fgetln.c revision 16335 
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)
38static char sccsid[] = "@(#)fgetln.c	8.2 (Berkeley) 1/2/94";
39#endif /* LIBC_SCCS and not lint */
40
41#include <stdio.h>
42#include <stdlib.h>
43#include <string.h>
44#include "local.h"
45
46/*
47 * Expand the line buffer.  Return -1 on error.
48#ifdef notdef
49 * The `new size' does not account for a terminating '\0',
50 * so we add 1 here.
51#endif
52 */
53int __slbexpand(fp, newsize)
54	FILE *fp;
55	size_t newsize;
56{
57	void *p;
58
59#ifdef notdef
60	++newsize;
61#endif
62	if (fp->_lb._size >= newsize)
63		return (0);
64	if ((p = realloc(fp->_lb._base, newsize)) == NULL)
65		return (-1);
66	fp->_lb._base = p;
67	fp->_lb._size = newsize;
68	return (0);
69}
70
71/*
72 * Get an input line.  The returned pointer often (but not always)
73 * points into a stdio buffer.  Fgetln does not alter the text of
74 * the returned line (which is thus not a C string because it will
75 * not necessarily end with '\0'), but does allow callers to modify
76 * it if they wish.  Thus, we set __SMOD in case the caller does.
77 */
78char *
79fgetln(fp, lenp)
80	register FILE *fp;
81	size_t *lenp;
82{
83	register unsigned char *p;
84	register size_t len;
85	size_t off;
86
87	/* make sure there is input */
88	if (fp->_r <= 0 && __srefill(fp)) {
89		*lenp = 0;
90		return (NULL);
91	}
92
93	/* look for a newline in the input */
94	if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
95		register char *ret;
96
97		/*
98		 * Found one.  Flag buffer as modified to keep fseek from
99		 * `optimising' a backward seek, in case the user stomps on
100		 * the text.
101		 */
102		p++;		/* advance over it */
103		ret = (char *)fp->_p;
104		*lenp = len = p - fp->_p;
105		fp->_flags |= __SMOD;
106		fp->_r -= len;
107		fp->_p = p;
108		return (ret);
109	}
110
111	/*
112	 * We have to copy the current buffered data to the line buffer.
113	 * As a bonus, though, we can leave off the __SMOD.
114	 *
115	 * OPTIMISTIC is length that we (optimistically) expect will
116	 * accomodate the `rest' of the string, on each trip through the
117	 * loop below.
118	 */
119#define OPTIMISTIC 80
120
121	for (len = fp->_r, off = 0;; len += fp->_r) {
122		register size_t diff;
123
124		/*
125		 * Make sure there is room for more bytes.  Copy data from
126		 * file buffer to line buffer, refill file and look for
127		 * newline.  The loop stops only when we find a newline.
128		 */
129		if (__slbexpand(fp, len + OPTIMISTIC))
130			goto error;
131		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
132		    len - off);
133		off = len;
134		if (__srefill(fp))
135			break;	/* EOF or error: return partial line */
136		if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
137			continue;
138
139		/* got it: finish up the line (like code above) */
140		p++;
141		diff = p - fp->_p;
142		len += diff;
143		if (__slbexpand(fp, len))
144			goto error;
145		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
146		    diff);
147		fp->_r -= diff;
148		fp->_p = p;
149		break;
150	}
151	*lenp = len;
152#ifdef notdef
153	fp->_lb._base[len] = 0;
154#endif
155	return ((char *)fp->_lb._base);
156
157error:
158	*lenp = 0;		/* ??? */
159	return (NULL);		/* ??? */
160}
161