1 /* $NetBSD: forward.c,v 1.8 1997/10/19 23:45:08 lukem 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. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #ifndef lint 41 #if 0 42 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 43 #endif 44 __RCSID("$NetBSD: forward.c,v 1.8 1997/10/19 23:45:08 lukem Exp $"); 45 #endif /* not lint */ 46 47 #include <sys/types.h> 48 #include <sys/stat.h> 49 #include <sys/time.h> 50 #include <sys/mman.h> 51 52 #include <limits.h> 53 #include <fcntl.h> 54 #include <errno.h> 55 #include <unistd.h> 56 #include <stdio.h> 57 #include <stdlib.h> 58 #include <string.h> 59 #include "extern.h" 60 61 static void rlines __P((FILE *, long, struct stat *)); 62 63 /* 64 * forward -- display the file, from an offset, forward. 65 * 66 * There are eight separate cases for this -- regular and non-regular 67 * files, by bytes or lines and from the beginning or end of the file. 68 * 69 * FBYTES byte offset from the beginning of the file 70 * REG seek 71 * NOREG read, counting bytes 72 * 73 * FLINES line offset from the beginning of the file 74 * REG read, counting lines 75 * NOREG read, counting lines 76 * 77 * RBYTES byte offset from the end of the file 78 * REG seek 79 * NOREG cyclically read characters into a wrap-around buffer 80 * 81 * RLINES 82 * REG mmap the file and step back until reach the correct offset. 83 * NOREG cyclically read lines into a wrap-around array of buffers 84 */ 85 void 86 forward(fp, style, off, sbp) 87 FILE *fp; 88 enum STYLE style; 89 long off; 90 struct stat *sbp; 91 { 92 int ch; 93 struct timeval second; 94 95 switch(style) { 96 case FBYTES: 97 if (off == 0) 98 break; 99 if (S_ISREG(sbp->st_mode)) { 100 if (sbp->st_size < off) 101 off = sbp->st_size; 102 if (fseek(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)) { 132 if (sbp->st_size >= off && 133 fseek(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 bytes(fp, off); 145 break; 146 case RLINES: 147 if (S_ISREG(sbp->st_mode)) 148 if (!off) { 149 if (fseek(fp, 0L, SEEK_END) == -1) { 150 ierr(); 151 return; 152 } 153 } else 154 rlines(fp, off, sbp); 155 else if (off == 0) { 156 while (getc(fp) != EOF); 157 if (ferror(fp)) { 158 ierr(); 159 return; 160 } 161 } else 162 lines(fp, off); 163 break; 164 default: 165 break; 166 } 167 168 for (;;) { 169 while ((ch = getc(fp)) != EOF) 170 if (putchar(ch) == EOF) 171 oerr(); 172 if (ferror(fp)) { 173 ierr(); 174 return; 175 } 176 (void)fflush(stdout); 177 if (!fflag) 178 break; 179 /* 180 * We pause for one second after displaying any data that has 181 * accumulated since we read the file. Since sleep(3) takes 182 * eight system calls, use select() instead. 183 */ 184 second.tv_sec = 1; 185 second.tv_usec = 0; 186 if (select(0, NULL, NULL, NULL, &second) == -1) 187 err(1, "select: %s", strerror(errno)); 188 clearerr(fp); 189 } 190 } 191 192 /* 193 * rlines -- display the last offset lines of the file. 194 */ 195 static void 196 rlines(fp, off, sbp) 197 FILE *fp; 198 long off; 199 struct stat *sbp; 200 { 201 off_t size; 202 char *p; 203 char *start; 204 205 if (!(size = sbp->st_size)) 206 return; 207 208 if (size > SIZE_T_MAX) { 209 err(0, "%s: %s", fname, strerror(EFBIG)); 210 return; 211 } 212 213 if ((start = mmap(NULL, (size_t)size, 214 PROT_READ, 0, fileno(fp), (off_t)0)) == (caddr_t)-1) { 215 err(0, "%s: %s", fname, strerror(EFBIG)); 216 return; 217 } 218 219 /* Last char is special, ignore whether newline or not. */ 220 for (p = start + size - 1; --size;) 221 if (*--p == '\n' && !--off) { 222 ++p; 223 break; 224 } 225 226 /* Set the file pointer to reflect the length displayed. */ 227 size = sbp->st_size - size; 228 WR(p, size); 229 if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) { 230 ierr(); 231 return; 232 } 233 if (munmap(start, (size_t)sbp->st_size)) { 234 err(0, "%s: %s", fname, strerror(errno)); 235 return; 236 } 237 } 238