Introduce Icinga\Util\Environment to manage limits

And replace the code in Icinga\File\Pdf with the new helper.

library/Icinga/File/Pdf.php

@@ -8,7 +8,7 @@ use Dompdf\Dompdf;
 use Dompdf\Options;
 use Icinga\Application\Icinga;
 use Icinga\Exception\ProgrammingError;
-use Icinga\Util\Format;
+use Icinga\Util\Environment;
 use Icinga\Web\Hook;
 use Icinga\Web\Url;
 
@@ -47,15 +47,8 @@ class Pdf
     {
         $this->assertNoHeadersSent();
 
-        $memLimit = 512 * 1024 ** 2;
-        if (Format::unpackShorthandBytes(ini_get('memory_limit')) < $memLimit) {
-            ini_set('memory_limit', $memLimit);
-        }
-
-        $maxExecTime = 300;
-        if ((int) ini_get('max_execution_time') < $maxExecTime) {
-            ini_set('max_execution_time', $maxExecTime);
-        }
+        Environment::raiseMemoryLimit('512M');
+        Environment::raiseExecutionTime(300);
 
         $viewRenderer = $controller->getHelper('viewRenderer');
         $controller->render(

library/Icinga/Util/Environment.php

@@ -0,0 +1,42 @@
+<?php
+/* Icinga Web 2 | (c) 2018 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Util;
+
+/**
+ * Helper for configuring the PHP environment
+ */
+class Environment
+{
+    /**
+     * Raise the PHP memory_limit
+     *
+     * Unless it is not already set to a higher limit
+     *
+     * @param string|int $minimum
+     */
+    public static function raiseMemoryLimit($minimum = '512M')
+    {
+        if (is_string($minimum)) {
+            $minimum = Format::unpackShorthandBytes($minimum);
+        }
+
+        if (Format::unpackShorthandBytes(ini_get('memory_limit')) < $minimum) {
+            ini_set('memory_limit', $minimum);
+        }
+    }
+
+    /**
+     * Raise the PHP max_execution_time
+     *
+     * Unless it is not already configured to a higher value.
+     *
+     * @param int $minimum
+     */
+    public static function raiseExecutionTime($minimum = 300)
+    {
+        if ((int) ini_get('max_execution_time') < $minimum) {
+            ini_set('max_execution_time', $minimum);
+        }
+    }
+}

test/php/library/Icinga/Util/EnvironmentTest.php

@@ -0,0 +1,43 @@
+<?php
+/* Icinga Web 2 | (c) 2018 Icinga Development Team | GPLv2+ */
+
+namespace Tests\Icinga\Util;
+
+use Icinga\Util\Environment;
+use Icinga\Test\BaseTestCase;
+
+class EnvironmentTest extends BaseTestCase
+{
+    public function testRaiseMemoryLimit()
+    {
+        // set a low limit
+        ini_set('memory_limit', '128M');
+
+        Environment::raiseMemoryLimit('512M');
+        $this->assertEquals('536870912' /* 512M */, ini_get('memory_limit'));
+
+        Environment::raiseMemoryLimit('1G');
+        $this->assertEquals('1073741824' /* 1G */, ini_get('memory_limit'));
+
+        Environment::raiseMemoryLimit('512M');
+        $this->assertEquals('1073741824' /* 1G */, ini_get('memory_limit'));
+
+        // in phpunit usually there is no limit
+        ini_set('memory_limit', '-1');
+    }
+
+    public function testRaiseExecutionTime()
+    {
+        Environment::raiseExecutionTime(300);
+        $this->assertEquals(300, ini_get('max_execution_time'));
+
+        Environment::raiseExecutionTime(600);
+        $this->assertEquals(600, ini_get('max_execution_time'));
+
+        Environment::raiseExecutionTime(300);
+        $this->assertEquals(600, ini_get('max_execution_time'));
+
+        // in phpunit usually there is no limit
+        ini_set('max_execution_time', '0');
+    }
+}