1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
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#if defined(LIBC_SCCS) && !defined(lint)
36static char sccsid[] = "@(#)fgets.c	8.2 (Berkeley) 12/22/93";
37#endif /* LIBC_SCCS and not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD$");
40
41#include "namespace.h"
42#include <errno.h>
43#include <stdio.h>
44#include <string.h>
45#include "un-namespace.h"
46#include "local.h"
47#include "libc_private.h"
48
49/*
50 * Read at most n-1 characters from the given file.
51 * Stop when a newline has been read, or the count runs out.
52 * Return first argument, or NULL if no characters were read.
53 */
54char *
55fgets(char * __restrict buf, int n, FILE * __restrict fp)
56{
57	size_t len;
58	char *s, *ret;
59	unsigned char *p, *t;
60
61	FLOCKFILE_CANCELSAFE(fp);
62	ORIENT(fp, -1);
63
64	if (n <= 0) {		/* sanity check */
65		fp->_flags |= __SERR;
66		errno = EINVAL;
67		ret = NULL;
68		goto end;
69	}
70
71	s = buf;
72	n--;			/* leave space for NUL */
73	while (n != 0) {
74		/*
75		 * If the buffer is empty, refill it.
76		 */
77		if ((len = fp->_r) <= 0) {
78			if (__srefill(fp)) {
79				/* EOF/error: stop with partial or no line */
80				if (!__sfeof(fp) || s == buf) {
81					ret = NULL;
82					goto end;
83				}
84				break;
85			}
86			len = fp->_r;
87		}
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			len = n;
98		t = memchr((void *)p, '\n', len);
99		if (t != NULL) {
100			len = ++t - p;
101			fp->_r -= len;
102			fp->_p = t;
103			(void)memcpy((void *)s, (void *)p, len);
104			s[len] = 0;
105			ret = buf;
106			goto end;
107		}
108		fp->_r -= len;
109		fp->_p += len;
110		(void)memcpy((void *)s, (void *)p, len);
111		s += len;
112		n -= len;
113	}
114	*s = 0;
115	ret = buf;
116end:
117	FUNLOCKFILE_CANCELSAFE();
118	return (ret);
119}
120