libs/libc/wchar: add wcsncat implementation

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

libs/libc/wchar/Make.defs

@@ -27,7 +27,7 @@ CSRCS += lib_wcscoll.c lib_wcstol.c lib_wcstoll.c lib_wcstoul.c
 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
+CSRCS += lib_wcscat.c lib_wcslcat.c lib_wcsncat.c
 
 # Add the wchar directory to the build
 

libs/libc/wchar/lib_wcsncat.c

@@ -0,0 +1,69 @@
+/****************************************************************************
+ * libs/libc/wchar/lib_wcsncat.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:  wcsncat
+ *
+ * Description:
+ *    Appends the first num wide characters of source to destination, plus a
+ *    terminating null wide character. If the length of the C wide string in
+ *    source is less than num, only the content up to the terminating null
+ *    wide character is copied.
+ *
+ * Input Parameters:
+ *   d - the dest wchar string that contains the concatenated resulting
+ *       string
+ *   s - the source wchar string to be appended
+ *   n - maximum number of characters to be appended
+ *
+ * Returned Value:
+ *   The pointer point to the begin of the concatenated string
+ *
+ ****************************************************************************/
+
+FAR wchar_t *wcsncat(FAR wchar_t *d, FAR const wchar_t *s, size_t n)
+{
+  FAR wchar_t *a = d;
+
+  d += wcslen(d);
+  while (n-- && *s)
+    {
+      *d++ = *s++;
+    }
+
+  *d++ = 0;
+  return a;
+}