sd_bus_message_open_container
systemd
sd_bus_message_open_container
3
sd_bus_message_open_container
sd_bus_message_close_container
sd_bus_message_enter_container
sd_bus_message_exit_container
Create and move between containers in D-Bus messages
#include <systemd/sd-bus.h>
int sd_bus_message_open_container
sd_bus_message *m
char type
const char *contents
int sd_bus_message_close_container
sd_bus_message *m
int sd_bus_message_enter_container
sd_bus_message *m
char type
const char *contents
int sd_bus_message_exit_container
sd_bus_message *m
Description
sd_bus_message_open_container() appends a new container to the message
m. After opening a new container, it can be filled with content using
sd_bus_message_append3
and similar functions. Containers behave like a stack. To nest containers inside each other, call
sd_bus_message_open_container() multiple times without calling
sd_bus_message_close_container() in between. Each container will be nested inside the
previous container. type represents the container type and should be one of
r, a, v or e as described in
sd_bus_message_append3.
Instead of literals, the corresponding constants SD_BUS_TYPE_STRUCT,
SD_BUS_TYPE_ARRAY, SD_BUS_TYPE_VARIANT or
SD_BUS_TYPE_DICT_ENTRY can also be used. contents describes
the type of the container's elements and should be a D-Bus type string following the rules described in
sd_bus_message_append3.
sd_bus_message_close_container() closes the last container opened with
sd_bus_message_open_container(). On success, the write pointer of the message
m is positioned after the closed container in its parent container or in
m itself if there is no parent container.
sd_bus_message_enter_container() enters the next container of the message
m for reading. It behaves mostly the same as
sd_bus_message_open_container(). Entering a container allows reading its contents
with
sd_bus_message_read3
and similar functions. type and contents are the same as in
sd_bus_message_open_container().
sd_bus_message_exit_container() exits the scope of the last container entered
with sd_bus_message_enter_container(). It behaves mostly the same as
sd_bus_message_close_container(). Note that
sd_bus_message_exit_container() may only be called after iterating through all
members of the container, i.e. reading or skipping them. Use
sd_bus_message_skip3
to skip over fields of a container in order to be able to exit the container with
sd_bus_message_exit_container() without reading all members.
Return Value
On success, these functions return a non-negative integer.
sd_bus_message_open_container() and sd_bus_message_close_container()
return 0.
sd_bus_message_enter_container() returns 1 if it successfully opened a new container, and 0 if
that was not possible because the end of the currently open container or message was reached.
sd_bus_message_exit_container() returns 1 on success.
On failure, all of these functions return a negative errno-style error code.
Errors
Returned errors may indicate the following problems:
-EINVAL
m or contents are
NULL or type is invalid.
-EPERM
The message m is already sealed.
-ESTALE
The message m is in an invalid state.
-ENOMEM
Memory allocation failed.
-EBUSY
sd_bus_message_exit_container() was called but there are
unread members left in the container.
Examples
Append an array of strings to a message
Read an array of strings from a message
See Also
systemd1,
sd-bus3,
sd_bus_message_append3,
sd_bus_message_read3,
sd_bus_message_skip3,
The D-Bus specification