libc/lib_memcpy.c: Add mempcpy method.

Signed-off-by: crafcat7 <chenrun1@xiaomi.com>

include/string.h

@@ -98,6 +98,7 @@ FAR void  *memrchr(FAR const void *s, int c, size_t n);
 FAR void  *memccpy(FAR void *s1, FAR const void *s2, int c, size_t n);
 int        memcmp(FAR const void *s1, FAR const void *s2, size_t n);
 FAR void  *memcpy(FAR void *dest, FAR const void *src, size_t n);
+FAR void  *mempcpy(FAR void *dest, FAR const void *src, size_t n);
 FAR void  *memmove(FAR void *dest, FAR const void *src, size_t count);
 FAR void  *memset(FAR void *s, int c, size_t n);
 FAR void  *memmem(FAR const void *haystack, size_t haystacklen,

libs/libc/string/Make.defs

@@ -30,6 +30,7 @@ CSRCS += lib_strndup.c lib_strcasestr.c lib_strpbrk.c lib_strrchr.c
 CSRCS += lib_strspn.c lib_strstr.c lib_strtok.c lib_strtokr.c
 CSRCS += lib_strsep.c lib_strerrorr.c lib_explicit_bzero.c lib_strsignal.c
 CSRCS += lib_index.c lib_rindex.c lib_timingsafe_bcmp.c lib_strverscmp.c
+CSRCS += lib_mempcpy.c
 
 ifneq ($(CONFIG_LIBC_ARCH_MEMCHR),y)
 CSRCS += lib_memchr.c

libs/libc/string/lib_mempcpy.c

@@ -0,0 +1,61 @@
+/****************************************************************************
+ * libs/libc/string/lib_mempcpy.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <string.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: mempcpy
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: mempcpy
+ *
+ * Description:
+ *   Like memcpy(), but returns address of byte after the last copied byte
+ *   in dest. This allows constructing data piecewise by copying its parts
+ *   into consecutive memory locations.
+ *
+ *   This function is not in POSIX.
+ *
+ * Input Parameters:
+ *   src  - Source location from which to copy.
+ *   dest - Destination location into which to copy.
+ *   n    - Size of data to be copied, in bytes.
+ *
+ * Returned Value:
+ *   A pointer to the byte in dest which immediately follows the last copied
+ *   byte.
+ *
+ ****************************************************************************/
+
+FAR void *mempcpy(FAR void *dest, FAR const void *src, size_t n)
+{
+  return (FAR char *)memcpy(dest, src, n) + n;
+}