lib: Add NonEmptyFileIterator

Add iterator for iterating over non-empty files.

library/Icinga/File/NonEmptyFileIterator.php

@@ -0,0 +1,49 @@
+<?php
+// {{{ICINGA_LICENSE_HEADER}}}
+// {{{ICINGA_LICENSE_HEADER}}
+
+namespace Icinga\File;
+
+use FilterIterator;
+
+/**
+ * Iterator over non-empty files
+ *
+ * Usage example:
+ * <code>
+ * <?php
+ *
+ * namespace Icinga\Example;
+ *
+ * use RecursiveDirectoryIterator;
+ * use RecursiveIteratorIterator;
+ * use Icinga\File\NonEmptyFilterIterator;
+ *
+ * $nonEmptyFiles = new NonEmptyFileIterator(
+ *     new RecursiveIteratorIterator(
+ *         new RecursiveDirectoryIterator(__DIR__),
+ *         RecursiveIteratorIterator::SELF_FIRST
+ *     )
+ * );
+ * </code>
+ */
+class NonEmptyFileIterator extends FilterIterator
+{
+    /**
+     * Accept non-empty files
+     *
+     * @return bool Whether the current element of the iterator is acceptable
+     *              through this filter
+     */
+    public function accept()
+    {
+        $current = $this->current();
+        /** @type $current \SplFileInfo */
+        if (! $current->isFile()
+            || $current->getSize() === 0
+        ) {
+            return false;
+        }
+        return true;
+    }
+}