2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
6 * Edward Sze-Tyan Wang.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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.
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
39 static char sccsid[] = "@(#)reverse.c 8.1 (Berkeley) 6/6/93";
41 static const char rcsid[] =
42 "$FreeBSD: src/usr.bin/tail/reverse.c,v 1.9.2.3 2001/12/19 20:29:31 iedowse Exp $";
45 #include <sys/param.h>
58 static void r_buf __P((FILE *));
59 static void r_reg __P((FILE *, enum STYLE, off_t, struct stat *));
62 * reverse -- display input in reverse order by line.
64 * There are six separate cases for this -- regular and non-regular
65 * files by bytes, lines or the whole file.
67 * BYTES display N bytes
68 * REG mmap the file and display the lines
69 * NOREG cyclically read characters into a wrap-around buffer
71 * LINES display N lines
72 * REG mmap the file and display the lines
73 * NOREG cyclically read lines into a wrap-around array of buffers
75 * FILE display the entire file
76 * REG mmap the file and display the lines
77 * NOREG cyclically read input into a linked list of buffers
80 reverse(fp, style, off, sbp)
86 if (style != REVERSE && off == 0)
89 if (S_ISREG(sbp->st_mode))
90 r_reg(fp, style, off, sbp);
108 * r_reg -- display a regular file in reverse order by line.
111 r_reg(fp, style, off, sbp)
118 off_t curoff, size, lineend;
121 if (!(size = sbp->st_size))
125 map.mapoff = map.maxoff = size;
129 * Last char is special, ignore whether newline or not. Note that
130 * size == 0 is dealt with above, and size == 1 sets curoff to -1.
134 while (curoff >= 0) {
135 if (curoff < map.mapoff || curoff >= map.mapoff + map.maplen) {
136 if (maparound(&map, curoff) != 0) {
141 for (i = curoff - map.mapoff; i >= 0; i--) {
142 if (style == RBYTES && --off == 0)
144 if (map.start[i] == '\n')
147 /* `i' is either the map offset of a '\n', or -1. */
148 curoff = map.mapoff + i;
152 /* Print the line and update offsets. */
153 if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) {
157 lineend = curoff + 1;
163 if (off == 0 && style != REVERSE) {
164 /* Avoid printing anything below. */
169 if (curoff < 0 && mapprint(&map, 0, lineend) != 0) {
173 if (map.start != NULL && munmap(map.start, map.maplen))
185 * r_buf -- display a non-regular file in reverse order by line.
187 * This is the function that saves the entire input, storing the data in a
188 * doubly linked list of buffers and then displays them in reverse order.
189 * It has the usual nastiness of trying to find the newlines, as there's no
190 * guarantee that a newline occurs anywhere in the file, let alone in any
191 * particular buffer. If we run out of memory, input is discarded (and the
203 #define BSZ (128 * 1024)
204 for (mark = NULL, enomem = 0;;) {
206 * Allocate a new block and link it into place in a doubly
207 * linked list. If out of memory, toss the LRU block and
210 if (enomem || (tl = malloc(sizeof(BF))) == NULL ||
211 (tl->l = malloc(BSZ)) == NULL) {
214 tl = enomem ? tl->next : mark;
218 tl->prev = mark->prev;
219 mark->prev->next = tl;
222 mark->next = mark->prev = (mark = tl);
224 /* Fill the block with input data. */
225 for (p = tl->l, len = 0;
226 len < BSZ && (ch = getc(fp)) != EOF; ++len)
235 * If no input data for this block and we tossed some data,
251 warnx("warning: %qd bytes discarded", enomem);
256 * Step through the blocks in the reverse order read. The last char
257 * is special, ignore whether newline or not.
260 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--;
269 for (tr = tl->next; tr->len; tr = tr->next) {
277 if ((tl = tl->prev) == mark)
285 while ((tl = tl->next)->len) {