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. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)reverse.c 8.1 (Berkeley) 6/6/93 33 * $FreeBSD: src/usr.bin/tail/reverse.c,v 1.9.2.3 2001/12/19 20:29:31 iedowse Exp $ 34 */ 35 36 #include <sys/param.h> 37 #include <sys/stat.h> 38 #include <sys/mman.h> 39 40 #include <limits.h> 41 #include <errno.h> 42 #include <unistd.h> 43 #include <stdint.h> 44 #include <stdio.h> 45 #include <stdlib.h> 46 #include <string.h> 47 #include <err.h> 48 #include "extern.h" 49 50 static void r_buf(FILE *); 51 static void r_reg(FILE *, enum STYLE, off_t, struct stat *); 52 53 /* 54 * reverse -- display input in reverse order by line. 55 * 56 * There are six separate cases for this -- regular and non-regular 57 * files by bytes, lines or the whole file. 58 * 59 * BYTES display N bytes 60 * REG mmap the file and display the lines 61 * NOREG cyclically read characters into a wrap-around buffer 62 * 63 * LINES display N lines 64 * REG mmap the file and display the lines 65 * NOREG cyclically read lines into a wrap-around array of buffers 66 * 67 * FILE display the entire file 68 * REG mmap the file and display the lines 69 * NOREG cyclically read input into a linked list of buffers 70 */ 71 void 72 reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 73 { 74 if (style != REVERSE && off == 0) 75 return; 76 77 if (S_ISREG(sbp->st_mode)) 78 r_reg(fp, style, off, sbp); 79 else 80 switch(style) { 81 case FBYTES: 82 case RBYTES: 83 display_bytes(fp, off); 84 break; 85 case FLINES: 86 case RLINES: 87 display_lines(fp, off); 88 break; 89 case REVERSE: 90 r_buf(fp); 91 break; 92 } 93 } 94 95 /* 96 * r_reg -- display a regular file in reverse order by line. 97 */ 98 static void 99 r_reg(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 100 { 101 struct mapinfo map; 102 off_t curoff, size, lineend; 103 int i; 104 105 if (!(size = sbp->st_size)) 106 return; 107 108 map.start = NULL; 109 map.mapoff = map.maxoff = size; 110 map.fd = fileno(fp); 111 112 /* 113 * Last char is special, ignore whether newline or not. Note that 114 * size == 0 is dealt with above, and size == 1 sets curoff to -1. 115 */ 116 curoff = size - 2; 117 lineend = size; 118 while (curoff >= 0) { 119 if (curoff < map.mapoff || 120 curoff >= (intmax_t)(map.mapoff + map.maplen)) { 121 if (maparound(&map, curoff) != 0) { 122 ierr(); 123 return; 124 } 125 } 126 for (i = curoff - map.mapoff; i >= 0; i--) { 127 if (style == RBYTES && --off == 0) 128 break; 129 if (map.start[i] == '\n') 130 break; 131 } 132 /* `i' is either the map offset of a '\n', or -1. */ 133 curoff = map.mapoff + i; 134 if (i < 0) 135 continue; 136 137 /* Print the line and update offsets. */ 138 if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) { 139 ierr(); 140 return; 141 } 142 lineend = curoff + 1; 143 curoff--; 144 145 if (style == RLINES) 146 off--; 147 148 if (off == 0 && style != REVERSE) { 149 /* Avoid printing anything below. */ 150 curoff = 0; 151 break; 152 } 153 } 154 if (curoff < 0 && mapprint(&map, 0, lineend) != 0) { 155 ierr(); 156 return; 157 } 158 if (map.start != NULL && munmap(map.start, map.maplen)) 159 ierr(); 160 } 161 162 typedef struct bf { 163 struct bf *next; 164 struct bf *prev; 165 int len; 166 char *l; 167 } BF; 168 169 /* 170 * r_buf -- display a non-regular file in reverse order by line. 171 * 172 * This is the function that saves the entire input, storing the data in a 173 * doubly linked list of buffers and then displays them in reverse order. 174 * It has the usual nastiness of trying to find the newlines, as there's no 175 * guarantee that a newline occurs anywhere in the file, let alone in any 176 * particular buffer. If we run out of memory, input is discarded (and the 177 * user warned). 178 */ 179 static void 180 r_buf(FILE *fp) 181 { 182 BF *mark, *tl = NULL, *tr = NULL; 183 int ch = 0, len, llen; 184 char *p; 185 off_t enomem; 186 187 #define BSZ (128 * 1024) 188 for (mark = NULL, enomem = 0;;) { 189 /* 190 * Allocate a new block and link it into place in a doubly 191 * linked list. If out of memory, toss the LRU block and 192 * keep going. 193 */ 194 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 195 (tl->l = malloc(BSZ)) == NULL) { 196 if (!mark) 197 err(1, "malloc"); 198 tl = enomem ? tl->next : mark; 199 enomem += tl->len; 200 } else if (mark) { 201 tl->next = mark; 202 tl->prev = mark->prev; 203 mark->prev->next = tl; 204 mark->prev = tl; 205 } else { 206 mark = tl; 207 mark->next = mark->prev = mark; 208 } 209 210 /* Fill the block with input data. */ 211 for (p = tl->l, len = 0; 212 len < BSZ && (ch = getc(fp)) != EOF; ++len) 213 *p++ = ch; 214 215 if (ferror(fp)) { 216 ierr(); 217 return; 218 } 219 220 /* 221 * If no input data for this block and we tossed some data, 222 * recover it. 223 */ 224 if (!len) { 225 if (enomem) 226 enomem -= tl->len; 227 tl = tl->prev; 228 break; 229 } 230 231 tl->len = len; 232 if (ch == EOF) 233 break; 234 } 235 236 if (enomem) { 237 warnx("warning: %jd bytes discarded", (intmax_t)enomem); 238 rval = 1; 239 } 240 241 /* 242 * Step through the blocks in the reverse order read. The last char 243 * is special, ignore whether newline or not. 244 */ 245 for (mark = tl;;) { 246 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 247 --p, ++llen) 248 if (*p == '\n') { 249 if (llen) { 250 WR(p + 1, llen); 251 llen = 0; 252 } 253 if (tl == mark) 254 continue; 255 for (tr = tl->next; tr->len; tr = tr->next) { 256 WR(tr->l, tr->len); 257 tr->len = 0; 258 if (tr == mark) 259 break; 260 } 261 } 262 tl->len = llen; 263 if ((tl = tl->prev) == mark) 264 break; 265 } 266 tl = tl->next; 267 if (tl->len) { 268 WR(tl->l, tl->len); 269 tl->len = 0; 270 } 271 while ((tl = tl->next)->len) { 272 WR(tl->l, tl->len); 273 tl->len = 0; 274 } 275 } 276