1 /* $OpenBSD: reverse.c,v 1.21 2015/11/19 17:50:04 tedu Exp $ */
2 /* $NetBSD: reverse.c,v 1.6 1994/11/23 07:42:10 jtc Exp $ */
3
4 /*-
5 * Copyright (c) 1991, 1993
6 * The Regents of the University of California. All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * Edward Sze-Tyan Wang.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #include <sys/stat.h>
37
38 #include <err.h>
39 #include <stdio.h>
40 #include <stdlib.h>
41 #include <unistd.h>
42
43 #include "extern.h"
44
45 static void r_buf(FILE *);
46 static int r_reg(struct tailfile *, enum STYLE, off_t);
47
48 #define COPYCHAR(tf, ch) \
49 do { \
50 if ((ch = getc(tf->fp)) == EOF) { \
51 ierr(tf->fname); \
52 return (0); \
53 } \
54 if (putchar(ch) == EOF) { \
55 oerr(); \
56 return (0); \
57 } \
58 } while (0)
59
60 /*
61 * reverse -- display input in reverse order by line.
62 *
63 * There are six separate cases for this -- regular and non-regular
64 * files by bytes, lines or the whole file.
65 *
66 * BYTES display N bytes
67 * REG reverse scan and display the lines
68 * NOREG cyclically read characters into a wrap-around buffer
69 *
70 * LINES display N lines
71 * REG reverse scan and display the lines
72 * NOREG cyclically read lines into a wrap-around array of buffers
73 *
74 * FILE display the entire file
75 * REG reverse scan and display the lines
76 * NOREG cyclically read input into a linked list of buffers
77 */
78 void
reverse(struct tailfile * tf,int nfiles,enum STYLE style,off_t off)79 reverse(struct tailfile *tf, int nfiles, enum STYLE style, off_t off)
80 {
81 int i;
82
83 if (style != REVERSE && off == 0)
84 return;
85
86 for (i = 0; i < nfiles; i++) {
87 if (nfiles > 1)
88 printfname(tf[i].fname);
89 if (!S_ISREG(tf[i].sb.st_mode) ||
90 r_reg(&(tf[i]), style, off) != 0) {
91 switch(style) {
92 case FBYTES:
93 case RBYTES:
94 (void)bytes(&(tf[i]), off);
95 break;
96 case FLINES:
97 case RLINES:
98 (void)lines(&(tf[i]), off);
99 break;
100 case REVERSE:
101 r_buf(tf[i].fp);
102 break;
103 default:
104 err(1, "Unsupported style");
105 }
106 }
107 }
108 }
109
110 /*
111 * r_reg -- display a regular file in reverse order by line.
112 */
113 static int
r_reg(struct tailfile * tf,enum STYLE style,off_t off)114 r_reg(struct tailfile *tf, enum STYLE style, off_t off)
115 {
116 off_t start, pos, end;
117 int ch;
118
119 end = tf->sb.st_size;
120 if (end == 0)
121 return (0);
122
123 /* Position before char, ignore last char whether newline or not */
124 pos = end-2;
125 ch = EOF;
126 start = 0;
127
128 if (style == RBYTES && off < end)
129 start = end - off;
130
131 for (; pos >= start; pos--) {
132 /* A seek per char isn't a problem with a smart stdio */
133 if (fseeko(tf->fp, pos, SEEK_SET) != 0) {
134 ierr(tf->fname);
135 return (0);
136 }
137 if ((ch = getc(tf->fp)) == '\n') {
138 while (--end > pos)
139 COPYCHAR(tf, ch);
140 end++;
141 if (style == RLINES && --off == 0)
142 break;
143 }
144 else if (ch == EOF) {
145 ierr(tf->fname);
146 return (0);
147 }
148 }
149 if (pos < start) {
150 if (ch != EOF && ungetc(ch, tf->fp) == EOF) {
151 ierr(tf->fname);
152 return (0);
153 }
154 while (--end >= start)
155 COPYCHAR(tf, ch);
156 }
157 return (0);
158 }
159
160 #define BSZ (128 * 1024)
161 struct bf {
162 struct bf *next;
163 struct bf *prev;
164 size_t len;
165 char l[BSZ];
166 };
167
168 /*
169 * r_buf -- display a non-regular file in reverse order by line.
170 *
171 * This is the function that saves the entire input, storing the data in a
172 * doubly linked list of buffers and then displays them in reverse order.
173 * It has the usual nastiness of trying to find the newlines, as there's no
174 * guarantee that a newline occurs anywhere in the file, let alone in any
175 * particular buffer. If we run out of memory, input is discarded (and the
176 * user warned).
177 */
178 static void
r_buf(FILE * fp)179 r_buf(FILE *fp)
180 {
181 struct bf *mark, *tr, *tl = NULL;
182 int ch;
183 size_t len, llen;
184 char *p;
185 off_t enomem;
186
187 for (mark = NULL, enomem = 0;;) {
188 /*
189 * Allocate a new block and link it into place in a doubly
190 * linked list. If out of memory, toss the LRU block and
191 * keep going.
192 */
193 if (enomem || (tl = malloc(sizeof(*tl))) == NULL) {
194 if (!mark)
195 err(1, NULL);
196 tl = enomem ? tl->next : mark;
197 enomem += tl->len;
198 } else if (mark) {
199 tl->next = mark;
200 tl->prev = mark->prev;
201 mark->prev->next = tl;
202 mark->prev = tl;
203 } else {
204 mark = tl;
205 mark->next = mark->prev = mark;
206 }
207
208 if (!enomem)
209 tl->len = 0;
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 /*
217 * If no input data for this block and we tossed some data,
218 * recover it.
219 */
220 if (!len) {
221 if (enomem)
222 enomem -= tl->len;
223 tl = tl->prev;
224 break;
225 }
226
227 tl->len = len;
228 if (ch == EOF)
229 break;
230 }
231
232 if (enomem) {
233 (void)fprintf(stderr,
234 "tail: warning: %lld bytes discarded\n", (long long)enomem);
235 rval = 1;
236 }
237
238 /*
239 * Step through the blocks in the reverse order read. The last char
240 * is special, ignore whether newline or not.
241 */
242 for (mark = tl;;) {
243 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--;
244 --p, ++llen)
245 if (*p == '\n') {
246 if (llen) {
247 WR(p + 1, llen);
248 llen = 0;
249 }
250 if (tl == mark)
251 continue;
252 for (tr = tl->next; tr->len; tr = tr->next) {
253 WR(tr->l, tr->len);
254 tr->len = 0;
255 if (tr == mark)
256 break;
257 }
258 }
259 tl->len = llen;
260 if ((tl = tl->prev) == mark)
261 break;
262 }
263 tl = tl->next;
264 if (tl->len) {
265 WR(tl->l, tl->len);
266 tl->len = 0;
267 }
268 while ((tl = tl->next)->len) {
269 WR(tl->l, tl->len);
270 tl->len = 0;
271 }
272
273 tl->prev->next = NULL;
274 while (tl != NULL) {
275 tr = tl->next;
276 free(tl);
277 tl = tr;
278 }
279 }
280