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1/* Iterating through multibyte strings: macros for multi-byte encodings.
2 Copyright (C) 2001, 2005 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 2, or (at your option)
7 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, write to the Free Software Foundation,
16 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
17
18/* Written by Bruno Haible <bruno@clisp.org>. */
19
20/* The macros in this file implement forward iteration through a
21 multi-byte string, without knowing its length a-priori.
22
23 With these macros, an iteration loop that looks like
24
25 char *iter;
26 for (iter = buf; *iter != '\0'; iter++)
27 {
28 do_something (*iter);
29 }
30
31 becomes
32
33 mbui_iterator_t iter;
34 for (mbui_init (iter, buf); mbui_avail (iter); mbui_advance (iter))
35 {
36 do_something (mbui_cur_ptr (iter), mb_len (mbui_cur (iter)));
37 }
38
39 The benefit of these macros over plain use of mbrtowc is:
40 - Handling of invalid multibyte sequences is possible without
41 making the code more complicated, while still preserving the
42 invalid multibyte sequences.
43
44 Compared to mbiter.h, the macros here don't need to know the string's
45 length a-priori. The downside is that at each step, the look-ahead
46 that guards against overrunning the terminating '\0' is more expensive.
47 The mbui_* macros are therefore suitable when there is a high probability
48 that only the first few multibyte characters need to be inspected.
49 Whereas the mbi_* macros are better if usually the iteration runs
50 through the entire string.
51
52 mbui_iterator_t
53 is a type usable for variable declarations.
54
55 mbui_init (iter, startptr)
56 initializes the iterator, starting at startptr.
57
58 mbui_avail (iter)
59 returns true if there are more multibyte chracters available before
60 the end of string is reached. In this case, mbui_cur (iter) is
61 initialized to the next multibyte chracter.
62
63 mbui_advance (iter)
64 advances the iterator by one multibyte character.
65
66 mbui_cur (iter)
67 returns the current multibyte character, of type mbchar_t. All the
68 macros defined in mbchar.h can be used on it.
69
70 mbui_cur_ptr (iter)
71 return a pointer to the beginning of the current multibyte character.
72
73 mbui_reloc (iter, ptrdiff)
74 relocates iterator when the string is moved by ptrdiff bytes.
75
76 Here are the function prototypes of the macros.
77
78 extern void mbui_init (mbui_iterator_t iter, const char *startptr);
79 extern bool mbui_avail (mbui_iterator_t iter);
80 extern void mbui_advance (mbui_iterator_t iter);
81 extern mbchar_t mbui_cur (mbui_iterator_t iter);
82 extern const char * mbui_cur_ptr (mbui_iterator_t iter);
83 extern void mbui_reloc (mbui_iterator_t iter, ptrdiff_t ptrdiff);
84 */
85
86#ifndef _MBUITER_H
87#define _MBUITER_H 1
88
89#include <assert.h>
90#include <stdbool.h>
91#include <stdlib.h>
92
93/* Tru64 with Desktop Toolkit C has a bug: <stdio.h> must be included before
94 <wchar.h>.
95 BSD/OS 4.1 has a bug: <stdio.h> and <time.h> must be included before
96 <wchar.h>. */
97#include <stdio.h>
98#include <time.h>
99#include <wchar.h>
100
101#include "mbchar.h"
102#include "strnlen1.h"
103
104struct mbuiter_multi
105{
106 bool in_shift; /* true if next byte may not be interpreted as ASCII */
107 mbstate_t state; /* if in_shift: current shift state */
108 bool next_done; /* true if mbui_avail has already filled the following */
109 struct mbchar cur; /* the current character:
110 const char *cur.ptr pointer to current character
111 The following are only valid after mbui_avail.
112 size_t cur.bytes number of bytes of current character
113 bool cur.wc_valid true if wc is a valid wide character
114 wchar_t cur.wc if wc_valid: the current character
115 */
116};
117
118static inline void
119mbuiter_multi_next (struct mbuiter_multi *iter)
120{
121 if (iter->next_done)
122 return;
123 if (iter->in_shift)
124 goto with_shift;
125 /* Handle most ASCII characters quickly, without calling mbrtowc(). */
126 if (is_basic (*iter->cur.ptr))
127 {
128 /* These characters are part of the basic character set. ISO C 99
129 guarantees that their wide character code is identical to their
130 char code. */
131 iter->cur.bytes = 1;
132 iter->cur.wc = *iter->cur.ptr;
133 iter->cur.wc_valid = true;
134 }
135 else
136 {
137 assert (mbsinit (&iter->state));
138 iter->in_shift = true;
139 with_shift:
140 iter->cur.bytes = mbrtowc (&iter->cur.wc, iter->cur.ptr,
141 strnlen1 (iter->cur.ptr, MB_CUR_MAX),
142 &iter->state);
143 if (iter->cur.bytes == (size_t) -1)
144 {
145 /* An invalid multibyte sequence was encountered. */
146 iter->cur.bytes = 1;
147 iter->cur.wc_valid = false;
148 /* Whether to set iter->in_shift = false and reset iter->state
149 or not is not very important; the string is bogus anyway. */
150 }
151 else if (iter->cur.bytes == (size_t) -2)
152 {
153 /* An incomplete multibyte character at the end. */
154 iter->cur.bytes = strlen (iter->cur.ptr);
155 iter->cur.wc_valid = false;
156 /* Whether to set iter->in_shift = false and reset iter->state
157 or not is not important; the string end is reached anyway. */
158 }
159 else
160 {
161 if (iter->cur.bytes == 0)
162 {
163 /* A null wide character was encountered. */
164 iter->cur.bytes = 1;
165 assert (*iter->cur.ptr == '\0');
166 assert (iter->cur.wc == 0);
167 }
168 iter->cur.wc_valid = true;
169
170 /* When in the initial state, we can go back treating ASCII
171 characters more quickly. */
172 if (mbsinit (&iter->state))
173 iter->in_shift = false;
174 }
175 }
176 iter->next_done = true;
177}
178
179static inline void
180mbuiter_multi_reloc (struct mbuiter_multi *iter, ptrdiff_t ptrdiff)
181{
182 iter->cur.ptr += ptrdiff;
183}
184
185/* Iteration macros. */
186typedef struct mbuiter_multi mbui_iterator_t;
187#define mbui_init(iter, startptr) \
188 ((iter).cur.ptr = (startptr), \
189 (iter).in_shift = false, memset (&(iter).state, '\0', sizeof (mbstate_t)), \
190 (iter).next_done = false)
191#define mbui_avail(iter) \
192 (mbuiter_multi_next (&(iter)), !mb_isnul ((iter).cur))
193#define mbui_advance(iter) \
194 ((iter).cur.ptr += (iter).cur.bytes, (iter).next_done = false)
195
196/* Access to the current character. */
197#define mbui_cur(iter) (iter).cur
198#define mbui_cur_ptr(iter) (iter).cur.ptr
199
200/* Relocation. */
201#define mbui_reloc(iter, ptrdiff) mbuiter_multi_reloc (&iter, ptrdiff)
202
203#endif /* _MBUITER_H */