/* Conversion UCS-4 to UTF-8.
   Copyright (C) 2002, 2006-2007, 2009-2019 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2002.

   This program is free software: you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published
   by the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program 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
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include "unistr.h"

#ifndef FALLTHROUGH
# if __GNUC__ < 7
#  define FALLTHROUGH ((void) 0)
# else
#  define FALLTHROUGH __attribute__ ((__fallthrough__))
# endif
#endif

int
u8_uctomb_aux (uint8_t *s, ucs4_t uc, int 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;
}