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#include <sys/param.h>
36#include <sys/queue.h>
37#include <sys/stat.h>
38#include <sys/mman.h>
39
40#include <err.h>
41#include <errno.h>
42#include <limits.h>
43#include <stdint.h>
44#include <stdio.h>
45#include <stdlib.h>
46#include <string.h>
47#include <unistd.h>
48
49#include <libcasper.h>
50#include <casper/cap_fileargs.h>
51
52#include "extern.h"
53
54static void r_buf(FILE *, const char *);
55static void r_reg(FILE *, const char *, 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 */
75void
76reverse(FILE *fp, const char *fn, 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, fn, style, off, sbp);
83	else
84		switch(style) {
85		case FBYTES:
86		case RBYTES:
87			bytes(fp, fn, off);
88			break;
89		case FLINES:
90		case RLINES:
91			lines(fp, fn, off);
92			break;
93		case REVERSE:
94			r_buf(fp, fn);
95			break;
96		default:
97			break;
98		}
99}
100
101/*
102 * r_reg -- display a regular file in reverse order by line.
103 */
104static void
105r_reg(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
106{
107	struct mapinfo map;
108	off_t curoff, size, lineend;
109	int i;
110
111	if (!(size = sbp->st_size))
112		return;
113
114	map.start = NULL;
115	map.mapoff = map.maxoff = size;
116	map.fd = fileno(fp);
117	map.maplen = 0;
118
119	/*
120	 * Last char is special, ignore whether newline or not. Note that
121	 * size == 0 is dealt with above, and size == 1 sets curoff to -1.
122	 */
123	curoff = size - 2;
124	lineend = size;
125	while (curoff >= 0) {
126		if (curoff < map.mapoff ||
127		    curoff >= map.mapoff + (off_t)map.maplen) {
128			if (maparound(&map, curoff) != 0) {
129				ierr(fn);
130				return;
131			}
132		}
133		for (i = curoff - map.mapoff; i >= 0; i--) {
134			if (style == RBYTES && --off == 0)
135				break;
136			if (map.start[i] == '\n')
137				break;
138		}
139		/* `i' is either the map offset of a '\n', or -1. */
140		curoff = map.mapoff + i;
141		if (i < 0)
142			continue;
143
144		/* Print the line and update offsets. */
145		if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) {
146			ierr(fn);
147			return;
148		}
149		lineend = curoff + 1;
150		curoff--;
151
152		if (style == RLINES)
153			off--;
154
155		if (off == 0 && style != REVERSE) {
156			/* Avoid printing anything below. */
157			curoff = 0;
158			break;
159		}
160	}
161	if (curoff < 0 && mapprint(&map, 0, lineend) != 0) {
162		ierr(fn);
163		return;
164	}
165	if (map.start != NULL && munmap(map.start, map.maplen))
166		ierr(fn);
167}
168
169#define BSZ	(128 * 1024)
170typedef struct bfelem {
171	TAILQ_ENTRY(bfelem) entries;
172	size_t len;
173	char l[BSZ];
174} bfelem_t;
175
176/*
177 * r_buf -- display a non-regular file in reverse order by line.
178 *
179 * This is the function that saves the entire input, storing the data in a
180 * doubly linked list of buffers and then displays them in reverse order.
181 * It has the usual nastiness of trying to find the newlines, as there's no
182 * guarantee that a newline occurs anywhere in the file, let alone in any
183 * particular buffer.  If we run out of memory, input is discarded (and the
184 * user warned).
185 */
186static void
187r_buf(FILE *fp, const char *fn)
188{
189	struct bfelem *tl, *first = NULL;
190	size_t llen;
191	char *p;
192	off_t enomem = 0;
193	TAILQ_HEAD(bfhead, bfelem) head;
194
195	TAILQ_INIT(&head);
196
197	while (!feof(fp)) {
198		size_t len;
199
200		/*
201		 * Allocate a new block and link it into place in a doubly
202		 * linked list.  If out of memory, toss the LRU block and
203		 * keep going.
204		 */
205		while ((tl = malloc(sizeof(bfelem_t))) == NULL) {
206			first = TAILQ_FIRST(&head);
207			if (TAILQ_EMPTY(&head))
208				err(1, "failed to allocate memory");
209			enomem += first->len;
210			TAILQ_REMOVE(&head, first, entries);
211			free(first);
212		}
213		TAILQ_INSERT_TAIL(&head, tl, entries);
214
215		/* Fill the block with input data. */
216		len = 0;
217		while ((!feof(fp)) && len < BSZ) {
218			p = tl->l + len;
219			len += fread(p, 1, BSZ - len, fp);
220			if (ferror(fp)) {
221				ierr(fn);
222				return;
223			}
224		}
225
226		tl->len = len;
227	}
228
229	if (enomem) {
230		warnx("warning: %jd bytes discarded", (intmax_t)enomem);
231		rval = 1;
232	}
233
234	/*
235	 * Now print the lines in reverse order
236	 * Outline:
237	 *    Scan backward for "\n",
238	 *    print forward to the end of the buffers
239	 *    free any buffers that start after the "\n" just found
240	 *    Loop
241	 */
242	tl = TAILQ_LAST(&head, bfhead);
243	first = TAILQ_FIRST(&head);
244	while (tl != NULL) {
245		struct bfelem *temp;
246
247		for (p = tl->l + tl->len - 1, llen = 0; p >= tl->l;
248		    --p, ++llen) {
249			int start = (tl == first && p == tl->l);
250
251			if ((*p == '\n') || start) {
252				struct bfelem *tr;
253
254				if (llen && start && *p != '\n')
255					WR(p, llen + 1);
256				else if (llen) {
257					WR(p + 1, llen);
258					if (start && *p == '\n')
259						WR(p, 1);
260				}
261				tr = TAILQ_NEXT(tl, entries);
262				llen = 0;
263				if (tr != NULL) {
264					TAILQ_FOREACH_FROM_SAFE(tr, &head,
265					    entries, temp) {
266						if (tr->len)
267							WR(&tr->l, tr->len);
268						TAILQ_REMOVE(&head, tr,
269						    entries);
270						free(tr);
271					}
272				}
273			}
274		}
275		tl->len = llen;
276		tl = TAILQ_PREV(tl, bfhead, entries);
277	}
278	TAILQ_REMOVE(&head, first, entries);
279	free(first);
280}
281