1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1991, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Edward Sze-Tyan Wang.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#if 0
36#ifndef lint
37static char sccsid[] = "@(#)reverse.c	8.1 (Berkeley) 6/6/93";
38#endif /* not lint */
39#endif
40
41#include <sys/cdefs.h>
42__FBSDID("$FreeBSD$");
43
44#include <sys/param.h>
45#include <sys/queue.h>
46#include <sys/stat.h>
47#include <sys/mman.h>
48
49#include <err.h>
50#include <errno.h>
51#include <limits.h>
52#include <stdint.h>
53#include <stdio.h>
54#include <stdlib.h>
55#include <string.h>
56#include <unistd.h>
57
58#include "extern.h"
59
60static void r_buf(FILE *, const char *);
61static void r_reg(FILE *, const char *, enum STYLE, off_t, struct stat *);
62
63/*
64 * reverse -- display input in reverse order by line.
65 *
66 * There are six separate cases for this -- regular and non-regular
67 * files by bytes, lines or the whole file.
68 *
69 * BYTES	display N bytes
70 *	REG	mmap the file and display the lines
71 *	NOREG	cyclically read characters into a wrap-around buffer
72 *
73 * LINES	display N lines
74 *	REG	mmap the file and display the lines
75 *	NOREG	cyclically read lines into a wrap-around array of buffers
76 *
77 * FILE		display the entire file
78 *	REG	mmap the file and display the lines
79 *	NOREG	cyclically read input into a linked list of buffers
80 */
81void
82reverse(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
83{
84	if (style != REVERSE && off == 0)
85		return;
86
87	if (S_ISREG(sbp->st_mode))
88		r_reg(fp, fn, style, off, sbp);
89	else
90		switch(style) {
91		case FBYTES:
92		case RBYTES:
93			bytes(fp, fn, off);
94			break;
95		case FLINES:
96		case RLINES:
97			lines(fp, fn, off);
98			break;
99		case REVERSE:
100			r_buf(fp, fn);
101			break;
102		default:
103			break;
104		}
105}
106
107/*
108 * r_reg -- display a regular file in reverse order by line.
109 */
110static void
111r_reg(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
112{
113	struct mapinfo map;
114	off_t curoff, size, lineend;
115	int i;
116
117	if (!(size = sbp->st_size))
118		return;
119
120	map.start = NULL;
121	map.mapoff = map.maxoff = size;
122	map.fd = fileno(fp);
123	map.maplen = 0;
124
125	/*
126	 * Last char is special, ignore whether newline or not. Note that
127	 * size == 0 is dealt with above, and size == 1 sets curoff to -1.
128	 */
129	curoff = size - 2;
130	lineend = size;
131	while (curoff >= 0) {
132		if (curoff < map.mapoff ||
133		    curoff >= map.mapoff + (off_t)map.maplen) {
134			if (maparound(&map, curoff) != 0) {
135				ierr(fn);
136				return;
137			}
138		}
139		for (i = curoff - map.mapoff; i >= 0; i--) {
140			if (style == RBYTES && --off == 0)
141				break;
142			if (map.start[i] == '\n')
143				break;
144		}
145		/* `i' is either the map offset of a '\n', or -1. */
146		curoff = map.mapoff + i;
147		if (i < 0)
148			continue;
149
150		/* Print the line and update offsets. */
151		if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) {
152			ierr(fn);
153			return;
154		}
155		lineend = curoff + 1;
156		curoff--;
157
158		if (style == RLINES)
159			off--;
160
161		if (off == 0 && style != REVERSE) {
162			/* Avoid printing anything below. */
163			curoff = 0;
164			break;
165		}
166	}
167	if (curoff < 0 && mapprint(&map, 0, lineend) != 0) {
168		ierr(fn);
169		return;
170	}
171	if (map.start != NULL && munmap(map.start, map.maplen))
172		ierr(fn);
173}
174
175#define BSZ	(128 * 1024)
176typedef struct bfelem {
177	TAILQ_ENTRY(bfelem) entries;
178	size_t len;
179	char l[BSZ];
180} bfelem_t;
181
182/*
183 * r_buf -- display a non-regular file in reverse order by line.
184 *
185 * This is the function that saves the entire input, storing the data in a
186 * doubly linked list of buffers and then displays them in reverse order.
187 * It has the usual nastiness of trying to find the newlines, as there's no
188 * guarantee that a newline occurs anywhere in the file, let alone in any
189 * particular buffer.  If we run out of memory, input is discarded (and the
190 * user warned).
191 */
192static void
193r_buf(FILE *fp, const char *fn)
194{
195	struct bfelem *tl, *first = NULL;
196	size_t llen;
197	char *p;
198	off_t enomem = 0;
199	TAILQ_HEAD(bfhead, bfelem) head;
200
201	TAILQ_INIT(&head);
202
203	while (!feof(fp)) {
204		size_t len;
205
206		/*
207		 * Allocate a new block and link it into place in a doubly
208		 * linked list.  If out of memory, toss the LRU block and
209		 * keep going.
210		 */
211		while ((tl = malloc(sizeof(bfelem_t))) == NULL) {
212			first = TAILQ_FIRST(&head);
213			if (TAILQ_EMPTY(&head))
214				err(1, "malloc");
215			enomem += first->len;
216			TAILQ_REMOVE(&head, first, entries);
217			free(first);
218		}
219		TAILQ_INSERT_TAIL(&head, tl, entries);
220
221		/* Fill the block with input data. */
222		len = 0;
223		while ((!feof(fp)) && len < BSZ) {
224			p = tl->l + len;
225			len += fread(p, 1, BSZ - len, fp);
226			if (ferror(fp)) {
227				ierr(fn);
228				return;
229			}
230		}
231
232		tl->len = len;
233	}
234
235	if (enomem) {
236		warnx("warning: %jd bytes discarded", (intmax_t)enomem);
237		rval = 1;
238	}
239
240	/*
241	 * Now print the lines in reverse order
242	 * Outline:
243	 *    Scan backward for "\n",
244	 *    print forward to the end of the buffers
245	 *    free any buffers that start after the "\n" just found
246	 *    Loop
247	 */
248	tl = TAILQ_LAST(&head, bfhead);
249	first = TAILQ_FIRST(&head);
250	while (tl != NULL) {
251		struct bfelem *temp;
252
253		for (p = tl->l + tl->len - 1, llen = 0; p >= tl->l;
254		    --p, ++llen) {
255			int start = (tl == first && p == tl->l);
256
257			if ((*p == '\n') || start) {
258				struct bfelem *tr;
259
260				if (llen && start && *p != '\n')
261					WR(p, llen + 1);
262				else if (llen) {
263					WR(p + 1, llen);
264					if (start && *p == '\n')
265						WR(p, 1);
266				}
267				tr = TAILQ_NEXT(tl, entries);
268				llen = 0;
269				if (tr != NULL) {
270					TAILQ_FOREACH_FROM_SAFE(tr, &head,
271					    entries, temp) {
272						if (tr->len)
273							WR(&tr->l, tr->len);
274						TAILQ_REMOVE(&head, tr,
275						    entries);
276						free(tr);
277					}
278				}
279			}
280		}
281		tl->len = llen;
282		tl = TAILQ_PREV(tl, bfhead, entries);
283	}
284	TAILQ_REMOVE(&head, first, entries);
285	free(first);
286}
287