libs/libc/wchar: add wcsncpy implementation

Signed-off-by: guoshichao <guoshichao@xiaomi.com>

libs/libc/wchar/Make.defs

@@ -28,6 +28,7 @@ CSRCS += lib_wcstoull.c lib_wcstold.c lib_wcstof.c lib_wcstod.c
 CSRCS += lib_swprintf.c lib_mbsnrtowcs.c lib_wcsnrtombs.c lib_mbsinit.c
 CSRCS += lib_mbrlen.c lib_mbsrtowcs.c lib_wcsrtombs.c lib_wcscpy.c
 CSRCS += lib_wcscat.c lib_wcslcat.c lib_wcsncat.c lib_wcsrchr.c lib_wcschr.c
+CSRCS += lib_wcsncpy.c
 
 # Add the wchar directory to the build
 

libs/libc/wchar/lib_wcsncpy.c

@@ -0,0 +1,69 @@
+/****************************************************************************
+ * libs/libc/wchar/lib_wcsncpy.c
+ *
+ * Copyright © 2005-2014 Rich Felker, et al.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <wchar.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name:  wcsncpy
+ *
+ * Description:
+ *    Copies the first num characters of source to destination. If the end
+ *    of the source C wide string (which is signaled by a null wide
+ *    character) is found before num characters have been copied, destination
+ *    is padded with additional null wide characters until a total of num
+ *    characters have been written to it.
+ *
+ * Input Parameters:
+ *   d - the destination wchar string where the content is to be copied
+ *   s - the wchar string to be copied
+ *   n - maximum number of wide characters to be copied from source
+ *
+ * Returned Value:
+ *   A pointer to the destination string
+ *
+ ****************************************************************************/
+
+FAR wchar_t *wcsncpy(FAR wchar_t *d, FAR const wchar_t *s, size_t n)
+{
+  FAR wchar_t *a = d;
+
+  while (n && *s)
+    {
+      *d++ = *s++;
+      n--;
+    }
+
+  wmemset(d, 0, n);
+  return a;
+}