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+/* Iterating through multibyte strings: macros for multi-byte encodings.
+   Copyright (C) 2001, 2005, 2007, 2009-2016 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 */