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 * @(#)fseek.c 8.3 (Berkeley) 1/2/94 37 * $FreeBSD: src/lib/libc/stdio/fseek.c,v 1.9.2.1 2001/03/05 10:56:58 obrien Exp $ 38 * $DragonFly: src/lib/libc/stdio/fseek.c,v 1.10 2005/11/20 11:07:30 swildner Exp $ 39 */ 40 41 #include "namespace.h" 42 #include <sys/types.h> 43 #include <sys/stat.h> 44 #include <fcntl.h> 45 #include <stdio.h> 46 #include <stdlib.h> 47 #include <errno.h> 48 #include "un-namespace.h" 49 50 #include "local.h" 51 #include "libc_private.h" 52 #include "priv_stdio.h" 53 54 #define POS_ERR (-(fpos_t)1) 55 56 int 57 fseek(FILE *fp, long offset, int whence) 58 { 59 return (fseeko(fp, offset, whence)); 60 } 61 62 int 63 fseeko(FILE *fp, off_t offset, int whence) 64 { 65 int ret; 66 67 /* make sure stdio is set up */ 68 if (!__sdidinit) 69 __sinit(); 70 71 FLOCKFILE(fp); 72 ret = _fseeko(fp, offset, whence); 73 FUNLOCKFILE(fp); 74 return (ret); 75 } 76 77 /* 78 * Seek the given file to the given offset. 79 * `Whence' must be one of the three SEEK_* macros. 80 */ 81 int 82 _fseeko(FILE *fp, off_t offset, int whence) 83 { 84 fpos_t (*seekfn) (void *, fpos_t, int); 85 fpos_t target, curoff; 86 size_t n; 87 struct stat st; 88 int havepos; 89 90 /* 91 * Have to be able to seek. 92 */ 93 if ((seekfn = fp->_seek) == NULL) { 94 errno = ESPIPE; /* historic practice */ 95 return (EOF); 96 } 97 98 /* 99 * Change any SEEK_CUR to SEEK_SET, and check `whence' argument. 100 * After this, whence is either SEEK_SET or SEEK_END. 101 */ 102 switch (whence) { 103 104 case SEEK_CUR: 105 /* 106 * In order to seek relative to the current stream offset, 107 * we have to first find the current stream offset a la 108 * ftell (see ftell for details). 109 */ 110 if (fp->pub._flags & __SOFF) 111 curoff = fp->_offset; 112 else { 113 curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR); 114 if (curoff == -1) { 115 return (EOF); 116 } 117 } 118 if (fp->pub._flags & __SRD) { 119 curoff -= fp->pub._r; 120 if (HASUB(fp)) 121 curoff -= fp->_ur; 122 } else if (fp->pub._flags & __SWR && fp->pub._p != NULL) 123 curoff += fp->pub._p - fp->_bf._base; 124 125 offset += curoff; 126 whence = SEEK_SET; 127 havepos = 1; 128 break; 129 130 case SEEK_SET: 131 case SEEK_END: 132 curoff = 0; /* XXX just to keep gcc quiet */ 133 havepos = 0; 134 break; 135 136 default: 137 errno = EINVAL; 138 return (EOF); 139 } 140 141 /* 142 * Can only optimise if: 143 * reading (and not reading-and-writing); 144 * not unbuffered; and 145 * this is a `regular' Unix file (and hence seekfn==__sseek). 146 * We must check __NBF first, because it is possible to have __NBF 147 * and __SOPT both set. 148 */ 149 if (fp->_bf._base == NULL) 150 __smakebuf(fp); 151 if (fp->pub._flags & (__SWR | __SRW | __SNBF | __SNPT)) 152 goto dumb; 153 if ((fp->pub._flags & __SOPT) == 0) { 154 if (seekfn != __sseek || 155 fp->pub._fileno < 0 || _fstat(fp->pub._fileno, &st) || 156 (st.st_mode & S_IFMT) != S_IFREG) { 157 fp->pub._flags |= __SNPT; 158 goto dumb; 159 } 160 fp->_blksize = st.st_blksize; 161 fp->pub._flags |= __SOPT; 162 } 163 164 /* 165 * We are reading; we can try to optimise. 166 * Figure out where we are going and where we are now. 167 */ 168 if (whence == SEEK_SET) 169 target = offset; 170 else { 171 if (_fstat(fp->pub._fileno, &st)) 172 goto dumb; 173 target = st.st_size + offset; 174 } 175 176 if (!havepos) { 177 if (fp->pub._flags & __SOFF) 178 curoff = fp->_offset; 179 else { 180 curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR); 181 if (curoff == POS_ERR) 182 goto dumb; 183 } 184 curoff -= fp->pub._r; 185 if (HASUB(fp)) 186 curoff -= fp->_ur; 187 } 188 189 /* 190 * Compute the number of bytes in the input buffer (pretending 191 * that any ungetc() input has been discarded). Adjust current 192 * offset backwards by this count so that it represents the 193 * file offset for the first byte in the current input buffer. 194 */ 195 if (HASUB(fp)) { 196 curoff += fp->pub._r; /* kill off ungetc */ 197 n = fp->_up - fp->_bf._base; 198 curoff -= n; 199 n += fp->_ur; 200 } else { 201 n = fp->pub._p - fp->_bf._base; 202 curoff -= n; 203 n += fp->pub._r; 204 } 205 206 /* 207 * If the target offset is within the current buffer, 208 * simply adjust the pointers, clear EOF, undo ungetc(), 209 * and return. (If the buffer was modified, we have to 210 * skip this; see fgetln.c.) 211 */ 212 if ((fp->pub._flags & __SMOD) == 0 && 213 target >= curoff && target < curoff + n) { 214 int o = target - curoff; 215 216 fp->pub._p = fp->_bf._base + o; 217 fp->pub._r = n - o; 218 if (HASUB(fp)) 219 FREEUB(fp); 220 fp->pub._flags &= ~__SEOF; 221 return (0); 222 } 223 224 /* 225 * The place we want to get to is not within the current buffer, 226 * but we can still be kind to the kernel copyout mechanism. 227 * By aligning the file offset to a block boundary, we can let 228 * the kernel use the VM hardware to map pages instead of 229 * copying bytes laboriously. Using a block boundary also 230 * ensures that we only read one block, rather than two. 231 */ 232 curoff = target & ~(fp->_blksize - 1); 233 if ((*seekfn)(fp->_cookie, curoff, SEEK_SET) == POS_ERR) 234 goto dumb; 235 fp->pub._r = 0; 236 fp->pub._p = fp->_bf._base; 237 if (HASUB(fp)) 238 FREEUB(fp); 239 fp->pub._flags &= ~__SEOF; 240 n = target - curoff; 241 if (n) { 242 if (__srefill(fp) || fp->pub._r < n) 243 goto dumb; 244 fp->pub._p += n; 245 fp->pub._r -= n; 246 } 247 return (0); 248 249 /* 250 * We get here if we cannot optimise the seek ... just 251 * do it. Allow the seek function to change fp->_bf._base. 252 */ 253 dumb: 254 if (__sflush(fp) || 255 (*seekfn)(fp->_cookie, (fpos_t)offset, whence) == POS_ERR) { 256 return (EOF); 257 } 258 /* success: clear EOF indicator and discard ungetc() data */ 259 if (HASUB(fp)) 260 FREEUB(fp); 261 fp->pub._p = fp->_bf._base; 262 fp->pub._r = 0; 263 /* fp->pub._w = 0; */ /* unnecessary (I think...) */ 264 fp->pub._flags &= ~__SEOF; 265 return (0); 266 } 267