1 /* Iterating through multibyte strings: macros for multi-byte encodings.
2 Copyright (C) 2001, 2005, 2007, 2009-2023 Free Software Foundation, Inc.
3
4 This file is free software: you can redistribute it and/or modify
5 it under the terms of the GNU Lesser General Public License as
6 published by the Free Software Foundation, either version 3 of the
7 License, or (at your option) any later version.
8
9 This file 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 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public License
15 along with this program. If not, see <https://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 /* This file uses _GL_INLINE_HEADER_BEGIN, _GL_INLINE,
93 _GL_ATTRIBUTE_ALWAYS_INLINE. */
94 #if !_GL_CONFIG_H_INCLUDED
95 #error "Please include config.h first."
96 #endif
97
98 #include <assert.h>
99 #include <stddef.h>
100 #include <stdlib.h>
101 #include <string.h>
102 #include <uchar.h>
103 #include <wchar.h>
104
105 #include "mbchar.h"
106 #include "strnlen1.h"
107
108 _GL_INLINE_HEADER_BEGIN
109 #ifndef MBUITER_INLINE
110 # define MBUITER_INLINE _GL_INLINE _GL_ATTRIBUTE_ALWAYS_INLINE
111 #endif
112
113 struct mbuiter_multi
114 {
115 #if !GNULIB_MBRTOC32_REGULAR
116 bool in_shift; /* true if next byte may not be interpreted as ASCII */
117 /* If GNULIB_MBRTOC32_REGULAR, it is always false,
118 so optimize it away. */
119 #endif
120 mbstate_t state; /* if in_shift: current shift state */
121 /* If GNULIB_MBRTOC32_REGULAR, it is in an initial state
122 before and after every mbuiter_multi_next invocation.
123 */
124 bool next_done; /* true if mbui_avail has already filled the following */
125 unsigned int cur_max; /* A cache of MB_CUR_MAX. */
126 struct mbchar cur; /* the current character:
127 const char *cur.ptr pointer to current character
128 The following are only valid after mbui_avail.
129 size_t cur.bytes number of bytes of current character
130 bool cur.wc_valid true if wc is a valid 32-bit wide character
131 char32_t cur.wc if wc_valid: the current character
132 */
133 };
134
135 MBUITER_INLINE void
136 mbuiter_multi_next (struct mbuiter_multi *iter)
137 {
138 if (iter->next_done)
139 return;
140 #if !GNULIB_MBRTOC32_REGULAR
141 if (iter->in_shift)
142 goto with_shift;
143 #endif
144 /* Handle most ASCII characters quickly, without calling mbrtowc(). */
145 if (is_basic (*iter->cur.ptr))
146 {
147 /* These characters are part of the POSIX portable character set.
148 For most of them, namely those in the ISO C basic character set,
149 ISO C 99 guarantees that their wide character code is identical to
150 their char code. For the few other ones, this is the case as well,
151 in all locale encodings that are in use. The 32-bit wide character
152 code is the same as well. */
153 iter->cur.bytes = 1;
154 iter->cur.wc = *iter->cur.ptr;
155 iter->cur.wc_valid = true;
156 }
157 else
158 {
159 assert (mbsinit (&iter->state));
160 #if !GNULIB_MBRTOC32_REGULAR
161 iter->in_shift = true;
162 with_shift:
163 #endif
164 iter->cur.bytes = mbrtoc32 (&iter->cur.wc, iter->cur.ptr,
165 strnlen1 (iter->cur.ptr, iter->cur_max),
166 &iter->state);
167 if (iter->cur.bytes == (size_t) -1)
168 {
169 /* An invalid multibyte sequence was encountered. */
170 iter->cur.bytes = 1;
171 iter->cur.wc_valid = false;
172 /* Allow the next invocation to continue from a sane state. */
173 #if !GNULIB_MBRTOC32_REGULAR
174 iter->in_shift = false;
175 #endif
176 mbszero (&iter->state);
177 }
178 else if (iter->cur.bytes == (size_t) -2)
179 {
180 /* An incomplete multibyte character at the end. */
181 iter->cur.bytes = strlen (iter->cur.ptr);
182 iter->cur.wc_valid = false;
183 /* Whether to set iter->in_shift = false and reset iter->state
184 or not is not important; the string end is reached anyway. */
185 }
186 else
187 {
188 if (iter->cur.bytes == 0)
189 {
190 /* A null wide character was encountered. */
191 iter->cur.bytes = 1;
192 assert (*iter->cur.ptr == '\0');
193 assert (iter->cur.wc == 0);
194 }
195 #if !GNULIB_MBRTOC32_REGULAR
196 else if (iter->cur.bytes == (size_t) -3)
197 /* The previous multibyte sequence produced an additional 32-bit
198 wide character. */
199 iter->cur.bytes = 0;
200 #endif
201 iter->cur.wc_valid = true;
202
203 /* When in an initial state, we can go back treating ASCII
204 characters more quickly. */
205 #if !GNULIB_MBRTOC32_REGULAR
206 if (mbsinit (&iter->state))
207 iter->in_shift = false;
208 #endif
209 }
210 }
211 iter->next_done = true;
212 }
213
214 MBUITER_INLINE void
215 mbuiter_multi_reloc (struct mbuiter_multi *iter, ptrdiff_t ptrdiff)
216 {
217 iter->cur.ptr += ptrdiff;
218 }
219
220 MBUITER_INLINE void
221 mbuiter_multi_copy (struct mbuiter_multi *new_iter, const struct mbuiter_multi *old_iter)
222 {
223 #if !GNULIB_MBRTOC32_REGULAR
224 if ((new_iter->in_shift = old_iter->in_shift))
225 memcpy (&new_iter->state, &old_iter->state, sizeof (mbstate_t));
226 else
227 #endif
228 mbszero (&new_iter->state);
229 new_iter->next_done = old_iter->next_done;
230 new_iter->cur_max = old_iter->cur_max;
231 mb_copy (&new_iter->cur, &old_iter->cur);
232 }
233
234 /* Iteration macros. */
235 typedef struct mbuiter_multi mbui_iterator_t;
236 #if !GNULIB_MBRTOC32_REGULAR
237 #define mbui_init(iter, startptr) \
238 ((iter).cur.ptr = (startptr), \
239 (iter).in_shift = false, mbszero (&(iter).state), \
240 (iter).next_done = false, \
241 (iter).cur_max = MB_CUR_MAX)
242 #else
243 /* Optimized: no in_shift. */
244 #define mbui_init(iter, startptr) \
245 ((iter).cur.ptr = (startptr), \
246 mbszero (&(iter).state), \
247 (iter).next_done = false, \
248 (iter).cur_max = MB_CUR_MAX)
249 #endif
250 #define mbui_avail(iter) \
251 (mbuiter_multi_next (&(iter)), !mb_isnul ((iter).cur))
252 #define mbui_advance(iter) \
253 ((iter).cur.ptr += (iter).cur.bytes, (iter).next_done = false)
254
255 /* Access to the current character. */
256 #define mbui_cur(iter) (iter).cur
257 #define mbui_cur_ptr(iter) (iter).cur.ptr
258
259 /* Relocation. */
260 #define mbui_reloc(iter, ptrdiff) mbuiter_multi_reloc (&iter, ptrdiff)
261
262 /* Copying an iterator. */
263 #define mbui_copy mbuiter_multi_copy
264
265 _GL_INLINE_HEADER_END
266
267 #endif /* _MBUITER_H */