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 * 4. 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
33 #include <sys/param.h>
34 #include <sys/stat.h>
35 #include <sys/mman.h>
36
37 #include <err.h>
38 #include <errno.h>
39 #include <limits.h>
40 #include <stdint.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include <unistd.h>
45
46 #include "extern.h"
47
48 static void r_buf(FILE *, const char *);
49 static void r_reg(FILE *, const char *, enum STYLE, off_t, struct stat *);
50
51 /*
52 * reverse -- display input in reverse order by line.
53 *
54 * There are six separate cases for this -- regular and non-regular
55 * files by bytes, lines or the whole file.
56 *
57 * BYTES display N bytes
58 * REG mmap the file and display the lines
59 * NOREG cyclically read characters into a wrap-around buffer
60 *
61 * LINES display N lines
62 * REG mmap the file and display the lines
63 * NOREG cyclically read lines into a wrap-around array of buffers
64 *
65 * FILE display the entire file
66 * REG mmap the file and display the lines
67 * NOREG cyclically read input into a linked list of buffers
68 */
69 void
reverse(FILE * fp,const char * fn,enum STYLE style,off_t off,struct stat * sbp)70 reverse(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
71 {
72 if (style != REVERSE && off == 0)
73 return;
74
75 if (S_ISREG(sbp->st_mode))
76 r_reg(fp, fn, style, off, sbp);
77 else
78 switch (style) {
79 case FBYTES:
80 case RBYTES:
81 (void) bytes(fp, fn, off);
82 break;
83 case FLINES:
84 case RLINES:
85 (void) lines(fp, fn, off);
86 break;
87 case REVERSE:
88 r_buf(fp, fn);
89 break;
90 default:
91 break;
92 }
93 }
94
95 /*
96 * r_reg -- display a regular file in reverse order by line.
97 */
98 static void
r_reg(FILE * fp,const char * fn,enum STYLE style,off_t off,struct stat * sbp)99 r_reg(FILE *fp, const char *fn, 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) == 0)
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 >= map.mapoff + (off_t)map.maplen) {
121 if (maparound(&map, curoff) != 0) {
122 ierr(fn);
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(fn);
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(fn);
156 return;
157 }
158 if (map.start != NULL && munmap(map.start, map.maplen))
159 ierr(fn);
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
r_buf(FILE * fp,const char * fn)180 r_buf(FILE *fp, const char *fn)
181 {
182 BF *mark, *tl, *tr;
183 int ch, len, llen;
184 char *p;
185 off_t enomem;
186
187 tl = NULL;
188 #define BSZ (128 * 1024)
189 for (mark = NULL, enomem = 0; ; ) {
190 /*
191 * Allocate a new block and link it into place in a doubly
192 * linked list. If out of memory, toss the LRU block and
193 * keep going.
194 */
195 if (enomem || (tl = malloc(sizeof (BF))) == NULL ||
196 (tl->l = malloc(BSZ)) == NULL) {
197 if (!mark)
198 err(1, "malloc");
199 tl = enomem ? tl->next : mark;
200 enomem += tl->len;
201 } else if (mark) {
202 tl->next = mark;
203 tl->prev = mark->prev;
204 mark->prev->next = tl;
205 mark->prev = tl;
206 } else {
207 mark = tl;
208 mark->next = mark->prev = mark;
209 }
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(fn);
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 && 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