Added decoding of messages

Also moved things out to their own files and setup require()s to bring it all together.

messages/SLMessage.js

@@ -0,0 +1,57 @@
+const SmartBuffer = require('smart-buffer').SmartBuffer;
+
+exports.SLMessage = class SLMessage extends SmartBuffer {
+  constructor(senderId, messageId) {
+    super();
+    this.writeUInt16LE(senderId);
+    this.writeUInt16LE(messageId);
+
+    this._wroteSize = false;
+  }
+
+  toBuffer() {
+    if (this._wroteSize === false) {
+      this.insertInt32LE(this.length - 4, 4);
+      this._wroteSize = true;
+    } else {
+      this.writeInt32LE(this.length - 8, 4);
+    }
+
+    return super.toBuffer();
+  }
+
+  writeSLString(str) {
+    this.writeInt32LE(str.length);
+    this.writeString(str);
+    if (str.length % 4 != 0) {
+      this.skipWrite(4 - (str.length % 4));
+    }
+  }
+
+  readSLString() {
+    var len = this.readInt32LE();
+    var str = this.readString(len);
+    if (len % 4 != 0) {
+      this.readOffset += 4 - (len % 4);
+    }
+    return str;
+  }
+
+  writeSLBuffer(buf) {
+    this.writeInt32LE(buf.length);
+    this.writeBuffer(buf);
+  }
+
+  skipWrite(num) {
+    if (num > 0) {
+      this.writeBuffer(Buffer.alloc(num));
+    }
+  }
+
+  decode() {
+    this.readOffset = 0;
+    this.senderId = this.readUInt16LE();
+    this.messageId = this.readUInt16LE();
+    this.dataLength = this.readInt32LE();
+  }
+}