xref: /freebsd/lib/libc/stdio/fgetln.c (revision 41466b50c1d5bfd1cf6adaae547a579a75d7c04e)
1 /*-
2  * Copyright (c) 1990, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * This code is derived from software contributed to Berkeley by
6  * Chris Torek.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 3. All advertising materials mentioning features or use of this software
17  *    must display the following acknowledgement:
18  *	This product includes software developed by the University of
19  *	California, Berkeley and its contributors.
20  * 4. Neither the name of the University nor the names of its contributors
21  *    may be used to endorse or promote products derived from this software
22  *    without specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  */
36 
37 #if defined(LIBC_SCCS) && !defined(lint)
38 #if 0
39 static char sccsid[] = "@(#)fgetln.c	8.2 (Berkeley) 1/2/94";
40 #endif
41 static const char rcsid[] =
42   "$FreeBSD$";
43 #endif /* LIBC_SCCS and not lint */
44 
45 #include "namespace.h"
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <string.h>
49 #include "un-namespace.h"
50 #include "libc_private.h"
51 #include "local.h"
52 
53 /*
54  * Expand the line buffer.  Return -1 on error.
55 #ifdef notdef
56  * The `new size' does not account for a terminating '\0',
57  * so we add 1 here.
58 #endif
59  */
60 static int
61 slbexpand(FILE *fp, size_t newsize)
62 {
63 	void *p;
64 
65 #ifdef notdef
66 	++newsize;
67 #endif
68 	if (fp->_lb._size >= newsize)
69 		return (0);
70 	if ((p = realloc(fp->_lb._base, newsize)) == NULL)
71 		return (-1);
72 	fp->_lb._base = p;
73 	fp->_lb._size = newsize;
74 	return (0);
75 }
76 
77 /*
78  * Get an input line.  The returned pointer often (but not always)
79  * points into a stdio buffer.  Fgetln does not alter the text of
80  * the returned line (which is thus not a C string because it will
81  * not necessarily end with '\0'), but does allow callers to modify
82  * it if they wish.  Thus, we set __SMOD in case the caller does.
83  */
84 char *
85 fgetln(FILE *fp, size_t *lenp)
86 {
87 	unsigned char *p;
88 	size_t len;
89 	size_t off;
90 
91 	FLOCKFILE(fp);
92 	/* make sure there is input */
93 	if (fp->_r <= 0 && __srefill(fp)) {
94 		*lenp = 0;
95 		FUNLOCKFILE(fp);
96 		return (NULL);
97 	}
98 
99 	/* look for a newline in the input */
100 	if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) != NULL) {
101 		char *ret;
102 
103 		/*
104 		 * Found one.  Flag buffer as modified to keep fseek from
105 		 * `optimising' a backward seek, in case the user stomps on
106 		 * the text.
107 		 */
108 		p++;		/* advance over it */
109 		ret = (char *)fp->_p;
110 		*lenp = len = p - fp->_p;
111 		fp->_flags |= __SMOD;
112 		fp->_r -= len;
113 		fp->_p = p;
114 		FUNLOCKFILE(fp);
115 		return (ret);
116 	}
117 
118 	/*
119 	 * We have to copy the current buffered data to the line buffer.
120 	 * As a bonus, though, we can leave off the __SMOD.
121 	 *
122 	 * OPTIMISTIC is length that we (optimistically) expect will
123 	 * accomodate the `rest' of the string, on each trip through the
124 	 * loop below.
125 	 */
126 #define OPTIMISTIC 80
127 
128 	for (len = fp->_r, off = 0;; len += fp->_r) {
129 		size_t diff;
130 
131 		/*
132 		 * Make sure there is room for more bytes.  Copy data from
133 		 * file buffer to line buffer, refill file and look for
134 		 * newline.  The loop stops only when we find a newline.
135 		 */
136 		if (slbexpand(fp, len + OPTIMISTIC))
137 			goto error;
138 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
139 		    len - off);
140 		off = len;
141 		if (__srefill(fp))
142 			break;	/* EOF or error: return partial line */
143 		if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) == NULL)
144 			continue;
145 
146 		/* got it: finish up the line (like code above) */
147 		p++;
148 		diff = p - fp->_p;
149 		len += diff;
150 		if (slbexpand(fp, len))
151 			goto error;
152 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
153 		    diff);
154 		fp->_r -= diff;
155 		fp->_p = p;
156 		break;
157 	}
158 	*lenp = len;
159 #ifdef notdef
160 	fp->_lb._base[len] = 0;
161 #endif
162 	FUNLOCKFILE(fp);
163 	return ((char *)fp->_lb._base);
164 
165 error:
166 	*lenp = 0;		/* ??? */
167 	FUNLOCKFILE(fp);
168 	return (NULL);		/* ??? */
169 }
170