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/* Iterating through multibyte strings: macros for multi-byte encodings.
Copyright (C) 2001, 2005, 2007, 2009-2023 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://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
/* This file uses _GL_INLINE_HEADER_BEGIN, _GL_INLINE. */
#if !_GL_CONFIG_H_INCLUDED
#error "Please include config.h first."
#endif
#include <assert.h>
#include <stddef.h>
#include <string.h>
#include <wchar.h>
#include "mbchar.h"
_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 */
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