1 /* $NetBSD: forward.c,v 1.31 2011/09/03 10:59:10 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 1991, 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 * Edward Sze-Tyan Wang. 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 <sys/cdefs.h> 36 #ifndef lint 37 #if 0 38 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 39 #endif 40 __RCSID("$NetBSD: forward.c,v 1.31 2011/09/03 10:59:10 christos Exp $"); 41 #endif /* not lint */ 42 43 #include <sys/types.h> 44 #include <sys/stat.h> 45 #include <sys/time.h> 46 #include <sys/mman.h> 47 #include <sys/event.h> 48 49 #include <limits.h> 50 #include <fcntl.h> 51 #include <errno.h> 52 #include <unistd.h> 53 #include <stdio.h> 54 #include <stdlib.h> 55 #include <string.h> 56 #include "extern.h" 57 58 static int rlines(FILE *, off_t, struct stat *); 59 60 /* defines for inner loop actions */ 61 #define USE_SLEEP 0 62 #define USE_KQUEUE 1 63 #define ADD_EVENTS 2 64 65 /* 66 * forward -- display the file, from an offset, forward. 67 * 68 * There are eight separate cases for this -- regular and non-regular 69 * files, by bytes or lines and from the beginning or end of the file. 70 * 71 * FBYTES byte offset from the beginning of the file 72 * REG seek 73 * NOREG read, counting bytes 74 * 75 * FLINES line offset from the beginning of the file 76 * REG read, counting lines 77 * NOREG read, counting lines 78 * 79 * RBYTES byte offset from the end of the file 80 * REG seek 81 * NOREG cyclically read characters into a wrap-around buffer 82 * 83 * RLINES 84 * REG mmap the file and step back until reach the correct offset. 85 * NOREG cyclically read lines into a wrap-around array of buffers 86 */ 87 void 88 forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 89 { 90 int ch, n; 91 int kq=-1, action=USE_SLEEP; 92 struct stat statbuf; 93 dev_t lastdev; 94 ino_t lastino; 95 struct kevent ev[2]; 96 97 /* Keep track of file's previous incarnation. */ 98 lastdev = sbp->st_dev; 99 lastino = sbp->st_ino; 100 101 switch(style) { 102 case FBYTES: 103 if (off == 0) 104 break; 105 if (S_ISREG(sbp->st_mode)) { 106 if (sbp->st_size < off) 107 off = sbp->st_size; 108 if (fseeko(fp, off, SEEK_SET) == -1) { 109 ierr(); 110 return; 111 } 112 } else while (off--) 113 if ((ch = getc(fp)) == EOF) { 114 if (ferror(fp)) { 115 ierr(); 116 return; 117 } 118 break; 119 } 120 break; 121 case FLINES: 122 if (off == 0) 123 break; 124 for (;;) { 125 if ((ch = getc(fp)) == EOF) { 126 if (ferror(fp)) { 127 ierr(); 128 return; 129 } 130 break; 131 } 132 if (ch == '\n' && !--off) 133 break; 134 } 135 break; 136 case RBYTES: 137 if (S_ISREG(sbp->st_mode)) { 138 if (sbp->st_size >= off && 139 fseeko(fp, -off, SEEK_END) == -1) { 140 ierr(); 141 return; 142 } 143 } else if (off == 0) { 144 while (getc(fp) != EOF); 145 if (ferror(fp)) { 146 ierr(); 147 return; 148 } 149 } else { 150 if (displaybytes(fp, off)) 151 return; 152 } 153 break; 154 case RLINES: 155 if (S_ISREG(sbp->st_mode)) { 156 if (!off) { 157 if (fseek(fp, 0L, SEEK_END) == -1) { 158 ierr(); 159 return; 160 } 161 } else { 162 if (rlines(fp, off, sbp)) 163 return; 164 } 165 } else if (off == 0) { 166 while (getc(fp) != EOF); 167 if (ferror(fp)) { 168 ierr(); 169 return; 170 } 171 } else { 172 if (displaylines(fp, off)) 173 return; 174 } 175 break; 176 default: 177 break; 178 } 179 180 if (fflag) { 181 kq = kqueue(); 182 if (kq < 0) 183 xerr(1, "kqueue"); 184 action = ADD_EVENTS; 185 } 186 187 for (;;) { 188 while ((ch = getc(fp)) != EOF) { 189 if (putchar(ch) == EOF) 190 oerr(); 191 } 192 if (ferror(fp)) { 193 ierr(); 194 return; 195 } 196 (void)fflush(stdout); 197 if (!fflag) 198 break; 199 200 clearerr(fp); 201 202 switch (action) { 203 case ADD_EVENTS: 204 n = 0; 205 206 memset(ev, 0, sizeof(ev)); 207 if (fflag == 2 && fileno(fp) != STDIN_FILENO) { 208 EV_SET(&ev[n], fileno(fp), EVFILT_VNODE, 209 EV_ADD | EV_ENABLE | EV_CLEAR, 210 NOTE_DELETE | NOTE_RENAME, 0, 0); 211 n++; 212 } 213 EV_SET(&ev[n], fileno(fp), EVFILT_READ, 214 EV_ADD | EV_ENABLE, 0, 0, 0); 215 n++; 216 217 if (kevent(kq, ev, n, NULL, 0, NULL) == -1) { 218 close(kq); 219 kq = -1; 220 action = USE_SLEEP; 221 } else { 222 action = USE_KQUEUE; 223 } 224 break; 225 226 case USE_KQUEUE: 227 if (kevent(kq, NULL, 0, ev, 1, NULL) == -1) 228 xerr(1, "kevent"); 229 230 if (ev[0].filter == EVFILT_VNODE) { 231 /* file was rotated, wait until it reappears */ 232 action = USE_SLEEP; 233 } else if (ev[0].data < 0) { 234 /* file shrank, reposition to end */ 235 if (fseek(fp, 0L, SEEK_END) == -1) { 236 ierr(); 237 return; 238 } 239 } 240 break; 241 242 case USE_SLEEP: 243 /* 244 * We pause for one second after displaying any data 245 * that has accumulated since we read the file. 246 */ 247 (void) sleep(1); 248 249 if (fflag == 2 && fileno(fp) != STDIN_FILENO && 250 stat(fname, &statbuf) != -1) { 251 if (statbuf.st_ino != sbp->st_ino || 252 statbuf.st_dev != sbp->st_dev || 253 statbuf.st_rdev != sbp->st_rdev || 254 statbuf.st_nlink == 0) { 255 fp = freopen(fname, "r", fp); 256 if (fp == NULL) { 257 ierr(); 258 goto out; 259 } 260 *sbp = statbuf; 261 if (kq != -1) 262 action = ADD_EVENTS; 263 } else if (kq != -1) 264 action = USE_KQUEUE; 265 } 266 break; 267 } 268 } 269 out: 270 if (fflag && kq != -1) 271 close(kq); 272 } 273 274 /* 275 * rlines -- display the last offset lines of the file. 276 * 277 * Non-zero return means than a (non-fatal) error occurred. 278 */ 279 static int 280 rlines(FILE *fp, off_t off, struct stat *sbp) 281 { 282 off_t file_size; 283 off_t file_remaining; 284 char *p = NULL; 285 char *start = NULL; 286 off_t mmap_size; 287 off_t mmap_offset; 288 off_t mmap_remaining = 0; 289 290 #define MMAP_MAXSIZE (10 * 1024 * 1024) 291 292 if (!(file_size = sbp->st_size)) 293 return 0; 294 file_remaining = file_size; 295 296 if (file_remaining > MMAP_MAXSIZE) { 297 mmap_size = MMAP_MAXSIZE; 298 mmap_offset = file_remaining - MMAP_MAXSIZE; 299 } else { 300 mmap_size = file_remaining; 301 mmap_offset = 0; 302 } 303 304 while (off) { 305 start = mmap(NULL, (size_t)mmap_size, PROT_READ, 306 MAP_FILE|MAP_SHARED, fileno(fp), mmap_offset); 307 if (start == MAP_FAILED) { 308 xerr(0, "%s", fname); 309 return 1; 310 } 311 312 mmap_remaining = mmap_size; 313 /* Last char is special, ignore whether newline or not. */ 314 for (p = start + mmap_remaining - 1 ; --mmap_remaining ; ) 315 if (*--p == '\n' && !--off) { 316 ++p; 317 break; 318 } 319 320 file_remaining -= mmap_size - mmap_remaining; 321 322 if (off == 0) 323 break; 324 325 if (file_remaining == 0) 326 break; 327 328 if (munmap(start, mmap_size)) { 329 xerr(0, "%s", fname); 330 return 1; 331 } 332 333 if (mmap_offset >= MMAP_MAXSIZE) { 334 mmap_offset -= MMAP_MAXSIZE; 335 } else { 336 mmap_offset = 0; 337 mmap_size = file_remaining; 338 } 339 } 340 341 /* 342 * Output the (perhaps partial) data in this mmap'd block. 343 */ 344 WR(p, mmap_size - mmap_remaining); 345 file_remaining += mmap_size - mmap_remaining; 346 if (munmap(start, mmap_size)) { 347 xerr(0, "%s", fname); 348 return 1; 349 } 350 351 /* 352 * Set the file pointer to reflect the length displayed. 353 * This will cause the caller to redisplay the data if/when 354 * needed. 355 */ 356 if (fseeko(fp, file_remaining, SEEK_SET) == -1) { 357 ierr(); 358 return 1; 359 } 360 return 0; 361 } 362