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
114 struct 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
128 MBUITER_INLINE void
mbuiter_multi_next(struct mbuiter_multi * iter)129 mbuiter_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
189 MBUITER_INLINE void
mbuiter_multi_reloc(struct mbuiter_multi * iter,ptrdiff_t ptrdiff)190 mbuiter_multi_reloc (struct mbuiter_multi *iter, ptrdiff_t ptrdiff)
191 {
192 iter->cur.ptr += ptrdiff;
193 }
194
195 MBUITER_INLINE void
mbuiter_multi_copy(struct mbuiter_multi * new_iter,const struct mbuiter_multi * old_iter)196 mbuiter_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. */
207 typedef 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