Provided by: libsystemd-dev_245.4-4ubuntu3_amd64 bug

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
       ┌──────────┬─────────────────────────┬───────────────────┬─────────────────────┐
       │SpecifierConstantDescriptionExpected C Type     │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"y"       │ SD_BUS_TYPE_BYTE        │ 8bit unsigned     │ uint8_t *           │
       │          │                         │ integer           │                     │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"b"       │ SD_BUS_TYPE_BOOLEAN     │ boolean           │ int * (NB: not bool │
       │          │                         │                   │ *)                  │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"n"       │ SD_BUS_TYPE_INT16       │ 16bit signed      │ int16_t *           │
       │          │                         │ integer           │                     │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"q"       │ SD_BUS_TYPE_UINT16      │ 16bit unsigned    │ uint16_t *          │
       │          │                         │ integer           │                     │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"i"       │ SD_BUS_TYPE_INT32       │ 32bit signed      │ int32_t *           │
       │          │                         │ integer           │                     │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"u"       │ SD_BUS_TYPE_UINT32      │ 32bit unsigned    │ uint32_t *          │
       │          │                         │ integer           │                     │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"x"       │ SD_BUS_TYPE_INT64       │ 64bit signed      │ int64_t *           │
       │          │                         │ integer           │                     │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"t"       │ SD_BUS_TYPE_UINT64      │ 64bit unsigned    │ uint64_t *          │
       │          │                         │ integer           │                     │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"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   │ const char **       │
       │          │                         │ string            │                     │
       ├──────────┼─────────────────────────┼───────────────────┼─────────────────────┤
       │"h"       │ SD_BUS_TYPE_UNIX_FD     │ UNIX file         │ int *               │
       │          │                         │ descriptor        │                     │
       └──────────┴─────────────────────────┴───────────────────┴─────────────────────┘

       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