fgetln.c revision 321074 
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. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)fgetln.c	8.2 (Berkeley) 1/2/94";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: stable/10/lib/libc/stdio/fgetln.c 321074 2017-07-17 14:09:34Z kib $");
38
39#include "namespace.h"
40#include <errno.h>
41#include <limits.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <string.h>
45#include "un-namespace.h"
46#include "libc_private.h"
47#include "local.h"
48
49/*
50 * Expand the line buffer.  Return -1 on error.
51#ifdef notdef
52 * The `new size' does not account for a terminating '\0',
53 * so we add 1 here.
54#endif
55 */
56int
57__slbexpand(FILE *fp, size_t newsize)
58{
59	void *p;
60
61#ifdef notdef
62	++newsize;
63#endif
64	if (fp->_lb._size >= newsize)
65		return (0);
66	if (newsize > INT_MAX) {
67		errno = ENOMEM;
68		return (-1);
69	}
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 */
84char *
85fgetln(FILE *fp, size_t *lenp)
86{
87	unsigned char *p;
88	char *ret;
89	size_t len;
90	size_t off;
91
92	FLOCKFILE_CANCELSAFE(fp);
93	ORIENT(fp, -1);
94	/* make sure there is input */
95	if (fp->_r <= 0 && __srefill(fp)) {
96		*lenp = 0;
97		ret = NULL;
98		goto end;
99	}
100
101	/* look for a newline in the input */
102	if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) != NULL) {
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		goto end;
115	}
116
117	/*
118	 * We have to copy the current buffered data to the line buffer.
119	 * As a bonus, though, we can leave off the __SMOD.
120	 *
121	 * OPTIMISTIC is length that we (optimistically) expect will
122	 * accommodate the `rest' of the string, on each trip through the
123	 * loop below.
124	 */
125#define OPTIMISTIC 80
126
127	for (len = fp->_r, off = 0;; len += fp->_r) {
128		size_t diff;
129
130		/*
131		 * Make sure there is room for more bytes.  Copy data from
132		 * file buffer to line buffer, refill file and look for
133		 * newline.  The loop stops only when we find a newline.
134		 */
135		if (__slbexpand(fp, len + OPTIMISTIC))
136			goto error;
137		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
138		    len - off);
139		off = len;
140		if (__srefill(fp)) {
141			if (__sfeof(fp))
142				break;
143			goto error;
144		}
145		if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) == NULL)
146			continue;
147
148		/* got it: finish up the line (like code above) */
149		p++;
150		diff = p - fp->_p;
151		len += diff;
152		if (__slbexpand(fp, len))
153			goto error;
154		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
155		    diff);
156		fp->_r -= diff;
157		fp->_p = p;
158		break;
159	}
160	*lenp = len;
161#ifdef notdef
162	fp->_lb._base[len] = '\0';
163#endif
164	ret = (char *)fp->_lb._base;
165end:
166	FUNLOCKFILE_CANCELSAFE();
167	return (ret);
168
169error:
170	*lenp = 0;		/* ??? */
171	fp->_flags |= __SERR;
172	ret = NULL;
173	goto end;
174}
175