diff --git a/libc/private/bionic_mbstate.h b/libc/private/bionic_mbstate.h
new file mode 100644
index 0000000..018b47c
--- /dev/null
+++ b/libc/private/bionic_mbstate.h
@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef _BIONIC_MBSTATE_H
+#define _BIONIC_MBSTATE_H
+
+#include <wchar.h>
+
+__BEGIN_DECLS
+
+/*
+ * These return values are specified by POSIX for multibyte conversion
+ * functions.
+ */
+#define __MB_ERR_ILLEGAL_SEQUENCE static_cast<size_t>(-1)
+#define __MB_ERR_INCOMPLETE_SEQUENCE static_cast<size_t>(-2)
+
+#define __MB_IS_ERR(rv) (rv == __MB_ERR_ILLEGAL_SEQUENCE || \
+                         rv == __MB_ERR_INCOMPLETE_SEQUENCE)
+
+size_t mbstate_bytes_so_far(const mbstate_t* ps);
+void mbstate_set_byte(mbstate_t* ps, int i, char byte);
+uint8_t mbstate_get_byte(const mbstate_t* ps, int n);
+size_t reset_and_return_illegal(int _errno, mbstate_t* ps);
+size_t reset_and_return(int _return, mbstate_t* ps);
+
+__END_DECLS
+
+#endif // _BIONIC_MBSTATE_H