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 #if defined(LIBC_SCCS) && !defined(lint) 36 static char sccsid[] = "@(#)fseek.c 8.3 (Berkeley) 1/2/94"; 37 #endif /* LIBC_SCCS and not lint */ 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include "namespace.h" 42 #include <sys/types.h> 43 #include <sys/stat.h> 44 #include <errno.h> 45 #include <fcntl.h> 46 #include <limits.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include "un-namespace.h" 50 #include "local.h" 51 #include "libc_private.h" 52 53 #define POS_ERR (-(fpos_t)1) 54 55 int 56 fseek(FILE *fp, long offset, int whence) 57 { 58 int ret; 59 int serrno = errno; 60 61 /* make sure stdio is set up */ 62 if (!__sdidinit) 63 __sinit(); 64 65 FLOCKFILE_CANCELSAFE(fp); 66 ret = _fseeko(fp, (off_t)offset, whence, 1); 67 FUNLOCKFILE_CANCELSAFE(); 68 if (ret == 0) 69 errno = serrno; 70 return (ret); 71 } 72 73 int 74 fseeko(FILE *fp, off_t offset, int whence) 75 { 76 int ret; 77 int serrno = errno; 78 79 /* make sure stdio is set up */ 80 if (!__sdidinit) 81 __sinit(); 82 83 FLOCKFILE_CANCELSAFE(fp); 84 ret = _fseeko(fp, offset, whence, 0); 85 FUNLOCKFILE_CANCELSAFE(); 86 if (ret == 0) 87 errno = serrno; 88 return (ret); 89 } 90 91 /* 92 * Seek the given file to the given offset. 93 * `Whence' must be one of the three SEEK_* macros. 94 */ 95 int 96 _fseeko(FILE *fp, off_t offset, int whence, int ltest) 97 { 98 fpos_t (*seekfn)(void *, fpos_t, int); 99 fpos_t target, curoff, ret; 100 size_t n; 101 struct stat st; 102 int havepos; 103 104 /* 105 * Have to be able to seek. 106 */ 107 if ((seekfn = fp->_seek) == NULL) { 108 errno = ESPIPE; /* historic practice */ 109 return (-1); 110 } 111 112 /* 113 * Change any SEEK_CUR to SEEK_SET, and check `whence' argument. 114 * After this, whence is either SEEK_SET or SEEK_END. 115 */ 116 switch (whence) { 117 118 case SEEK_CUR: 119 /* 120 * In order to seek relative to the current stream offset, 121 * we have to first find the current stream offset via 122 * ftell (see ftell for details). 123 */ 124 if (_ftello(fp, &curoff)) 125 return (-1); 126 if (curoff < 0) { 127 /* Unspecified position because of ungetc() at 0 */ 128 errno = ESPIPE; 129 return (-1); 130 } 131 if (offset > 0 && curoff > OFF_MAX - offset) { 132 errno = EOVERFLOW; 133 return (-1); 134 } 135 offset += curoff; 136 if (offset < 0) { 137 errno = EINVAL; 138 return (-1); 139 } 140 if (ltest && offset > LONG_MAX) { 141 errno = EOVERFLOW; 142 return (-1); 143 } 144 whence = SEEK_SET; 145 havepos = 1; 146 break; 147 148 case SEEK_SET: 149 if (offset < 0) { 150 errno = EINVAL; 151 return (-1); 152 } 153 case SEEK_END: 154 curoff = 0; /* XXX just to keep gcc quiet */ 155 havepos = 0; 156 break; 157 158 default: 159 errno = EINVAL; 160 return (-1); 161 } 162 163 /* 164 * Can only optimise if: 165 * reading (and not reading-and-writing); 166 * not unbuffered; and 167 * this is a `regular' Unix file (and hence seekfn==__sseek). 168 * We must check __NBF first, because it is possible to have __NBF 169 * and __SOPT both set. 170 */ 171 if (fp->_bf._base == NULL) 172 __smakebuf(fp); 173 if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT)) 174 goto dumb; 175 if ((fp->_flags & __SOPT) == 0) { 176 if (seekfn != __sseek || 177 fp->_file < 0 || _fstat(fp->_file, &st) || 178 (st.st_mode & S_IFMT) != S_IFREG) { 179 fp->_flags |= __SNPT; 180 goto dumb; 181 } 182 fp->_blksize = st.st_blksize; 183 fp->_flags |= __SOPT; 184 } 185 186 /* 187 * We are reading; we can try to optimise. 188 * Figure out where we are going and where we are now. 189 */ 190 if (whence == SEEK_SET) 191 target = offset; 192 else { 193 if (_fstat(fp->_file, &st)) 194 goto dumb; 195 if (offset > 0 && st.st_size > OFF_MAX - offset) { 196 errno = EOVERFLOW; 197 return (-1); 198 } 199 target = st.st_size + offset; 200 if ((off_t)target < 0) { 201 errno = EINVAL; 202 return (-1); 203 } 204 if (ltest && (off_t)target > LONG_MAX) { 205 errno = EOVERFLOW; 206 return (-1); 207 } 208 } 209 210 if (!havepos && _ftello(fp, &curoff)) 211 goto dumb; 212 213 /* 214 * (If the buffer was modified, we have to 215 * skip this; see fgetln.c.) 216 */ 217 if (fp->_flags & __SMOD) 218 goto abspos; 219 220 /* 221 * Compute the number of bytes in the input buffer (pretending 222 * that any ungetc() input has been discarded). Adjust current 223 * offset backwards by this count so that it represents the 224 * file offset for the first byte in the current input buffer. 225 */ 226 if (HASUB(fp)) { 227 curoff += fp->_r; /* kill off ungetc */ 228 n = fp->_up - fp->_bf._base; 229 curoff -= n; 230 n += fp->_ur; 231 } else { 232 n = fp->_p - fp->_bf._base; 233 curoff -= n; 234 n += fp->_r; 235 } 236 237 /* 238 * If the target offset is within the current buffer, 239 * simply adjust the pointers, clear EOF, undo ungetc(), 240 * and return. 241 */ 242 if (target >= curoff && target < curoff + n) { 243 size_t o = target - curoff; 244 245 fp->_p = fp->_bf._base + o; 246 fp->_r = n - o; 247 if (HASUB(fp)) 248 FREEUB(fp); 249 fp->_flags &= ~__SEOF; 250 memset(&fp->_mbstate, 0, sizeof(mbstate_t)); 251 return (0); 252 } 253 254 abspos: 255 /* 256 * The place we want to get to is not within the current buffer, 257 * but we can still be kind to the kernel copyout mechanism. 258 * By aligning the file offset to a block boundary, we can let 259 * the kernel use the VM hardware to map pages instead of 260 * copying bytes laboriously. Using a block boundary also 261 * ensures that we only read one block, rather than two. 262 */ 263 curoff = target & ~(fp->_blksize - 1); 264 if (_sseek(fp, curoff, SEEK_SET) == POS_ERR) 265 goto dumb; 266 fp->_r = 0; 267 fp->_p = fp->_bf._base; 268 if (HASUB(fp)) 269 FREEUB(fp); 270 n = target - curoff; 271 if (n) { 272 if (__srefill(fp) || fp->_r < n) 273 goto dumb; 274 fp->_p += n; 275 fp->_r -= n; 276 } 277 fp->_flags &= ~__SEOF; 278 memset(&fp->_mbstate, 0, sizeof(mbstate_t)); 279 return (0); 280 281 /* 282 * We get here if we cannot optimise the seek ... just 283 * do it. Allow the seek function to change fp->_bf._base. 284 */ 285 dumb: 286 if (__sflush(fp) || 287 (ret = _sseek(fp, (fpos_t)offset, whence)) == POS_ERR) 288 return (-1); 289 if (ltest && ret > LONG_MAX) { 290 fp->_flags |= __SERR; 291 errno = EOVERFLOW; 292 return (-1); 293 } 294 /* success: clear EOF indicator and discard ungetc() data */ 295 if (HASUB(fp)) 296 FREEUB(fp); 297 fp->_p = fp->_bf._base; 298 fp->_r = 0; 299 /* fp->_w = 0; */ /* unnecessary (I think...) */ 300 fp->_flags &= ~__SEOF; 301 memset(&fp->_mbstate, 0, sizeof(mbstate_t)); 302 return (0); 303 } 304