string/mbstowcs.c

/*	A part of the Windows CE C Extra Library (celibc)
	Copyright 2007-2015 PC GO Ld.

	This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, 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 General Public License for more details.
*/

#include <windows.h>

size_t mbstowcs(wchar_t *wcstr, const char *mbstr, size_t count) {
	if(!wcstr) return (size_t)(MultiByteToWideChar(CP_ACP, 0, mbstr, -1, NULL, 0) - 1);
	if(!count) return 0;

	const char *t = mbstr;
	while(*t && t - mbstr < count) t++;
	SetLastError(0);
	int r = MultiByteToWideChar(CP_ACP, 0, mbstr, ((size_t)(t - mbstr) < count) ? -1 : count, wcstr, count);
	if(r) return wcstr[r - 1] ? r : r - 1;
	if(GetLastError()) return (size_t)-1;		// Error
	return 0;
}