[UCRT] Import Microsoft.Windows.SDK.CRTSource version 10.0.22621.3

Imported from https://www.nuget.org/packages/Microsoft.Windows.SDK.CRTSource/10.0.22621.3
License: MIT

sdk/lib/ucrt/mbstring/mbsnextc.cpp

@@ -0,0 +1,64 @@
+/***
+*mbsnextc.c - Get the next character in an MBCS string.
+*
+*       Copyright (c) Microsoft Corporation. All rights reserved.
+*
+*Purpose:
+*       To return the value of the next character in an MBCS string.
+*
+*******************************************************************************/
+#ifndef _MBCS
+    #error This file should only be compiled with _MBCS defined
+#endif
+
+#include <corecrt_internal_mbstring.h>
+#include <locale.h>
+#include <stdlib.h>
+
+#pragma warning(disable:__WARNING_POTENTIAL_BUFFER_OVERFLOW_NULLTERMINATED) // 26018
+
+/***
+*_mbsnextc:  Returns the next character in a string.
+*
+*Purpose:
+*       To return the value of the next character in an MBCS string.
+*       Does not advance pointer to the next character.
+*
+*Entry:
+*       unsigned char *s = string
+*
+*Exit:
+*       unsigned int next = next character.
+*
+*Exceptions:
+*       Input parameters are validated. Refer to the validation section of the function.
+*
+*******************************************************************************/
+
+extern "C" unsigned int __cdecl _mbsnextc_l(
+        const unsigned char *s,
+        _locale_t plocinfo
+        )
+{
+        unsigned int  next = 0;
+        _LocaleUpdate _loc_update(plocinfo);
+
+        /* validation section */
+        _VALIDATE_RETURN(s != nullptr, EINVAL, 0);
+
+        /* don't skip forward 2 if the leadbyte is followed by EOS (dud string)
+           also don't assert as we are too low-level
+        */
+        if ( _ismbblead_l(*s, _loc_update.GetLocaleT()) && s[1]!='\0')
+            next = ((unsigned int) *s++) << 8;
+
+        next += (unsigned int) *s;
+
+        return(next);
+}
+extern "C" unsigned int (__cdecl _mbsnextc)(
+        const unsigned char *s
+        )
+{
+    return _mbsnextc_l(s, nullptr);
+}