fgetln.c revision 330897 
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: stable/11/lib/libc/stdio/fgetln.c 330897 2018-03-14 03:19:51Z eadler $");
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#ifdef notdef
54 * The `new size' does not account for a terminating '\0',
55 * so we add 1 here.
56#endif
57 */
58int
59__slbexpand(FILE *fp, size_t newsize)
60{
61	void *p;
62
63#ifdef notdef
64	++newsize;
65#endif
66	if (fp->_lb._size >= newsize)
67		return (0);
68	if (newsize > INT_MAX) {
69		errno = ENOMEM;
70		return (-1);
71	}
72	if ((p = realloc(fp->_lb._base, newsize)) == NULL)
73		return (-1);
74	fp->_lb._base = p;
75	fp->_lb._size = newsize;
76	return (0);
77}
78
79/*
80 * Get an input line.  The returned pointer often (but not always)
81 * points into a stdio buffer.  Fgetln does not alter the text of
82 * the returned line (which is thus not a C string because it will
83 * not necessarily end with '\0'), but does allow callers to modify
84 * it if they wish.  Thus, we set __SMOD in case the caller does.
85 */
86char *
87fgetln(FILE *fp, size_t *lenp)
88{
89	unsigned char *p;
90	char *ret;
91	size_t len;
92	size_t off;
93
94	FLOCKFILE_CANCELSAFE(fp);
95	ORIENT(fp, -1);
96	/* make sure there is input */
97	if (fp->_r <= 0 && __srefill(fp)) {
98		*lenp = 0;
99		ret = NULL;
100		goto end;
101	}
102
103	/* look for a newline in the input */
104	if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) != NULL) {
105		/*
106		 * Found one.  Flag buffer as modified to keep fseek from
107		 * `optimising' a backward seek, in case the user stomps on
108		 * the text.
109		 */
110		p++;		/* advance over it */
111		ret = (char *)fp->_p;
112		*lenp = len = p - fp->_p;
113		fp->_flags |= __SMOD;
114		fp->_r -= len;
115		fp->_p = p;
116		goto end;
117	}
118
119	/*
120	 * We have to copy the current buffered data to the line buffer.
121	 * As a bonus, though, we can leave off the __SMOD.
122	 *
123	 * OPTIMISTIC is length that we (optimistically) expect will
124	 * accommodate the `rest' of the string, on each trip through the
125	 * loop below.
126	 */
127#define OPTIMISTIC 80
128
129	for (len = fp->_r, off = 0;; len += fp->_r) {
130		size_t diff;
131
132		/*
133		 * Make sure there is room for more bytes.  Copy data from
134		 * file buffer to line buffer, refill file and look for
135		 * newline.  The loop stops only when we find a newline.
136		 */
137		if (__slbexpand(fp, len + OPTIMISTIC))
138			goto error;
139		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
140		    len - off);
141		off = len;
142		if (__srefill(fp)) {
143			if (__sfeof(fp))
144				break;
145			goto error;
146		}
147		if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) == NULL)
148			continue;
149
150		/* got it: finish up the line (like code above) */
151		p++;
152		diff = p - fp->_p;
153		len += diff;
154		if (__slbexpand(fp, len))
155			goto error;
156		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
157		    diff);
158		fp->_r -= diff;
159		fp->_p = p;
160		break;
161	}
162	*lenp = len;
163#ifdef notdef
164	fp->_lb._base[len] = '\0';
165#endif
166	ret = (char *)fp->_lb._base;
167end:
168	FUNLOCKFILE_CANCELSAFE();
169	return (ret);
170
171error:
172	*lenp = 0;		/* ??? */
173	fp->_flags |= __SERR;
174	ret = NULL;
175	goto end;
176}
177