1 /*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Chris Torek. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #if defined(LIBC_SCCS) && !defined(lint) 38 static char sccsid[] = "@(#)fseek.c 8.3 (Berkeley) 1/2/94"; 39 #endif /* LIBC_SCCS and not lint */ 40 #include <sys/cdefs.h> 41 __FBSDID("$FreeBSD$"); 42 43 #include "namespace.h" 44 #include <sys/types.h> 45 #include <sys/stat.h> 46 #include <errno.h> 47 #include <fcntl.h> 48 #include <limits.h> 49 #include <stdio.h> 50 #include <stdlib.h> 51 #include "un-namespace.h" 52 #include "local.h" 53 #include "libc_private.h" 54 55 #define POS_ERR (-(fpos_t)1) 56 57 int 58 fseek(fp, offset, whence) 59 FILE *fp; 60 long offset; 61 int whence; 62 { 63 int ret; 64 int serrno = errno; 65 66 /* make sure stdio is set up */ 67 if (!__sdidinit) 68 __sinit(); 69 70 FLOCKFILE(fp); 71 ret = _fseeko(fp, (off_t)offset, whence, 1); 72 FUNLOCKFILE(fp); 73 if (ret == 0) 74 errno = serrno; 75 return (ret); 76 } 77 78 int 79 fseeko(fp, offset, whence) 80 FILE *fp; 81 off_t offset; 82 int whence; 83 { 84 int ret; 85 int serrno = errno; 86 87 /* make sure stdio is set up */ 88 if (!__sdidinit) 89 __sinit(); 90 91 FLOCKFILE(fp); 92 ret = _fseeko(fp, offset, whence, 0); 93 FUNLOCKFILE(fp); 94 if (ret == 0) 95 errno = serrno; 96 return (ret); 97 } 98 99 /* 100 * Seek the given file to the given offset. 101 * `Whence' must be one of the three SEEK_* macros. 102 */ 103 int 104 _fseeko(fp, offset, whence, ltest) 105 FILE *fp; 106 off_t offset; 107 int whence; 108 int ltest; 109 { 110 fpos_t (*seekfn)(void *, fpos_t, int); 111 fpos_t target, curoff, ret; 112 size_t n; 113 struct stat st; 114 int havepos; 115 116 /* 117 * Have to be able to seek. 118 */ 119 if ((seekfn = fp->_seek) == NULL) { 120 errno = ESPIPE; /* historic practice */ 121 return (-1); 122 } 123 124 /* 125 * Change any SEEK_CUR to SEEK_SET, and check `whence' argument. 126 * After this, whence is either SEEK_SET or SEEK_END. 127 */ 128 switch (whence) { 129 130 case SEEK_CUR: 131 /* 132 * In order to seek relative to the current stream offset, 133 * we have to first find the current stream offset via 134 * ftell (see ftell for details). 135 */ 136 if (_ftello(fp, &curoff)) 137 return (-1); 138 if (curoff < 0) { 139 /* Unspecified position because of ungetc() at 0 */ 140 errno = ESPIPE; 141 return (-1); 142 } 143 if (offset > 0 && curoff > OFF_MAX - offset) { 144 errno = EOVERFLOW; 145 return (-1); 146 } 147 offset += curoff; 148 if (offset < 0) { 149 errno = EINVAL; 150 return (-1); 151 } 152 if (ltest && offset > LONG_MAX) { 153 errno = EOVERFLOW; 154 return (-1); 155 } 156 whence = SEEK_SET; 157 havepos = 1; 158 break; 159 160 case SEEK_SET: 161 if (offset < 0) { 162 errno = EINVAL; 163 return (-1); 164 } 165 case SEEK_END: 166 curoff = 0; /* XXX just to keep gcc quiet */ 167 havepos = 0; 168 break; 169 170 default: 171 errno = EINVAL; 172 return (-1); 173 } 174 175 /* 176 * Can only optimise if: 177 * reading (and not reading-and-writing); 178 * not unbuffered; and 179 * this is a `regular' Unix file (and hence seekfn==__sseek). 180 * We must check __NBF first, because it is possible to have __NBF 181 * and __SOPT both set. 182 */ 183 if (fp->_bf._base == NULL) 184 __smakebuf(fp); 185 if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT)) 186 goto dumb; 187 if ((fp->_flags & __SOPT) == 0) { 188 if (seekfn != __sseek || 189 fp->_file < 0 || _fstat(fp->_file, &st) || 190 (st.st_mode & S_IFMT) != S_IFREG) { 191 fp->_flags |= __SNPT; 192 goto dumb; 193 } 194 fp->_blksize = st.st_blksize; 195 fp->_flags |= __SOPT; 196 } 197 198 /* 199 * We are reading; we can try to optimise. 200 * Figure out where we are going and where we are now. 201 */ 202 if (whence == SEEK_SET) 203 target = offset; 204 else { 205 if (_fstat(fp->_file, &st)) 206 goto dumb; 207 if (offset > 0 && st.st_size > OFF_MAX - offset) { 208 errno = EOVERFLOW; 209 return (-1); 210 } 211 target = st.st_size + offset; 212 if ((off_t)target < 0) { 213 errno = EINVAL; 214 return (-1); 215 } 216 if (ltest && (off_t)target > LONG_MAX) { 217 errno = EOVERFLOW; 218 return (-1); 219 } 220 } 221 222 if (!havepos && _ftello(fp, &curoff)) 223 goto dumb; 224 225 /* 226 * (If the buffer was modified, we have to 227 * skip this; see fgetln.c.) 228 */ 229 if (fp->_flags & __SMOD) 230 goto abspos; 231 232 /* 233 * Compute the number of bytes in the input buffer (pretending 234 * that any ungetc() input has been discarded). Adjust current 235 * offset backwards by this count so that it represents the 236 * file offset for the first byte in the current input buffer. 237 */ 238 if (HASUB(fp)) { 239 curoff += fp->_r; /* kill off ungetc */ 240 n = fp->_extra->_up - fp->_bf._base; 241 curoff -= n; 242 n += fp->_ur; 243 } else { 244 n = fp->_p - fp->_bf._base; 245 curoff -= n; 246 n += fp->_r; 247 } 248 249 /* 250 * If the target offset is within the current buffer, 251 * simply adjust the pointers, clear EOF, undo ungetc(), 252 * and return. 253 */ 254 if (target >= curoff && target < curoff + n) { 255 size_t o = target - curoff; 256 257 fp->_p = fp->_bf._base + o; 258 fp->_r = n - o; 259 if (HASUB(fp)) 260 FREEUB(fp); 261 fp->_flags &= ~__SEOF; 262 memset(&fp->_extra->mbstate, 0, sizeof(mbstate_t)); 263 return (0); 264 } 265 266 abspos: 267 /* 268 * The place we want to get to is not within the current buffer, 269 * but we can still be kind to the kernel copyout mechanism. 270 * By aligning the file offset to a block boundary, we can let 271 * the kernel use the VM hardware to map pages instead of 272 * copying bytes laboriously. Using a block boundary also 273 * ensures that we only read one block, rather than two. 274 */ 275 curoff = target & ~(fp->_blksize - 1); 276 if (_sseek(fp, curoff, SEEK_SET) == POS_ERR) 277 goto dumb; 278 fp->_r = 0; 279 fp->_p = fp->_bf._base; 280 if (HASUB(fp)) 281 FREEUB(fp); 282 n = target - curoff; 283 if (n) { 284 if (__srefill(fp) || fp->_r < n) 285 goto dumb; 286 fp->_p += n; 287 fp->_r -= n; 288 } 289 fp->_flags &= ~__SEOF; 290 return (0); 291 292 /* 293 * We get here if we cannot optimise the seek ... just 294 * do it. Allow the seek function to change fp->_bf._base. 295 */ 296 dumb: 297 if (__sflush(fp) || 298 (ret = _sseek(fp, (fpos_t)offset, whence)) == POS_ERR) 299 return (-1); 300 /* success: clear EOF indicator and discard ungetc() data */ 301 if (HASUB(fp)) 302 FREEUB(fp); 303 fp->_p = fp->_bf._base; 304 fp->_r = 0; 305 /* fp->_w = 0; */ /* unnecessary (I think...) */ 306 fp->_flags &= ~__SEOF; 307 memset(&fp->_extra->mbstate, 0, sizeof(mbstate_t)); 308 if (ltest && ret > LONG_MAX) { 309 fp->_flags |= __SERR; 310 errno = EOVERFLOW; 311 return (-1); 312 } 313 return (0); 314 } 315