libs/libc/string/lib_strncpy.c

/****************************************************************************
 * libs/libc/string/lib_strncpy.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>

#include "libc.h"

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: strncpy
 *
 * Description:
 *   Copies the string pointed to by 'src' (including the terminating NUL
 *   character) into the array pointed to by 'dest'.  strncpy() will not
 *   copy more than 'n' bytes from 'src' to 'dest' array (including the
 *   NUL terminator).
 *
 *   If the array pointed to by 'src' is a string that is shorter than 'n'
 *   bytes, NUL characters will be appended to the copy in the array
 *   pointed to by 'dest', until 'n' bytes in all are written.
 *
 *   If copying takes place between objects that overlap, the behavior is
 *   undefined.
 *
 * Returned Value:
 *   The strncpy() function returns the pointer to 'dest'
 *
 ****************************************************************************/

#if !defined(CONFIG_LIBC_ARCH_STRNCPY) && defined(LIBC_BUILD_STRNCPY)
#undef strncpy /* See mm/README.txt */
FAR char *strncpy(FAR char *dest, FAR const char *src, size_t n)
{
  FAR char *ret = dest;     /* Value to be returned */
  FAR char *end = dest + n; /* End of dest buffer + 1 byte */

  /* Copy up n bytes, breaking out of the loop early if a NUL terminator is
   * encountered.
   */

  while ((dest != end) && (*dest++ = *src++) != '\0')
    {
    }

  /* Note that there may be no NUL terminator in 'dest' */

  /* Pad the remainder of the array pointer to 'dest' with NULs */

  while (dest != end)
    {
      *dest++ = '\0';
    }

  return ret;
}
#endif