1 files changed, 98 insertions, 0 deletions
diff --git a/netwerk/dns/mdns/libmdns/fallback/DataWriter.jsm b/netwerk/dns/mdns/libmdns/fallback/DataWriter.jsm
new file mode 100644
index 000000000..af20d65f5
--- /dev/null
+++ b/netwerk/dns/mdns/libmdns/fallback/DataWriter.jsm
@@ -0,0 +1,98 @@
+/* -*- Mode: js; js-indent-level: 2; indent-tabs-mode: nil; tab-width: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* jshint esnext: true, moz: true */
+
+'use strict';
+
+this.EXPORTED_SYMBOLS = ['DataWriter'];
+
+class DataWriter {
+  constructor(data, maxBytes = 512) {
+    if (typeof data === 'number') {
+      maxBytes = data;
+      data = undefined;
+    }
+
+    this._buffer = new ArrayBuffer(maxBytes);
+    this._data = new Uint8Array(this._buffer);
+    this._cursor = 0;
+
+    if (data) {
+      this.putBytes(data);
+    }
+  }
+
+  get buffer() {
+    return this._buffer.slice(0, this._cursor);
+  }
+
+  get data() {
+    return new Uint8Array(this.buffer);
+  }
+
+  // `data` is `Uint8Array`
+  putBytes(data) {
+    if (this._cursor + data.length > this._data.length) {
+      throw new Error('DataWriter buffer is exceeded');
+    }
+
+    for (let i = 0, length = data.length; i < length; i++) {
+      this._data[this._cursor] = data[i];
+      this._cursor++;
+    }
+  }
+
+  putByte(byte) {
+    if (this._cursor + 1 > this._data.length) {
+      throw new Error('DataWriter buffer is exceeded');
+    }
+
+    this._data[this._cursor] = byte
+    this._cursor++;
+  }
+
+  putValue(value, length) {
+    length = length || 1;
+    if (length == 1) {
+      this.putByte(value);
+    } else {
+      this.putBytes(_valueToUint8Array(value, length));
+    }
+  }
+
+  putLabel(label) {
+    // Eliminate any trailing '.'s in the label (valid in text representation).
+    label = label.replace(/\.$/, '');
+    let parts = label.split('.');
+    parts.forEach((part) => {
+      this.putLengthString(part);
+    });
+    this.putValue(0);
+  }
+
+  putLengthString(string) {
+    if (string.length > 0xff) {
+        throw new Error("String too long.");
+    }
+    this.putValue(string.length);
+    for (let i = 0; i < string.length; i++) {
+      this.putValue(string.charCodeAt(i));
+    }
+  }
+}
+
+/**
+ * @private
+ */
+function _valueToUint8Array(value, length) {
+  let arrayBuffer = new ArrayBuffer(length);
+  let uint8Array = new Uint8Array(arrayBuffer);
+  for (let i = length - 1; i >= 0; i--) {
+    uint8Array[i] = value & 0xff;
+    value = value >> 8;
+  }
+
+  return uint8Array;
+}