/* Convert multibyte character to wide character.

   Copyright (C) 1999-2002, 2005-2018 Free Software Foundation, Inc.

   Written by Bruno Haible <bruno@clisp.org>, 2008.

   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 <wchar.h>

#if C_LOCALE_MAYBE_EILSEQ

# include "hard-locale.h"

# include <locale.h>

#endif

#if GNULIB_defined_mbstate_t

/* Implement mbrtowc() on top of mbtowc().  */

# include <errno.h>

# include <stdlib.h>

# include "localcharset.h"

# include "streq.h"

# include "verify.h"

# ifndef FALLTHROUGH

#  if __GNUC__ < 7

#   define FALLTHROUGH ((void) 0)

#  else

#   define FALLTHROUGH __attribute__ ((__fallthrough__))

#  endif

# endif

/* Returns a classification of special values of the encoding of the current

   locale.  */

typedef enum {

  enc_other,      /* other */

  enc_utf8,       /* UTF-8 */

  enc_eucjp,      /* EUC-JP */

  enc_94,         /* EUC-KR, GB2312, BIG5 */

  enc_euctw,      /* EUC-TW */

  enc_gb18030,    /* GB18030 */

  enc_sjis        /* SJIS */

} enc_t;

static inline enc_t

locale_enc (void)

{

  const char *encoding = locale_charset ();

  if (STREQ_OPT (encoding, "UTF-8", 'U', 'T', 'F', '-', '8', 0, 0, 0, 0))

    return enc_utf8;

  if (STREQ_OPT (encoding, "EUC-JP", 'E', 'U', 'C', '-', 'J', 'P', 0, 0, 0))

    return enc_eucjp;

  if (STREQ_OPT (encoding, "EUC-KR", 'E', 'U', 'C', '-', 'K', 'R', 0, 0, 0)

      || STREQ_OPT (encoding, "GB2312", 'G', 'B', '2', '3', '1', '2', 0, 0, 0)

      || STREQ_OPT (encoding, "BIG5", 'B', 'I', 'G', '5', 0, 0, 0, 0, 0))

    return enc_94;

  if (STREQ_OPT (encoding, "EUC-TW", 'E', 'U', 'C', '-', 'T', 'W', 0, 0, 0))

    return enc_euctw;

  if (STREQ_OPT (encoding, "GB18030", 'G', 'B', '1', '8', '0', '3', '0', 0, 0))

    return enc_gb18030;

  if (STREQ_OPT (encoding, "SJIS", 'S', 'J', 'I', 'S', 0, 0, 0, 0, 0))

    return enc_sjis;

  return enc_other;

}

#if GNULIB_WCHAR_SINGLE

/* When we know that the locale does not change, provide a speedup by

   caching the value of locale_enc.  */

static int cached_locale_enc = -1;

static inline enc_t

locale_enc_cached (void)

{

  if (cached_locale_enc < 0)

    cached_locale_enc = locale_enc ();

  return cached_locale_enc;

}

#else

/* By default, don't make assumptions, hence no caching.  */

# define locale_enc_cached locale_enc

#endif

verify (sizeof (mbstate_t) >= 4);

static char internal_state[4];

size_t

mbrtowc (wchar_t *pwc, const char *s, size_t n, mbstate_t *ps)

{

  char *pstate = (char *)ps;

  if (s == NULL)

    {

      pwc = NULL;

      s = "";

      n = 1;

    }

  if (n == 0)

    return (size_t)(-2);

  /* Here n > 0.  */

  if (pstate == NULL)

    pstate = internal_state;

  {

    size_t nstate = pstate[0];

    char buf[4];

    const char *p;

    size_t m;

    switch (nstate)

      {

      case 0:

        p = s;

        m = n;

        break;

      case 3:

        buf[2] = pstate[3];

        FALLTHROUGH;

      case 2:

        buf[1] = pstate[2];

        FALLTHROUGH;

      case 1:

        buf[0] = pstate[1];

        p = buf;

        m = nstate;

        buf[m++] = s[0];

        if (n >= 2 && m < 4)

          {

            buf[m++] = s[1];

            if (n >= 3 && m < 4)

              buf[m++] = s[2];

          }

        break;

      default:

        errno = EINVAL;

        return (size_t)(-1);

      }

    /* Here m > 0.  */

# if __GLIBC__ || defined __UCLIBC__

    /* Work around bug <https://sourceware.org/bugzilla/show_bug.cgi?id=9674> */

    mbtowc (NULL, NULL, 0);

# endif

    {

      int res = mbtowc (pwc, p, m);

      if (res >= 0)

        {

          if (pwc != NULL && ((*pwc == 0) != (res == 0)))

            abort ();

          if (nstate >= (res > 0 ? res : 1))

            abort ();

          res -= nstate;

          pstate[0] = 0;

          return res;

        }

      /* mbtowc does not distinguish between invalid and incomplete multibyte

         sequences.  But mbrtowc needs to make this distinction.

         There are two possible approaches:

           - Use iconv() and its return value.

           - Use built-in knowledge about the possible encodings.

         Given the low quality of implementation of iconv() on the systems that

         lack mbrtowc(), we use the second approach.

         The possible encodings are:

           - 8-bit encodings,

           - EUC-JP, EUC-KR, GB2312, EUC-TW, BIG5, GB18030, SJIS,

           - UTF-8.

         Use specialized code for each.  */

      if (m >= 4 || m >= MB_CUR_MAX)

        goto invalid;

      /* Here MB_CUR_MAX > 1 and 0 < m < 4.  */

      switch (locale_enc_cached ())

        {

        case enc_utf8: /* UTF-8 */

          {

            /* Cf. unistr/u8-mblen.c.  */

            unsigned char c = (unsigned char) p[0];

            if (c >= 0xc2)

              {

                if (c < 0xe0)

                  {

                    if (m == 1)

                      goto incomplete;

                  }

                else if (c < 0xf0)

                  {

                    if (m == 1)

                      goto incomplete;

                    if (m == 2)

                      {

                        unsigned char c2 = (unsigned char) p[1];

                        if ((c2 ^ 0x80) < 0x40

                            && (c >= 0xe1 || c2 >= 0xa0)

                            && (c != 0xed || c2 < 0xa0))

                          goto incomplete;

                      }

                  }

                else if (c <= 0xf4)

                  {

                    if (m == 1)

                      goto incomplete;

                    else /* m == 2 || m == 3 */

                      {

                        unsigned char c2 = (unsigned char) p[1];

                        if ((c2 ^ 0x80) < 0x40

                            && (c >= 0xf1 || c2 >= 0x90)

                            && (c < 0xf4 || (c == 0xf4 && c2 < 0x90)))

                          {

                            if (m == 2)

                              goto incomplete;

                            else /* m == 3 */

                              {

                                unsigned char c3 = (unsigned char) p[2];

                                if ((c3 ^ 0x80) < 0x40)

                                  goto incomplete;

                              }

                          }

                      }

                  }

              }

            goto invalid;

          }

        /* As a reference for this code, you can use the GNU libiconv

           implementation.  Look for uses of the RET_TOOFEW macro.  */

        case enc_eucjp: /* EUC-JP */

          {

            if (m == 1)

              {

                unsigned char c = (unsigned char) p[0];

                if ((c >= 0xa1 && c < 0xff) || c == 0x8e || c == 0x8f)

                  goto incomplete;

              }

            if (m == 2)

              {

                unsigned char c = (unsigned char) p[0];

                if (c == 0x8f)

                  {

                    unsigned char c2 = (unsigned char) p[1];

                    if (c2 >= 0xa1 && c2 < 0xff)

                      goto incomplete;

                  }

              }

            goto invalid;

          }

        case enc_94: /* EUC-KR, GB2312, BIG5 */

          {

            if (m == 1)

              {

                unsigned char c = (unsigned char) p[0];

                if (c >= 0xa1 && c < 0xff)

                  goto incomplete;

              }

            goto invalid;

          }

        case enc_euctw: /* EUC-TW */

          {

            if (m == 1)

              {

                unsigned char c = (unsigned char) p[0];

                if ((c >= 0xa1 && c < 0xff) || c == 0x8e)

                  goto incomplete;

              }

            else /* m == 2 || m == 3 */

              {

                unsigned char c = (unsigned char) p[0];

                if (c == 0x8e)

                  goto incomplete;

              }

            goto invalid;

          }

        case enc_gb18030: /* GB18030 */

          {

            if (m == 1)

              {

                unsigned char c = (unsigned char) p[0];

                if ((c >= 0x90 && c <= 0xe3) || (c >= 0xf8 && c <= 0xfe))

                  goto incomplete;

              }

            else /* m == 2 || m == 3 */

              {

                unsigned char c = (unsigned char) p[0];

                if (c >= 0x90 && c <= 0xe3)

                  {

                    unsigned char c2 = (unsigned char) p[1];

                    if (c2 >= 0x30 && c2 <= 0x39)

                      {

                        if (m == 2)

                          goto incomplete;

                        else /* m == 3 */

                          {

                            unsigned char c3 = (unsigned char) p[2];

                            if (c3 >= 0x81 && c3 <= 0xfe)

                              goto incomplete;

                          }

                      }

                  }

              }

            goto invalid;

          }

        case enc_sjis: /* SJIS */

          {

            if (m == 1)

              {

                unsigned char c = (unsigned char) p[0];

                if ((c >= 0x81 && c <= 0x9f) || (c >= 0xe0 && c <= 0xea)

                    || (c >= 0xf0 && c <= 0xf9))

                  goto incomplete;

              }

            goto invalid;

          }

        default:

          /* An unknown multibyte encoding.  */

          goto incomplete;

        }

     incomplete:

      {

        size_t k = nstate;

        /* Here 0 <= k < m < 4.  */

        pstate[++k] = s[0];

        if (k < m)

          {

            pstate[++k] = s[1];

            if (k < m)

              pstate[++k] = s[2];

          }

        if (k != m)

          abort ();

      }

      pstate[0] = m;

      return (size_t)(-2);

     invalid:

      errno = EILSEQ;

      /* The conversion state is undefined, says POSIX.  */

      return (size_t)(-1);

    }

  }

}

#else

/* Override the system's mbrtowc() function.  */

# undef mbrtowc

size_t

rpl_mbrtowc (wchar_t *pwc, const char *s, size_t n, mbstate_t *ps)

{

  size_t ret;

  wchar_t wc;

# if MBRTOWC_NULL_ARG2_BUG || MBRTOWC_RETVAL_BUG || MBRTOWC_EMPTY_INPUT_BUG

  if (s == NULL)

    {

      pwc = NULL;

      s = "";

      n = 1;

    }

# endif

# if MBRTOWC_EMPTY_INPUT_BUG

  if (n == 0)

    return (size_t) -2;

# endif

  if (! pwc)

    pwc = &wc;

# if MBRTOWC_RETVAL_BUG

  {

    static mbstate_t internal_state;

    /* Override mbrtowc's internal state.  We cannot call mbsinit() on the

       hidden internal state, but we can call it on our variable.  */

    if (ps == NULL)

      ps = &internal_state;

    if (!mbsinit (ps))

      {

        /* Parse the rest of the multibyte character byte for byte.  */

        size_t count = 0;

        for (; n > 0; s++, n--)

          {

            ret = mbrtowc (&wc, s, 1, ps);

            if (ret == (size_t)(-1))

              return (size_t)(-1);

            count++;

            if (ret != (size_t)(-2))

              {

                /* The multibyte character has been completed.  */

                *pwc = wc;

                return (wc == 0 ? 0 : count);

              }

          }

        return (size_t)(-2);

      }

  }

# endif

  ret = mbrtowc (pwc, s, n, ps);

# if MBRTOWC_NUL_RETVAL_BUG

  if (ret < (size_t) -2 && !*pwc)

    return 0;

# endif

# if C_LOCALE_MAYBE_EILSEQ

  if ((size_t) -2 <= ret && n != 0 && ! hard_locale (LC_CTYPE))

    {

      unsigned char uc = *s;

      *pwc = uc;

      return 1;

    }

# endif

  return ret;

}

#endif