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 1.4 2005/03/01 21:37:33 cpressey 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 || curoff >= map.mapoff + map.maplen) { 124 if (maparound(&map, curoff) != 0) { 125 ierr(); 126 return; 127 } 128 } 129 for (i = curoff - map.mapoff; i >= 0; i--) { 130 if (style == RBYTES && --off == 0) 131 break; 132 if (map.start[i] == '\n') 133 break; 134 } 135 /* `i' is either the map offset of a '\n', or -1. */ 136 curoff = map.mapoff + i; 137 if (i < 0) 138 continue; 139 140 /* Print the line and update offsets. */ 141 if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) { 142 ierr(); 143 return; 144 } 145 lineend = curoff + 1; 146 curoff--; 147 148 if (style == RLINES) 149 off--; 150 151 if (off == 0 && style != REVERSE) { 152 /* Avoid printing anything below. */ 153 curoff = 0; 154 break; 155 } 156 } 157 if (curoff < 0 && mapprint(&map, 0, lineend) != 0) { 158 ierr(); 159 return; 160 } 161 if (map.start != NULL && munmap(map.start, map.maplen)) 162 ierr(); 163 } 164 165 typedef struct bf { 166 struct bf *next; 167 struct bf *prev; 168 int len; 169 char *l; 170 } BF; 171 172 /* 173 * r_buf -- display a non-regular file in reverse order by line. 174 * 175 * This is the function that saves the entire input, storing the data in a 176 * doubly linked list of buffers and then displays them in reverse order. 177 * It has the usual nastiness of trying to find the newlines, as there's no 178 * guarantee that a newline occurs anywhere in the file, let alone in any 179 * particular buffer. If we run out of memory, input is discarded (and the 180 * user warned). 181 */ 182 static void 183 r_buf(FILE *fp) 184 { 185 BF *mark, *tl = NULL, *tr = NULL; 186 int ch = 0, len, llen; 187 char *p; 188 off_t enomem; 189 190 #define BSZ (128 * 1024) 191 for (mark = NULL, enomem = 0;;) { 192 /* 193 * Allocate a new block and link it into place in a doubly 194 * linked list. If out of memory, toss the LRU block and 195 * keep going. 196 */ 197 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 198 (tl->l = malloc(BSZ)) == NULL) { 199 if (!mark) 200 err(1, "malloc"); 201 tl = enomem ? tl->next : mark; 202 enomem += tl->len; 203 } else if (mark) { 204 tl->next = mark; 205 tl->prev = mark->prev; 206 mark->prev->next = tl; 207 mark->prev = tl; 208 } else 209 mark->next = mark->prev = (mark = tl); 210 211 /* Fill the block with input data. */ 212 for (p = tl->l, len = 0; 213 len < BSZ && (ch = getc(fp)) != EOF; ++len) 214 *p++ = ch; 215 216 if (ferror(fp)) { 217 ierr(); 218 return; 219 } 220 221 /* 222 * If no input data for this block and we tossed some data, 223 * recover it. 224 */ 225 if (!len) { 226 if (enomem) 227 enomem -= tl->len; 228 tl = tl->prev; 229 break; 230 } 231 232 tl->len = len; 233 if (ch == EOF) 234 break; 235 } 236 237 if (enomem) { 238 warnx("warning: %qd bytes discarded", enomem); 239 rval = 1; 240 } 241 242 /* 243 * Step through the blocks in the reverse order read. The last char 244 * is special, ignore whether newline or not. 245 */ 246 for (mark = tl;;) { 247 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 248 --p, ++llen) 249 if (*p == '\n') { 250 if (llen) { 251 WR(p + 1, llen); 252 llen = 0; 253 } 254 if (tl == mark) 255 continue; 256 for (tr = tl->next; tr->len; tr = tr->next) { 257 WR(tr->l, tr->len); 258 tr->len = 0; 259 if (tr == mark) 260 break; 261 } 262 } 263 tl->len = llen; 264 if ((tl = tl->prev) == mark) 265 break; 266 } 267 tl = tl->next; 268 if (tl->len) { 269 WR(tl->l, tl->len); 270 tl->len = 0; 271 } 272 while ((tl = tl->next)->len) { 273 WR(tl->l, tl->len); 274 tl->len = 0; 275 } 276 } 277