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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 01:46:30 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 01:46:30 +0000
commitb5896ba9f6047e7031e2bdee0622d543e11a6734 (patch)
treefd7b460593a2fee1be579bec5697e6d887ea3421 /src/util/timed_write.c
parentInitial commit. (diff)
downloadpostfix-b5896ba9f6047e7031e2bdee0622d543e11a6734.tar.xz
postfix-b5896ba9f6047e7031e2bdee0622d543e11a6734.zip
Adding upstream version 3.4.23.upstream/3.4.23upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/util/timed_write.c')
-rw-r--r--src/util/timed_write.c92
1 files changed, 92 insertions, 0 deletions
diff --git a/src/util/timed_write.c b/src/util/timed_write.c
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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);
+ }
+ }
+}