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 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 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 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