new file mode 100644
--- /dev/null
+++ b/lib/unistr/u8-uctomb-aux.c
@@ -0,0 +1,71 @@
+/* Conversion UCS-4 to UTF-8.
+   Copyright (C) 2002, 2006-2007 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2002.
+
+   This program is free software; you can redistribute it and/or modify it
+   under the terms of the GNU Library General Public License as published
+   by the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+   USA.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "unistr.h"
+
+int
+u8_uctomb_aux (uint8_t *s, ucs4_t uc, int n)
+{
+  int count;
+
+  if (uc < 0x80)
+    /* The case n >= 1 is already handled by the caller.  */
+    return -2;
+  else if (uc < 0x800)
+    count = 2;
+  else if (uc < 0x10000)
+    {
+      if (uc < 0xd800 || uc >= 0xe000)
+	count = 3;
+      else
+	return -1;
+    }
+#if 0
+  else if (uc < 0x200000)
+    count = 4;
+  else if (uc < 0x4000000)
+    count = 5;
+  else if (uc <= 0x7fffffff)
+    count = 6;
+#else
+  else if (uc < 0x110000)
+    count = 4;
+#endif
+  else
+    return -1;
+
+  if (n < count)
+    return -2;
+
+  switch (count) /* note: code falls through cases! */
+    {
+#if 0
+    case 6: s[5] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x4000000;
+    case 5: s[4] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x200000;
+#endif
+    case 4: s[3] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x10000;
+    case 3: s[2] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x800;
+    case 2: s[1] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0xc0;
+  /*case 1:*/ s[0] = uc;
+    }
+  return count;
+}