/* Conversion from UTF-16 to legacy encodings.
   Copyright (C) 2002, 2006-2017 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or
   modify it under the terms of either:

     * 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.

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at your
       option) any later version.

   or both in parallel, as here.
   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/>.  */

/* Written by Bruno Haible <bruno@clisp.org>.  */

#include <config.h>

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

#include <errno.h>
#include <stdlib.h>
#include <string.h>

#include "striconveha.h"
#include "unistr.h"

#define SIZEOF(array) (sizeof (array) / sizeof (array[0]))

/* Name of UTF-16 encoding with machine dependent endianness and alignment.  */
#if defined _LIBICONV_VERSION || (((__GLIBC__ > 2) || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 2)) && !defined __UCLIBC__)
# ifdef WORDS_BIGENDIAN
#  define UTF16_NAME "UTF-16BE"
# else
#  define UTF16_NAME "UTF-16LE"
# endif
#endif


#if !defined UTF16_NAME

/* A variant of u16_to_u8 that treats an incomplete sequence of units at the
   end as a harmless no-op, rather than reporting it as an EILSEQ error.  */

#define FUNC u16_to_u8_lenient
#define SRC_UNIT uint16_t
#define DST_UNIT uint8_t

static DST_UNIT *
FUNC (const SRC_UNIT *s, size_t n, DST_UNIT *resultbuf, size_t *lengthp)
{
  const SRC_UNIT *s_end = s + n;
  /* Output string accumulator.  */
  DST_UNIT *result;
  size_t allocated;
  size_t length;

  if (resultbuf != NULL)
    {
      result = resultbuf;
      allocated = *lengthp;
    }
  else
    {
      result = NULL;
      allocated = 0;
    }
  length = 0;
  /* Invariants:
     result is either == resultbuf or == NULL or malloc-allocated.
     If length > 0, then result != NULL.  */

  while (s < s_end)
    {
      ucs4_t uc;
      int count;

      /* Fetch a Unicode character from the input string.  */
      count = u16_mbtoucr (&uc, s, s_end - s);
      if (count < 0)
        {
          if (count == -2)
            /* Incomplete sequence of units.  */
            break;
          if (!(result == resultbuf || result == NULL))
            free (result);
          errno = EILSEQ;
          return NULL;
        }
      s += count;

      /* Store it in the output string.  */
      count = u8_uctomb (result + length, uc, allocated - length);
      if (count == -1)
        {
          if (!(result == resultbuf || result == NULL))
            free (result);
          errno = EILSEQ;
          return NULL;
        }
      if (count == -2)
        {
          DST_UNIT *memory;

          allocated = (allocated > 0 ? 2 * allocated : 12);
          if (length + 6 > allocated)
            allocated = length + 6;
          if (result == resultbuf || result == NULL)
            memory = (DST_UNIT *) malloc (allocated * sizeof (DST_UNIT));
          else
            memory =
              (DST_UNIT *) realloc (result, allocated * sizeof (DST_UNIT));

          if (memory == NULL)
            {
              if (!(result == resultbuf || result == NULL))
                free (result);
              errno = ENOMEM;
              return NULL;
            }
          if (result == resultbuf && length > 0)
            memcpy ((char *) memory, (char *) result,
                    length * sizeof (DST_UNIT));
          result = memory;
          count = u8_uctomb (result + length, uc, allocated - length);
          if (count < 0)
            abort ();
        }
      length += count;
    }

  if (length == 0)
    {
      if (result == NULL)
        {
          /* Return a non-NULL value.  NULL means error.  */
          result = (DST_UNIT *) malloc (1);
          if (result == NULL)
            {
              errno = ENOMEM;
              return NULL;
            }
        }
    }
  else if (result != resultbuf && length < allocated)
    {
      /* Shrink the allocated memory if possible.  */
      DST_UNIT *memory;

      memory = (DST_UNIT *) realloc (result, length * sizeof (DST_UNIT));
      if (memory != NULL)
        result = memory;
    }

  *lengthp = length;
  return result;
}

#undef DST_UNIT
#undef SRC_UNIT
#undef FUNC

#endif


#define FUNC u16_conv_to_encoding
#define UNIT uint16_t
#define U_TO_U8 u16_to_u8_lenient
#define U_MBLEN u16_mblen
#if defined UTF16_NAME
# define UTF_NAME UTF16_NAME
# define HAVE_UTF_NAME 1
#endif
#include "u-conv-to-enc.h"