x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_BUS_MESSAGE_APPEND_ARRAsd_bus_message_append_SD_BUS_MESSAGE_APPEND_ARRAY(3)
NAME
sd_bus_message_append_array, sd_bus_message_append_array_memfd,
sd_bus_message_append_array_iovec, sd_bus_message_append_array_space -
Append an array of fields to a D-Bus message
SYNOPSIS
#include <systemd/sd-bus.h>
int sd_bus_message_append_array(sd_bus_message *m, char type,
const void *ptr, size_t size);
int sd_bus_message_append_array_memfd(sd_bus_message *m, char type,
int memfd, uint64_t offset,
uint64_t size);
int sd_bus_message_append_array_iovec(sd_bus_message *m, char type,
const struct iovec *iov,
unsigned n);
int sd_bus_message_append_array_space(sd_bus_message *m, char type,
size_t size, void **ptr);
DESCRIPTION
The sd_bus_message_append_array() function appends an array to a D-Bus
message m. A container will be opened, the array contents appended, and
the container closed. The parameter type determines how the pointer p
is interpreted. type must be one of the "trivial" types "y", "n", "q",
"i", "u", "x", "t", "d" (but not "b"), as defined by the Basic Types[1]
section of the D-Bus specification, and listed in
sd_bus_message_append_basic(3). Pointer p must point to an array of
size size bytes containing items of the respective type. Size size must
be a multiple of the size of the type type. As a special case, p may be
NULL, if size is 0. The memory pointed to by p is copied into the
memory area containing the message and stays in possession of the
caller. The caller may hence freely change the data after this call
without affecting the message the array was appended to.
The sd_bus_message_append_array_memfd() function appends an array of a
trivial type to message m, similar to sd_bus_message_append_array().
The contents of the memory file descriptor memfd starting at the
specified offset and of the specified size is used as the contents of
the array. The offset and size must be a multiple of the size of the
type type. However, as a special exception, if the offset is specified
as zero and the size specified as UINT64_MAX the full memory file
descriptor contents is used. The memory file descriptor is sealed by
this call if it has not been sealed yet, and cannot be modified after
this call. See memfd_create(2) for details about memory file
descriptors. Appending arrays with memory file descriptors enables
efficient zero-copy data transfer, as the memory file descriptor may be
passed as-is to the destination, without copying the memory in it to
the destination process. Not all protocol transports support passing
memory file descriptors between participants, in which case this call
will automatically fall back to copying. Also, as memory file
descriptor passing is inefficient for smaller amounts of data, copying
might still be enforced even where memory file descriptor passing is
supported.
The sd_bus_message_append_array_iovec() function appends an array of a
trivial type to the message m, similar to
sd_bus_message_append_array(). Contents of the I/O vector array iov are
used as the contents of the array. The total size of iov payload (the
sum of iov_len fields) must be a multiple of the size of the type type.
The iov argument must point to n I/O vector structures. Each structure
may have the iov_base field set, in which case the memory pointed to
will be copied into the message, or unset (set to zero), in which case
a block of zeros of length iov_len bytes will be inserted. The memory
pointed at by iov may be changed after this call.
The sd_bus_message_append_array_space() function appends space for an
array of a trivial type to message m. It behaves the same as
sd_bus_message_append_array(), but instead of copying items to the
message, it returns a pointer to the destination area to the caller in
pointer p. The caller should subsequently write the array contents to
this memory. Modifications to the memory pointed to should only occur
until the next operation on the bus message is invoked. Most
importantly, the memory should not be altered anymore when another
field has been added to the message or the message has been sealed.
RETURN VALUE
On success, these calls return 0 or a positive integer. On failure,
they return a negative errno-style error code.
Errors
Returned errors may indicate the following problems:
-EINVAL
Specified parameter is invalid.
-EPERM
Message has been sealed.
-ESTALE
Message is in invalid state.
-ENXIO
Message cannot be appended to.
-ENOMEM
Memory allocation failed.
NOTES
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.
SEE ALSO
systemd(1), sd-bus(3), sd_bus_message_append(3),
sd_bus_message_append_basic(3), memfd_create(2), The D-Bus
specification[2]
NOTES
1. Basic Types
https://dbus.freedesktop.org/doc/dbus-specification.html#basic-types
2. The D-Bus specification
https://dbus.freedesktop.org/doc/dbus-specification.html
systemd 254 SD_BUS_MESSAGE_APPEND_ARRAY(3)
Want to link to this manual page? Use this URL:
<http://star2.abcm.com/cgi-bin/bsdi-man?query=sd_bus_message_append_array&sektion=3&manpath=>