/****************************************************************************
 * libs/libc/wchar/lib_wcsnrtombs.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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 <wchar.h>
#include <string.h>
#include <limits.h>

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

/****************************************************************************
 * Name: wcsnrtombs
 *
 * Description:
 *   The 'wcsrtombs' function converts a string of wide characters
 *   indirectly pointed to by 'src' to a corresponding multibyte character
 *   string stored in the array pointed to by 'dst'.  No more than 'len'
 *   bytes are written to'dst'.
 *
 *   If 'dst' is NULL, no characters are stored.
 *
 *   If 'dst' is not NULL, the pointer pointed to by 'src' is updated to
 *   point to the character after the one that conversion stopped at.  If
 *   conversion stops because a null character is encountered, *'src' is set
 *   to NULL.
 *
 *   The mbstate_t argument, 'ps', is used to keep track of the shift state.
 *   If it is NULL, 'wcsrtombs' uses an internal, static mbstate_t object,
 *   which is initialized to the initial conversion state at program startup.
 *
 *   The 'wcsnrtombs' function behaves identically to 'wcsrtombs', except
 *   that conversion stops after reading at most 'nwc' characters from the
 *   buffer pointed to by 'src'.
 *
 * Returned Value:
 *   The 'wcsrtombs' and 'wcsnrtombs' functions return the number of bytes
 *   stored in the array pointed to by 'dst' (not including any terminating
 *   null), if successful, otherwise it returns (size_t)-1.
 *
 * Portability:
 *   'wcsrtombs' is defined by C99 standard.
 *   'wcsnrtombs' is defined by the POSIX.1-2008 standard.
 ****************************************************************************/

size_t wcsnrtombs(FAR char *dst, FAR const wchar_t **src, size_t nwc,
                  size_t len, FAR mbstate_t *ps)
{
  FAR const wchar_t *ws = *src;
  size_t cnt = 0;

  if (dst == NULL)
    {
      len = 0;
    }

  while (ws != NULL && nwc != 0)
    {
      char tmp[MB_LEN_MAX];
      size_t res;

      if (*ws == 0)
        {
          ws = NULL;
          break;
        }

      res = wcrtomb(len < MB_LEN_MAX ? tmp : dst, *ws, ps);
      if ((ssize_t)res < 0)
        {
          cnt = res;
          break;
        }

      if (dst != NULL)
        {
          if (len < MB_LEN_MAX)
            {
              if (res > len)
                {
                  break;
                }

              memcpy(dst, tmp, res);
            }

          dst += res;
          len -= res;
        }

      ws++;
      nwc--;
      cnt += res;
    }

  if (dst != NULL)
    {
      *src = ws;
    }

  return cnt;
}