module.exports.HBDMRGateway = require('./HBDMRGateway');