1 /* Multibyte character I/O: macros for multi-byte encodings.
2 Copyright (C) 2001, 2005, 2009-2021 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 Mitsuru Chinen <mchinen@yamato.ibm.com>
18 and Bruno Haible <bruno@clisp.org>. */
19
20 /* The macros in this file implement multi-byte character input from a
21 stream.
22
23 mb_file_t
24 is the type for multibyte character input stream, usable for variable
25 declarations.
26
27 mbf_char_t
28 is the type for multibyte character or EOF, usable for variable
29 declarations.
30
31 mbf_init (mbf, stream)
32 initializes the MB_FILE for reading from stream.
33
34 mbf_getc (mbc, mbf)
35 reads the next multibyte character from mbf and stores it in mbc.
36
37 mb_iseof (mbc)
38 returns true if mbc represents the EOF value.
39
40 Here are the function prototypes of the macros.
41
42 extern void mbf_init (mb_file_t mbf, FILE *stream);
43 extern void mbf_getc (mbf_char_t mbc, mb_file_t mbf);
44 extern bool mb_iseof (const mbf_char_t mbc);
45 */
46
47 #ifndef _MBFILE_H
48 #define _MBFILE_H 1
49
50 #include <assert.h>
51 #include <stdbool.h>
52 #include <stdio.h>
53 #include <string.h>
54 #include <wchar.h>
55
56 #include "mbchar.h"
57
58 #ifndef _GL_INLINE_HEADER_BEGIN
59 #error "Please include config.h first."
60 #endif
61 _GL_INLINE_HEADER_BEGIN
62 #ifndef MBFILE_INLINE
63 # define MBFILE_INLINE _GL_INLINE
64 #endif
65
66 struct mbfile_multi {
67 FILE *fp;
68 bool eof_seen;
69 bool have_pushback;
70 mbstate_t state;
71 unsigned int bufcount;
72 char buf[MBCHAR_BUF_SIZE];
73 struct mbchar pushback;
74 };
75
76 MBFILE_INLINE void
77 mbfile_multi_getc (struct mbchar *mbc, struct mbfile_multi *mbf)
78 {
79 size_t bytes;
80
81 /* If EOF has already been seen, don't use getc. This matters if
82 mbf->fp is connected to an interactive tty. */
83 if (mbf->eof_seen)
84 goto eof;
85
86 /* Return character pushed back, if there is one. */
87 if (mbf->have_pushback)
88 {
89 mb_copy (mbc, &mbf->pushback);
90 mbf->have_pushback = false;
91 return;
92 }
93
94 /* Before using mbrtowc, we need at least one byte. */
95 if (mbf->bufcount == 0)
96 {
97 int c = getc (mbf->fp);
98 if (c == EOF)
99 {
100 mbf->eof_seen = true;
101 goto eof;
102 }
103 mbf->buf[0] = (unsigned char) c;
104 mbf->bufcount++;
105 }
106
107 /* Handle most ASCII characters quickly, without calling mbrtowc(). */
108 if (mbf->bufcount == 1 && mbsinit (&mbf->state) && is_basic (mbf->buf[0]))
109 {
110 /* These characters are part of the basic character set. ISO C 99
111 guarantees that their wide character code is identical to their
112 char code. */
113 mbc->wc = mbc->buf[0] = mbf->buf[0];
114 mbc->wc_valid = true;
115 mbc->ptr = &mbc->buf[0];
116 mbc->bytes = 1;
117 mbf->bufcount = 0;
118 return;
119 }
120
121 /* Use mbrtowc on an increasing number of bytes. Read only as many bytes
122 from mbf->fp as needed. This is needed to give reasonable interactive
123 behaviour when mbf->fp is connected to an interactive tty. */
124 for (;;)
125 {
126 /* We don't know whether the 'mbrtowc' function updates the state when
127 it returns -2, - this is the ISO C 99 and glibc-2.2 behaviour - or
128 not - amended ANSI C, glibc-2.1 and Solaris 2.7 behaviour. We
129 don't have an autoconf test for this, yet.
130 The new behaviour would allow us to feed the bytes one by one into
131 mbrtowc. But the old behaviour forces us to feed all bytes since
132 the end of the last character into mbrtowc. Since we want to retry
133 with more bytes when mbrtowc returns -2, we must backup the state
134 before calling mbrtowc, because implementations with the new
135 behaviour will clobber it. */
136 mbstate_t backup_state = mbf->state;
137
138 bytes = mbrtowc (&mbc->wc, &mbf->buf[0], mbf->bufcount, &mbf->state);
139
140 if (bytes == (size_t) -1)
141 {
142 /* An invalid multibyte sequence was encountered. */
143 /* Return a single byte. */
144 bytes = 1;
145 mbc->wc_valid = false;
146 break;
147 }
148 else if (bytes == (size_t) -2)
149 {
150 /* An incomplete multibyte character. */
151 mbf->state = backup_state;
152 if (mbf->bufcount == MBCHAR_BUF_SIZE)
153 {
154 /* An overlong incomplete multibyte sequence was encountered. */
155 /* Return a single byte. */
156 bytes = 1;
157 mbc->wc_valid = false;
158 break;
159 }
160 else
161 {
162 /* Read one more byte and retry mbrtowc. */
163 int c = getc (mbf->fp);
164 if (c == EOF)
165 {
166 /* An incomplete multibyte character at the end. */
167 mbf->eof_seen = true;
168 bytes = mbf->bufcount;
169 mbc->wc_valid = false;
170 break;
171 }
172 mbf->buf[mbf->bufcount] = (unsigned char) c;
173 mbf->bufcount++;
174 }
175 }
176 else
177 {
178 if (bytes == 0)
179 {
180 /* A null wide character was encountered. */
181 bytes = 1;
182 assert (mbf->buf[0] == '\0');
183 assert (mbc->wc == 0);
184 }
185 mbc->wc_valid = true;
186 break;
187 }
188 }
189
190 /* Return the multibyte sequence mbf->buf[0..bytes-1]. */
191 mbc->ptr = &mbc->buf[0];
192 memcpy (&mbc->buf[0], &mbf->buf[0], bytes);
193 mbc->bytes = bytes;
194
195 mbf->bufcount -= bytes;
196 if (mbf->bufcount > 0)
197 {
198 /* It's not worth calling memmove() for so few bytes. */
199 unsigned int count = mbf->bufcount;
200 char *p = &mbf->buf[0];
201
202 do
203 {
204 *p = *(p + bytes);
205 p++;
206 }
207 while (--count > 0);
208 }
209 return;
210
211 eof:
212 /* An mbchar_t with bytes == 0 is used to indicate EOF. */
213 mbc->ptr = NULL;
214 mbc->bytes = 0;
215 mbc->wc_valid = false;
216 return;
217 }
218
219 MBFILE_INLINE void
220 mbfile_multi_ungetc (const struct mbchar *mbc, struct mbfile_multi *mbf)
221 {
222 mb_copy (&mbf->pushback, mbc);
223 mbf->have_pushback = true;
224 }
225
226 typedef struct mbfile_multi mb_file_t;
227
228 typedef mbchar_t mbf_char_t;
229
230 #define mbf_init(mbf, stream) \
231 ((mbf).fp = (stream), \
232 (mbf).eof_seen = false, \
233 (mbf).have_pushback = false, \
234 memset (&(mbf).state, '\0', sizeof (mbstate_t)), \
235 (mbf).bufcount = 0)
236
237 #define mbf_getc(mbc, mbf) mbfile_multi_getc (&(mbc), &(mbf))
238
239 #define mbf_ungetc(mbc, mbf) mbfile_multi_ungetc (&(mbc), &(mbf))
240
241 #define mb_iseof(mbc) ((mbc).bytes == 0)
242
243 _GL_INLINE_HEADER_END
244
245 #endif /* _MBFILE_H */