1 /* $NetBSD: timed_read.c,v 1.1.1.1 2009/06/23 10:09:01 tron Exp $ */
2
3 /*++
4 /* NAME
5 /* timed_read 3
6 /* SUMMARY
7 /* read operation with pre-read timeout
8 /* SYNOPSIS
9 /* #include <iostuff.h>
10 /*
11 /* ssize_t timed_read(fd, buf, len, timeout, context)
12 /* int fd;
13 /* void *buf;
14 /* size_t len;
15 /* int timeout;
16 /* void *context;
17 /* DESCRIPTION
18 /* timed_read() performs a read() operation when the specified
19 /* descriptor becomes readable within a user-specified deadline.
20 /*
21 /* Arguments:
22 /* .IP fd
23 /* File descriptor in the range 0..FD_SETSIZE.
24 /* .IP buf
25 /* Read buffer pointer.
26 /* .IP len
27 /* Read buffer size.
28 /* .IP timeout
29 /* The deadline in seconds. If this is <= 0, the deadline feature
30 /* is disabled.
31 /* .IP context
32 /* Application context. This parameter is unused. It exists only
33 /* for the sake of VSTREAM compatibility.
34 /* DIAGNOSTICS
35 /* When the operation does not complete within the deadline, the
36 /* result value is -1, and errno is set to ETIMEDOUT.
37 /* All other returns are identical to those of a read(2) operation.
38 /* LICENSE
39 /* .ad
40 /* .fi
41 /* The Secure Mailer license must be distributed with this software.
42 /* AUTHOR(S)
43 /* Wietse Venema
44 /* IBM T.J. Watson Research
45 /* P.O. Box 704
46 /* Yorktown Heights, NY 10598, USA
47 /*--*/
48
49 /* System library. */
50
51 #include <sys_defs.h>
52 #include <unistd.h>
53 #include <errno.h>
54
55 /* Utility library. */
56
57 #include <msg.h>
58 #include <iostuff.h>
59
60 /* timed_read - read with deadline */
61
timed_read(int fd,void * buf,size_t len,int timeout,void * unused_context)62 ssize_t timed_read(int fd, void *buf, size_t len,
63 int timeout, void *unused_context)
64 {
65 ssize_t ret;
66
67 /*
68 * Wait for a limited amount of time for something to happen. If nothing
69 * happens, report an ETIMEDOUT error.
70 *
71 * XXX Solaris 8 read() fails with EAGAIN after read-select() returns
72 * success.
73 */
74 for (;;) {
75 if (timeout > 0 && read_wait(fd, timeout) < 0)
76 return (-1);
77 if ((ret = read(fd, buf, len)) < 0 && timeout > 0 && errno == EAGAIN) {
78 msg_warn("read() returns EAGAIN on a readable file descriptor!");
79 msg_warn("pausing to avoid going into a tight select/read loop!");
80 sleep(1);
81 continue;
82 } else if (ret < 0 && errno == EINTR) {
83 continue;
84 } else {
85 return (ret);
86 }
87 }
88 }
89