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