/* Conversion UCS-4 to UTF-8.

   Copyright (C) 2002, 2006-2007, 2009-2025 Free Software Foundation, Inc.

   Written by Bruno Haible <bruno@clisp.org>, 2002.

   This file is free software: you can redistribute it and/or modify

   it under the terms of the GNU Lesser General Public License as

   published by the Free Software Foundation; either version 2.1 of the

   License, or (at your option) any later version.

   This file is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License

   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#include "unistr.h"

#include "attribute.h"

int

u8_uctomb_aux (uint8_t *s, ucs4_t uc, ptrdiff_t n)

{

  int count;

  if (uc < 0x80)

    /* The case n >= 1 is already handled by the caller.  */

    return -2;

  else if (uc < 0x800)

    count = 2;

  else if (uc < 0x10000)

    {

      if (uc < 0xd800 || uc >= 0xe000)

        count = 3;

      else

        return -1;

    }

  else if (uc < 0x110000)

    count = 4;

  else

    return -1;

  if (n < count)

    return -2;

  switch (count) /* note: code falls through cases! */

    {

    case 4: s[3] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x10000;

      FALLTHROUGH;

    case 3: s[2] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x800;

      FALLTHROUGH;

    case 2: s[1] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0xc0;

  /*case 1:*/ s[0] = uc;

    }

  return count;

}