1/*	$NetBSD: fgets.c,v 1.26 2009/10/25 17:09:34 dsl 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
38static char sccsid[] = "@(#)fgets.c	8.2 (Berkeley) 12/22/93";
39#else
40__RCSID("$NetBSD: fgets.c,v 1.26 2009/10/25 17:09:34 dsl 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 */
59char *
60fgets(buf, n, fp)
61	char *buf;
62	int n;
63	FILE *fp;
64{
65	int len;
66	char *s;
67	unsigned char *p, *t;
68
69	_DIAGASSERT(buf != NULL);
70	_DIAGASSERT(fp != NULL);
71
72	FLOCKFILE(fp);
73	_SET_ORIENTATION(fp, -1);
74	s = buf;
75	n--;			/* leave space for NUL */
76	do {
77		/*
78		 * If the buffer is empty, refill it.
79		 */
80		if (fp->_r <= 0) {
81			if (__srefill(fp)) {
82				/* EOF/error: stop with partial or no line */
83				if (s == buf) {
84					FUNLOCKFILE(fp);
85					return (NULL);
86				}
87				break;
88			}
89		}
90		len = fp->_r;
91		p = fp->_p;
92
93		/*
94		 * Scan through at most n bytes of the current buffer,
95		 * looking for '\n'.  If found, copy up to and including
96		 * newline, and stop.  Otherwise, copy entire chunk
97		 * and loop.
98		 */
99		if (len > n) {
100			if (n < 0) {
101				/*
102				 * Caller's length <= 0
103				 * We can't write into the buffer, so cannot
104				 * return a string, so must return NULL.
105				 * Set errno and __SERR so it is consistent.
106				 * TOG gives no indication of what to do here!
107				 */
108				errno = EINVAL;
109				fp->_flags |= __SERR;
110				FUNLOCKFILE(fp);
111				return NULL;
112			}
113			len = n;
114		}
115		t = memchr(p, '\n', (size_t)len);
116		if (t != NULL) {
117			len = (int)(++t - p);
118			fp->_r -= len;
119			fp->_p = t;
120			(void)memcpy(s, p, (size_t)len);
121			s[len] = 0;
122			FUNLOCKFILE(fp);
123			return (buf);
124		}
125		fp->_r -= len;
126		fp->_p += len;
127		(void)memcpy(s, p, (size_t)len);
128		s += len;
129		n -= len;
130	} while (n != 0);
131	*s = 0;
132	FUNLOCKFILE(fp);
133	return (buf);
134}
135