new file mode 100644
--- /dev/null
+++ b/lib/wcsxfrm-impl.h
@@ -0,0 +1,96 @@
+/* Transform wide string for comparison using the current locale.
+   Copyright (C) 2011 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2011.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+size_t
+wcsxfrm (wchar_t *s1, const wchar_t *s2, size_t n)
+{
+  char mbbuf2[1024];
+  char *mbs2;
+
+  {
+    int saved_errno = errno;
+    size_t result;
+
+    /* Convert s2 to a multibyte string, trying to avoid malloc().  */
+    {
+      size_t ret;
+
+      ret = wcstombs (mbbuf2, s2, sizeof (mbbuf2));
+      if (ret == (size_t)-1)
+        goto failed;
+      if (ret < sizeof (mbbuf2))
+        mbs2 = mbbuf2;
+      else
+        {
+          size_t need = wcstombs (NULL, s2, 0);
+          if (need == (size_t)-1)
+            goto failed;
+          mbs2 = (char *) malloc (need + 1);
+          if (mbs2 == NULL)
+            goto out_of_memory;
+          ret = wcstombs (mbs2, s2, need + 1);
+          if (ret != need)
+            abort ();
+        }
+    }
+
+    /* Transform the multibyte string.  */
+    errno = 0;
+    result = strxfrm ((char *)s1, mbs2, n);
+    if (errno != 0)
+      {
+        /* An error occurred.  */
+        if (mbs2 != mbbuf2)
+          {
+            saved_errno = errno;
+            free (mbs2);
+            errno = saved_errno;
+          }
+        return 0;
+      }
+
+    if (result < n)
+      {
+        /* Convert the result by mapping char[] -> wchar_t[].
+           Since strcmp() compares the elements as 'unsigned char' values,
+           whereas wcscmp() compares the elements as 'wchar_t' values, we need
+           to map 1 'unsigned char' to 1 'wchar_t'.  (We could also map 2
+           consecutive 'unsigned char' values to 1 'wchar_t' value, but this is
+           not needed.  */
+        wchar_t *wcp = s1 + n;
+        char *cp = (char *)s1 + n;
+
+        while (wcp > s1)
+          *--wcp = (wchar_t) (unsigned char) *--cp;
+      }
+
+    if (mbs2 != mbbuf2)
+      free (mbs2);
+
+    /* No error.  */
+    errno = saved_errno;
+    return result;
+  }
+
+ out_of_memory:
+  errno = ENOMEM;
+  return 0;
+
+ failed:
+  errno = EILSEQ;
+  return 0;
+}