feat(dirent): directory iteration

src/dirent/telldir.c

@@ -0,0 +1,22 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <dirent.h>
+
+#include "dirent_impl.h"
+
+/*
+ * telldir (todo 24): return the stream's current directory location.
+ * readdir stores the kernel's d_off cookie of every entry it hands out —
+ * the offset at which iteration resumes AFTER that entry — so the cookie
+ * of the most recently returned entry is exactly the location a matching
+ * seekdir must restore. A fresh or rewound stream reports 0, the start.
+ */
+long
+telldir(DIR *dir)
+{
+    struct vlibc_DIR *d = dir;
+
+    return (long)d->de.d_off;
+}