1 /*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Edward Sze-Tyan Wang. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #ifndef lint 38 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; 39 #endif /* not lint */ 40 41 #include <sys/types.h> 42 #include <sys/stat.h> 43 #include <sys/time.h> 44 #include <sys/mman.h> 45 46 #include <limits.h> 47 #include <fcntl.h> 48 #include <errno.h> 49 #include <unistd.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include <err.h> 54 #include "extern.h" 55 56 static void rlines __P((FILE *, long, struct stat *)); 57 58 /* 59 * forward -- display the file, from an offset, forward. 60 * 61 * There are eight separate cases for this -- regular and non-regular 62 * files, by bytes or lines and from the beginning or end of the file. 63 * 64 * FBYTES byte offset from the beginning of the file 65 * REG seek 66 * NOREG read, counting bytes 67 * 68 * FLINES line offset from the beginning of the file 69 * REG read, counting lines 70 * NOREG read, counting lines 71 * 72 * RBYTES byte offset from the end of the file 73 * REG seek 74 * NOREG cyclically read characters into a wrap-around buffer 75 * 76 * RLINES 77 * REG mmap the file and step back until reach the correct offset. 78 * NOREG cyclically read lines into a wrap-around array of buffers 79 */ 80 void 81 forward(fp, style, off, sbp) 82 FILE *fp; 83 enum STYLE style; 84 long off; 85 struct stat *sbp; 86 { 87 register int ch; 88 struct timeval interval; 89 90 switch(style) { 91 case FBYTES: 92 if (off == 0) 93 break; 94 if (S_ISREG(sbp->st_mode)) { 95 if (sbp->st_size < off) 96 off = sbp->st_size; 97 if (fseek(fp, off, SEEK_SET) == -1) { 98 ierr(); 99 return; 100 } 101 } else while (off--) 102 if ((ch = getc(fp)) == EOF) { 103 if (ferror(fp)) { 104 ierr(); 105 return; 106 } 107 break; 108 } 109 break; 110 case FLINES: 111 if (off == 0) 112 break; 113 for (;;) { 114 if ((ch = getc(fp)) == EOF) { 115 if (ferror(fp)) { 116 ierr(); 117 return; 118 } 119 break; 120 } 121 if (ch == '\n' && !--off) 122 break; 123 } 124 break; 125 case RBYTES: 126 if (S_ISREG(sbp->st_mode)) { 127 if (sbp->st_size >= off && 128 fseek(fp, -off, SEEK_END) == -1) { 129 ierr(); 130 return; 131 } 132 } else if (off == 0) { 133 while (getc(fp) != EOF); 134 if (ferror(fp)) { 135 ierr(); 136 return; 137 } 138 } else 139 if (bytes(fp, off)) 140 return; 141 break; 142 case RLINES: 143 if (S_ISREG(sbp->st_mode)) 144 if (!off) { 145 if (fseek(fp, 0L, SEEK_END) == -1) { 146 ierr(); 147 return; 148 } 149 } else 150 rlines(fp, off, sbp); 151 else if (off == 0) { 152 while (getc(fp) != EOF); 153 if (ferror(fp)) { 154 ierr(); 155 return; 156 } 157 } else 158 if (lines(fp, off)) 159 return; 160 break; 161 } 162 163 /* 164 * We pause for 1/4 second after displaying any data that has 165 * accumulated since we read the file. 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 interval.tv_sec = 0; 181 interval.tv_usec = 250000; 182 if (select(0, NULL, NULL, NULL, &interval) == -1) 183 if (errno != EINTR) 184 err(1, "select"); 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 errno = EFBIG; 207 ierr(); 208 return; 209 } 210 211 if ((start = mmap(NULL, (size_t)size, 212 PROT_READ, MAP_SHARED, fileno(fp), (off_t)0)) == MAP_FAILED) { 213 ierr(); 214 return; 215 } 216 217 /* Last char is special, ignore whether newline or not. */ 218 for (p = start + size - 1; --size;) 219 if (*--p == '\n' && !--off) { 220 ++p; 221 break; 222 } 223 224 /* Set the file pointer to reflect the length displayed. */ 225 size = sbp->st_size - size; 226 WR(p, size); 227 if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) { 228 ierr(); 229 return; 230 } 231 if (munmap(start, (size_t)sbp->st_size)) { 232 ierr(); 233 return; 234 } 235 } 236