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 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33#if defined(LIBC_SCCS) && !defined(lint) 34static char sccsid[] = "@(#)fseek.c 8.3 (Berkeley) 1/2/94"; 35#endif /* LIBC_SCCS and not lint */ 36#include <sys/cdefs.h> 37__FBSDID("$FreeBSD: src/lib/libc/stdio/fseek.c,v 1.44 2008/04/17 22:17:54 jhb Exp $"); 38 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 53int 54fseek(fp, offset, whence) 55 FILE *fp; 56 long offset; 57 int whence; 58{ 59 int ret; 60 int serrno = errno; 61 62 /* make sure stdio is set up */ 63 pthread_once(&__sdidinit, __sinit); 64 65 FLOCKFILE(fp); 66 ret = _fseeko(fp, (off_t)offset, whence, 1); 67 FUNLOCKFILE(fp); 68 if (ret == 0) 69 errno = serrno; 70 return (ret); 71} 72 73int 74fseeko(fp, offset, whence) 75 FILE *fp; 76 off_t offset; 77 int whence; 78{ 79 int ret; 80 int serrno = errno; 81 82 /* make sure stdio is set up */ 83 pthread_once(&__sdidinit, __sinit); 84 85 FLOCKFILE(fp); 86 ret = _fseeko(fp, offset, whence, 0); 87 FUNLOCKFILE(fp); 88 if (ret == 0) 89 errno = serrno; 90 return (ret); 91} 92 93/* 94 * Seek the given file to the given offset. 95 * `Whence' must be one of the three SEEK_* macros. 96 */ 97int 98_fseeko(fp, offset, whence, ltest) 99 FILE *fp; 100 off_t offset; 101 int whence; 102 int ltest; 103{ 104 fpos_t (*seekfn)(void *, fpos_t, int); 105 fpos_t target, curoff, ret; 106 size_t n; 107 struct stat st; 108 int havepos; 109 110 /* 111 * Have to be able to seek. 112 */ 113 if ((seekfn = fp->_seek) == NULL) { 114 errno = ESPIPE; /* historic practice */ 115 return (-1); 116 } 117 118 /* 119 * Change any SEEK_CUR to SEEK_SET, and check `whence' argument. 120 * After this, whence is either SEEK_SET or SEEK_END. 121 */ 122 switch (whence) { 123 124 case SEEK_CUR: 125 /* 126 * In order to seek relative to the current stream offset, 127 * we have to first find the current stream offset via 128 * ftell (see ftell for details). 129 */ 130 if (_ftello(fp, &curoff)) 131 return (-1); 132 if (curoff < 0) { 133 /* Unspecified position because of ungetc() at 0 */ 134 errno = ESPIPE; 135 return (-1); 136 } 137 if (offset > 0 && curoff > OFF_MAX - offset) { 138 errno = EOVERFLOW; 139 return (-1); 140 } 141 offset += curoff; 142 if (offset < 0) { 143 errno = EINVAL; 144 return (-1); 145 } 146 if (ltest && offset > LONG_MAX) { 147 errno = EOVERFLOW; 148 return (-1); 149 } 150 whence = SEEK_SET; 151 havepos = 1; 152 break; 153 154 case SEEK_SET: 155 if (offset < 0) { 156 errno = EINVAL; 157 return (-1); 158 } 159 case SEEK_END: 160 curoff = 0; /* XXX just to keep gcc quiet */ 161 havepos = 0; 162 break; 163 164 default: 165 errno = EINVAL; 166 return (-1); 167 } 168 169 /* 170 * Can only optimise if: 171 * reading (and not reading-and-writing); 172 * not unbuffered; and 173 * this is a `regular' Unix file (and hence seekfn==__sseek). 174 * We must check __NBF first, because it is possible to have __NBF 175 * and __SOPT both set. 176 */ 177 if (fp->_bf._base == NULL) 178 __smakebuf(fp); 179 if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT)) 180 goto dumb; 181 if ((fp->_flags & __SOPT) == 0) { 182 if (seekfn != __sseek || 183 fp->_file < 0 || _fstat(fp->_file, &st) || 184 (st.st_mode & S_IFMT) != S_IFREG) { 185 fp->_flags |= __SNPT; 186 goto dumb; 187 } 188 fp->_blksize = st.st_blksize; 189 fp->_flags |= __SOPT; 190 } 191 192 /* 193 * We are reading; we can try to optimise. 194 * Figure out where we are going and where we are now. 195 */ 196 if (whence == SEEK_SET) 197 target = offset; 198 else { 199 if (_fstat(fp->_file, &st)) 200 goto dumb; 201 if (offset > 0 && st.st_size > OFF_MAX - offset) { 202 errno = EOVERFLOW; 203 return (-1); 204 } 205 target = st.st_size + offset; 206 if ((off_t)target < 0) { 207 errno = EINVAL; 208 return (-1); 209 } 210 if (ltest && (off_t)target > LONG_MAX) { 211 errno = EOVERFLOW; 212 return (-1); 213 } 214 } 215 216 if (!havepos && _ftello(fp, &curoff)) 217 goto dumb; 218 219 /* 220 * (If the buffer was modified, we have to 221 * skip this; see fgetln.c.) 222 */ 223 if (fp->_flags & __SMOD) 224 goto abspos; 225 226 /* 227 * Compute the number of bytes in the input buffer (pretending 228 * that any ungetc() input has been discarded). Adjust current 229 * offset backwards by this count so that it represents the 230 * file offset for the first byte in the current input buffer. 231 */ 232 if (HASUB(fp)) { 233 curoff += fp->_r; /* kill off ungetc */ 234 n = fp->_up - fp->_bf._base; 235 curoff -= n; 236 n += fp->_ur; 237 } else { 238 n = fp->_p - fp->_bf._base; 239 curoff -= n; 240 n += fp->_r; 241 } 242 243 /* 244 * If the target offset is within the current buffer, 245 * simply adjust the pointers, clear EOF, undo ungetc(), 246 * and return. 247 */ 248 if (target >= curoff && target < curoff + n) { 249 size_t o = target - curoff; 250 251 fp->_p = fp->_bf._base + o; 252 fp->_r = n - o; 253 if (HASUB(fp)) 254 FREEUB(fp); 255 fp->_flags &= ~__SEOF; 256 memset(&fp->_mbstate, 0, sizeof(mbstate_t)); 257 return (0); 258 } 259 260abspos: 261 /* 262 * The place we want to get to is not within the current buffer, 263 * but we can still be kind to the kernel copyout mechanism. 264 * By aligning the file offset to a block boundary, we can let 265 * the kernel use the VM hardware to map pages instead of 266 * copying bytes laboriously. Using a block boundary also 267 * ensures that we only read one block, rather than two. 268 */ 269 curoff = target & ~(fp->_blksize - 1); 270 if (_sseek(fp, curoff, SEEK_SET) == POS_ERR) 271 goto dumb; 272 fp->_r = 0; 273 fp->_p = fp->_bf._base; 274 if (HASUB(fp)) 275 FREEUB(fp); 276 n = target - curoff; 277 if (n) { 278 if (__srefill(fp) || fp->_r < n) 279 goto dumb; 280 fp->_p += n; 281 fp->_r -= n; 282 } 283 fp->_flags &= ~__SEOF; 284 memset(&fp->_mbstate, 0, sizeof(mbstate_t)); 285 return (0); 286 287 /* 288 * We get here if we cannot optimise the seek ... just 289 * do it. Allow the seek function to change fp->_bf._base. 290 */ 291dumb: 292 if (__sflush(fp) || 293 (ret = _sseek(fp, (fpos_t)offset, whence)) == POS_ERR) 294 return (-1); 295 if (ltest && ret > LONG_MAX) { 296 fp->_flags |= __SERR; 297 errno = EOVERFLOW; 298 return (-1); 299 } 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->_mbstate, 0, sizeof(mbstate_t)); 308 return (0); 309} 310