1 /* $OpenBSD: fgetln.c,v 1.7 2005/08/08 08:05:36 espie 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 ((size_t)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
80 /* make sure there is input */
81 if (fp->_r <= 0 && __srefill(fp))
82 goto error;
83
84 /* look for a newline in the input */
85 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
86 /*
87 * Found one. Flag buffer as modified to keep fseek from
88 * `optimising' a backward seek, in case the user stomps on
89 * the text.
90 */
91 p++; /* advance over it */
92 ret = (char *)fp->_p;
93 *lenp = len = p - fp->_p;
94 fp->_flags |= __SMOD;
95 fp->_r -= len;
96 fp->_p = p;
97 FUNLOCKFILE(fp);
98 return (ret);
99 }
100
101 /*
102 * We have to copy the current buffered data to the line buffer.
103 * As a bonus, though, we can leave off the __SMOD.
104 *
105 * OPTIMISTIC is length that we (optimistically) expect will
106 * accommodate the `rest' of the string, on each trip through the
107 * loop below.
108 */
109 #define OPTIMISTIC 80
110
111 for (len = fp->_r, off = 0;; len += fp->_r) {
112 size_t diff;
113
114 /*
115 * Make sure there is room for more bytes. Copy data from
116 * file buffer to line buffer, refill file and look for
117 * newline. The loop stops only when we find a newline.
118 */
119 if (__slbexpand(fp, len + OPTIMISTIC))
120 goto error;
121 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
122 len - off);
123 off = len;
124 if (__srefill(fp))
125 break; /* EOF or error: return partial line */
126 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
127 continue;
128
129 /* got it: finish up the line (like code above) */
130 p++;
131 diff = p - fp->_p;
132 len += diff;
133 if (__slbexpand(fp, len))
134 goto error;
135 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
136 diff);
137 fp->_r -= diff;
138 fp->_p = p;
139 break;
140 }
141 *lenp = len;
142 ret = (char *)fp->_lb._base;
143 #ifdef notdef
144 ret[len] = '\0';
145 #endif
146 FUNLOCKFILE(fp);
147 return (ret);
148
149 error:
150 *lenp = 0; /* ??? */
151 FUNLOCKFILE(fp);
152 return (NULL); /* ??? */
153 }
154