NAME

       sd_bus_message_read_basic - Read a basic type from a message

SYNOPSIS

       #include <systemd/sd-bus.h>

       int sd_bus_message_read_basic(sd_bus_message *m, char type, void *p);

DESCRIPTION

       sd_bus_message_read_basic() reads a basic type from a message and advances the read position in the
       message. The set of basic types and their ascii codes passed in type are described in the D-Bus
       Specification[1].

       If p is not NULL, it should contain a pointer to an appropriate object. For example, if type is 'y', the
       object passed in p should have type uint8_t *. If type is 's', the object passed in p should have type
       const char **. Note that, if the basic type is a pointer (e.g., const char * in the case of a string),
       the pointer is only borrowed and the contents must be copied if they are to be used after the end of the
       messages lifetime. Similarly, during the lifetime of such a pointer, the message must not be modified.
       See the table below for a complete list of allowed types.

       Table 1. Item type specifiers
       ┌───────────┬─────────────────────────┬────────────────────────┬────────────────────────┐
       │ Specifier │ Constant                │ Description            │ Expected C Type        │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "y"       │ SD_BUS_TYPE_BYTE        │ 8bit unsigned integer  │ uint8_t *              │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "b"       │ SD_BUS_TYPE_BOOLEAN     │ boolean                │ int * (NB: not bool *) │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "n"       │ SD_BUS_TYPE_INT16       │ 16bit signed integer   │ int16_t *              │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "q"       │ SD_BUS_TYPE_UINT16      │ 16bit unsigned integer │ uint16_t *             │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "i"       │ SD_BUS_TYPE_INT32       │ 32bit signed integer   │ int32_t *              │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "u"       │ SD_BUS_TYPE_UINT32      │ 32bit unsigned integer │ uint32_t *             │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "x"       │ SD_BUS_TYPE_INT64       │ 64bit signed integer   │ int64_t *              │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "t"       │ SD_BUS_TYPE_UINT64      │ 64bit unsigned integer │ uint64_t *             │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "d"       │ SD_BUS_TYPE_DOUBLE      │ IEEE 754 double        │ double *               │
       │           │                         │ precision              │                        │
       │           │                         │ floating-point         │                        │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "s"       │ SD_BUS_TYPE_STRING      │ UTF-8 string           │ const char **          │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "o"       │ SD_BUS_TYPE_OBJECT_PATH │ D-Bus object path      │ const char **          │
       │           │                         │ string                 │                        │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "g"       │ SD_BUS_TYPE_SIGNATURE   │ D-Bus signature string │ const char **          │
       ├───────────┼─────────────────────────┼────────────────────────┼────────────────────────┤
       │ "h"       │ SD_BUS_TYPE_UNIX_FD     │ UNIX file descriptor   │ int *                  │
       └───────────┴─────────────────────────┴────────────────────────┴────────────────────────┘

       If there is no object of the specified type at the current position in the message, an error is returned.

RETURN VALUE

       On success, sd_bus_message_read_basic() 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 type string is invalid or the message parameter is NULL.

       -ENXIO
           The message does not contain the specified type at current position.

       -EBADMSG
           The message cannot be parsed.

SEE ALSO

       systemd(1), sd-bus(3), sd_bus_message_append_basic(3), sd_bus_message_skip(3), sd_bus_message_read(3)

NOTES

        1. D-Bus Specification
           https://dbus.freedesktop.org/doc/dbus-specification.html

systemd 245                                                                         SD_BUS_MESSAGE_READ_BASIC(3)