sd_bus_message_append_basic — Attach a single field to a message
#include <systemd/sd-bus.h>
int sd_bus_message_append_basic( | sd_bus_message *m, |
| char type, | |
const void *p); |
sd_bus_message_append_basic() appends a
single field to the message m. The
parameter type determines how the pointer
p is interpreted.
type must be one of the basic types as
defined by the Basic
Types section of the D-Bus specification, and listed in
the table below.
Table 1. Item type specifiers
| Specifier | Constant | Description | Size | Expected C Type |
|---|---|---|---|---|
"y" | SD_BUS_TYPE_BYTE | unsigned integer | 1 byte | uint8_t |
"b" | SD_BUS_TYPE_BOOLEAN | boolean | 4 bytes | int |
"n" | SD_BUS_TYPE_INT16 | signed integer | 2 bytes | int16_t |
"q" | SD_BUS_TYPE_UINT16 | unsigned integer | 2 bytes | uint16_t |
"i" | SD_BUS_TYPE_INT32 | signed integer | 4 bytes | int32_t |
"u" | SD_BUS_TYPE_UINT32 | unsigned integer | 4 bytes | uint32_t |
"x" | SD_BUS_TYPE_INT64 | signed integer | 8 bytes | int64_t |
"t" | SD_BUS_TYPE_UINT64 | unsigned integer | 8 bytes | uint64_t |
"d" | SD_BUS_TYPE_DOUBLE | floating-point | 8 bytes | double |
"s" | SD_BUS_TYPE_STRING | Unicode string | variable | char[] |
"o" | SD_BUS_TYPE_OBJECT_PATH | object path | variable | char[] |
"g" | SD_BUS_TYPE_SIGNATURE | signature | variable | char[] |
"h" | SD_BUS_TYPE_UNIX_FD | UNIX file descriptor | 4 bytes | int |
The value of the parameter is copied into a memory area held
by the message object, stays in the possession of the caller and
may hence be freely changed after this call without affecting the
bus message it has been added to. If type
is "h" (UNIX file descriptor), the descriptor is
duplicated by this call and the passed descriptor stays in
possession of the caller.
For types "s", "o", and
"g", the parameter p is
interpreted as a pointer to a NUL-terminated
character sequence. As a special case, a NULL
pointer is interpreted as an empty string. The string should be
valid Unicode string encoded as UTF-8. In case of the two latter
types, the additional requirements for a D-Bus object path or
type signature should be satisfied. Those requirements should be
verified by the recipient of the message.
On success, this call returns 0 or a positive integer. On failure, it returns a negative errno-style error code.
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.