получить временные метки отправителя и порядковый номер сообщения (Retrieve the sender timestamps and sequence number of a message)
Имя (Name)
sd_bus_message_get_monotonic_usec,
sd_bus_message_get_realtime_usec, sd_bus_message_get_seqnum -
Retrieve the sender timestamps and sequence number of a message
Синопсис (Synopsis)
#include <systemd/sd-bus.h>
int sd_bus_message_get_monotonic_usec(sd_bus_message *message,
uint64_t *usec);
int sd_bus_message_get_realtime_usec(sd_bus_message *message,
uint64_t *usec);
int sd_bus_message_get_seqnum(sd_bus_message *message,
uint64_t *seqnum);
Описание (Description)
sd_bus_message_get_monotonic_usec() returns the monotonic
timestamp of the time the message was sent. This value is in
microseconds since the CLOCK_MONOTONIC epoch, see
clock_gettime(2) for details.
Similarly, sd_bus_message_get_realtime_usec() returns the
realtime (wallclock) timestamp of the time the message was sent.
This value is in microseconds since Jan 1st, 1970, i.e. in the
CLOCK_REALTIME clock.
sd_bus_message_get_seqnum() returns the kernel-assigned sequence
number of the message. The kernel assigns a global, monotonically
increasing sequence number to all messages transmitted on the
local system, at the time the message was sent. This sequence
number is useful for determining message send order, even across
different buses of the local system. The sequence number combined
with the boot ID of the system (as returned by
sd_id128_get_boot(3)) is a suitable globally unique identifier
for bus messages.
Note that the sending order and receiving order of messages might
differ, in particular for broadcast messages. This means that the
sequence number and the timestamps of messages a client reads are
not necessarily monotonically increasing.
These timestamps and the sequence number are attached to each
message by the kernel and cannot be manipulated by the sender.
Note that these timestamps are only available on some bus
transports, and only after support for them has been negotiated
with the sd_bus_negotiate_timestamp(3) call.
Возвращаемое значение (Return value)
On success, these calls return 0 or a positive integer. On
failure, these calls return a negative errno-style error code.
On success, the timestamp or sequence number is returned in the
specified 64-bit unsigned integer variable.
Errors
Returned errors may indicate the following problems:
-EINVAL
A specified parameter is invalid.
-ENODATA
No timestamp or sequence number information is attached to
the passed message. This error is returned if the underlying
transport does not support timestamping or assigning of
sequence numbers, or if this feature has not been negotiated
with sd_bus_negotiate_timestamp(3).
Примечание (Note)
These APIs are implemented as a shared library, which can be
compiled and linked to with the libsystemd pkg-config(1) file.
Смотри также (See also)
systemd(1), sd-bus(3), sd_bus_new(3),
sd_bus_negotiate_timestamp(3), clock_gettime(2),
sd_id128_get_boot(3)
