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/*++
/* NAME
/* timed_write 3
/* SUMMARY
/* write operation with pre-write timeout
/* SYNOPSIS
/* #include <iostuff.h>
/*
/* ssize_t timed_write(fd, buf, len, timeout, context)
/* int fd;
/* const void *buf;
/* size_t len;
/* int timeout;
/* void *context;
/* DESCRIPTION
/* timed_write() performs a write() operation when the specified
/* descriptor becomes writable within a user-specified deadline.
/*
/* Arguments:
/* .IP fd
/* File descriptor in the range 0..FD_SETSIZE.
/* .IP buf
/* Write buffer pointer.
/* .IP len
/* Write buffer size.
/* .IP timeout
/* The deadline in seconds. If this is <= 0, the deadline feature
/* is disabled.
/* .IP context
/* Application context. This parameter is unused. It exists only
/* for the sake of VSTREAM compatibility.
/* DIAGNOSTICS
/* When the operation does not complete within the deadline, the
/* result value is -1, and errno is set to ETIMEDOUT.
/* All other returns are identical to those of a write(2) operation.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*--*/
/* System library. */
#include <sys_defs.h>
#include <unistd.h>
#include <errno.h>
/* Utility library. */
#include <msg.h>
#include <iostuff.h>
/* timed_write - write with deadline */
ssize_t timed_write(int fd, const void *buf, size_t len,
int timeout, void *unused_context)
{
ssize_t ret;
/*
* Wait for a limited amount of time for something to happen. If nothing
* happens, report an ETIMEDOUT error.
*
* XXX Solaris 8 read() fails with EAGAIN after read-select() returns
* success. The code below exists just in case their write implementation
* is equally broken.
*
* This condition may also be found on systems where select() returns
* success on pipes with less than PIPE_BUF bytes of space, and with
* badly designed software where multiple writers are fighting for access
* to the same resource.
*/
for (;;) {
if (timeout > 0 && write_wait(fd, timeout) < 0)
return (-1);
if ((ret = write(fd, buf, len)) < 0 && timeout > 0 && errno == EAGAIN) {
msg_warn("write() returns EAGAIN on a writable file descriptor!");
msg_warn("pausing to avoid going into a tight select/write loop!");
sleep(1);
continue;
} else if (ret < 0 && errno == EINTR) {
continue;
} else {
return (ret);
}
}
}
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