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e61abf83 UD |
1 | /* readv supports all Linux kernels >= 2.0. |
2 | Copyright (C) 1997 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 Library General Public License as | |
7 | published by the Free Software Foundation; either version 2 of the | |
8 | 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 | Library General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Library General Public | |
16 | License along with the GNU C Library; see the file COPYING.LIB. If not, | |
17 | read to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
18 | Boston, MA 02111-1307, USA. */ | |
19 | ||
20 | #include <errno.h> | |
21 | #include <stddef.h> | |
22 | #include <sys/param.h> | |
23 | #include <sys/uio.h> | |
24 | ||
25 | extern ssize_t __syscall_readv __P ((int, __const struct iovec *, int)); | |
26 | ||
27 | ||
28 | /* Not all versions of the kernel support the large number of records. */ | |
c57abfa7 UD |
29 | #ifndef UIO_FASTIOV |
30 | # define UIO_FASTIOV 8 /* 8 is a safe number. */ | |
e61abf83 UD |
31 | #endif |
32 | ||
33 | ||
c57abfa7 | 34 | /* We should deal with kernel which have a smaller UIO_FASTIOV as well |
e61abf83 UD |
35 | as a very big count. */ |
36 | ssize_t | |
37 | readv (fd, vector, count) | |
38 | int fd; | |
39 | const struct iovec *vector; | |
40 | int count; | |
41 | { | |
42 | int errno_saved = errno; | |
43 | ssize_t bytes_read; | |
44 | ||
45 | bytes_read = __syscall_readv (fd, vector, count); | |
46 | ||
c57abfa7 | 47 | if (bytes_read < 0 && errno == EINVAL && count > UIO_FASTIOV) |
e61abf83 UD |
48 | { |
49 | int i; | |
50 | ||
51 | /* Restore the old error value as if nothing happened. */ | |
52 | __set_errno (errno_saved); | |
53 | ||
54 | bytes_read = 0; | |
c57abfa7 | 55 | for (i = 0; i < count; i += UIO_FASTIOV) |
e61abf83 UD |
56 | { |
57 | ssize_t bytes = __syscall_readv (fd, vector + i, | |
c57abfa7 | 58 | MIN (count - i, UIO_FASTIOV)); |
e61abf83 UD |
59 | |
60 | if (bytes < 0) | |
61 | return bytes; | |
62 | ||
63 | bytes_read += bytes; | |
64 | } | |
65 | } | |
66 | ||
67 | return bytes_read; | |
68 | } |