/* Convert multibyte character to wide character.
   Copyright (C) 1999-2002, 2005-2019 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"
# include "glthread/lock.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

/* This lock protects the internal state of mbtowc against multiple simultaneous
   calls of mbrtowc.  */
gl_lock_define_initialized(static, mbtowc_lock)

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;
    enc_t enc;
    int res;

    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.  */

    enc = locale_enc_cached ();

    if (enc == enc_utf8) /* UTF-8 */
      {
        /* Achieve multi-thread safety by not calling mbtowc() at all.  */
        /* Cf. unistr/u8-mbtouc.c.  */
        unsigned char c = (unsigned char) p[0];

        if (c < 0x80)
          {
            if (pwc != NULL)
              *pwc = c;
            res = (c == 0 ? 0 : 1);
            goto success;
          }
        if (c >= 0xc2)
          {
            if (c < 0xe0)
              {
                if (m == 1)
                  goto incomplete;
                else /* m >= 2 */
                  {
                    unsigned char c2 = (unsigned char) p[1];

                    if ((c2 ^ 0x80) < 0x40)
                      {
                        if (pwc != NULL)
                          *pwc = ((unsigned int) (c & 0x1f) << 6)
                                 | (unsigned int) (c2 ^ 0x80);
                        res = 2;
                        goto success;
                      }
                  }
              }
            else if (c < 0xf0)
              {
                if (m == 1)
                  goto incomplete;
                else
                  {
                    unsigned char c2 = (unsigned char) p[1];

                    if ((c2 ^ 0x80) < 0x40
                        && (c >= 0xe1 || c2 >= 0xa0)
                        && (c != 0xed || c2 < 0xa0))
                      {
                        if (m == 2)
                          goto incomplete;
                        else /* m >= 3 */
                          {
                            unsigned char c3 = (unsigned char) p[2];

                            if ((c3 ^ 0x80) < 0x40)
                              {
                                if (pwc != NULL)
                                  *pwc = ((unsigned int) (c & 0x0f) << 12)
                                         | ((unsigned int) (c2 ^ 0x80) << 6)
                                         | (unsigned int) (c3 ^ 0x80);
                                res = 3;
                                goto success;
                              }
                          }
                      }
                  }
              }
            else if (c <= 0xf4)
              {
                if (m == 1)
                  goto incomplete;
                else
                  {
                    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
                          {
                            unsigned char c3 = (unsigned char) p[2];

                            if ((c3 ^ 0x80) < 0x40)
                              {
                                if (m == 3)
                                  goto incomplete;
                                else /* m >= 4 */
                                  {
                                    unsigned char c4 = (unsigned char) p[3];

                                    if ((c4 ^ 0x80) < 0x40)
                                      {
                                        if (pwc != NULL)
                                          *pwc = ((unsigned int) (c & 0x07) << 18)
                                                 | ((unsigned int) (c2 ^ 0x80) << 12)
                                                 | ((unsigned int) (c3 ^ 0x80) << 6)
                                                 | (unsigned int) (c4 ^ 0x80);
                                        res = 4;
                                        goto success;
                                      }
                                  }
                              }
                          }
                      }
                  }
              }
          }
        goto invalid;
      }
    else
      {
        /* The hidden internal state of mbtowc would make this function not
           multi-thread safe.  Achieve multi-thread safety through a lock.  */
        gl_lock_lock (mbtowc_lock);

        /* Put the hidden internal state of mbtowc into its initial state.
           This is needed at least with glibc, uClibc, and MSVC CRT.
           See <https://sourceware.org/bugzilla/show_bug.cgi?id=9674>.  */
        mbtowc (NULL, NULL, 0);

        res = mbtowc (pwc, p, m);

        gl_lock_unlock (mbtowc_lock);

        if (res >= 0)
          {
            if (pwc != NULL && ((*pwc == 0) != (res == 0)))
              abort ();
            goto success;
          }

        /* 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 (already handled above).
           Use specialized code for each.  */
        if (m >= 4 || m >= MB_CUR_MAX)
          goto invalid;
        /* Here MB_CUR_MAX > 1 and 0 < m < 4.  */
        switch (enc)
          {
          /* 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;
          }
      }

   success:
    /* res >= 0 is the corrected return value of mbtowc (pwc, p, m).  */
    if (nstate >= (res > 0 ? res : 1))
      abort ();
    res -= nstate;
    pstate[0] = 0;
    return res;

   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