1/* Iterating through multibyte strings: macros for multi-byte encodings.
2   Copyright (C) 2001, 2005, 2007, 2009-2012 Free Software Foundation, Inc.
3
4   This program is free software: you can redistribute it and/or modify
5   it under the terms of the GNU General Public License as published by
6   the Free Software Foundation; either version 3 of the License, or
7   (at your option) any later version.
8
9   This program is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   GNU General Public License for more details.
13
14   You should have received a copy of the GNU General Public License
15   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
16
17/* Written by Bruno Haible <bruno@clisp.org>.  */
18
19/* The macros in this file implement forward iteration through a
20   multi-byte string, without knowing its length a-priori.
21
22   With these macros, an iteration loop that looks like
23
24      char *iter;
25      for (iter = buf; *iter != '\0'; iter++)
26        {
27          do_something (*iter);
28        }
29
30   becomes
31
32      mbui_iterator_t iter;
33      for (mbui_init (iter, buf); mbui_avail (iter); mbui_advance (iter))
34        {
35          do_something (mbui_cur_ptr (iter), mb_len (mbui_cur (iter)));
36        }
37
38   The benefit of these macros over plain use of mbrtowc is:
39   - Handling of invalid multibyte sequences is possible without
40     making the code more complicated, while still preserving the
41     invalid multibyte sequences.
42
43   Compared to mbiter.h, the macros here don't need to know the string's
44   length a-priori.  The downside is that at each step, the look-ahead
45   that guards against overrunning the terminating '\0' is more expensive.
46   The mbui_* macros are therefore suitable when there is a high probability
47   that only the first few multibyte characters need to be inspected.
48   Whereas the mbi_* macros are better if usually the iteration runs
49   through the entire string.
50
51   mbui_iterator_t
52     is a type usable for variable declarations.
53
54   mbui_init (iter, startptr)
55     initializes the iterator, starting at startptr.
56
57   mbui_avail (iter)
58     returns true if there are more multibyte characters available before
59     the end of string is reached. In this case, mbui_cur (iter) is
60     initialized to the next multibyte character.
61
62   mbui_advance (iter)
63     advances the iterator by one multibyte character.
64
65   mbui_cur (iter)
66     returns the current multibyte character, of type mbchar_t.  All the
67     macros defined in mbchar.h can be used on it.
68
69   mbui_cur_ptr (iter)
70     return a pointer to the beginning of the current multibyte character.
71
72   mbui_reloc (iter, ptrdiff)
73     relocates iterator when the string is moved by ptrdiff bytes.
74
75   mbui_copy (&destiter, &srciter)
76     copies srciter to destiter.
77
78   Here are the function prototypes of the macros.
79
80   extern void          mbui_init (mbui_iterator_t iter, const char *startptr);
81   extern bool          mbui_avail (mbui_iterator_t iter);
82   extern void          mbui_advance (mbui_iterator_t iter);
83   extern mbchar_t      mbui_cur (mbui_iterator_t iter);
84   extern const char *  mbui_cur_ptr (mbui_iterator_t iter);
85   extern void          mbui_reloc (mbui_iterator_t iter, ptrdiff_t ptrdiff);
86   extern void          mbui_copy (mbui_iterator_t *new, const mbui_iterator_t *old);
87 */
88
89#ifndef _MBUITER_H
90#define _MBUITER_H 1
91
92#include <assert.h>
93#include <stdbool.h>
94#include <stddef.h>
95#include <stdlib.h>
96#include <string.h>
97
98/* Tru64 with Desktop Toolkit C has a bug: <stdio.h> must be included before
99   <wchar.h>.
100   BSD/OS 4.1 has a bug: <stdio.h> and <time.h> must be included before
101   <wchar.h>.  */
102#include <stdio.h>
103#include <time.h>
104#include <wchar.h>
105
106#include "mbchar.h"
107#include "strnlen1.h"
108
109_GL_INLINE_HEADER_BEGIN
110#ifndef MBUITER_INLINE
111# define MBUITER_INLINE _GL_INLINE
112#endif
113
114struct mbuiter_multi
115{
116  bool in_shift;        /* true if next byte may not be interpreted as ASCII */
117  mbstate_t state;      /* if in_shift: current shift state */
118  bool next_done;       /* true if mbui_avail has already filled the following */
119  struct mbchar cur;    /* the current character:
120        const char *cur.ptr             pointer to current character
121        The following are only valid after mbui_avail.
122        size_t cur.bytes                number of bytes of current character
123        bool cur.wc_valid               true if wc is a valid wide character
124        wchar_t cur.wc                  if wc_valid: the current character
125        */
126};
127
128MBUITER_INLINE void
129mbuiter_multi_next (struct mbuiter_multi *iter)
130{
131  if (iter->next_done)
132    return;
133  if (iter->in_shift)
134    goto with_shift;
135  /* Handle most ASCII characters quickly, without calling mbrtowc().  */
136  if (is_basic (*iter->cur.ptr))
137    {
138      /* These characters are part of the basic character set.  ISO C 99
139         guarantees that their wide character code is identical to their
140         char code.  */
141      iter->cur.bytes = 1;
142      iter->cur.wc = *iter->cur.ptr;
143      iter->cur.wc_valid = true;
144    }
145  else
146    {
147      assert (mbsinit (&iter->state));
148      iter->in_shift = true;
149    with_shift:
150      iter->cur.bytes = mbrtowc (&iter->cur.wc, iter->cur.ptr,
151                                 strnlen1 (iter->cur.ptr, MB_CUR_MAX),
152                                 &iter->state);
153      if (iter->cur.bytes == (size_t) -1)
154        {
155          /* An invalid multibyte sequence was encountered.  */
156          iter->cur.bytes = 1;
157          iter->cur.wc_valid = false;
158          /* Whether to set iter->in_shift = false and reset iter->state
159             or not is not very important; the string is bogus anyway.  */
160        }
161      else if (iter->cur.bytes == (size_t) -2)
162        {
163          /* An incomplete multibyte character at the end.  */
164          iter->cur.bytes = strlen (iter->cur.ptr);
165          iter->cur.wc_valid = false;
166          /* Whether to set iter->in_shift = false and reset iter->state
167             or not is not important; the string end is reached anyway.  */
168        }
169      else
170        {
171          if (iter->cur.bytes == 0)
172            {
173              /* A null wide character was encountered.  */
174              iter->cur.bytes = 1;
175              assert (*iter->cur.ptr == '\0');
176              assert (iter->cur.wc == 0);
177            }
178          iter->cur.wc_valid = true;
179
180          /* When in the initial state, we can go back treating ASCII
181             characters more quickly.  */
182          if (mbsinit (&iter->state))
183            iter->in_shift = false;
184        }
185    }
186  iter->next_done = true;
187}
188
189MBUITER_INLINE void
190mbuiter_multi_reloc (struct mbuiter_multi *iter, ptrdiff_t ptrdiff)
191{
192  iter->cur.ptr += ptrdiff;
193}
194
195MBUITER_INLINE void
196mbuiter_multi_copy (struct mbuiter_multi *new_iter, const struct mbuiter_multi *old_iter)
197{
198  if ((new_iter->in_shift = old_iter->in_shift))
199    memcpy (&new_iter->state, &old_iter->state, sizeof (mbstate_t));
200  else
201    memset (&new_iter->state, 0, sizeof (mbstate_t));
202  new_iter->next_done = old_iter->next_done;
203  mb_copy (&new_iter->cur, &old_iter->cur);
204}
205
206/* Iteration macros.  */
207typedef struct mbuiter_multi mbui_iterator_t;
208#define mbui_init(iter, startptr) \
209  ((iter).cur.ptr = (startptr), \
210   (iter).in_shift = false, memset (&(iter).state, '\0', sizeof (mbstate_t)), \
211   (iter).next_done = false)
212#define mbui_avail(iter) \
213  (mbuiter_multi_next (&(iter)), !mb_isnul ((iter).cur))
214#define mbui_advance(iter) \
215  ((iter).cur.ptr += (iter).cur.bytes, (iter).next_done = false)
216
217/* Access to the current character.  */
218#define mbui_cur(iter) (iter).cur
219#define mbui_cur_ptr(iter) (iter).cur.ptr
220
221/* Relocation.  */
222#define mbui_reloc(iter, ptrdiff) mbuiter_multi_reloc (&iter, ptrdiff)
223
224/* Copying an iterator.  */
225#define mbui_copy mbuiter_multi_copy
226
227_GL_INLINE_HEADER_END
228
229#endif /* _MBUITER_H */
230