1 /* $NetBSD: forward.c,v 1.7 1996/02/13 16:49:10 ghudson 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 #ifndef lint 40 #if 0 41 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 42 #endif 43 static char rcsid[] = "$NetBSD: forward.c,v 1.7 1996/02/13 16:49:10 ghudson Exp $"; 44 #endif /* not lint */ 45 46 #include <sys/types.h> 47 #include <sys/stat.h> 48 #include <sys/time.h> 49 #include <sys/mman.h> 50 51 #include <limits.h> 52 #include <fcntl.h> 53 #include <errno.h> 54 #include <unistd.h> 55 #include <stdio.h> 56 #include <stdlib.h> 57 #include <string.h> 58 #include "extern.h" 59 60 static void rlines __P((FILE *, long, struct stat *)); 61 62 /* 63 * forward -- display the file, from an offset, forward. 64 * 65 * There are eight separate cases for this -- regular and non-regular 66 * files, by bytes or lines and from the beginning or end of the file. 67 * 68 * FBYTES byte offset from the beginning of the file 69 * REG seek 70 * NOREG read, counting bytes 71 * 72 * FLINES line offset from the beginning of the file 73 * REG read, counting lines 74 * NOREG read, counting lines 75 * 76 * RBYTES byte offset from the end of the file 77 * REG seek 78 * NOREG cyclically read characters into a wrap-around buffer 79 * 80 * RLINES 81 * REG mmap the file and step back until reach the correct offset. 82 * NOREG cyclically read lines into a wrap-around array of buffers 83 */ 84 void 85 forward(fp, style, off, sbp) 86 FILE *fp; 87 enum STYLE style; 88 long off; 89 struct stat *sbp; 90 { 91 register int ch; 92 struct timeval second; 93 94 switch(style) { 95 case FBYTES: 96 if (off == 0) 97 break; 98 if (S_ISREG(sbp->st_mode)) { 99 if (sbp->st_size < off) 100 off = sbp->st_size; 101 if (fseek(fp, off, SEEK_SET) == -1) { 102 ierr(); 103 return; 104 } 105 } else while (off--) 106 if ((ch = getc(fp)) == EOF) { 107 if (ferror(fp)) { 108 ierr(); 109 return; 110 } 111 break; 112 } 113 break; 114 case FLINES: 115 if (off == 0) 116 break; 117 for (;;) { 118 if ((ch = getc(fp)) == EOF) { 119 if (ferror(fp)) { 120 ierr(); 121 return; 122 } 123 break; 124 } 125 if (ch == '\n' && !--off) 126 break; 127 } 128 break; 129 case RBYTES: 130 if (S_ISREG(sbp->st_mode)) { 131 if (sbp->st_size >= off && 132 fseek(fp, -off, SEEK_END) == -1) { 133 ierr(); 134 return; 135 } 136 } else if (off == 0) { 137 while (getc(fp) != EOF); 138 if (ferror(fp)) { 139 ierr(); 140 return; 141 } 142 } else 143 bytes(fp, off); 144 break; 145 case RLINES: 146 if (S_ISREG(sbp->st_mode)) 147 if (!off) { 148 if (fseek(fp, 0L, SEEK_END) == -1) { 149 ierr(); 150 return; 151 } 152 } else 153 rlines(fp, off, sbp); 154 else if (off == 0) { 155 while (getc(fp) != EOF); 156 if (ferror(fp)) { 157 ierr(); 158 return; 159 } 160 } else 161 lines(fp, off); 162 break; 163 } 164 165 for (;;) { 166 while ((ch = getc(fp)) != EOF) 167 if (putchar(ch) == EOF) 168 oerr(); 169 if (ferror(fp)) { 170 ierr(); 171 return; 172 } 173 (void)fflush(stdout); 174 if (!fflag) 175 break; 176 /* 177 * We pause for one second after displaying any data that has 178 * accumulated since we read the file. Since sleep(3) takes 179 * eight system calls, use select() instead. 180 */ 181 second.tv_sec = 1; 182 second.tv_usec = 0; 183 if (select(0, NULL, NULL, NULL, &second) == -1) 184 err(1, "select: %s", strerror(errno)); 185 clearerr(fp); 186 } 187 } 188 189 /* 190 * rlines -- display the last offset lines of the file. 191 */ 192 static void 193 rlines(fp, off, sbp) 194 FILE *fp; 195 long off; 196 struct stat *sbp; 197 { 198 register off_t size; 199 register char *p; 200 char *start; 201 202 if (!(size = sbp->st_size)) 203 return; 204 205 if (size > SIZE_T_MAX) { 206 err(0, "%s: %s", fname, strerror(EFBIG)); 207 return; 208 } 209 210 if ((start = mmap(NULL, (size_t)size, 211 PROT_READ, 0, fileno(fp), (off_t)0)) == (caddr_t)-1) { 212 err(0, "%s: %s", fname, strerror(EFBIG)); 213 return; 214 } 215 216 /* Last char is special, ignore whether newline or not. */ 217 for (p = start + size - 1; --size;) 218 if (*--p == '\n' && !--off) { 219 ++p; 220 break; 221 } 222 223 /* Set the file pointer to reflect the length displayed. */ 224 size = sbp->st_size - size; 225 WR(p, size); 226 if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) { 227 ierr(); 228 return; 229 } 230 if (munmap(start, (size_t)sbp->st_size)) { 231 err(0, "%s: %s", fname, strerror(errno)); 232 return; 233 } 234 } 235