new file mode 100644
--- /dev/null
+++ b/lib/unistr/u16-check.c
@@ -0,0 +1,53 @@
+/* Check UTF-16 string.
+   Copyright (C) 2002, 2006 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"
+
+const uint16_t *
+u16_check (const uint16_t *s, size_t n)
+{
+  const uint16_t *s_end = s + n;
+
+  while (s < s_end)
+    {
+      /* Keep in sync with utf16-ucs4.h and utf16-ucs4.c.  */
+      uint16_t c = *s;
+
+      if (c < 0xd800 || c >= 0xe000)
+	{
+	  s++;
+	  continue;
+	}
+      if (c < 0xdc00)
+	{
+	  if (s + 2 <= s_end
+	      && s[1] >= 0xdc00 && s[1] < 0xe000)
+	    {
+	      s += 2;
+	      continue;
+	    }
+	}
+      /* invalid or incomplete multibyte character */
+      return s;
+    }
+  return NULL;
+}

new file mode 100644
--- /dev/null
+++ b/lib/unistr/u32-check.c
@@ -0,0 +1,41 @@
+/* Check UTF-32 string.
+   Copyright (C) 2002, 2006 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"
+
+const uint32_t *
+u32_check (const uint32_t *s, size_t n)
+{
+  const uint32_t *s_end = s + n;
+
+  while (s < s_end)
+    {
+      uint32_t c = *s;
+
+      if (c < 0xd800 || (c >= 0xe000 && c < 0x110000))
+	s++;
+      else
+	/* invalid Unicode character */
+	return s;
+    }
+  return NULL;
+}

new file mode 100644
--- /dev/null
+++ b/lib/unistr/u8-check.c
@@ -0,0 +1,107 @@
+/* Check UTF-8 string.
+   Copyright (C) 2002, 2006 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"
+
+const uint8_t *
+u8_check (const uint8_t *s, size_t n)
+{
+  const uint8_t *s_end = s + n;
+
+  while (s < s_end)
+    {
+      /* Keep in sync with utf8-ucs4.h and utf8-ucs4.c.  */
+      uint8_t c = *s;
+
+      if (c < 0x80)
+	{
+	  s++;
+	  continue;
+	}
+      if (c >= 0xc2)
+	{
+	  if (c < 0xe0)
+	    {
+	      if (s + 2 <= s_end
+		  && (s[1] ^ 0x80) < 0x40)
+		{
+		  s += 2;
+		  continue;
+		}
+	    }
+	  else if (c < 0xf0)
+	    {
+	      if (s + 3 <= s_end
+		  && (s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
+		  && (c >= 0xe1 || s[1] >= 0xa0)
+		  && (c != 0xed || s[1] < 0xa0))
+		{
+		  s += 3;
+		  continue;
+		}
+	    }
+	  else if (c < 0xf8)
+	    {
+	      if (s + 4 <= s_end
+		  && (s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
+		  && (s[3] ^ 0x80) < 0x40
+		  && (c >= 0xf1 || s[1] >= 0x90)
+#if 1
+		  && (c < 0xf4 || (c == 0xf4 && s[1] < 0x90))
+#endif
+		 )
+		{
+		  s += 4;
+		  continue;
+		}
+	    }
+#if 0
+	  else if (c < 0xfc)
+	    {
+	      if (s + 5 <= s_end
+		  && (s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
+		  && (s[3] ^ 0x80) < 0x40 && (s[4] ^ 0x80) < 0x40
+		  && (c >= 0xf9 || s[1] >= 0x88))
+		{
+		  s += 5;
+		  continue;
+		}
+	    }
+	  else if (c < 0xfe)
+	    {
+	      if (s + 6 <= s_end
+		  && (s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
+		  && (s[3] ^ 0x80) < 0x40 && (s[4] ^ 0x80) < 0x40
+		  && (s[5] ^ 0x80) < 0x40
+		  && (c >= 0xfd || s[1] >= 0x84))
+		{
+		  s += 6;
+		  continue;
+		}
+	    }
+#endif
+	}
+      /* invalid or incomplete multibyte character */
+      return s;
+    }
+  return NULL;
+}

new file mode 100644
--- /dev/null
+++ b/modules/unistr/u16-check
@@ -0,0 +1,23 @@
+Description:
+Check UTF-16 string.
+
+Files:
+lib/unistr/u16-check.c
+
+Depends-on:
+unistr/base
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += unistr/u16-check.c
+
+Include:
+"unistr.h"
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible
+

new file mode 100644
--- /dev/null
+++ b/modules/unistr/u32-check
@@ -0,0 +1,23 @@
+Description:
+Check UTF-32 string.
+
+Files:
+lib/unistr/u32-check.c
+
+Depends-on:
+unistr/base
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += unistr/u32-check.c
+
+Include:
+"unistr.h"
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible
+

new file mode 100644
--- /dev/null
+++ b/modules/unistr/u8-check
@@ -0,0 +1,23 @@
+Description:
+Check UTF-8 string.
+
+Files:
+lib/unistr/u8-check.c
+
+Depends-on:
+unistr/base
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += unistr/u8-check.c
+
+Include:
+"unistr.h"
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible
+