1/* $NetBSD: forward.c,v 1.34 2024/01/14 17:37:32 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 38static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 39#endif 40__RCSID("$NetBSD: forward.c,v 1.34 2024/01/14 17:37:32 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 58static 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 */ 87void 88forward(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 struct kevent ev[2]; 94 95 switch(style) { 96 case FBYTES: 97 if (off == 0) 98 break; 99 if (S_ISREG(sbp->st_mode) && sbp->st_size > 0) { 100 if (sbp->st_size < off) 101 off = sbp->st_size; 102 if (fseeko(fp, off, SEEK_SET) == -1) { 103 ierr(); 104 return; 105 } 106 } else while (off--) 107 if ((ch = getc(fp)) == EOF) { 108 if (ferror(fp)) { 109 ierr(); 110 return; 111 } 112 break; 113 } 114 break; 115 case FLINES: 116 if (off == 0) 117 break; 118 for (;;) { 119 if ((ch = getc(fp)) == EOF) { 120 if (ferror(fp)) { 121 ierr(); 122 return; 123 } 124 break; 125 } 126 if (ch == '\n' && !--off) 127 break; 128 } 129 break; 130 case RBYTES: 131 if (S_ISREG(sbp->st_mode) && sbp->st_size > 0) { 132 if (sbp->st_size >= off && 133 fseeko(fp, -off, SEEK_END) == -1) { 134 ierr(); 135 return; 136 } 137 } else if (off == 0) { 138 while (getc(fp) != EOF); 139 if (ferror(fp)) { 140 ierr(); 141 return; 142 } 143 } else { 144 if (displaybytes(fp, off)) 145 return; 146 } 147 break; 148 case RLINES: 149 if (S_ISREG(sbp->st_mode) && sbp->st_size > 0) { 150 if (!off) { 151 if (fseek(fp, 0L, SEEK_END) == -1) { 152 ierr(); 153 return; 154 } 155 } else { 156 if (rlines(fp, off, sbp)) 157 return; 158 } 159 } else if (off == 0) { 160 while (getc(fp) != EOF); 161 if (ferror(fp)) { 162 ierr(); 163 return; 164 } 165 } else { 166 if (displaylines(fp, off)) 167 return; 168 } 169 break; 170 default: 171 break; 172 } 173 174 if (fflag) { 175 kq = kqueue(); 176 if (kq < 0) 177 xerr(1, "kqueue"); 178 action = ADD_EVENTS; 179 } 180 181 for (;;) { 182 while ((ch = getc(fp)) != EOF) { 183 if (putchar(ch) == EOF) 184 oerr(); 185 } 186 if (ferror(fp)) { 187 ierr(); 188 return; 189 } 190 (void)fflush(stdout); 191 if (!fflag) 192 break; 193 194 clearerr(fp); 195 196 switch (action) { 197 case ADD_EVENTS: 198 n = 0; 199 200 memset(ev, 0, sizeof(ev)); 201 if (fflag == 2 && fp != stdin) { 202 EV_SET(&ev[n], fileno(fp), EVFILT_VNODE, 203 EV_ADD | EV_ENABLE | EV_CLEAR, 204 NOTE_DELETE | NOTE_RENAME, 0, 0); 205 n++; 206 } 207 EV_SET(&ev[n], fileno(fp), EVFILT_READ, 208 EV_ADD | EV_ENABLE, 0, 0, 0); 209 n++; 210 211 if (kevent(kq, ev, n, NULL, 0, NULL) == -1) { 212 close(kq); 213 kq = -1; 214 action = USE_SLEEP; 215 } else { 216 action = USE_KQUEUE; 217 } 218 break; 219 220 case USE_KQUEUE: 221 if (kevent(kq, NULL, 0, ev, 1, NULL) == -1) 222 xerr(1, "kevent"); 223 224 if (ev[0].filter == EVFILT_VNODE) { 225 /* file was rotated, wait until it reappears */ 226 action = USE_SLEEP; 227 } else if (ev[0].data < 0) { 228 /* file shrank, reposition to end */ 229 if (fseek(fp, 0L, SEEK_END) == -1) { 230 ierr(); 231 return; 232 } 233 } 234 break; 235 236 case USE_SLEEP: 237 /* 238 * We pause for one second after displaying any data 239 * that has accumulated since we read the file. 240 */ 241 (void) sleep(1); 242 243 if (fflag == 2 && fp != stdin && 244 stat(fname, &statbuf) != -1) { 245 if (statbuf.st_ino != sbp->st_ino || 246 statbuf.st_dev != sbp->st_dev || 247 statbuf.st_rdev != sbp->st_rdev || 248 statbuf.st_nlink == 0) { 249 fp = freopen(fname, "r", fp); 250 if (fp == NULL) { 251 ierr(); 252 goto out; 253 } 254 *sbp = statbuf; 255 if (kq != -1) 256 action = ADD_EVENTS; 257 } else if (kq != -1) 258 action = USE_KQUEUE; 259 } 260 break; 261 } 262 } 263out: 264 if (fflag && kq != -1) 265 close(kq); 266} 267 268/* 269 * rlines -- display the last offset lines of the file. 270 * 271 * Non-zero return means than a (non-fatal) error occurred. 272 */ 273static int 274rlines(FILE *fp, off_t off, struct stat *sbp) 275{ 276 off_t file_size; 277 off_t file_remaining; 278 char *p = NULL; 279 char *start = NULL; 280 off_t mmap_size; 281 off_t mmap_offset; 282 off_t mmap_remaining = 0; 283 284#define MMAP_MAXSIZE (10 * 1024 * 1024) 285 286 if (!(file_size = sbp->st_size)) 287 return 0; 288 file_remaining = file_size; 289 290 if (file_remaining > MMAP_MAXSIZE) { 291 mmap_size = MMAP_MAXSIZE; 292 mmap_offset = file_remaining - MMAP_MAXSIZE; 293 } else { 294 mmap_size = file_remaining; 295 mmap_offset = 0; 296 } 297 298 while (off) { 299 start = mmap(NULL, (size_t)mmap_size, PROT_READ, 300 MAP_FILE|MAP_SHARED, fileno(fp), mmap_offset); 301 if (start == MAP_FAILED) { 302 xerr(0, "%s", fname); 303 return 1; 304 } 305 306 mmap_remaining = mmap_size; 307 /* Last char is special, ignore whether newline or not. */ 308 for (p = start + mmap_remaining - 1 ; --mmap_remaining ; ) 309 if (*--p == '\n' && !--off) { 310 ++p; 311 break; 312 } 313 314 file_remaining -= mmap_size - mmap_remaining; 315 316 if (off == 0) 317 break; 318 319 if (file_remaining == 0) 320 break; 321 322 if (munmap(start, mmap_size)) { 323 xerr(0, "%s", fname); 324 return 1; 325 } 326 327 if (mmap_offset >= MMAP_MAXSIZE) { 328 mmap_offset -= MMAP_MAXSIZE; 329 } else { 330 mmap_offset = 0; 331 mmap_size = file_remaining; 332 } 333 } 334 335 /* 336 * Output the (perhaps partial) data in this mmap'd block. 337 */ 338 WR(p, mmap_size - mmap_remaining); 339 file_remaining += mmap_size - mmap_remaining; 340 if (munmap(start, mmap_size)) { 341 xerr(0, "%s", fname); 342 return 1; 343 } 344 345 /* 346 * Set the file pointer to reflect the length displayed. 347 * This will cause the caller to redisplay the data if/when 348 * needed. 349 */ 350 if (fseeko(fp, file_remaining, SEEK_SET) == -1) { 351 ierr(); 352 return 1; 353 } 354 return 0; 355} 356