1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include "namespace.h"
36 #include <sys/types.h>
37 #include <sys/stat.h>
38 #include <errno.h>
39 #include <fcntl.h>
40 #include <limits.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include "un-namespace.h"
44 #include "local.h"
45 #include "libc_private.h"
46
47 #define POS_ERR (-(fpos_t)1)
48
49 int
fseek(FILE * fp,long offset,int whence)50 fseek(FILE *fp, long offset, int whence)
51 {
52 int ret;
53 int serrno = errno;
54
55 /* make sure stdio is set up */
56 if (!__sdidinit)
57 __sinit();
58
59 FLOCKFILE_CANCELSAFE(fp);
60 ret = _fseeko(fp, (off_t)offset, whence, 1);
61 FUNLOCKFILE_CANCELSAFE();
62 if (ret == 0)
63 errno = serrno;
64 return (ret);
65 }
66
67 int
fseeko(FILE * fp,off_t offset,int whence)68 fseeko(FILE *fp, off_t offset, int whence)
69 {
70 int ret;
71 int serrno = errno;
72
73 /* make sure stdio is set up */
74 if (!__sdidinit)
75 __sinit();
76
77 FLOCKFILE_CANCELSAFE(fp);
78 ret = _fseeko(fp, offset, whence, 0);
79 FUNLOCKFILE_CANCELSAFE();
80 if (ret == 0)
81 errno = serrno;
82 return (ret);
83 }
84
85 /*
86 * Seek the given file to the given offset.
87 * `Whence' must be one of the three SEEK_* macros.
88 */
89 int
_fseeko(FILE * fp,off_t offset,int whence,int ltest)90 _fseeko(FILE *fp, off_t offset, int whence, int ltest)
91 {
92 fpos_t (*seekfn)(void *, fpos_t, int);
93 fpos_t target, curoff, ret;
94 size_t n;
95 struct stat st;
96 int havepos;
97
98 /*
99 * Have to be able to seek.
100 */
101 if ((seekfn = fp->_seek) == NULL) {
102 errno = ESPIPE; /* historic practice */
103 return (-1);
104 }
105
106 /*
107 * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
108 * After this, whence is either SEEK_SET or SEEK_END.
109 */
110 switch (whence) {
111
112 case SEEK_CUR:
113 /*
114 * In order to seek relative to the current stream offset,
115 * we have to first find the current stream offset via
116 * ftell (see ftell for details).
117 */
118 if (_ftello(fp, &curoff))
119 return (-1);
120 if (curoff < 0) {
121 /* Unspecified position because of ungetc() at 0 */
122 errno = ESPIPE;
123 return (-1);
124 }
125 if (offset > 0 && curoff > OFF_MAX - offset) {
126 errno = EOVERFLOW;
127 return (-1);
128 }
129 offset += curoff;
130 if (offset < 0) {
131 errno = EINVAL;
132 return (-1);
133 }
134 if (ltest && offset > LONG_MAX) {
135 errno = EOVERFLOW;
136 return (-1);
137 }
138 whence = SEEK_SET;
139 havepos = 1;
140 break;
141
142 case SEEK_SET:
143 if (offset < 0) {
144 errno = EINVAL;
145 return (-1);
146 }
147 case SEEK_END:
148 curoff = 0; /* XXX just to keep gcc quiet */
149 havepos = 0;
150 break;
151
152 default:
153 errno = EINVAL;
154 return (-1);
155 }
156
157 /*
158 * Can only optimise if:
159 * reading (and not reading-and-writing);
160 * not unbuffered; and
161 * this is a `regular' Unix file (and hence seekfn==__sseek).
162 * We must check __NBF first, because it is possible to have __NBF
163 * and __SOPT both set.
164 */
165 if (fp->_bf._base == NULL)
166 __smakebuf(fp);
167 if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT))
168 goto dumb;
169 if ((fp->_flags & __SOPT) == 0) {
170 if (seekfn != __sseek ||
171 fp->_file < 0 || _fstat(fp->_file, &st) ||
172 (st.st_mode & S_IFMT) != S_IFREG) {
173 fp->_flags |= __SNPT;
174 goto dumb;
175 }
176 fp->_blksize = st.st_blksize;
177 fp->_flags |= __SOPT;
178 }
179
180 /*
181 * We are reading; we can try to optimise.
182 * Figure out where we are going and where we are now.
183 */
184 if (whence == SEEK_SET)
185 target = offset;
186 else {
187 if (_fstat(fp->_file, &st))
188 goto dumb;
189 if (offset > 0 && st.st_size > OFF_MAX - offset) {
190 errno = EOVERFLOW;
191 return (-1);
192 }
193 target = st.st_size + offset;
194 if ((off_t)target < 0) {
195 errno = EINVAL;
196 return (-1);
197 }
198 if (ltest && (off_t)target > LONG_MAX) {
199 errno = EOVERFLOW;
200 return (-1);
201 }
202 }
203
204 if (!havepos && _ftello(fp, &curoff))
205 goto dumb;
206
207 /*
208 * (If the buffer was modified, we have to
209 * skip this; see fgetln.c.)
210 */
211 if (fp->_flags & __SMOD)
212 goto abspos;
213
214 /*
215 * Compute the number of bytes in the input buffer (pretending
216 * that any ungetc() input has been discarded). Adjust current
217 * offset backwards by this count so that it represents the
218 * file offset for the first byte in the current input buffer.
219 */
220 if (HASUB(fp)) {
221 curoff += fp->_r; /* kill off ungetc */
222 n = fp->_up - fp->_bf._base;
223 curoff -= n;
224 n += fp->_ur;
225 } else {
226 n = fp->_p - fp->_bf._base;
227 curoff -= n;
228 n += fp->_r;
229 }
230
231 /*
232 * If the target offset is within the current buffer,
233 * simply adjust the pointers, clear EOF, undo ungetc(),
234 * and return.
235 */
236 if (target >= curoff && target < curoff + n) {
237 size_t o = target - curoff;
238
239 fp->_p = fp->_bf._base + o;
240 fp->_r = n - o;
241 if (HASUB(fp))
242 FREEUB(fp);
243 fp->_flags &= ~__SEOF;
244 memset(&fp->_mbstate, 0, sizeof(mbstate_t));
245 return (0);
246 }
247
248 abspos:
249 /*
250 * The place we want to get to is not within the current buffer,
251 * but we can still be kind to the kernel copyout mechanism.
252 * By aligning the file offset to a block boundary, we can let
253 * the kernel use the VM hardware to map pages instead of
254 * copying bytes laboriously. Using a block boundary also
255 * ensures that we only read one block, rather than two.
256 */
257 curoff = target & ~(fp->_blksize - 1);
258 if (_sseek(fp, curoff, SEEK_SET) == POS_ERR)
259 goto dumb;
260 fp->_r = 0;
261 fp->_p = fp->_bf._base;
262 if (HASUB(fp))
263 FREEUB(fp);
264 n = target - curoff;
265 if (n) {
266 if (__srefill(fp) || fp->_r < n)
267 goto dumb;
268 fp->_p += n;
269 fp->_r -= n;
270 }
271 fp->_flags &= ~__SEOF;
272 memset(&fp->_mbstate, 0, sizeof(mbstate_t));
273 return (0);
274
275 /*
276 * We get here if we cannot optimise the seek ... just
277 * do it. Allow the seek function to change fp->_bf._base.
278 */
279 dumb:
280 if (__sflush(fp) ||
281 (ret = _sseek(fp, (fpos_t)offset, whence)) == POS_ERR)
282 return (-1);
283 if (ltest && ret > LONG_MAX) {
284 fp->_flags |= __SERR;
285 errno = EOVERFLOW;
286 return (-1);
287 }
288 /* success: clear EOF indicator and discard ungetc() data */
289 if (HASUB(fp))
290 FREEUB(fp);
291 fp->_p = fp->_bf._base;
292 fp->_r = 0;
293 /* fp->_w = 0; */ /* unnecessary (I think...) */
294 fp->_flags &= ~__SEOF;
295 memset(&fp->_mbstate, 0, sizeof(mbstate_t));
296 return (0);
297 }
298