--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2011-02-04  Bruno Haible  <bruno@clisp.org>
 
+	wcsrtombs: Prepare for new module wwcsrtombs.
+	* lib/wcsrtombs-impl.h: New file, extracted from lib/wcsrtombs.c.
+	* lib/wcsrtombs.c: Include it.
+	* modules/wcsrtombs (Files): Add lib/wcsrtombs-impl.h.
+
 	mbsnrtowcs: Prepare for new module mbsnrtowwcs.
 	* lib/mbsnrtowcs-impl.h: New file, extracted from lib/mbsnrtowcs.c.
 	* lib/mbsnrtowcs.c: Include it.

new file mode 100644
--- /dev/null
+++ b/lib/wcsrtombs-impl.h
@@ -0,0 +1,90 @@
+/* Convert wide string to string.
+   Copyright (C) 2008, 2010-2011 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2008.
+
+   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
+wcsrtombs (char *dest, const wchar_t **srcp, size_t len, mbstate_t *ps)
+{
+  if (ps == NULL)
+    ps = &_gl_wcsrtombs_state;
+  {
+    const wchar_t *src = *srcp;
+    size_t cur_max = MB_CUR_MAX;
+    char buf[64];
+
+    if (!(cur_max <= sizeof (buf)))
+      abort ();
+
+    if (dest != NULL)
+      {
+        char *destptr = dest;
+
+        for (; len > 0; src++)
+          {
+            wchar_t wc = *src;
+            size_t ret = wcrtomb (len >= cur_max ? destptr : buf, wc, ps);
+
+            if (ret == (size_t)(-1))
+              goto bad_input;
+            if (!(ret <= cur_max))
+              abort ();
+            if (len < ret)
+              break;
+            if (len < cur_max)
+              memcpy (destptr, buf, ret);
+            if (wc == 0)
+              {
+                src = NULL;
+                /* Here mbsinit (ps).  */
+                break;
+              }
+            destptr += ret;
+            len -= ret;
+          }
+        *srcp = src;
+        return destptr - dest;
+      }
+    else
+      {
+        /* Ignore dest and len, don't store *srcp at the end, and
+           don't clobber *ps.  */
+        mbstate_t state = *ps;
+        size_t totalcount = 0;
+
+        for (;; src++)
+          {
+            wchar_t wc = *src;
+            size_t ret = wcrtomb (buf, wc, &state);
+
+            if (ret == (size_t)(-1))
+              goto bad_input2;
+            if (wc == 0)
+              {
+                /* Here mbsinit (&state).  */
+                break;
+              }
+            totalcount += ret;
+          }
+        return totalcount;
+      }
+
+   bad_input:
+    *srcp = src;
+   bad_input2:
+    errno = EILSEQ;
+    return (size_t)(-1);
+  }
+}

--- a/lib/wcsrtombs.c
+++ b/lib/wcsrtombs.c
@@ -51,78 +51,6 @@
 # include <stdlib.h>
 # include <string.h>
 
-size_t
-wcsrtombs (char *dest, const wchar_t **srcp, size_t len, mbstate_t *ps)
-{
-  if (ps == NULL)
-    ps = &_gl_wcsrtombs_state;
-  {
-    const wchar_t *src = *srcp;
-    size_t cur_max = MB_CUR_MAX;
-    char buf[64];
-
-    if (!(cur_max <= sizeof (buf)))
-      abort ();
-
-    if (dest != NULL)
-      {
-        char *destptr = dest;
-
-        for (; len > 0; src++)
-          {
-            wchar_t wc = *src;
-            size_t ret = wcrtomb (len >= cur_max ? destptr : buf, wc, ps);
-
-            if (ret == (size_t)(-1))
-              goto bad_input;
-            if (!(ret <= cur_max))
-              abort ();
-            if (len < ret)
-              break;
-            if (len < cur_max)
-              memcpy (destptr, buf, ret);
-            if (wc == 0)
-              {
-                src = NULL;
-                /* Here mbsinit (ps).  */
-                break;
-              }
-            destptr += ret;
-            len -= ret;
-          }
-        *srcp = src;
-        return destptr - dest;
-      }
-    else
-      {
-        /* Ignore dest and len, don't store *srcp at the end, and
-           don't clobber *ps.  */
-        mbstate_t state = *ps;
-        size_t totalcount = 0;
-
-        for (;; src++)
-          {
-            wchar_t wc = *src;
-            size_t ret = wcrtomb (buf, wc, &state);
-
-            if (ret == (size_t)(-1))
-              goto bad_input2;
-            if (wc == 0)
-              {
-                /* Here mbsinit (&state).  */
-                break;
-              }
-            totalcount += ret;
-          }
-        return totalcount;
-      }
-
-   bad_input:
-    *srcp = src;
-   bad_input2:
-    errno = EILSEQ;
-    return (size_t)(-1);
-  }
-}
+# include "wcsrtombs-impl.h"
 
 #endif

--- a/modules/wcsrtombs
+++ b/modules/wcsrtombs
@@ -3,6 +3,7 @@
 
 Files:
 lib/wcsrtombs.c
+lib/wcsrtombs-impl.h
 lib/wcsrtombs-state.c
 m4/wcsrtombs.m4
 m4/mbrtowc.m4