1/*	$OpenBSD: fgets.c,v 1.16 2016/09/21 04:38:56 guenther Exp $ */
2/*-
3 * Copyright (c) 1990, 1993
4 *	The Regents of the University of California.  All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include <errno.h>
35#include <stdio.h>
36#include <string.h>
37#include "local.h"
38
39/*
40 * Read at most n-1 characters from the given file.
41 * Stop when a newline has been read, or the count runs out.
42 * Return first argument, or NULL if no characters were read.
43 * Do not return NULL if n == 1.
44 */
45char *
46fgets(char *buf, int n, FILE *fp)
47{
48	size_t len;
49	char *s;
50	unsigned char *p, *t;
51
52	if (n <= 0) {		/* sanity check */
53		errno = EINVAL;
54		return (NULL);
55	}
56
57	FLOCKFILE(fp);
58	_SET_ORIENTATION(fp, -1);
59	s = buf;
60	n--;			/* leave space for NUL */
61	while (n != 0) {
62		/*
63		 * If the buffer is empty, refill it.
64		 */
65		if (fp->_r <= 0) {
66			if (__srefill(fp)) {
67				/* EOF/error: stop with partial or no line */
68				if (s == buf) {
69					FUNLOCKFILE(fp);
70					return (NULL);
71				}
72				break;
73			}
74		}
75		len = fp->_r;
76		p = fp->_p;
77
78		/*
79		 * Scan through at most n bytes of the current buffer,
80		 * looking for '\n'.  If found, copy up to and including
81		 * newline, and stop.  Otherwise, copy entire chunk
82		 * and loop.
83		 */
84		if (len > n)
85			len = n;
86		t = memchr(p, '\n', len);
87		if (t != NULL) {
88			len = ++t - p;
89			fp->_r -= len;
90			fp->_p = t;
91			(void)memcpy(s, p, len);
92			s[len] = '\0';
93			FUNLOCKFILE(fp);
94			return (buf);
95		}
96		fp->_r -= len;
97		fp->_p += len;
98		(void)memcpy(s, p, len);
99		s += len;
100		n -= len;
101	}
102	*s = '\0';
103	FUNLOCKFILE(fp);
104	return (buf);
105}
106DEF_STRONG(fgets);
107