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