sd_bus_message_at_end - Check if a message has been fully read
sd_bus_message_at_end() returns whether all data from the currently
opened container in m or all data from all containers in m has
been read. If complete is zero, this function returns whether all data
from the currently opened container has been read. If complete is
non-zero, this function returns whether all data from all containers in
m has been read.
If all data from all containers or the current container (depending on the value
of complete) has been read, sd_bus_message_at_end() returns a
positive integer. If there is still data left to be read, it returns zero. On
failure, it returns a negative errno-style error code.
Returned errors may indicate the following problems:
The m parameter is NULL.
The message is not sealed.
These APIs are implemented as a shared library, which can be compiled and linked
to with the libsystemd pkg-config(1) file.