/* Iterating through multibyte strings: macros for multi-byte encodings.

   Copyright (C) 2001, 2005, 2007, 2009-2017 Free Software Foundation, Inc.

   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 <http://www.gnu.org/licenses/>.  */

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

/* The macros in this file implement forward iteration through a

   multi-byte string.

   With these macros, an iteration loop that looks like

      char *iter;

      for (iter = buf; iter < buf + buflen; iter++)

        {

          do_something (*iter);

        }

   becomes

      mbi_iterator_t iter;

      for (mbi_init (iter, buf, buflen); mbi_avail (iter); mbi_advance (iter))

        {

          do_something (mbi_cur_ptr (iter), mb_len (mbi_cur (iter)));

        }

   The benefit of these macros over plain use of mbrtowc is:

   - Handling of invalid multibyte sequences is possible without

     making the code more complicated, while still preserving the

     invalid multibyte sequences.

   mbi_iterator_t

     is a type usable for variable declarations.

   mbi_init (iter, startptr, length)

     initializes the iterator, starting at startptr and crossing length bytes.

   mbi_avail (iter)

     returns true if there are more multibyte characters available before

     the end of string is reached. In this case, mbi_cur (iter) is

     initialized to the next multibyte character.

   mbi_advance (iter)

     advances the iterator by one multibyte character.

   mbi_cur (iter)

     returns the current multibyte character, of type mbchar_t.  All the

     macros defined in mbchar.h can be used on it.

   mbi_cur_ptr (iter)

     return a pointer to the beginning of the current multibyte character.

   mbi_reloc (iter, ptrdiff)

     relocates iterator when the string is moved by ptrdiff bytes.

   mbi_copy (&destiter, &srciter)

     copies srciter to destiter.

   Here are the function prototypes of the macros.

   extern void          mbi_init (mbi_iterator_t iter,

                                  const char *startptr, size_t length);

   extern bool          mbi_avail (mbi_iterator_t iter);

   extern void          mbi_advance (mbi_iterator_t iter);

   extern mbchar_t      mbi_cur (mbi_iterator_t iter);

   extern const char *  mbi_cur_ptr (mbi_iterator_t iter);

   extern void          mbi_reloc (mbi_iterator_t iter, ptrdiff_t ptrdiff);

   extern void          mbi_copy (mbi_iterator_t *new, const mbi_iterator_t *old);

 */

#ifndef _MBITER_H

#define _MBITER_H 1

#include <assert.h>

#include <stdbool.h>

#include <stddef.h>

#include <string.h>

/* Tru64 with Desktop Toolkit C has a bug: <stdio.h> must be included before

   <wchar.h>.

   BSD/OS 4.1 has a bug: <stdio.h> and <time.h> must be included before

   <wchar.h>.  */

#include <stdio.h>

#include <time.h>

#include <wchar.h>

#include "mbchar.h"

#ifndef _GL_INLINE_HEADER_BEGIN

 #error "Please include config.h first."

#endif

_GL_INLINE_HEADER_BEGIN

#ifndef MBITER_INLINE

# define MBITER_INLINE _GL_INLINE

#endif

struct mbiter_multi

{

  const char *limit;    /* pointer to end of string */

  bool in_shift;        /* true if next byte may not be interpreted as ASCII */

  mbstate_t state;      /* if in_shift: current shift state */

  bool next_done;       /* true if mbi_avail has already filled the following */

  struct mbchar cur;    /* the current character:

        const char *cur.ptr             pointer to current character

        The following are only valid after mbi_avail.

        size_t cur.bytes                number of bytes of current character

        bool cur.wc_valid               true if wc is a valid wide character

        wchar_t cur.wc                  if wc_valid: the current character

        */

};

MBITER_INLINE void

mbiter_multi_next (struct mbiter_multi *iter)

{

  if (iter->next_done)

    return;

  if (iter->in_shift)

    goto with_shift;

  /* Handle most ASCII characters quickly, without calling mbrtowc().  */

  if (is_basic (*iter->cur.ptr))

    {

      /* These characters are part of the basic character set.  ISO C 99

         guarantees that their wide character code is identical to their

         char code.  */

      iter->cur.bytes = 1;

      iter->cur.wc = *iter->cur.ptr;

      iter->cur.wc_valid = true;

    }

  else

    {

      assert (mbsinit (&iter->state));

      iter->in_shift = true;

    with_shift:

      iter->cur.bytes = mbrtowc (&iter->cur.wc, iter->cur.ptr,

                                 iter->limit - iter->cur.ptr, &iter->state);

      if (iter->cur.bytes == (size_t) -1)

        {

          /* An invalid multibyte sequence was encountered.  */

          iter->cur.bytes = 1;

          iter->cur.wc_valid = false;

          /* Whether to set iter->in_shift = false and reset iter->state

             or not is not very important; the string is bogus anyway.  */

        }

      else if (iter->cur.bytes == (size_t) -2)

        {

          /* An incomplete multibyte character at the end.  */

          iter->cur.bytes = iter->limit - iter->cur.ptr;

          iter->cur.wc_valid = false;

          /* Whether to set iter->in_shift = false and reset iter->state

             or not is not important; the string end is reached anyway.  */

        }

      else

        {

          if (iter->cur.bytes == 0)

            {

              /* A null wide character was encountered.  */

              iter->cur.bytes = 1;

              assert (*iter->cur.ptr == '\0');

              assert (iter->cur.wc == 0);

            }

          iter->cur.wc_valid = true;

          /* When in the initial state, we can go back treating ASCII

             characters more quickly.  */

          if (mbsinit (&iter->state))

            iter->in_shift = false;

        }

    }

  iter->next_done = true;

}

MBITER_INLINE void

mbiter_multi_reloc (struct mbiter_multi *iter, ptrdiff_t ptrdiff)

{

  iter->cur.ptr += ptrdiff;

  iter->limit += ptrdiff;

}

MBITER_INLINE void

mbiter_multi_copy (struct mbiter_multi *new_iter, const struct mbiter_multi *old_iter)

{

  new_iter->limit = old_iter->limit;

  if ((new_iter->in_shift = old_iter->in_shift))

    memcpy (&new_iter->state, &old_iter->state, sizeof (mbstate_t));

  else

    memset (&new_iter->state, 0, sizeof (mbstate_t));

  new_iter->next_done = old_iter->next_done;

  mb_copy (&new_iter->cur, &old_iter->cur);

}

/* Iteration macros.  */

typedef struct mbiter_multi mbi_iterator_t;

#define mbi_init(iter, startptr, length) \

  ((iter).cur.ptr = (startptr), (iter).limit = (iter).cur.ptr + (length), \

   (iter).in_shift = false, memset (&(iter).state, '\0', sizeof (mbstate_t)), \

   (iter).next_done = false)

#define mbi_avail(iter) \

  ((iter).cur.ptr < (iter).limit && (mbiter_multi_next (&(iter)), true))

#define mbi_advance(iter) \

  ((iter).cur.ptr += (iter).cur.bytes, (iter).next_done = false)

/* Access to the current character.  */

#define mbi_cur(iter) (iter).cur

#define mbi_cur_ptr(iter) (iter).cur.ptr

/* Relocation.  */

#define mbi_reloc(iter, ptrdiff) mbiter_multi_reloc (&iter, ptrdiff)

/* Copying an iterator.  */

#define mbi_copy mbiter_multi_copy

_GL_INLINE_HEADER_END

#endif /* _MBITER_H */