gnulib/lib/unistr/u32-prev.c

/* Iterate over previous character in UTF-32 string.
   Copyright (C) 2002, 2006-2007, 2009-2020 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 Lesser 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
   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"

const uint32_t *
u32_prev (ucs4_t *puc, const uint32_t *s, const uint32_t *start)
{
  if (s != start)
    {
      uint32_t c_1 = s[-1];

      if (c_1 < 0xd800 || (c_1 >= 0xe000 && c_1 < 0x110000))
        {
          *puc = c_1;
          return s - 1;
        }
    }
  return NULL;
}