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. 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 * @(#)fseek.c 8.3 (Berkeley) 1/2/94 33 * $FreeBSD: src/lib/libc/stdio/fseek.c,v 1.44 2008/04/17 22:17:54 jhb Exp $ 34 */ 35 36 #include "namespace.h" 37 #include <sys/param.h> 38 #include <sys/stat.h> 39 #include <errno.h> 40 #include <fcntl.h> 41 #include <limits.h> 42 #include <stdio.h> 43 #include <stdlib.h> 44 #include "un-namespace.h" 45 #include "local.h" 46 #include "libc_private.h" 47 48 #define POS_ERR (-(fpos_t)1) 49 50 int 51 fseek(FILE *fp, long offset, int whence) 52 { 53 int ret; 54 int serrno = errno; 55 56 /* make sure stdio is set up */ 57 if (!__sdidinit) 58 __sinit(); 59 60 FLOCKFILE(fp); 61 ret = _fseeko(fp, (off_t)offset, whence, 1); 62 FUNLOCKFILE(fp); 63 if (ret == 0) 64 errno = serrno; 65 return (ret); 66 } 67 68 int 69 fseeko(FILE *fp, off_t offset, int whence) 70 { 71 int ret; 72 int serrno = errno; 73 74 /* make sure stdio is set up */ 75 if (!__sdidinit) 76 __sinit(); 77 78 FLOCKFILE(fp); 79 ret = _fseeko(fp, offset, whence, 0); 80 FUNLOCKFILE(fp); 81 if (ret == 0) 82 errno = serrno; 83 return (ret); 84 } 85 86 /* 87 * Seek the given file to the given offset. 88 * `Whence' must be one of the three SEEK_* macros. 89 */ 90 int 91 _fseeko(FILE *fp, off_t offset, int whence, int ltest) 92 { 93 fpos_t (*seekfn)(void *, fpos_t, int); 94 fpos_t target, curoff, ret; 95 size_t n; 96 struct stat st; 97 int havepos; 98 99 /* 100 * Have to be able to seek. 101 */ 102 if ((seekfn = fp->_seek) == NULL) { 103 errno = ESPIPE; /* historic practice */ 104 return (-1); 105 } 106 107 /* 108 * Change any SEEK_CUR to SEEK_SET, and check `whence' argument. 109 * After this, whence is either SEEK_SET or SEEK_END. 110 */ 111 switch (whence) { 112 113 case SEEK_CUR: 114 /* 115 * In order to seek relative to the current stream offset, 116 * we have to first find the current stream offset via 117 * ftell (see ftell for details). 118 */ 119 if (_ftello(fp, &curoff)) 120 return (-1); 121 if (curoff < 0) { 122 /* Unspecified position because of ungetc() at 0 */ 123 errno = ESPIPE; 124 return (-1); 125 } 126 if (offset > 0 && curoff > OFF_MAX - offset) { 127 errno = EOVERFLOW; 128 return (-1); 129 } 130 offset += curoff; 131 if (offset < 0) { 132 errno = EINVAL; 133 return (-1); 134 } 135 if (ltest && offset > LONG_MAX) { 136 errno = EOVERFLOW; 137 return (-1); 138 } 139 whence = SEEK_SET; 140 havepos = 1; 141 break; 142 143 case SEEK_SET: 144 if (offset < 0) { 145 errno = EINVAL; 146 return (-1); 147 } 148 case SEEK_END: 149 curoff = 0; /* XXX just to keep gcc quiet */ 150 havepos = 0; 151 break; 152 153 default: 154 errno = EINVAL; 155 return (-1); 156 } 157 158 /* 159 * Can only optimise if: 160 * reading (and not reading-and-writing); 161 * not unbuffered; and 162 * this is a `regular' Unix file (and hence seekfn==__sseek). 163 * We must check __NBF first, because it is possible to have __NBF 164 * and __SOPT both set. 165 */ 166 if (fp->_bf._base == NULL) 167 __smakebuf(fp); 168 if (fp->pub._flags & (__SWR | __SRW | __SNBF | __SNPT)) 169 goto dumb; 170 if ((fp->pub._flags & __SOPT) == 0) { 171 if (seekfn != __sseek || 172 fp->pub._fileno < 0 || _fstat(fp->pub._fileno, &st) || 173 (st.st_mode & S_IFMT) != S_IFREG) { 174 fp->pub._flags |= __SNPT; 175 goto dumb; 176 } 177 fp->_blksize = st.st_blksize; 178 fp->pub._flags |= __SOPT; 179 } 180 181 /* 182 * We are reading; we can try to optimise. 183 * Figure out where we are going and where we are now. 184 */ 185 if (whence == SEEK_SET) 186 target = offset; 187 else { 188 if (_fstat(fp->pub._fileno, &st)) 189 goto dumb; 190 if (offset > 0 && st.st_size > OFF_MAX - offset) { 191 errno = EOVERFLOW; 192 return (-1); 193 } 194 target = st.st_size + offset; 195 if ((off_t)target < 0) { 196 errno = EINVAL; 197 return (-1); 198 } 199 if (ltest && (off_t)target > LONG_MAX) { 200 errno = EOVERFLOW; 201 return (-1); 202 } 203 } 204 205 if (!havepos && _ftello(fp, &curoff)) 206 goto dumb; 207 208 /* 209 * (If the buffer was modified, we have to 210 * skip this; see fgetln.c.) 211 */ 212 if (fp->pub._flags & __SMOD) 213 goto abspos; 214 215 /* 216 * Compute the number of bytes in the input buffer (pretending 217 * that any ungetc() input has been discarded). Adjust current 218 * offset backwards by this count so that it represents the 219 * file offset for the first byte in the current input buffer. 220 */ 221 if (HASUB(fp)) { 222 curoff += fp->pub._r; /* kill off ungetc */ 223 n = fp->_up - fp->_bf._base; 224 curoff -= n; 225 n += fp->_ur; 226 } else { 227 n = fp->pub._p - fp->_bf._base; 228 curoff -= n; 229 n += fp->pub._r; 230 } 231 232 /* 233 * If the target offset is within the current buffer, 234 * simply adjust the pointers, clear EOF, undo ungetc(), 235 * and return. 236 */ 237 if (target >= curoff && target < curoff + n) { 238 size_t o = target - curoff; 239 240 fp->pub._p = fp->_bf._base + o; 241 fp->pub._r = n - o; 242 if (HASUB(fp)) 243 FREEUB(fp); 244 fp->pub._flags &= ~__SEOF; 245 memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data)); 246 return (0); 247 } 248 249 abspos: 250 /* 251 * The place we want to get to is not within the current buffer, 252 * but we can still be kind to the kernel copyout mechanism. 253 * By aligning the file offset to a block boundary, we can let 254 * the kernel use the VM hardware to map pages instead of 255 * copying bytes laboriously. Using a block boundary also 256 * ensures that we only read one block, rather than two. 257 */ 258 curoff = rounddown2(target, fp->_blksize); 259 if (_sseek(fp, curoff, SEEK_SET) == POS_ERR) 260 goto dumb; 261 fp->pub._r = 0; 262 fp->pub._p = fp->_bf._base; 263 if (HASUB(fp)) 264 FREEUB(fp); 265 n = target - curoff; 266 if (n) { 267 if (__srefill(fp) || fp->pub._r < n) 268 goto dumb; 269 fp->pub._p += n; 270 fp->pub._r -= n; 271 } 272 fp->pub._flags &= ~__SEOF; 273 memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data)); 274 return (0); 275 276 /* 277 * We get here if we cannot optimise the seek ... just 278 * do it. Allow the seek function to change fp->_bf._base. 279 */ 280 dumb: 281 if (__sflush(fp) || 282 (ret = _sseek(fp, (fpos_t)offset, whence)) == POS_ERR) 283 return (-1); 284 if (ltest && ret > LONG_MAX) { 285 fp->pub._flags |= __SERR; 286 errno = EOVERFLOW; 287 return (-1); 288 } 289 /* success: clear EOF indicator and discard ungetc() data */ 290 if (HASUB(fp)) 291 FREEUB(fp); 292 fp->pub._p = fp->_bf._base; 293 fp->pub._r = 0; 294 /* fp->pub._w = 0; */ /* unnecessary (I think...) */ 295 fp->pub._flags &= ~__SEOF; 296 memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data)); 297 return (0); 298 } 299