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 * @(#)reverse.c 8.1 (Berkeley) 6/6/93 37 * $FreeBSD: src/usr.bin/tail/reverse.c,v 1.9.2.3 2001/12/19 20:29:31 iedowse Exp $ 38 * $DragonFly: src/usr.bin/tail/reverse.c,v 1.5 2006/08/13 02:12:18 swildner Exp $ 39 */ 40 41 #include <sys/param.h> 42 #include <sys/stat.h> 43 #include <sys/mman.h> 44 45 #include <limits.h> 46 #include <errno.h> 47 #include <unistd.h> 48 #include <stdio.h> 49 #include <stdlib.h> 50 #include <string.h> 51 #include <err.h> 52 #include "extern.h" 53 54 static void r_buf(FILE *); 55 static void r_reg(FILE *, enum STYLE, off_t, struct stat *); 56 57 /* 58 * reverse -- display input in reverse order by line. 59 * 60 * There are six separate cases for this -- regular and non-regular 61 * files by bytes, lines or the whole file. 62 * 63 * BYTES display N bytes 64 * REG mmap the file and display the lines 65 * NOREG cyclically read characters into a wrap-around buffer 66 * 67 * LINES display N lines 68 * REG mmap the file and display the lines 69 * NOREG cyclically read lines into a wrap-around array of buffers 70 * 71 * FILE display the entire file 72 * REG mmap the file and display the lines 73 * NOREG cyclically read input into a linked list of buffers 74 */ 75 void 76 reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 77 { 78 if (style != REVERSE && off == 0) 79 return; 80 81 if (S_ISREG(sbp->st_mode)) 82 r_reg(fp, style, off, sbp); 83 else 84 switch(style) { 85 case FBYTES: 86 case RBYTES: 87 display_bytes(fp, off); 88 break; 89 case FLINES: 90 case RLINES: 91 display_lines(fp, off); 92 break; 93 case REVERSE: 94 r_buf(fp); 95 break; 96 } 97 } 98 99 /* 100 * r_reg -- display a regular file in reverse order by line. 101 */ 102 static void 103 r_reg(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 104 { 105 struct mapinfo map; 106 off_t curoff, size, lineend; 107 int i; 108 109 if (!(size = sbp->st_size)) 110 return; 111 112 map.start = NULL; 113 map.mapoff = map.maxoff = size; 114 map.fd = fileno(fp); 115 116 /* 117 * Last char is special, ignore whether newline or not. Note that 118 * size == 0 is dealt with above, and size == 1 sets curoff to -1. 119 */ 120 curoff = size - 2; 121 lineend = size; 122 while (curoff >= 0) { 123 if (curoff < map.mapoff || 124 curoff >= (intmax_t)(map.mapoff + map.maplen)) { 125 if (maparound(&map, curoff) != 0) { 126 ierr(); 127 return; 128 } 129 } 130 for (i = curoff - map.mapoff; i >= 0; i--) { 131 if (style == RBYTES && --off == 0) 132 break; 133 if (map.start[i] == '\n') 134 break; 135 } 136 /* `i' is either the map offset of a '\n', or -1. */ 137 curoff = map.mapoff + i; 138 if (i < 0) 139 continue; 140 141 /* Print the line and update offsets. */ 142 if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) { 143 ierr(); 144 return; 145 } 146 lineend = curoff + 1; 147 curoff--; 148 149 if (style == RLINES) 150 off--; 151 152 if (off == 0 && style != REVERSE) { 153 /* Avoid printing anything below. */ 154 curoff = 0; 155 break; 156 } 157 } 158 if (curoff < 0 && mapprint(&map, 0, lineend) != 0) { 159 ierr(); 160 return; 161 } 162 if (map.start != NULL && munmap(map.start, map.maplen)) 163 ierr(); 164 } 165 166 typedef struct bf { 167 struct bf *next; 168 struct bf *prev; 169 int len; 170 char *l; 171 } BF; 172 173 /* 174 * r_buf -- display a non-regular file in reverse order by line. 175 * 176 * This is the function that saves the entire input, storing the data in a 177 * doubly linked list of buffers and then displays them in reverse order. 178 * It has the usual nastiness of trying to find the newlines, as there's no 179 * guarantee that a newline occurs anywhere in the file, let alone in any 180 * particular buffer. If we run out of memory, input is discarded (and the 181 * user warned). 182 */ 183 static void 184 r_buf(FILE *fp) 185 { 186 BF *mark, *tl = NULL, *tr = NULL; 187 int ch = 0, len, llen; 188 char *p; 189 off_t enomem; 190 191 #define BSZ (128 * 1024) 192 for (mark = NULL, enomem = 0;;) { 193 /* 194 * Allocate a new block and link it into place in a doubly 195 * linked list. If out of memory, toss the LRU block and 196 * keep going. 197 */ 198 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 199 (tl->l = malloc(BSZ)) == NULL) { 200 if (!mark) 201 err(1, "malloc"); 202 tl = enomem ? tl->next : mark; 203 enomem += tl->len; 204 } else if (mark) { 205 tl->next = mark; 206 tl->prev = mark->prev; 207 mark->prev->next = tl; 208 mark->prev = tl; 209 } else { 210 mark = tl; 211 mark->next = mark->prev = mark; 212 } 213 214 /* Fill the block with input data. */ 215 for (p = tl->l, len = 0; 216 len < BSZ && (ch = getc(fp)) != EOF; ++len) 217 *p++ = ch; 218 219 if (ferror(fp)) { 220 ierr(); 221 return; 222 } 223 224 /* 225 * If no input data for this block and we tossed some data, 226 * recover it. 227 */ 228 if (!len) { 229 if (enomem) 230 enomem -= tl->len; 231 tl = tl->prev; 232 break; 233 } 234 235 tl->len = len; 236 if (ch == EOF) 237 break; 238 } 239 240 if (enomem) { 241 warnx("warning: %jd bytes discarded", (intmax_t)enomem); 242 rval = 1; 243 } 244 245 /* 246 * Step through the blocks in the reverse order read. The last char 247 * is special, ignore whether newline or not. 248 */ 249 for (mark = tl;;) { 250 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 251 --p, ++llen) 252 if (*p == '\n') { 253 if (llen) { 254 WR(p + 1, llen); 255 llen = 0; 256 } 257 if (tl == mark) 258 continue; 259 for (tr = tl->next; tr->len; tr = tr->next) { 260 WR(tr->l, tr->len); 261 tr->len = 0; 262 if (tr == mark) 263 break; 264 } 265 } 266 tl->len = llen; 267 if ((tl = tl->prev) == mark) 268 break; 269 } 270 tl = tl->next; 271 if (tl->len) { 272 WR(tl->l, tl->len); 273 tl->len = 0; 274 } 275 while ((tl = tl->next)->len) { 276 WR(tl->l, tl->len); 277 tl->len = 0; 278 } 279 } 280