+#include <uchar.h>
+#include <wchar.h>
+
+size_t mbrtoc16(char16_t *restrict pc16, const char *restrict s, size_t n, mbstate_t *restrict ps)
+{
+ unsigned *pending = (unsigned *)ps;
+
+ if (!s) return mbrtoc16(0, "", 1, ps);
+
+ /* mbrtowc states for partial UTF-8 characters have the high bit set;
+ * we use nonzero states without high bit for pending surrogates. */
+ if ((int)*pending > 0) {
+ if (pc16) *pc16 = *pending;
+ *pending = 0;
+ return -3;
+ }
+
+ wchar_t wc;
+ size_t ret = mbrtowc(&wc, s, n, ps);
+ if (ret <= 4) {
+ if (wc >= 0x10000) {
+ *pending = (wc & 0x3ff) + 0xdc00;
+ wc = 0xd7c0 + (wc >> 10);
+ }
+ if (pc16) *pc16 = wc;
+ }
+ return ret;
+}