1/* Read a line from an nss_files database file.
2 Copyright (C) 2020-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <nss_files.h>
20
21#include <ctype.h>
22#include <errno.h>
23#include <string.h>
24
25int
26__nss_readline (FILE *fp, char *buf, size_t len, off64_t *poffset)
27{
28 /* We need space for at least one character, the line terminator,
29 and the NUL byte. */
30 if (len < 3)
31 {
32 *poffset = -1;
33 __set_errno (ERANGE);
34 return ERANGE;
35 }
36
37 while (true)
38 {
39 /* Keep original offset for retries. */
40 *poffset = __ftello64 (fp);
41
42 buf[len - 1] = '\xff'; /* Marker to recognize truncation. */
43 if (__fgets_unlocked (buf, len, fp) == NULL)
44 {
45 if (__feof_unlocked (fp))
46 {
47 __set_errno (ENOENT);
48 return ENOENT;
49 }
50 else
51 {
52 /* Any other error. Do not return ERANGE in this case
53 because the caller would retry. */
54 if (errno == ERANGE)
55 __set_errno (EINVAL);
56 return errno;
57 }
58 }
59 else if (buf[len - 1] != '\xff')
60 /* The buffer is too small. Arrange for re-reading the same
61 line on the next call. */
62 return __nss_readline_seek (fp, *poffset);
63
64 /* __fgets_unlocked succeeded. */
65
66 /* Remove leading whitespace. */
67 char *p = buf;
68 while (isspace (*p))
69 ++p;
70 if (*p == '\0' || *p == '#')
71 /* Skip empty lines and comments. */
72 continue;
73 if (p != buf)
74 memmove (buf, p, strlen (p));
75
76 /* Return line to the caller. */
77 return 0;
78 }
79}
80libc_hidden_def (__nss_readline)
81
82int
83__nss_readline_seek (FILE *fp, off64_t offset)
84{
85 if (offset < 0 /* __ftello64 failed. */
86 || __fseeko64 (fp, offset, SEEK_SET) < 0)
87 {
88 /* Without seeking support, it is not possible to
89 re-read the same line, so this is a hard failure. */
90 fseterr_unlocked (fp);
91 __set_errno (ESPIPE);
92 return ESPIPE;
93 }
94 else
95 {
96 __set_errno (ERANGE);
97 return ERANGE;
98 }
99}
100