libs/libc/wchar: add wcsrchr 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 lib_wcsncat.c
+CSRCS += lib_wcscat.c lib_wcslcat.c lib_wcsncat.c lib_wcsrchr.c
 
 # Add the wchar directory to the build
 

libs/libc/wchar/lib_wcsrchr.c

@@ -0,0 +1,58 @@
+/****************************************************************************
+ * libs/libc/wchar/lib_wcsrchr.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:  wcsrchr
+ *
+ * Description:
+ *    Locate last occurrence of character in wide string
+ *
+ * Input Parameters:
+ *   s - the wide string that to search on
+ *   c - the character to be located
+ *
+ * Returned Value:
+ *   A pointer to the last occurrence of "c" in "s".
+ *
+ ****************************************************************************/
+
+FAR wchar_t *wcsrchr(FAR const wchar_t *s, wchar_t c)
+{
+  FAR const wchar_t *p;
+  for (p = s + wcslen(s); p >= s && *p != c; p--);
+
+  return p >= s ? (FAR wchar_t *)p : 0;
+}