прикрепите к сообщению одно поле (Attach a single field to a message)
Имя (Name)
sd_bus_message_append_basic - Attach a single field to a message
Синопсис (Synopsis)
#include <systemd/sd-bus.h>
int sd_bus_message_append_basic(sd_bus_message *m, char type,
const void *p);
Описание (Description)
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
Table 1. Item type specifiers
┌──────────┬─────────────────────────┬────────────────┬──────────┬────────────┐
│Specifier │ Constant │ Description │ Size │ Expected C │
│ │ │ │ │ Type │
├──────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│"y" │ SD_BUS_TYPE_BYTE │ unsigned │ 1 byte │ uint8_t │
│ │ │ integer │ │ │
├──────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│"b" │ SD_BUS_TYPE_BOOLEAN │ boolean │ 4 bytes │ int │
├──────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│"n" │ SD_BUS_TYPE_INT16 │ signed │ 2 bytes │ int16_t │
│ │ │ integer │ │ │
├──────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│"q" │ SD_BUS_TYPE_UINT16 │ unsigned │ 2 bytes │ uint16_t │
│ │ │ integer │ │ │
├──────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│"i" │ SD_BUS_TYPE_INT32 │ signed │ 4 bytes │ int32_t │
│ │ │ integer │ │ │
├──────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│"u" │ SD_BUS_TYPE_UINT32 │ unsigned │ 4 bytes │ uint32_t │
│ │ │ integer │ │ │
├──────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│"x" │ SD_BUS_TYPE_INT64 │ signed │ 8 bytes │ int64_t │
│ │ │ integer │ │ │
├──────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│"t" │ SD_BUS_TYPE_UINT64 │ unsigned │ 8 bytes │ uint64_t │
│ │ │ integer │ │ │
├──────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│"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 │ 4 bytes │ int │
│ │ │ descriptor │ │ │
└──────────┴─────────────────────────┴────────────────┴──────────┴────────────┘
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.
