1 /*-
2 * Copyright (c) 1990, 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 * Chris Torek.
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. 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 #if defined(LIBC_SCCS) && !defined(lint)
34 static char sccsid[] = "@(#)fgets.c 8.2 (Berkeley) 12/22/93";
35 #endif /* LIBC_SCCS and not lint */
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD: stable/10/lib/libc/stdio/fgets.c 321074 2017-07-17 14:09:34Z kib $");
38
39 #include "namespace.h"
40 #include <errno.h>
41 #include <stdio.h>
42 #include <string.h>
43 #include "un-namespace.h"
44 #include "local.h"
45 #include "libc_private.h"
46
47 /*
48 * Read at most n-1 characters from the given file.
49 * Stop when a newline has been read, or the count runs out.
50 * Return first argument, or NULL if no characters were read.
51 */
52 char *
fgets(char * __restrict buf,int n,FILE * __restrict fp)53 fgets(char * __restrict buf, int n, FILE * __restrict fp)
54 {
55 size_t len;
56 char *s, *ret;
57 unsigned char *p, *t;
58
59 FLOCKFILE_CANCELSAFE(fp);
60 ORIENT(fp, -1);
61
62 if (n <= 0) { /* sanity check */
63 fp->_flags |= __SERR;
64 errno = EINVAL;
65 ret = NULL;
66 goto end;
67 }
68
69 s = buf;
70 n--; /* leave space for NUL */
71 while (n != 0) {
72 /*
73 * If the buffer is empty, refill it.
74 */
75 if ((len = fp->_r) <= 0) {
76 if (__srefill(fp)) {
77 /* EOF/error: stop with partial or no line */
78 if (!__sfeof(fp) || s == buf) {
79 ret = NULL;
80 goto end;
81 }
82 break;
83 }
84 len = fp->_r;
85 }
86 p = fp->_p;
87
88 /*
89 * Scan through at most n bytes of the current buffer,
90 * looking for '\n'. If found, copy up to and including
91 * newline, and stop. Otherwise, copy entire chunk
92 * and loop.
93 */
94 if (len > n)
95 len = n;
96 t = memchr((void *)p, '\n', len);
97 if (t != NULL) {
98 len = ++t - p;
99 fp->_r -= len;
100 fp->_p = t;
101 (void)memcpy((void *)s, (void *)p, len);
102 s[len] = 0;
103 ret = buf;
104 goto end;
105 }
106 fp->_r -= len;
107 fp->_p += len;
108 (void)memcpy((void *)s, (void *)p, len);
109 s += len;
110 n -= len;
111 }
112 *s = 0;
113 ret = buf;
114 end:
115 FUNLOCKFILE_CANCELSAFE();
116 return (ret);
117 }
118