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