1 /* $NetBSD: fgets.c,v 1.28 2012/03/15 18:22:30 christos Exp $ */
2
3 /*-
4 * Copyright (c) 1990, 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 * Chris Torek.
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/cdefs.h>
36 #if defined(LIBC_SCCS) && !defined(lint)
37 #if 0
38 static char sccsid[] = "@(#)fgets.c 8.2 (Berkeley) 12/22/93";
39 #else
40 __RCSID("$NetBSD: fgets.c,v 1.28 2012/03/15 18:22:30 christos Exp $");
41 #endif
42 #endif /* LIBC_SCCS and not lint */
43
44 #include <assert.h>
45 #include <stdio.h>
46 #include <errno.h>
47 #include <string.h>
48 #include "reentrant.h"
49 #include "local.h"
50 #ifdef _FORTIFY_SOURCE
51 #undef fgets
52 #endif
53
54 /*
55 * Read at most n-1 characters from the given file.
56 * Stop when a newline has been read, or the count runs out.
57 * Return first argument, or NULL if no characters were read.
58 */
59 char *
fgets(char * buf,int n,FILE * fp)60 fgets(char *buf, int n, FILE *fp)
61 {
62 int len;
63 char *s;
64 unsigned char *p, *t;
65
66 _DIAGASSERT(buf != NULL);
67 _DIAGASSERT(fp != NULL);
68
69 FLOCKFILE(fp);
70 _SET_ORIENTATION(fp, -1);
71 s = buf;
72 n--; /* leave space for NUL */
73 do {
74 /*
75 * If the buffer is empty, refill it.
76 */
77 if (fp->_r <= 0) {
78 if (__srefill(fp)) {
79 /* EOF/error: stop with partial or no line */
80 if (s == buf) {
81 FUNLOCKFILE(fp);
82 return (NULL);
83 }
84 break;
85 }
86 }
87 len = fp->_r;
88 p = fp->_p;
89
90 /*
91 * Scan through at most n bytes of the current buffer,
92 * looking for '\n'. If found, copy up to and including
93 * newline, and stop. Otherwise, copy entire chunk
94 * and loop.
95 */
96 if (len > n) {
97 if (n < 0) {
98 /*
99 * Caller's length <= 0
100 * We can't write into the buffer, so cannot
101 * return a string, so must return NULL.
102 * Set errno and __SERR so it is consistent.
103 * TOG gives no indication of what to do here!
104 */
105 errno = EINVAL;
106 fp->_flags |= __SERR;
107 FUNLOCKFILE(fp);
108 return NULL;
109 }
110 len = n;
111 }
112 t = memchr(p, '\n', (size_t)len);
113 if (t != NULL) {
114 len = (int)(++t - p);
115 fp->_r -= len;
116 fp->_p = t;
117 (void)memcpy(s, p, (size_t)len);
118 s[len] = 0;
119 FUNLOCKFILE(fp);
120 return buf;
121 }
122 fp->_r -= len;
123 fp->_p += len;
124 (void)memcpy(s, p, (size_t)len);
125 s += len;
126 n -= len;
127 } while (n != 0);
128 *s = 0;
129 FUNLOCKFILE(fp);
130 return buf;
131 }
132