/* Character set conversion.
   Copyright (C) 1999-2001, 2007, 2009-2018 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 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 <iconv.h>

#include <stddef.h>

#if REPLACE_ICONV_UTF
# include <errno.h>
# include <stdint.h>
# include <stdlib.h>
# include "unistr.h"
# ifndef uintptr_t
#  define uintptr_t unsigned long
# endif
#endif

#if REPLACE_ICONV_UTF

/* UTF-{16,32}{BE,LE} converters taken from GNU libiconv 1.11.  */

/* Return code if invalid. (xxx_mbtowc) */
# define RET_ILSEQ      -1
/* Return code if no bytes were read. (xxx_mbtowc) */
# define RET_TOOFEW     -2

/* Return code if invalid. (xxx_wctomb) */
# define RET_ILUNI      -1
/* Return code if output buffer is too small. (xxx_wctomb, xxx_reset) */
# define RET_TOOSMALL   -2

/*
 * UTF-16BE
 */

/* Specification: RFC 2781 */

static int
utf16be_mbtowc (ucs4_t *pwc, const unsigned char *s, size_t n)
{
  if (n >= 2)
    {
      ucs4_t wc = (s[0] << 8) + s[1];
      if (wc >= 0xd800 && wc < 0xdc00)
        {
          if (n >= 4)
            {
              ucs4_t wc2 = (s[2] << 8) + s[3];
              if (!(wc2 >= 0xdc00 && wc2 < 0xe000))
                return RET_ILSEQ;
              *pwc = 0x10000 + ((wc - 0xd800) << 10) + (wc2 - 0xdc00);
              return 4;
            }
        }
      else if (wc >= 0xdc00 && wc < 0xe000)
        {
          return RET_ILSEQ;
        }
      else
        {
          *pwc = wc;
          return 2;
        }
    }
  return RET_TOOFEW;
}

static int
utf16be_wctomb (unsigned char *r, ucs4_t wc, size_t n)
{
  if (!(wc >= 0xd800 && wc < 0xe000))
    {
      if (wc < 0x10000)
        {
          if (n >= 2)
            {
              r[0] = (unsigned char) (wc >> 8);
              r[1] = (unsigned char) wc;
              return 2;
            }
          else
            return RET_TOOSMALL;
        }
      else if (wc < 0x110000)
        {
          if (n >= 4)
            {
              ucs4_t wc1 = 0xd800 + ((wc - 0x10000) >> 10);
              ucs4_t wc2 = 0xdc00 + ((wc - 0x10000) & 0x3ff);
              r[0] = (unsigned char) (wc1 >> 8);
              r[1] = (unsigned char) wc1;
              r[2] = (unsigned char) (wc2 >> 8);
              r[3] = (unsigned char) wc2;
              return 4;
            }
          else
            return RET_TOOSMALL;
        }
    }
  return RET_ILUNI;
}

/*
 * UTF-16LE
 */

/* Specification: RFC 2781 */

static int
utf16le_mbtowc (ucs4_t *pwc, const unsigned char *s, size_t n)
{
  if (n >= 2)
    {
      ucs4_t wc = s[0] + (s[1] << 8);
      if (wc >= 0xd800 && wc < 0xdc00)
        {
          if (n >= 4)
            {
              ucs4_t wc2 = s[2] + (s[3] << 8);
              if (!(wc2 >= 0xdc00 && wc2 < 0xe000))
                return RET_ILSEQ;
              *pwc = 0x10000 + ((wc - 0xd800) << 10) + (wc2 - 0xdc00);
              return 4;
            }
        }
      else if (wc >= 0xdc00 && wc < 0xe000)
        {
          return RET_ILSEQ;
        }
      else
        {
          *pwc = wc;
          return 2;
        }
    }
  return RET_TOOFEW;
}

static int
utf16le_wctomb (unsigned char *r, ucs4_t wc, size_t n)
{
  if (!(wc >= 0xd800 && wc < 0xe000))
    {
      if (wc < 0x10000)
        {
          if (n >= 2)
            {
              r[0] = (unsigned char) wc;
              r[1] = (unsigned char) (wc >> 8);
              return 2;
            }
          else
            return RET_TOOSMALL;
        }
      else if (wc < 0x110000)
        {
          if (n >= 4)
            {
              ucs4_t wc1 = 0xd800 + ((wc - 0x10000) >> 10);
              ucs4_t wc2 = 0xdc00 + ((wc - 0x10000) & 0x3ff);
              r[0] = (unsigned char) wc1;
              r[1] = (unsigned char) (wc1 >> 8);
              r[2] = (unsigned char) wc2;
              r[3] = (unsigned char) (wc2 >> 8);
              return 4;
            }
          else
            return RET_TOOSMALL;
        }
    }
  return RET_ILUNI;
}

/*
 * UTF-32BE
 */

/* Specification: Unicode 3.1 Standard Annex #19 */

static int
utf32be_mbtowc (ucs4_t *pwc, const unsigned char *s, size_t n)
{
  if (n >= 4)
    {
      ucs4_t wc = (s[0] << 24) + (s[1] << 16) + (s[2] << 8) + s[3];
      if (wc < 0x110000 && !(wc >= 0xd800 && wc < 0xe000))
        {
          *pwc = wc;
          return 4;
        }
      else
        return RET_ILSEQ;
    }
  return RET_TOOFEW;
}

static int
utf32be_wctomb (unsigned char *r, ucs4_t wc, size_t n)
{
  if (wc < 0x110000 && !(wc >= 0xd800 && wc < 0xe000))
    {
      if (n >= 4)
        {
          r[0] = 0;
          r[1] = (unsigned char) (wc >> 16);
          r[2] = (unsigned char) (wc >> 8);
          r[3] = (unsigned char) wc;
          return 4;
        }
      else
        return RET_TOOSMALL;
    }
  return RET_ILUNI;
}

/*
 * UTF-32LE
 */

/* Specification: Unicode 3.1 Standard Annex #19 */

static int
utf32le_mbtowc (ucs4_t *pwc, const unsigned char *s, size_t n)
{
  if (n >= 4)
    {
      ucs4_t wc = s[0] + (s[1] << 8) + (s[2] << 16) + (s[3] << 24);
      if (wc < 0x110000 && !(wc >= 0xd800 && wc < 0xe000))
        {
          *pwc = wc;
          return 4;
        }
      else
        return RET_ILSEQ;
    }
  return RET_TOOFEW;
}

static int
utf32le_wctomb (unsigned char *r, ucs4_t wc, size_t n)
{
  if (wc < 0x110000 && !(wc >= 0xd800 && wc < 0xe000))
    {
      if (n >= 4)
        {
          r[0] = (unsigned char) wc;
          r[1] = (unsigned char) (wc >> 8);
          r[2] = (unsigned char) (wc >> 16);
          r[3] = 0;
          return 4;
        }
      else
        return RET_TOOSMALL;
    }
  return RET_ILUNI;
}

#endif

size_t
rpl_iconv (iconv_t cd,
           ICONV_CONST char **inbuf, size_t *inbytesleft,
           char **outbuf, size_t *outbytesleft)
#undef iconv
{
#if REPLACE_ICONV_UTF
  switch ((uintptr_t) cd)
    {
      {
        int (*xxx_wctomb) (unsigned char *, ucs4_t, size_t);

        case (uintptr_t) _ICONV_UTF8_UTF16BE:
          xxx_wctomb = utf16be_wctomb;
          goto loop_from_utf8;
        case (uintptr_t) _ICONV_UTF8_UTF16LE:
          xxx_wctomb = utf16le_wctomb;
          goto loop_from_utf8;
        case (uintptr_t) _ICONV_UTF8_UTF32BE:
          xxx_wctomb = utf32be_wctomb;
          goto loop_from_utf8;
        case (uintptr_t) _ICONV_UTF8_UTF32LE:
          xxx_wctomb = utf32le_wctomb;
          goto loop_from_utf8;

       loop_from_utf8:
        if (inbuf == NULL || *inbuf == NULL)
          return 0;
        {
          ICONV_CONST char *inptr = *inbuf;
          size_t inleft = *inbytesleft;
          char *outptr = *outbuf;
          size_t outleft = *outbytesleft;
          size_t res = 0;
          while (inleft > 0)
            {
              ucs4_t uc;
              int m = u8_mbtoucr (&uc, (const uint8_t *) inptr, inleft);
              if (m <= 0)
                {
                  if (m == -1)
                    {
                      errno = EILSEQ;
                      res = (size_t)(-1);
                      break;
                    }
                  if (m == -2)
                    {
                      errno = EINVAL;
                      res = (size_t)(-1);
                      break;
                    }
                  abort ();
                }
              else
                {
                  int n = xxx_wctomb ((uint8_t *) outptr, uc, outleft);
                  if (n < 0)
                    {
                      if (n == RET_ILUNI)
                        {
                          errno = EILSEQ;
                          res = (size_t)(-1);
                          break;
                        }
                      if (n == RET_TOOSMALL)
                        {
                          errno = E2BIG;
                          res = (size_t)(-1);
                          break;
                        }
                      abort ();
                    }
                  else
                    {
                      inptr += m;
                      inleft -= m;
                      outptr += n;
                      outleft -= n;
                    }
                }
            }
          *inbuf = inptr;
          *inbytesleft = inleft;
          *outbuf = outptr;
          *outbytesleft = outleft;
          return res;
        }
      }

      {
        int (*xxx_mbtowc) (ucs4_t *, const unsigned char *, size_t);

        case (uintptr_t) _ICONV_UTF16BE_UTF8:
          xxx_mbtowc = utf16be_mbtowc;
          goto loop_to_utf8;
        case (uintptr_t) _ICONV_UTF16LE_UTF8:
          xxx_mbtowc = utf16le_mbtowc;
          goto loop_to_utf8;
        case (uintptr_t) _ICONV_UTF32BE_UTF8:
          xxx_mbtowc = utf32be_mbtowc;
          goto loop_to_utf8;
        case (uintptr_t) _ICONV_UTF32LE_UTF8:
          xxx_mbtowc = utf32le_mbtowc;
          goto loop_to_utf8;

       loop_to_utf8:
        if (inbuf == NULL || *inbuf == NULL)
          return 0;
        {
          ICONV_CONST char *inptr = *inbuf;
          size_t inleft = *inbytesleft;
          char *outptr = *outbuf;
          size_t outleft = *outbytesleft;
          size_t res = 0;
          while (inleft > 0)
            {
              ucs4_t uc;
              int m = xxx_mbtowc (&uc, (const uint8_t *) inptr, inleft);
              if (m <= 0)
                {
                  if (m == RET_ILSEQ)
                    {
                      errno = EILSEQ;
                      res = (size_t)(-1);
                      break;
                    }
                  if (m == RET_TOOFEW)
                    {
                      errno = EINVAL;
                      res = (size_t)(-1);
                      break;
                    }
                  abort ();
                }
              else
                {
                  int n = u8_uctomb ((uint8_t *) outptr, uc, outleft);
                  if (n < 0)
                    {
                      if (n == -1)
                        {
                          errno = EILSEQ;
                          res = (size_t)(-1);
                          break;
                        }
                      if (n == -2)
                        {
                          errno = E2BIG;
                          res = (size_t)(-1);
                          break;
                        }
                      abort ();
                    }
                  else
                    {
                      inptr += m;
                      inleft -= m;
                      outptr += n;
                      outleft -= n;
                    }
                }
            }
          *inbuf = inptr;
          *inbytesleft = inleft;
          *outbuf = outptr;
          *outbytesleft = outleft;
          return res;
        }
      }
    }
#endif
  return iconv (cd, inbuf, inbytesleft, outbuf, outbytesleft);
}