1 /* $NetBSD: forward.c,v 1.6 1994/11/23 07:42:02 jtc 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 1.6 1994/11/23 07:42:02 jtc 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 fd_set zero; 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 } 165 166 /* 167 * We pause for one second after displaying any data that has 168 * accumulated since we read the file. 169 */ 170 if (fflag) { 171 FD_ZERO(&zero); 172 second.tv_sec = 1; 173 second.tv_usec = 0; 174 } 175 176 for (;;) { 177 while ((ch = getc(fp)) != EOF) 178 if (putchar(ch) == EOF) 179 oerr(); 180 if (ferror(fp)) { 181 ierr(); 182 return; 183 } 184 (void)fflush(stdout); 185 if (!fflag) 186 break; 187 /* Sleep(3) is eight system calls. Do it fast. */ 188 if (select(0, &zero, &zero, &zero, &second) == -1) 189 err(1, "select: %s", strerror(errno)); 190 clearerr(fp); 191 } 192 } 193 194 /* 195 * rlines -- display the last offset lines of the file. 196 */ 197 static void 198 rlines(fp, off, sbp) 199 FILE *fp; 200 long off; 201 struct stat *sbp; 202 { 203 register off_t size; 204 register char *p; 205 char *start; 206 207 if (!(size = sbp->st_size)) 208 return; 209 210 if (size > SIZE_T_MAX) { 211 err(0, "%s: %s", fname, strerror(EFBIG)); 212 return; 213 } 214 215 if ((start = mmap(NULL, (size_t)size, 216 PROT_READ, 0, fileno(fp), (off_t)0)) == (caddr_t)-1) { 217 err(0, "%s: %s", fname, strerror(EFBIG)); 218 return; 219 } 220 221 /* Last char is special, ignore whether newline or not. */ 222 for (p = start + size - 1; --size;) 223 if (*--p == '\n' && !--off) { 224 ++p; 225 break; 226 } 227 228 /* Set the file pointer to reflect the length displayed. */ 229 size = sbp->st_size - size; 230 WR(p, size); 231 if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) { 232 ierr(); 233 return; 234 } 235 if (munmap(start, (size_t)sbp->st_size)) { 236 err(0, "%s: %s", fname, strerror(errno)); 237 return; 238 } 239 } 240