doc/lib: Add `NonEmptyFileIterator' for iterating over non-empty files

refs #4820

modules/doc/library/Doc/NonEmptyFileIterator.php

@@ -0,0 +1,31 @@
+<?php
+// {{{ICINGA_LICENSE_HEADER}}}
+// {{{ICINGA_LICENSE_HEADER}}
+
+namespace Icinga\Module\Doc;
+
+use RecursiveFilterIterator;
+
+/**
+ * Recursive iterator over non-empty files
+ */
+class NonEmptyFileIterator extends RecursiveFilterIterator
+{
+    /**
+     * Accept non-empty files
+     *
+     * @return bool Whether the current element of the iterator is acceptable
+     *              through this filter
+     */
+    public function accept()
+    {
+        $current = $this->getInnerIterator()->current();
+        /* @var $current \SplFileInfo */
+        if (! $current->isFile()
+            || $current->getSize() === 0
+        ) {
+            return false;
+        }
+        return true;
+    }
+}