Add HostsFile configuration loader and parser

Author: clue

src/Config/HostsFile.php

@@ -0,0 +1,108 @@
+<?php
+
+namespace React\Dns\Config;
+
+use RuntimeException;
+
+/**
+ * Represents a static hosts file which maps hostnames to IPs
+ *
+ * Hosts files are used on most systems to avoid actually hitting the DNS for
+ * certain common hostnames.
+ *
+ * Most notably, this file usually contains an entry to map "localhost" to the
+ * local IP. Windows is a notable exception here, as Windows does not actually
+ * include "localhost" in this file by default.
+ *
+ * This class mostly exists to abstract the parsing/extraction process so this
+ * can be replaced with a faster alternative in the future.
+ */
+class HostsFile
+{
+    /**
+     * Returns the default path for the hosts file on this system
+     *
+     * @return string
+     * @codeCoverageIgnore
+     */
+    public static function getDefaultPath()
+    {
+        // use static path for all Unix-based systems
+        if (DIRECTORY_SEPARATOR !== '\\') {
+            return '/etc/hosts';
+        }
+
+        // Windows actually stores the path in the registry under
+        // \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\DataBasePath
+        $path = '%SystemRoot%\\system32\drivers\etc\hosts';
+
+        $base = getenv('SystemRoot');
+        if ($base === false) {
+            $base = 'C:\\Windows';
+        }
+
+        return str_replace('%SystemRoot%', $base, $path);
+    }
+
+    /**
+     * Loads a hosts file (from the given path or default location)
+     *
+     * Note that this method blocks while loading the given path and should
+     * thus be used with care! While this should be relatively fast for normal
+     * hosts file, this may be an issue if this file is located on a slow device
+     * or contains an excessive number of entries. In particular, this method
+     * should only be executed before the loop starts, not while it is running.
+     *
+     * @param ?string $path (optional) path to hosts file or null=load default location
+     * @return self
+     * @throws RuntimeException if the path can not be loaded (does not exist)
+     */
+    public static function loadFromPathBlocking($path = null)
+    {
+        if ($path === null) {
+            $path = self::getDefaultPath();
+        }
+
+        $contents = @file_get_contents($path);
+        if ($contents === false) {
+            throw new RuntimeException('Unable to load hosts file "' . $path . '"');
+        }
+
+        return new self($contents);
+    }
+
+    /**
+     * Instantiate new hosts file with the given hosts file contents
+     *
+     * @param string $contents
+     */
+    public function __construct($contents)
+    {
+        // remove all comments from the contents
+        $contents = preg_replace('/ *#.*/', '', strtolower($contents));
+
+        $this->contents = $contents;
+    }
+
+    /**
+     * Returns all IPs for the given hostname
+     *
+     * @param string $name
+     * @return string[]
+     */
+    public function getIpsForHost($name)
+    {
+        $name = strtolower($name);
+
+        $ips = array();
+        foreach (preg_split('/\r?\n/', $this->contents) as $line) {
+            $parts = preg_split('/\s+/', $line);
+            $ip = array_shift($parts);
+            if ($parts && array_search($name, $parts) !== false) {
+                $ips[] = $ip;
+            }
+        }
+
+        return $ips;
+    }
+}

tests/Config/HostsFileTest.php

@@ -0,0 +1,80 @@
+<?php
+
+namespace React\Tests\Dns\Config;
+
+use React\Tests\Dns\TestCase;
+use React\Dns\Config\HostsFile;
+
+class HostsFileTest extends TestCase
+{
+    public function testLoadsFromDefaultPath()
+    {
+        $hosts = HostsFile::loadFromPathBlocking();
+
+        $this->assertInstanceOf('React\Dns\Config\HostsFile', $hosts);
+    }
+
+    public function testDefaultShouldHaveLocalhostMapped()
+    {
+        if (DIRECTORY_SEPARATOR === '\\') {
+            $this->markTestSkipped('Not supported on Windows');
+        }
+
+        $hosts = HostsFile::loadFromPathBlocking();
+
+        $this->assertContains('127.0.0.1', $hosts->getIpsForHost('localhost'));
+    }
+
+    /**
+     * @expectedException RuntimeException
+     */
+    public function testLoadThrowsForInvalidPath()
+    {
+        HostsFile::loadFromPathBlocking('does/not/exist');
+    }
+
+    public function testContainsSingleLocalhostEntry()
+    {
+        $hosts = new HostsFile('127.0.0.1 localhost');
+
+        $this->assertEquals(array('127.0.0.1'), $hosts->getIpsForHost('localhost'));
+        $this->assertEquals(array(), $hosts->getIpsForHost('example.com'));
+    }
+
+    public function testSkipsComments()
+    {
+        $hosts = new HostsFile('# start' . PHP_EOL .'#127.0.0.1 localhost' . PHP_EOL . '127.0.0.2 localhost # example.com');
+
+        $this->assertEquals(array('127.0.0.2'), $hosts->getIpsForHost('localhost'));
+        $this->assertEquals(array(), $hosts->getIpsForHost('example.com'));
+    }
+
+    public function testContainsSingleLocalhostEntryWithCaseIgnored()
+    {
+        $hosts = new HostsFile('127.0.0.1 LocalHost');
+
+        $this->assertEquals(array('127.0.0.1'), $hosts->getIpsForHost('LOCALHOST'));
+    }
+
+    public function testEmptyFileContainsNothing()
+    {
+        $hosts = new HostsFile('');
+
+        $this->assertEquals(array(), $hosts->getIpsForHost('example.com'));
+    }
+
+    public function testSingleEntryWithMultipleNames()
+    {
+        $hosts = new HostsFile('127.0.0.1 localhost example.com');
+
+        $this->assertEquals(array('127.0.0.1'), $hosts->getIpsForHost('example.com'));
+        $this->assertEquals(array('127.0.0.1'), $hosts->getIpsForHost('localhost'));
+    }
+
+    public function testMergesEntriesOverMultipleLines()
+    {
+        $hosts = new HostsFile("127.0.0.1 localhost\n127.0.0.2 localhost\n127.0.0.3 a localhost b\n127.0.0.4 a localhost");
+
+        $this->assertEquals(array('127.0.0.1', '127.0.0.2', '127.0.0.3', '127.0.0.4'), $hosts->getIpsForHost('localhost'));
+    }
+}