[dns] Factory to load config from /etc/resolv.conf

Author: igorw

Config/Config.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace React\Dns\Config;
+
+class Config
+{
+    public $nameservers = array();
+}

Config/FilesystemFactory.php

@@ -0,0 +1,63 @@
+<?php
+
+namespace React\Dns\Config;
+
+use React\EventLoop\LoopInterface;
+use React\Stream\Stream;
+
+class FilesystemFactory
+{
+    private $loop;
+
+    public function __construct(LoopInterface $loop)
+    {
+        $this->loop = $loop;
+    }
+
+    public function create($filename, $callback)
+    {
+        $that = $this;
+
+        $this->loadEtcResolvConf($filename, function ($contents) use ($that, $callback) {
+            return $that->parseEtcResolvConf($contents, $callback);
+        });
+    }
+
+    public function parseEtcResolvConf($contents, $callback)
+    {
+        $nameservers = array();
+
+        $contents = preg_replace('/^#/', '', $contents);
+        $lines = preg_split('/\r?\n/is', $contents);
+        foreach ($lines as $line) {
+            if (preg_match('/^nameserver (.+)/', $line, $match)) {
+                $nameservers[] = $match[1];
+            }
+        }
+
+        $config = new Config();
+        $config->nameservers = $nameservers;
+
+        $callback($config);
+    }
+
+    public function loadEtcResolvConf($filename, $callback)
+    {
+        if (!file_exists($filename)) {
+            throw new \InvalidArgumentException("The filename for /etc/resolv.conf given does not exist: $filename");
+        }
+
+        $fd = fopen($filename, 'r');
+        stream_set_blocking($fd, 0);
+
+        $contents = '';
+
+        $stream = new Stream($fd, $this->loop);
+        $stream->on('data', function ($data) use (&$contents) {
+            $contents .= $data;
+        });
+        $stream->on('end', function () use (&$contents, $callback) {
+            call_user_func($callback, $contents);
+        });
+    }
+}