xref: /freebsd/usr.bin/tail/read.c (revision 2f6a179eb910129fb812c1ad1bdc300da1203dc0)
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  * 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.
23  *
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
34  * SUCH DAMAGE.
35  */
36 
37 #include <sys/cdefs.h>
38 
39 __FBSDID("$FreeBSD$");
40 
41 #ifndef lint
42 static const char sccsid[] = "@(#)read.c	8.1 (Berkeley) 6/6/93";
43 #endif
44 
45 #include <sys/types.h>
46 #include <sys/stat.h>
47 
48 #include <err.h>
49 #include <errno.h>
50 #include <fcntl.h>
51 #include <stdio.h>
52 #include <stdlib.h>
53 #include <string.h>
54 #include <unistd.h>
55 
56 #include "extern.h"
57 
58 /*
59  * bytes -- read bytes to an offset from the end and display.
60  *
61  * This is the function that reads to a byte offset from the end of the input,
62  * storing the data in a wrap-around buffer which is then displayed.  If the
63  * rflag is set, the data is displayed in lines in reverse order, and this
64  * routine has the usual nastiness of trying to find the newlines.  Otherwise,
65  * it is displayed from the character closest to the beginning of the input to
66  * the end.
67  */
68 int
69 bytes(FILE *fp, off_t off)
70 {
71 	int ch, len, tlen;
72 	char *ep, *p, *t;
73 	int wrap;
74 	char *sp;
75 
76 	if ((sp = p = malloc(off)) == NULL)
77 		err(1, "malloc");
78 
79 	for (wrap = 0, ep = p + off; (ch = getc(fp)) != EOF;) {
80 		*p = ch;
81 		if (++p == ep) {
82 			wrap = 1;
83 			p = sp;
84 		}
85 	}
86 	if (ferror(fp)) {
87 		ierr();
88 		free(sp);
89 		return 1;
90 	}
91 
92 	if (rflag) {
93 		for (t = p - 1, len = 0; t >= sp; --t, ++len)
94 			if (*t == '\n' && len) {
95 				WR(t + 1, len);
96 				len = 0;
97 		}
98 		if (wrap) {
99 			tlen = len;
100 			for (t = ep - 1, len = 0; t >= p; --t, ++len)
101 				if (*t == '\n') {
102 					if (len) {
103 						WR(t + 1, len);
104 						len = 0;
105 					}
106 					if (tlen) {
107 						WR(sp, tlen);
108 						tlen = 0;
109 					}
110 				}
111 			if (len)
112 				WR(t + 1, len);
113 			if (tlen)
114 				WR(sp, tlen);
115 		}
116 	} else {
117 		if (wrap && (len = ep - p))
118 			WR(p, len);
119 		len = p - sp;
120 		if (len)
121 			WR(sp, len);
122 	}
123 
124 	free(sp);
125 	return 0;
126 }
127 
128 /*
129  * lines -- read lines to an offset from the end and display.
130  *
131  * This is the function that reads to a line offset from the end of the input,
132  * storing the data in an array of buffers which is then displayed.  If the
133  * rflag is set, the data is displayed in lines in reverse order, and this
134  * routine has the usual nastiness of trying to find the newlines.  Otherwise,
135  * it is displayed from the line closest to the beginning of the input to
136  * the end.
137  */
138 int
139 lines(FILE *fp, off_t off)
140 {
141 	struct {
142 		int blen;
143 		u_int len;
144 		char *l;
145 	} *llines;
146 	int ch, rc;
147 	char *p, *sp;
148 	int blen, cnt, recno, wrap;
149 
150 	if ((llines = malloc(off * sizeof(*llines))) == NULL)
151 		err(1, "malloc");
152 	bzero(llines, off * sizeof(*llines));
153 	p = sp = NULL;
154 	blen = cnt = recno = wrap = 0;
155 	rc = 0;
156 
157 	while ((ch = getc(fp)) != EOF) {
158 		if (++cnt > blen) {
159 			if ((sp = realloc(sp, blen += 1024)) == NULL)
160 				err(1, "realloc");
161 			p = sp + cnt - 1;
162 		}
163 		*p++ = ch;
164 		if (ch == '\n') {
165 			if ((int)llines[recno].blen < cnt) {
166 				llines[recno].blen = cnt + 256;
167 				if ((llines[recno].l = realloc(llines[recno].l,
168 				    llines[recno].blen)) == NULL)
169 					err(1, "realloc");
170 			}
171 			bcopy(sp, llines[recno].l, llines[recno].len = cnt);
172 			cnt = 0;
173 			p = sp;
174 			if (++recno == off) {
175 				wrap = 1;
176 				recno = 0;
177 			}
178 		}
179 	}
180 	if (ferror(fp)) {
181 		ierr();
182 		rc = 1;
183 		goto done;
184 	}
185 	if (cnt) {
186 		llines[recno].l = sp;
187 		sp = NULL;
188 		llines[recno].len = cnt;
189 		if (++recno == off) {
190 			wrap = 1;
191 			recno = 0;
192 		}
193 	}
194 
195 	if (rflag) {
196 		for (cnt = recno - 1; cnt >= 0; --cnt)
197 			WR(llines[cnt].l, llines[cnt].len);
198 		if (wrap)
199 			for (cnt = off - 1; cnt >= recno; --cnt)
200 				WR(llines[cnt].l, llines[cnt].len);
201 	} else {
202 		if (wrap)
203 			for (cnt = recno; cnt < off; ++cnt)
204 				WR(llines[cnt].l, llines[cnt].len);
205 		for (cnt = 0; cnt < recno; ++cnt)
206 			WR(llines[cnt].l, llines[cnt].len);
207 	}
208 done:
209 	for (cnt = 0; cnt < off; cnt++)
210 		free(llines[cnt].l);
211 	free(sp);
212 	free(llines);
213 	return (rc);
214 }
215