1 /* $OpenBSD: fgetln.c,v 1.12 2013/11/12 07:04:06 deraadt Exp $ */
2 /*-
3 * Copyright (c) 1990, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <string.h>
37 #include "local.h"
38
39 /*
40 * Expand the line buffer. Return -1 on error.
41 #ifdef notdef
42 * The `new size' does not account for a terminating '\0',
43 * so we add 1 here.
44 #endif
45 */
46 static int
__slbexpand(FILE * fp,size_t newsize)47 __slbexpand(FILE *fp, size_t newsize)
48 {
49 void *p;
50
51 #ifdef notdef
52 ++newsize;
53 #endif
54 if (fp->_lb._size >= newsize)
55 return (0);
56 if ((p = realloc(fp->_lb._base, newsize)) == NULL)
57 return (-1);
58 fp->_lb._base = p;
59 fp->_lb._size = newsize;
60 return (0);
61 }
62
63 /*
64 * Get an input line. The returned pointer often (but not always)
65 * points into a stdio buffer. Fgetline does not alter the text of
66 * the returned line (which is thus not a C string because it will
67 * not necessarily end with '\0'), but does allow callers to modify
68 * it if they wish. Thus, we set __SMOD in case the caller does.
69 */
70 char *
fgetln(FILE * fp,size_t * lenp)71 fgetln(FILE *fp, size_t *lenp)
72 {
73 unsigned char *p;
74 char *ret;
75 size_t len;
76 size_t off;
77
78 FLOCKFILE(fp);
79 _SET_ORIENTATION(fp, -1);
80
81 /* make sure there is input */
82 if (fp->_r <= 0 && __srefill(fp))
83 goto error;
84
85 /* look for a newline in the input */
86 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
87 /*
88 * Found one. Flag buffer as modified to keep fseek from
89 * `optimising' a backward seek, in case the user stomps on
90 * the text.
91 */
92 p++; /* advance over it */
93 ret = (char *)fp->_p;
94 *lenp = len = p - fp->_p;
95 fp->_flags |= __SMOD;
96 fp->_r -= len;
97 fp->_p = p;
98 FUNLOCKFILE(fp);
99 return (ret);
100 }
101
102 /*
103 * We have to copy the current buffered data to the line buffer.
104 * As a bonus, though, we can leave off the __SMOD.
105 *
106 * OPTIMISTIC is length that we (optimistically) expect will
107 * accommodate the `rest' of the string, on each trip through the
108 * loop below.
109 */
110 #define OPTIMISTIC 80
111
112 for (len = fp->_r, off = 0;; len += fp->_r) {
113 size_t diff;
114
115 /*
116 * Make sure there is room for more bytes. Copy data from
117 * file buffer to line buffer, refill file and look for
118 * newline. The loop stops only when we find a newline.
119 */
120 if (__slbexpand(fp, len + OPTIMISTIC))
121 goto error;
122 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
123 len - off);
124 off = len;
125 if (__srefill(fp))
126 break; /* EOF or error: return partial line */
127 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
128 continue;
129
130 /* got it: finish up the line (like code above) */
131 p++;
132 diff = p - fp->_p;
133 len += diff;
134 if (__slbexpand(fp, len))
135 goto error;
136 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
137 diff);
138 fp->_r -= diff;
139 fp->_p = p;
140 break;
141 }
142 *lenp = len;
143 ret = (char *)fp->_lb._base;
144 #ifdef notdef
145 ret[len] = '\0';
146 #endif
147 FUNLOCKFILE(fp);
148 return (ret);
149
150 error:
151 *lenp = 0; /* ??? */
152 FUNLOCKFILE(fp);
153 return (NULL); /* ??? */
154 }
155