1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * %sccs.include.redist.c%
9 */
10
11 #if defined(LIBC_SCCS) && !defined(lint)
12 static char sccsid[] = "@(#)fgetln.c 8.2 (Berkeley) 01/02/94";
13 #endif /* LIBC_SCCS and not lint */
14
15 #include <stdio.h>
16 #include <stdlib.h>
17 #include <string.h>
18 #include "local.h"
19
20 /*
21 * Expand the line buffer. Return -1 on error.
22 #ifdef notdef
23 * The `new size' does not account for a terminating '\0',
24 * so we add 1 here.
25 #endif
26 */
__slbexpand(fp,newsize)27 __slbexpand(fp, newsize)
28 FILE *fp;
29 size_t newsize;
30 {
31 void *p;
32
33 #ifdef notdef
34 ++newsize;
35 #endif
36 if (fp->_lb._size >= newsize)
37 return (0);
38 if ((p = realloc(fp->_lb._base, newsize)) == NULL)
39 return (-1);
40 fp->_lb._base = p;
41 fp->_lb._size = newsize;
42 return (0);
43 }
44
45 /*
46 * Get an input line. The returned pointer often (but not always)
47 * points into a stdio buffer. Fgetln does not alter the text of
48 * the returned line (which is thus not a C string because it will
49 * not necessarily end with '\0'), but does allow callers to modify
50 * it if they wish. Thus, we set __SMOD in case the caller does.
51 */
52 char *
fgetln(fp,lenp)53 fgetln(fp, lenp)
54 register FILE *fp;
55 size_t *lenp;
56 {
57 register unsigned char *p;
58 register size_t len;
59 size_t off;
60
61 /* make sure there is input */
62 if (fp->_r <= 0 && __srefill(fp)) {
63 *lenp = 0;
64 return (NULL);
65 }
66
67 /* look for a newline in the input */
68 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
69 register char *ret;
70
71 /*
72 * Found one. Flag buffer as modified to keep fseek from
73 * `optimising' a backward seek, in case the user stomps on
74 * the text.
75 */
76 p++; /* advance over it */
77 ret = (char *)fp->_p;
78 *lenp = len = p - fp->_p;
79 fp->_flags |= __SMOD;
80 fp->_r -= len;
81 fp->_p = p;
82 return (ret);
83 }
84
85 /*
86 * We have to copy the current buffered data to the line buffer.
87 * As a bonus, though, we can leave off the __SMOD.
88 *
89 * OPTIMISTIC is length that we (optimistically) expect will
90 * accomodate the `rest' of the string, on each trip through the
91 * loop below.
92 */
93 #define OPTIMISTIC 80
94
95 for (len = fp->_r, off = 0;; len += fp->_r) {
96 register size_t diff;
97
98 /*
99 * Make sure there is room for more bytes. Copy data from
100 * file buffer to line buffer, refill file and look for
101 * newline. The loop stops only when we find a newline.
102 */
103 if (__slbexpand(fp, len + OPTIMISTIC))
104 goto error;
105 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
106 len - off);
107 off = len;
108 if (__srefill(fp))
109 break; /* EOF or error: return partial line */
110 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
111 continue;
112
113 /* got it: finish up the line (like code above) */
114 p++;
115 diff = p - fp->_p;
116 len += diff;
117 if (__slbexpand(fp, len))
118 goto error;
119 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
120 diff);
121 fp->_r -= diff;
122 fp->_p = p;
123 break;
124 }
125 *lenp = len;
126 #ifdef notdef
127 fp->_lb._base[len] = 0;
128 #endif
129 return ((char *)fp->_lb._base);
130
131 error:
132 *lenp = 0; /* ??? */
133 return (NULL); /* ??? */
134 }
135