1 /* $OpenBSD: fgetln.c,v 1.13 2015/01/05 21:58:52 millert 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 */
42 static int
__slbexpand(FILE * fp,size_t newsize)43 __slbexpand(FILE *fp, size_t newsize)
44 {
45 void *p;
46
47 if (fp->_lb._size >= newsize)
48 return (0);
49 if ((p = realloc(fp->_lb._base, newsize)) == NULL)
50 return (-1);
51 fp->_lb._base = p;
52 fp->_lb._size = newsize;
53 return (0);
54 }
55
56 /*
57 * Get an input line. The returned pointer often (but not always)
58 * points into a stdio buffer. Fgetline does not alter the text of
59 * the returned line (which is thus not a C string because it will
60 * not necessarily end with '\0'), but does allow callers to modify
61 * it if they wish. Thus, we set __SMOD in case the caller does.
62 */
63 char *
fgetln(FILE * fp,size_t * lenp)64 fgetln(FILE *fp, size_t *lenp)
65 {
66 unsigned char *p;
67 char *ret;
68 size_t len;
69 size_t off;
70
71 FLOCKFILE(fp);
72 _SET_ORIENTATION(fp, -1);
73
74 /* make sure there is input */
75 if (fp->_r <= 0 && __srefill(fp))
76 goto error;
77
78 /* look for a newline in the input */
79 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
80 /*
81 * Found one. Flag buffer as modified to keep fseek from
82 * `optimising' a backward seek, in case the user stomps on
83 * the text.
84 */
85 p++; /* advance over it */
86 ret = (char *)fp->_p;
87 *lenp = len = p - fp->_p;
88 fp->_flags |= __SMOD;
89 fp->_r -= len;
90 fp->_p = p;
91 FUNLOCKFILE(fp);
92 return (ret);
93 }
94
95 /*
96 * We have to copy the current buffered data to the line buffer.
97 * As a bonus, though, we can leave off the __SMOD.
98 *
99 * OPTIMISTIC is length that we (optimistically) expect will
100 * accommodate the `rest' of the string, on each trip through the
101 * loop below.
102 */
103 #define OPTIMISTIC 80
104
105 for (len = fp->_r, off = 0;; len += fp->_r) {
106 size_t diff;
107
108 /*
109 * Make sure there is room for more bytes. Copy data from
110 * file buffer to line buffer, refill file and look for
111 * newline. The loop stops only when we find a newline.
112 */
113 if (__slbexpand(fp, len + OPTIMISTIC))
114 goto error;
115 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
116 len - off);
117 off = len;
118 if (__srefill(fp))
119 break; /* EOF or error: return partial line */
120 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
121 continue;
122
123 /* got it: finish up the line (like code above) */
124 p++;
125 diff = p - fp->_p;
126 len += diff;
127 if (__slbexpand(fp, len))
128 goto error;
129 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
130 diff);
131 fp->_r -= diff;
132 fp->_p = p;
133 break;
134 }
135 *lenp = len;
136 ret = (char *)fp->_lb._base;
137 FUNLOCKFILE(fp);
138 return (ret);
139
140 error:
141 FUNLOCKFILE(fp);
142 *lenp = 0;
143 return (NULL);
144 }
145