sd_bus_message_get_signature, sd_bus_message_is_empty, sd_bus_message_has_signature - Query bus message signature
const char* sd_bus_message_get_signature(sd_bus_message *message, int complete);
int sd_bus_message_is_empty(sd_bus_message *message);
int sd_bus_message_has_signature(sd_bus_message *message, const char *signature);
sd_bus_message_get_signature() returns the signature of message message. If complete is true, the signature of the whole message is returned, and just the signature of the currently open container otherwise.
sd_bus_message_is_empty() returns true if the message is empty, i.e. when its signature is empty.
sd_bus_message_has_signature() returns true if the signature of the message message matches given signature. Parameter signature may be NULL, this is treated the same as an empty string, which is equivalent to calling sd_bus_message_is_empty().
On success, sd_bus_message_get_signature() returns the signature, and NULL on error.
The other functions return 0 or a positive integer on success. On failure, they return a negative errno-style error code.
Returned errors may indicate the following problems:
Functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config(1) file.
The code described here uses getenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not call setenv(3) from a parallel thread. It is recommended to only do calls to setenv() from an early phase of the program when no other threads have been started.