1 /* $OpenBSD: fgets.c,v 1.14 2009/11/09 00:18:27 kurt 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 */
45 char *
fgets(char * buf,int n,FILE * fp)46 fgets(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((void *)p, '\n', len);
87 if (t != NULL) {
88 len = ++t - p;
89 fp->_r -= len;
90 fp->_p = t;
91 (void)memcpy((void *)s, (void *)p, len);
92 s[len] = '\0';
93 FUNLOCKFILE(fp);
94 return (buf);
95 }
96 fp->_r -= len;
97 fp->_p += len;
98 (void)memcpy((void *)s, (void *)p, len);
99 s += len;
100 n -= len;
101 }
102 *s = '\0';
103 FUNLOCKFILE(fp);
104 return (buf);
105 }
106