sd_bus_message_append_basic - Attach a single field to a message

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 BasicTypes[1] section of the D-Bus specification, and listed in the table below. Table1.Itemtypespecifiers ┌───────────┬─────────────────────────┬──────────────────┬──────────┬─────────────────┐ │ Specifier │ Constant │ Description │ Size │ ExpectedCType │ ├───────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤ │ "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 │ 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.

sd_bus_message_append_basic - Attach a single field to a message

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 257.7 SD_BUS_MESSAGE_APPEND_BASIC(3)

On success, this call returns 0 or a positive integer. On failure, it returns 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.

systemd(1), sd-bus(3), sd_bus_message_read_basic(3), sd_bus_message_append(3), TheD-Busspecification[2]