sd_bus_message_read_array

systemd

Access an array of elements in a message

#include <systemd/sd-bus.h>

int

sd_bus_message_read_array

sd_bus_message *

char

type

const void **

ret_ptr

size_t *

ret_size

Description

sd_bus_message_read_array() provides access to an array of elements in the bus message m. The "read pointer" in the message must be right before an array of type type. A pointer to the array data is returned in the parameter ret_ptr and the size of the array data (in bytes) is returned in the parameter ret_size. If this returns a positive value and the returned ret_size is 0, a valid non-NULL pointer will be returned as ret_ptr, but it may not be dereferenced. The data is aligned as appropriate for the data type. The data is part of the message — it may not be modified and is valid only as long as the message is referenced. If this returns a positive value, the "read pointer" points at the next element after the array.

Note that this function only supports arrays of trivial types, i.e. arrays of booleans, the various integer types, as well as floating point numbers. In particular it may not be used for arrays of strings, structures or similar.

Return Value

On success and when an array was read, sd_bus_message_read_array() returns an integer greater than zero. If invoked while inside a container element (such as an array, e.g. when operating on an array of arrays) and the final element of the outer container has been read already and the read pointer is thus behind the last element of the outer container this call returns 0 (and the returned pointer will be NULL and the size will be 0). On failure, it returns a negative errno-style error code.

Errors

Returned errors may indicate the following problems:

-EINVAL
Specified type is invalid or not a trivial type (see above), or the message parameter or one of the output parameters are NULL.

-EOPNOTSUPP
The byte order in the message is different than native byte order.

-EPERM
The message is not sealed.

-EBADMSG
The message cannot be parsed.

History

sd_bus_message_read_array() was added in version 240.