1 files changed, 92 insertions, 0 deletions
diff --git a/src/util/timed_write.c b/src/util/timed_write.c
new file mode 100644
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--- /dev/null
+++ b/src/util/timed_write.c
@@ -0,0 +1,92 @@
+/*++
+/* 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);
+	}
+    }
+}