diff --git a/libc/Android.mk b/libc/Android.mk
index c573e30..3ac74b7 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -103,6 +103,8 @@
     bionic/__bionic_name_mem.cpp \
     bionic/bionic_time_conversions.cpp \
     bionic/brk.cpp \
+    bionic/c16rtomb.cpp \
+    bionic/c32rtomb.cpp \
     bionic/chmod.cpp \
     bionic/chown.cpp \
     bionic/clearenv.cpp \
@@ -139,6 +141,9 @@
     bionic/link.cpp \
     bionic/locale.cpp \
     bionic/lstat.cpp \
+    bionic/mbrtoc16.cpp \
+    bionic/mbrtoc32.cpp \
+    bionic/mbstate.cpp \
     bionic/mkdir.cpp \
     bionic/mkfifo.cpp \
     bionic/mknod.cpp \
diff --git a/libc/bionic/c16rtomb.cpp b/libc/bionic/c16rtomb.cpp
new file mode 100644
index 0000000..77512be
--- /dev/null
+++ b/libc/bionic/c16rtomb.cpp
@@ -0,0 +1,67 @@
+/*
+ * 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.
+ */
+
+#include <errno.h>
+#include <uchar.h>
+#include <wchar.h>
+
+#include "private/bionic_mbstate.h"
+
+static inline constexpr bool is_high_surrogate(char16_t c16) {
+  return c16 >= 0xd800 && c16 < 0xdc00;
+}
+
+static inline constexpr bool is_low_surrogate(char16_t c16) {
+  return c16 >= 0xdc00 && c16 < 0xe000;
+}
+
+size_t c16rtomb(char* s, char16_t c16, mbstate_t* ps) {
+  static mbstate_t __private_state;
+  mbstate_t* state = (ps == NULL) ? &__private_state : ps;
+  if (mbsinit(state)) {
+    if (is_high_surrogate(c16)) {
+      char32_t c32 = (c16 & ~0xd800) << 10;
+      mbstate_set_byte(state, 3, (c32 & 0xff0000) >> 16);
+      mbstate_set_byte(state, 2, (c32 & 0x00ff00) >> 8);
+      return 0;
+    } else if (is_low_surrogate(c16)) {
+      return reset_and_return_illegal(EINVAL, state);
+    } else {
+      return c32rtomb(s, static_cast<char32_t>(c16), state);
+    }
+  } else {
+    if (!is_low_surrogate(c16)) {
+      return reset_and_return_illegal(EINVAL, state);
+    }
+
+    char32_t c32 = ((mbstate_get_byte(state, 3) << 16) |
+                    (mbstate_get_byte(state, 2) << 8) |
+                    (c16 & ~0xdc00)) + 0x10000;
+    return reset_and_return(c32rtomb(s, c32, NULL), state);
+  }
+}
diff --git a/libc/bionic/c32rtomb.cpp b/libc/bionic/c32rtomb.cpp
new file mode 100644
index 0000000..d3231c0
--- /dev/null
+++ b/libc/bionic/c32rtomb.cpp
@@ -0,0 +1,97 @@
+/*
+ * 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.
+ */
+
+#include <errno.h>
+#include <uchar.h>
+#include <wchar.h>
+
+#include "private/bionic_mbstate.h"
+
+size_t c32rtomb(char* s, char32_t c32, mbstate_t* ps) {
+  static mbstate_t __private_state;
+  mbstate_t* state = (ps == NULL) ? &__private_state : ps;
+
+  if (s == NULL) {
+    // Equivalent to c32rtomb(buf, U'\0', ps).
+    return reset_and_return(1, state);
+  }
+
+  // POSIX states that if char32_t is a null wide character, a null byte shall
+  // be stored, preceded by any shift sequence needed to restore the initial
+  // shift state. Since shift states are not supported, only the null byte is
+  // stored.
+  if (c32 == U'\0') {
+    *s = '\0';
+    reset_and_return(1, state);
+  }
+
+  if (!mbsinit(state)) {
+    return reset_and_return_illegal(EILSEQ, state);
+  }
+
+  if ((c32 & ~0x7f) == 0) {
+    // Fast path for plain ASCII characters.
+    *s = c32;
+    return 1;
+  }
+
+  // Determine the number of octets needed to represent this character.
+  // We always output the shortest sequence possible. Also specify the
+  // first few bits of the first octet, which contains the information
+  // about the sequence length.
+  uint8_t lead;
+  size_t length;
+  if ((c32 & ~0x7f) == 0) {
+    lead = 0;
+    length = 1;
+  } else if ((c32 & ~0x7ff) == 0) {
+    lead = 0xc0;
+    length = 2;
+  } else if ((c32 & ~0xffff) == 0) {
+    lead = 0xe0;
+    length = 3;
+  } else if ((c32 & ~0x1fffff) == 0) {
+    lead = 0xf0;
+    length = 4;
+  } else {
+    errno = EILSEQ;
+    return __MB_ERR_ILLEGAL_SEQUENCE;
+  }
+
+  // Output the octets representing the character in chunks
+  // of 6 bits, least significant last. The first octet is
+  // a special case because it contains the sequence length
+  // information.
+  for (size_t i = length - 1; i > 0; i--) {
+    s[i] = (c32 & 0x3f) | 0x80;
+    c32 >>= 6;
+  }
+  *s = (c32 & 0xff) | lead;
+
+  return length;
+}
diff --git a/libc/bionic/mbrtoc16.cpp b/libc/bionic/mbrtoc16.cpp
new file mode 100644
index 0000000..6878a11
--- /dev/null
+++ b/libc/bionic/mbrtoc16.cpp
@@ -0,0 +1,89 @@
+/*
+ * 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.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <uchar.h>
+#include <wchar.h>
+
+#include "private/bionic_mbstate.h"
+
+static inline bool mbspartialc16(const mbstate_t* state) {
+  return mbstate_get_byte(state, 3) != 0;
+}
+
+static size_t begin_surrogate(char32_t c32, char16_t* pc16,
+                              size_t nconv, mbstate_t* state) {
+  c32 -= 0x10000;
+  char16_t trail = (c32 & 0x3ff) | 0xdc00;
+
+  mbstate_set_byte(state, 0, trail & 0x00ff);
+  mbstate_set_byte(state, 1, (trail & 0xff00) >> 8);
+  mbstate_set_byte(state, 3, nconv & 0xff);
+
+  *pc16 = ((c32 & 0xffc00) >> 10) | 0xd800;
+  // Defined by POSIX as return value for first surrogate character.
+  return static_cast<size_t>(-3);
+}
+
+static size_t finish_surrogate(char16_t* pc16, mbstate_t* state) {
+  char16_t trail = mbstate_get_byte(state, 1) << 8 |
+                   mbstate_get_byte(state, 0);
+  *pc16 = trail;
+  return reset_and_return(mbstate_get_byte(state, 3), state);
+}
+
+size_t mbrtoc16(char16_t* pc16, const char* s, size_t n, mbstate_t* ps) {
+  static mbstate_t __private_state;
+  mbstate_t* state = (ps == NULL) ? &__private_state : ps;
+
+  char16_t __private_pc16;
+  if (pc16 == NULL) {
+    pc16 = &__private_pc16;
+  }
+
+  if (mbspartialc16(state)) {
+    return finish_surrogate(pc16, state);
+  }
+
+  char32_t c32;
+  size_t nconv = mbrtoc32(&c32, s, n, state);
+  if (__MB_IS_ERR(nconv)) {
+    return nconv;
+  } else if (nconv == 0) {
+    return reset_and_return(nconv, state);
+  } else if (c32 > 0x10ffff) {
+    // Input cannot be encoded as UTF-16.
+    return reset_and_return_illegal(EILSEQ, state);
+  } else if (c32 < 0x10000) {
+    *pc16 = static_cast<char16_t>(c32);
+    return reset_and_return(nconv, state);
+  } else {
+    return begin_surrogate(c32, pc16, nconv, state);
+  }
+}
diff --git a/libc/bionic/mbrtoc32.cpp b/libc/bionic/mbrtoc32.cpp
new file mode 100644
index 0000000..bd40ecf
--- /dev/null
+++ b/libc/bionic/mbrtoc32.cpp
@@ -0,0 +1,138 @@
+/*
+ * 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.
+ */
+
+#include <errno.h>
+#include <sys/param.h>
+#include <uchar.h>
+#include <wchar.h>
+
+#include "private/bionic_mbstate.h"
+
+size_t mbrtoc32(char32_t* pc32, const char* s, size_t n, mbstate_t* ps) {
+  static mbstate_t __private_state;
+  mbstate_t* state = (ps == NULL) ? &__private_state : ps;
+
+  // We should never get to a state which has all 4 bytes of the sequence set.
+  // Full state verification is done when decoding the sequence (after we have
+  // all the bytes).
+  if (mbstate_get_byte(state, 3) != 0) {
+    return reset_and_return_illegal(EINVAL, state);
+  }
+
+  if (s == NULL) {
+    s = "";
+    n = 1;
+    pc32 = NULL;
+  }
+
+  if (n == 0) {
+    return 0;
+  }
+
+  uint8_t ch;
+  if (mbsinit(state) && (((ch = static_cast<uint8_t>(*s)) & ~0x7f) == 0)) {
+    // Fast path for plain ASCII characters.
+    if (pc32 != NULL) {
+      *pc32 = ch;
+    }
+    return (ch != '\0' ? 1 : 0);
+  }
+
+  // Determine the number of octets that make up this character
+  // from the first octet, and a mask that extracts the
+  // interesting bits of the first octet. We already know
+  // the character is at least two bytes long.
+  size_t length;
+  int mask;
+
+  // We also specify a lower bound for the character code to
+  // detect redundant, non-"shortest form" encodings. For
+  // example, the sequence C0 80 is _not_ a legal representation
+  // of the null character. This enforces a 1-to-1 mapping
+  // between character codes and their multibyte representations.
+  char32_t lower_bound;
+
+  // The first byte in the state (if any) tells the length.
+  size_t bytes_so_far = mbstate_bytes_so_far(state);
+  ch = bytes_so_far > 0 ? mbstate_get_byte(state, 0) : static_cast<uint8_t>(*s);
+  if ((ch & 0x80) == 0) {
+    mask = 0x7f;
+    length = 1;
+    lower_bound = 0;
+  } else if ((ch & 0xe0) == 0xc0) {
+    mask = 0x1f;
+    length = 2;
+    lower_bound = 0x80;
+  } else if ((ch & 0xf0) == 0xe0) {
+    mask = 0x0f;
+    length = 3;
+    lower_bound = 0x800;
+  } else if ((ch & 0xf8) == 0xf0) {
+    mask = 0x07;
+    length = 4;
+    lower_bound = 0x10000;
+  } else {
+    // Malformed input; input is not UTF-8. See RFC 3629.
+    return reset_and_return_illegal(EILSEQ, state);
+  }
+
+  // Fill in the state.
+  size_t bytes_wanted = length - bytes_so_far;
+  size_t i;
+  for (i = 0; i < MIN(bytes_wanted, n); i++) {
+    if (!mbsinit(state) && ((*s & 0xc0) != 0x80)) {
+      // Malformed input; bad characters in the middle of a character.
+      return reset_and_return_illegal(EILSEQ, state);
+    }
+    mbstate_set_byte(state, bytes_so_far + i, *s++);
+  }
+  if (i < bytes_wanted) {
+    return __MB_ERR_INCOMPLETE_SEQUENCE;
+  }
+
+  // Decode the octet sequence representing the character in chunks
+  // of 6 bits, most significant first.
+  char32_t c32 = mbstate_get_byte(state, 0) & mask;
+  for (i = 1; i < length; i++) {
+    c32 <<= 6;
+    c32 |= mbstate_get_byte(state, i) & 0x3f;
+  }
+
+  if (c32 < lower_bound) {
+    // Malformed input; redundant encoding.
+    return reset_and_return_illegal(EILSEQ, state);
+  }
+  if ((c32 >= 0xd800 && c32 <= 0xdfff) || c32 == 0xfffe || c32 == 0xffff) {
+    // Malformed input; invalid code points.
+    return reset_and_return_illegal(EILSEQ, state);
+  }
+  if (pc32 != NULL) {
+    *pc32 = c32;
+  }
+  return reset_and_return(c32 == U'\0' ? 0 : bytes_wanted, state);
+}
diff --git a/libc/bionic/mbstate.cpp b/libc/bionic/mbstate.cpp
new file mode 100644
index 0000000..cb327d8
--- /dev/null
+++ b/libc/bionic/mbstate.cpp
@@ -0,0 +1,57 @@
+/*
+ * 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.
+ */
+
+#include "private/bionic_mbstate.h"
+
+#include <errno.h>
+
+__LIBC_HIDDEN__ size_t mbstate_bytes_so_far(const mbstate_t* ps) {
+  return
+    (ps->__seq[2] != 0) ? 3 :
+    (ps->__seq[1] != 0) ? 2 :
+    (ps->__seq[0] != 0) ? 1 : 0;
+}
+
+__LIBC_HIDDEN__ void mbstate_set_byte(mbstate_t* ps, int i, char byte) {
+  ps->__seq[i] = static_cast<uint8_t>(byte);
+}
+
+__LIBC_HIDDEN__ uint8_t mbstate_get_byte(const mbstate_t* ps, int n) {
+  return ps->__seq[n];
+}
+
+__LIBC_HIDDEN__ size_t reset_and_return_illegal(int _errno, mbstate_t* ps) {
+  errno = _errno;
+  *(reinterpret_cast<uint32_t*>(ps->__seq)) = 0;
+  return __MB_ERR_ILLEGAL_SEQUENCE;
+}
+
+__LIBC_HIDDEN__ size_t reset_and_return(int _return, mbstate_t* ps) {
+  *(reinterpret_cast<uint32_t*>(ps->__seq)) = 0;
+  return _return;
+}
diff --git a/libc/bionic/wchar.cpp b/libc/bionic/wchar.cpp
index 5da882f..acb2761 100644
--- a/libc/bionic/wchar.cpp
+++ b/libc/bionic/wchar.cpp
@@ -27,9 +27,12 @@
  */
 
 #include <errno.h>
-#include <string.h>
 #include <sys/param.h>
+#include <string.h>
 #include <wchar.h>
+#include <uchar.h>
+
+#include "private/bionic_mbstate.h"
 
 //
 // This file is basically OpenBSD's citrus_utf8.c but rewritten to not require a
@@ -50,36 +53,6 @@
 // function pointers.
 //
 
-#define ERR_ILLEGAL_SEQUENCE static_cast<size_t>(-1)
-#define ERR_INCOMPLETE_SEQUENCE static_cast<size_t>(-2)
-
-static size_t mbstate_bytes_so_far(const mbstate_t* ps) {
-  return
-    (ps->__seq[2] != 0) ? 3 :
-    (ps->__seq[1] != 0) ? 2 :
-    (ps->__seq[0] != 0) ? 1 : 0;
-}
-
-static void mbstate_set_byte(mbstate_t* ps, int i, char byte) {
-  ps->__seq[i] = static_cast<uint8_t>(byte);
-}
-
-static uint8_t mbstate_get_byte(const mbstate_t* ps, int n) {
-  return ps->__seq[n];
-}
-
-static size_t reset_and_return_illegal(int _errno, mbstate_t* ps) {
-  errno = _errno;
-  *(reinterpret_cast<uint32_t*>(ps->__seq)) = 0;
-  return ERR_ILLEGAL_SEQUENCE;
-}
-
-static size_t reset_and_return(int _return, mbstate_t* ps) {
-  *(reinterpret_cast<uint32_t*>(ps->__seq)) = 0;
-  return _return;
-}
-
-
 int mbsinit(const mbstate_t* ps) {
   return (ps == NULL || (*(reinterpret_cast<const uint32_t*>(ps->__seq)) == 0));
 }
@@ -88,104 +61,8 @@
   static mbstate_t __private_state;
   mbstate_t* state = (ps == NULL) ? &__private_state : ps;
 
-  // We should never get to a state which has all 4 bytes of the sequence set.
-  // Full state verification is done when decoding the sequence (after we have
-  // all the bytes).
-  if (mbstate_get_byte(state, 3) != 0) {
-    return reset_and_return_illegal(EINVAL, state);
-  }
-
-  if (s == NULL) {
-    s = "";
-    n = 1;
-    pwc = NULL;
-  }
-
-  if (n == 0) {
-    return 0;
-  }
-
-  uint8_t ch;
-  if (mbsinit(state) && (((ch = static_cast<uint8_t>(*s)) & ~0x7f) == 0)) {
-    // Fast path for plain ASCII characters.
-    if (pwc != NULL) {
-      *pwc = ch;
-    }
-    return (ch != '\0' ? 1 : 0);
-  }
-
-  // Determine the number of octets that make up this character
-  // from the first octet, and a mask that extracts the
-  // interesting bits of the first octet. We already know
-  // the character is at least two bytes long.
-  size_t length;
-  int mask;
-
-  // We also specify a lower bound for the character code to
-  // detect redundant, non-"shortest form" encodings. For
-  // example, the sequence C0 80 is _not_ a legal representation
-  // of the null character. This enforces a 1-to-1 mapping
-  // between character codes and their multibyte representations.
-  wchar_t lower_bound;
-
-  // The first byte in the state (if any) tells the length.
-  size_t bytes_so_far = mbstate_bytes_so_far(state);
-  ch = bytes_so_far > 0 ? mbstate_get_byte(state, 0) : static_cast<uint8_t>(*s);
-  if ((ch & 0x80) == 0) {
-    mask = 0x7f;
-    length = 1;
-    lower_bound = 0;
-  } else if ((ch & 0xe0) == 0xc0) {
-    mask = 0x1f;
-    length = 2;
-    lower_bound = 0x80;
-  } else if ((ch & 0xf0) == 0xe0) {
-    mask = 0x0f;
-    length = 3;
-    lower_bound = 0x800;
-  } else if ((ch & 0xf8) == 0xf0) {
-    mask = 0x07;
-    length = 4;
-    lower_bound = 0x10000;
-  } else {
-    // Malformed input; input is not UTF-8. See RFC 3629.
-    return reset_and_return_illegal(EILSEQ, state);
-  }
-
-  // Fill in the state.
-  size_t bytes_wanted = length - bytes_so_far;
-  size_t i;
-  for (i = 0; i < MIN(bytes_wanted, n); i++) {
-    if (!mbsinit(state) && ((*s & 0xc0) != 0x80)) {
-      // Malformed input; bad characters in the middle of a character.
-      return reset_and_return_illegal(EILSEQ, state);
-    }
-    mbstate_set_byte(state, bytes_so_far + i, *s++);
-  }
-  if (i < bytes_wanted) {
-    return ERR_INCOMPLETE_SEQUENCE;
-  }
-
-  // Decode the octet sequence representing the character in chunks
-  // of 6 bits, most significant first.
-  wchar_t wch = mbstate_get_byte(state, 0) & mask;
-  for (i = 1; i < length; i++) {
-    wch <<= 6;
-    wch |= mbstate_get_byte(state, i) & 0x3f;
-  }
-
-  if (wch < lower_bound) {
-    // Malformed input; redundant encoding.
-    return reset_and_return_illegal(EILSEQ, state);
-  }
-  if ((wch >= 0xd800 && wch <= 0xdfff) || wch == 0xfffe || wch == 0xffff) {
-    // Malformed input; invalid code points.
-    return reset_and_return_illegal(EILSEQ, state);
-  }
-  if (pwc != NULL) {
-    *pwc = wch;
-  }
-  return reset_and_return(wch == L'\0' ? 0 : bytes_wanted, state);
+  // Our wchar_t is UTF-32
+  return mbrtoc32(reinterpret_cast<char32_t*>(pwc), s, n, state);
 }
 
 size_t mbsnrtowcs(wchar_t* dst, const char** src, size_t nmc, size_t len, mbstate_t* ps) {
@@ -212,10 +89,10 @@
         r = 1;
       } else {
         r = mbrtowc(NULL, *src + i, nmc - i, state);
-        if (r == ERR_ILLEGAL_SEQUENCE) {
+        if (r == __MB_ERR_ILLEGAL_SEQUENCE) {
           return reset_and_return_illegal(EILSEQ, state);
         }
-        if (r == ERR_INCOMPLETE_SEQUENCE) {
+        if (r == __MB_ERR_INCOMPLETE_SEQUENCE) {
           return reset_and_return_illegal(EILSEQ, state);
         }
         if (r == 0) {
@@ -246,11 +123,11 @@
       r = 1;
     } else {
       r = mbrtowc(dst + o, *src + i, nmc - i, state);
-      if (r == ERR_ILLEGAL_SEQUENCE) {
+      if (r == __MB_ERR_ILLEGAL_SEQUENCE) {
         *src += i;
         return reset_and_return_illegal(EILSEQ, state);
       }
-      if (r == ERR_INCOMPLETE_SEQUENCE) {
+      if (r == __MB_ERR_INCOMPLETE_SEQUENCE) {
         *src += nmc;
         return reset_and_return(EILSEQ, state);
       }
@@ -272,63 +149,8 @@
   static mbstate_t __private_state;
   mbstate_t* state = (ps == NULL) ? &__private_state : ps;
 
-  if (s == NULL) {
-    // Equivalent to wcrtomb(buf, L'\0', ps).
-    return reset_and_return(1, state);
-  }
-
-  // POSIX states that if wc is a null wide character, a null byte shall be
-  // stored, preceded by any shift sequence needed to restore the initial shift
-  // state. Since shift states are not supported, only the null byte is stored.
-  if (wc == L'\0') {
-    *s = '\0';
-    reset_and_return(1, state);
-  }
-
-  if (!mbsinit(state)) {
-    return reset_and_return_illegal(EILSEQ, state);
-  }
-
-  if ((wc & ~0x7f) == 0) {
-    // Fast path for plain ASCII characters.
-    *s = wc;
-    return 1;
-  }
-
-  // Determine the number of octets needed to represent this character.
-  // We always output the shortest sequence possible. Also specify the
-  // first few bits of the first octet, which contains the information
-  // about the sequence length.
-  uint8_t lead;
-  size_t length;
-  if ((wc & ~0x7f) == 0) {
-    lead = 0;
-    length = 1;
-  } else if ((wc & ~0x7ff) == 0) {
-    lead = 0xc0;
-    length = 2;
-  } else if ((wc & ~0xffff) == 0) {
-    lead = 0xe0;
-    length = 3;
-  } else if ((wc & ~0x1fffff) == 0) {
-    lead = 0xf0;
-    length = 4;
-  } else {
-    errno = EILSEQ;
-    return ERR_ILLEGAL_SEQUENCE;
-  }
-
-  // Output the octets representing the character in chunks
-  // of 6 bits, least significant last. The first octet is
-  // a special case because it contains the sequence length
-  // information.
-  for (size_t i = length - 1; i > 0; i--) {
-    s[i] = (wc & 0x3f) | 0x80;
-    wc >>= 6;
-  }
-  *s = (wc & 0xff) | lead;
-
-  return length;
+  // Our wchar_t is UTF-32
+  return c32rtomb(s, static_cast<char32_t>(wc), state);
 }
 
 size_t wcsnrtombs(char* dst, const wchar_t** src, size_t nwc, size_t len, mbstate_t* ps) {
@@ -352,7 +174,7 @@
         r = 1;
       } else {
         r = wcrtomb(buf, wc, state);
-        if (r == ERR_ILLEGAL_SEQUENCE) {
+        if (r == __MB_ERR_ILLEGAL_SEQUENCE) {
           return r;
         }
       }
@@ -373,14 +195,14 @@
     } else if (len - o >= sizeof(buf)) {
       // Enough space to translate in-place.
       r = wcrtomb(dst + o, wc, state);
-      if (r == ERR_ILLEGAL_SEQUENCE) {
+      if (r == __MB_ERR_ILLEGAL_SEQUENCE) {
         *src += i;
         return r;
       }
     } else {
       // May not be enough space; use temp buffer.
       r = wcrtomb(buf, wc, state);
-      if (r == ERR_ILLEGAL_SEQUENCE) {
+      if (r == __MB_ERR_ILLEGAL_SEQUENCE) {
         *src += i;
         return r;
       }
diff --git a/libc/include/uchar.h b/libc/include/uchar.h
new file mode 100644
index 0000000..e1fcb5c
--- /dev/null
+++ b/libc/include/uchar.h
@@ -0,0 +1,53 @@
+/*
+ * 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 _UCHAR_H_
+#define _UCHAR_H_
+
+#include <sys/cdefs.h>
+#include <wchar.h>
+
+__BEGIN_DECLS
+
+#define __STD_UTF_16__ 1
+#define __STD_UTF_32__ 1
+
+size_t c16rtomb(char* __restrict, char16_t, mbstate_t* __restrict);
+size_t c32rtomb(char* __restrict, char32_t, mbstate_t* __restrict);
+size_t mbrtoc16(char16_t* __restrict,
+                const char* __restrict,
+                size_t,
+                mbstate_t* __restrict);
+size_t mbrtoc32(char32_t* __restrict,
+                const char* __restrict,
+                size_t,
+                mbstate_t* __restrict);
+
+__END_DECLS
+
+#endif /* _UCHAR_H_ */
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