1/*	$OpenBSD: fgets.c,v 1.10 2005/08/08 08:05:36 espie 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 <stdio.h>
35#include <string.h>
36#include "local.h"
37
38/*
39 * Read at most n-1 characters from the given file.
40 * Stop when a newline has been read, or the count runs out.
41 * Return first argument, or NULL if no characters were read.
42 * Do not return NULL if n == 1.
43 */
44char *
45fgets(char *buf, int n, FILE *fp)
46{
47	size_t len;
48	char *s;
49	unsigned char *p, *t;
50
51	if (n <= 0)		/* sanity check */
52		return (NULL);
53
54	FLOCKFILE(fp);
55	_SET_ORIENTATION(fp, -1);
56	s = buf;
57	n--;			/* leave space for NUL */
58	while (n != 0) {
59		/*
60		 * If the buffer is empty, refill it.
61		 */
62		if (fp->_r <= 0) {
63			if (__srefill(fp)) {
64				/* EOF/error: stop with partial or no line */
65				if (s == buf) {
66					FUNLOCKFILE(fp);
67					return (NULL);
68                                }
69				break;
70			}
71		}
72		len = fp->_r;
73		p = fp->_p;
74
75		/*
76		 * Scan through at most n bytes of the current buffer,
77		 * looking for '\n'.  If found, copy up to and including
78		 * newline, and stop.  Otherwise, copy entire chunk
79		 * and loop.
80		 */
81		if ((int)len > n)
82			len = n;
83		t = memchr((void *)p, '\n', len);
84		if (t != NULL) {
85			len = ++t - p;
86			fp->_r -= len;
87			fp->_p = t;
88			(void)memcpy((void *)s, (void *)p, len);
89			s[len] = '\0';
90			FUNLOCKFILE(fp);
91			return (buf);
92		}
93		fp->_r -= len;
94		fp->_p += len;
95		(void)memcpy((void *)s, (void *)p, len);
96		s += len;
97		n -= len;
98	}
99	*s = '\0';
100	FUNLOCKFILE(fp);
101	return (buf);
102}
103