Package ch.bailu.gtk.glib

Klasse VariantType

java.lang.Object
ch.bailu.gtk.type.Type
ch.bailu.gtk.type.Pointer
ch.bailu.gtk.type.Record
ch.bailu.gtk.glib.VariantType
Alle implementierten Schnittstellen:
PointerInterface
public class VariantType extends Record
A type in the [type@GLib.Variant] type system.

This section introduces the [type@GLib.Variant] type system. It is based, in
large part, on the D-Bus type system, with two major changes and
some minor lifting of restrictions. The
[D-Bus specification](http://dbus.freedesktop.org/doc/dbus-specification.html),
therefore, provides a significant amount of
information that is useful when working with [type@GLib.Variant].

The first major change with respect to the D-Bus type system is the
introduction of maybe (or ‘nullable’) types. Any type in [type@GLib.Variant]
can be converted to a maybe type, in which case, `nothing` (or `null`)
becomes a valid value. Maybe types have been added by introducing the
character `m` to type strings.

The second major change is that the [type@GLib.Variant] type system supports
the concept of ‘indefinite types’ — types that are less specific than
the normal types found in D-Bus. For example, it is possible to speak
of ‘an array of any type’ in [type@GLib.Variant], where the D-Bus type system
would require you to speak of ‘an array of integers’ or ‘an array of
strings’. Indefinite types have been added by introducing the
characters `*`, `?` and `r` to type strings.

Finally, all arbitrary restrictions relating to the complexity of
types are lifted along with the restriction that dictionary entries
may only appear nested inside of arrays.

Just as in D-Bus, [type@GLib.Variant] types are described with strings (‘type
strings’). Subject to the differences mentioned above, these strings
are of the same form as those found in D-Bus. Note, however: D-Bus
always works in terms of messages and therefore individual type
strings appear nowhere in its interface. Instead, ‘signatures’
are a concatenation of the strings of the type of each argument in a
message. [type@GLib.Variant] deals with single values directly so
[type@GLib.Variant] type strings always describe the type of exactly one
value. This means that a D-Bus signature string is generally not a valid
[type@GLib.Variant] type string — except in the case that it is the signature
of a message containing exactly one argument.

An indefinite type is similar in spirit to what may be called an
abstract type in other type systems. No value can exist that has an
indefinite type as its type, but values can exist that have types
that are subtypes of indefinite types. That is to say,
[method@GLib.Variant.get_type] will never return an indefinite type, but
calling [method@GLib.Variant.is_of_type] with an indefinite type may return
true. For example, you cannot have a value that represents ‘an
array of no particular type’, but you can have an ‘array of integers’
which certainly matches the type of ‘an array of no particular type’,
since ‘array of integers’ is a subtype of ‘array of no particular
type’.

This is similar to how instances of abstract classes may not
directly exist in other type systems, but instances of their
non-abstract subtypes may. For example, in GTK, no object that has
the type of [`GtkWidget`](https://docs.gtk.org/gtk4/class.Widget.html) can
exist (since `GtkWidget` is an abstract class), but a [`GtkWindow`](https://docs.gtk.org/gtk4/class.Window.html)
can certainly be instantiated, and you would say that a `GtkWindow` is a
`GtkWidget` (since `GtkWindow` is a subclass of `GtkWidget`).

Two types may not be compared by value; use [method@GLib.VariantType.equal]
or [method@GLib.VariantType.is_subtype_of] May be copied using
[method@GLib.VariantType.copy] and freed using [method@GLib.VariantType.free].

## GVariant Type Strings

A [type@GLib.Variant] type string can be any of the following:

- any basic type string (listed below)
- `v`, `r` or `*`
- one of the characters `a` or `m`, followed by another type string
- the character `(`, followed by a concatenation of zero or more other
type strings, followed by the character `)`
- the character `{`, followed by a basic type string (see below),
followed by another type string, followed by the character `}`

A basic type string describes a basic type (as per
[method@GLib.VariantType.is_basic]) and is always a single character in
length. The valid basic type strings are `b`, `y`, `n`, `q`, `i`, `u`, `x`,
`t`, `h`, `d`, `s`, `o`, `g` and `?`.

The above definition is recursive to arbitrary depth. `aaaaai` and
`(ui(nq((y)))s)` are both valid type strings, as is
`a(aa(ui)(qna{ya(yd)}))`. In order to not hit memory limits,
[type@GLib.Variant] imposes a limit on recursion depth of 65 nested
containers. This is the limit in the D-Bus specification (64) plus one to
allow a [`GDBusMessage`](../gio/class.DBusMessage.html) to be nested in
a top-level tuple.

The meaning of each of the characters is as follows:

- `b`: the type string of `G_VARIANT_TYPE_BOOLEAN`; a boolean value.
- `y`: the type string of `G_VARIANT_TYPE_BYTE`; a byte.
- `n`: the type string of `G_VARIANT_TYPE_INT16`; a signed 16 bit integer.
- `q`: the type string of `G_VARIANT_TYPE_UINT16`; an unsigned 16 bit integer.
- `i`: the type string of `G_VARIANT_TYPE_INT32`; a signed 32 bit integer.
- `u`: the type string of `G_VARIANT_TYPE_UINT32`; an unsigned 32 bit integer.
- `x`: the type string of `G_VARIANT_TYPE_INT64`; a signed 64 bit integer.
- `t`: the type string of `G_VARIANT_TYPE_UINT64`; an unsigned 64 bit integer.
- `h`: the type string of `G_VARIANT_TYPE_HANDLE`; a signed 32 bit value
that, by convention, is used as an index into an array of file
descriptors that are sent alongside a D-Bus message.
- `d`: the type string of `G_VARIANT_TYPE_DOUBLE`; a double precision
floating point value.
- `s`: the type string of `G_VARIANT_TYPE_STRING`; a string.
- `o`: the type string of `G_VARIANT_TYPE_OBJECT_PATH`; a string in the form
of a D-Bus object path.
- `g`: the type string of `G_VARIANT_TYPE_SIGNATURE`; a string in the form of
a D-Bus type signature.
- `?`: the type string of `G_VARIANT_TYPE_BASIC`; an indefinite type that
is a supertype of any of the basic types.
- `v`: the type string of `G_VARIANT_TYPE_VARIANT`; a container type that
contain any other type of value.
- `a`: used as a prefix on another type string to mean an array of that
type; the type string `ai`, for example, is the type of an array of
signed 32-bit integers.
- `m`: used as a prefix on another type string to mean a ‘maybe’, or
‘nullable’, version of that type; the type string `ms`, for example,
is the type of a value that maybe contains a string, or maybe contains
nothing.
- `()`: used to enclose zero or more other concatenated type strings to
create a tuple type; the type string `(is)`, for example, is the type of
a pair of an integer and a string.
- `r`: the type string of `G_VARIANT_TYPE_TUPLE`; an indefinite type that is
a supertype of any tuple type, regardless of the number of items.
- `{}`: used to enclose a basic type string concatenated with another type
string to create a dictionary entry type, which usually appears inside of
an array to form a dictionary; the type string `a{sd}`, for example, is
the type of a dictionary that maps strings to double precision floating
point values.

The first type (the basic type) is the key type and the second type is
the value type. The reason that the first type is restricted to being a
basic type is so that it can easily be hashed.
- `*`: the type string of `G_VARIANT_TYPE_ANY`; the indefinite type that is
a supertype of all types. Note that, as with all type strings, this
character represents exactly one type. It cannot be used inside of tuples
to mean ‘any number of items’.

Any type string of a container that contains an indefinite type is,
itself, an indefinite type. For example, the type string `a*`
(corresponding to `G_VARIANT_TYPE_ARRAY`) is an indefinite type
that is a supertype of every array type. `(*s)` is a supertype
of all tuples that contain exactly two items where the second
item is a string.

`a{?*}` is an indefinite type that is a supertype of all arrays
containing dictionary entries where the key is any basic type and
the value is any type at all. This is, by definition, a dictionary,
so this type string corresponds to `G_VARIANT_TYPE_DICTIONARY`. Note
that, due to the restriction that the key of a dictionary entry must
be a basic type, `{**}` is not a valid type string.

https://docs.gtk.org/glib/struct.VariantType.html

  • Konstruktordetails

    • VariantType

      public VariantType(PointerContainer pointer)

    • VariantType

      public VariantType(@Nonnull Str type_string)
      Creates a new [type@GLib.VariantType] corresponding to the type string given
      by @type_string.

      It is appropriate to call [method@GLib.VariantType.free] on the return value.

      It is a programmer error to call this function with an invalid type
      string. Use [func@GLib.VariantType.string_is_valid] if you are unsure.
      Parameter:
      type_string - a valid [GVariant type string](./struct.VariantType.html#gvariant-type-strings)

    • VariantType

      public VariantType(String type_string)
      Creates a new [type@GLib.VariantType] corresponding to the type string given
      by @type_string.

      It is appropriate to call [method@GLib.VariantType.free] on the return value.

      It is a programmer error to call this function with an invalid type
      string. Use [func@GLib.VariantType.string_is_valid] if you are unsure.
      Parameter:
      type_string - a valid [GVariant type string](./struct.VariantType.html#gvariant-type-strings)

  • Methodendetails

    • getClassHandler

      public static ClassHandler getClassHandler()

    • newArrayVariantType

      public static VariantType newArrayVariantType(@Nonnull VariantType element)
      Constructs the type corresponding to an array of elements of the
      type @type.

      It is appropriate to call [method@GLib.VariantType.first] on the return value.
      Parameter:
      element - an element type
      Gibt zurück:
      a new array type Since 2.24

    • newDictEntryVariantType

      public static VariantType newDictEntryVariantType(@Nonnull VariantType key, @Nonnull VariantType value)
      Constructs the type corresponding to a dictionary entry with a key
      of type @key and a value of type @value.

      It is appropriate to call [method@GLib.VariantType.free] on the return value.
      Parameter:
      key - a basic type to use for the key
      value - a type to use for the value
      Gibt zurück:
      a new dictionary entry type Since 2.24

    • newMaybeVariantType

      public static VariantType newMaybeVariantType(@Nonnull VariantType element)
      Constructs the type corresponding to a ‘maybe’ instance containing
      type @type or `Nothing`.

      It is appropriate to call [method@GLib.VariantType.free] on the return value.
      Parameter:
      element - an element type
      Gibt zurück:
      a new ‘maybe’ type Since 2.24

    • copy

      public VariantType copy()
      Makes a copy of a [type@GLib.VariantType].

      It is appropriate to call [method@GLib.VariantType.free] on the return value.
      @type may not be `NULL`.
      Gibt zurück:
      a new [type@GLib.VariantType] Since 2.24

    • dupString

      public Str dupString()
      Returns a newly-allocated copy of the type string corresponding to @type.

      The returned string is nul-terminated. It is appropriate to call
      [func@GLib.free] on the return value.
      Gibt zurück:
      the corresponding type string Since 2.24

    • element

      public VariantType element()
      Determines the element type of an array or ‘maybe’ type.

      This function may only be used with array or ‘maybe’ types.
      Gibt zurück:
      the element type of @type Since 2.24

    • equal

      public boolean equal(@Nonnull Pointer type2)
      Compares @type1 and @type2 for equality.

      Only returns true if the types are exactly equal. Even if one type
      is an indefinite type and the other is a subtype of it, false will
      be returned if they are not exactly equal. If you want to check for
      subtypes, use [method@GLib.VariantType.is_subtype_of].

      The argument types of @type1 and @type2 are only `gconstpointer` to
      allow use with [type@GLib.HashTable] without function pointer casting. For
      both arguments, a valid [type@GLib.VariantType] must be provided.
      Parameter:
      type2 - another type to compare
      Gibt zurück:
      true if @type1 and @type2 are exactly equal Since 2.24

    • first

      public VariantType first()
      Determines the first item type of a tuple or dictionary entry
      type.

      This function may only be used with tuple or dictionary entry types,
      but must not be used with the generic tuple type
      `G_VARIANT_TYPE_TUPLE`.

      In the case of a dictionary entry type, this returns the type of
      the key.

      `NULL` is returned in case of @type being `G_VARIANT_TYPE_UNIT`.

      This call, together with [method@GLib.VariantType.next] provides an iterator
      interface over tuple and dictionary entry types.
      Gibt zurück:
      the first item type of @type, or `NULL` if the type has no item types Since 2.24

    • free

      public void free()
      Frees a [type@GLib.VariantType] that was allocated with
      [method@GLib.VariantType.copy], [ctor@GLib.VariantType.new] or one of the
      container type constructor functions.

      In the case that @type is `NULL`, this function does nothing.

      Since 2.24

    • getStringLength

      public long getStringLength()
      Returns the length of the type string corresponding to the given @type.

      This function must be used to determine the valid extent of
      the memory region returned by [method@GLib.VariantType.peek_string].
      Gibt zurück:
      the length of the corresponding type string Since 2.24

    • hash

      public int hash()
      Hashes @type.

      The argument type of @type is only `gconstpointer` to allow use with
      [type@GLib.HashTable] without function pointer casting. A valid
      [type@GLib.VariantType] must be provided.
      Gibt zurück:
      the hash value Since 2.24

    • isArray

      public boolean isArray()
      Determines if the given @type is an array type.

      This is true if the type string for @type starts with an `a`.

      This function returns true for any indefinite type for which every
      definite subtype is an array type — `G_VARIANT_TYPE_ARRAY`, for
      example.
      Gibt zurück:
      true if @type is an array type Since 2.24

    • isBasic

      public boolean isBasic()
      Determines if the given @type is a basic type.

      Basic types are booleans, bytes, integers, doubles, strings, object
      paths and signatures.

      Only a basic type may be used as the key of a dictionary entry.

      This function returns `FALSE` for all indefinite types except
      `G_VARIANT_TYPE_BASIC`.
      Gibt zurück:
      true if @type is a basic type Since 2.24

    • isContainer

      public boolean isContainer()
      Determines if the given @type is a container type.

      Container types are any array, maybe, tuple, or dictionary
      entry types plus the variant type.

      This function returns true for any indefinite type for which every
      definite subtype is a container — `G_VARIANT_TYPE_ARRAY`, for
      example.
      Gibt zurück:
      true if @type is a container type Since 2.24

    • isDefinite

      public boolean isDefinite()
      Determines if the given @type is definite (ie: not indefinite).

      A type is definite if its type string does not contain any indefinite
      type characters (`*`, `?`, or `r`).

      A [type@GLib.Variant] instance may not have an indefinite type, so calling
      this function on the result of [method@GLib.Variant.get_type] will always
      result in true being returned. Calling this function on an
      indefinite type like `G_VARIANT_TYPE_ARRAY`, however, will result in
      `FALSE` being returned.
      Gibt zurück:
      true if @type is definite Since 2.24

    • isDictEntry

      public boolean isDictEntry()
      Determines if the given @type is a dictionary entry type.

      This is true if the type string for @type starts with a `{`.

      This function returns true for any indefinite type for which every
      definite subtype is a dictionary entry type —
      `G_VARIANT_TYPE_DICT_ENTRY`, for example.
      Gibt zurück:
      true if @type is a dictionary entry type Since 2.24

    • isMaybe

      public boolean isMaybe()
      Determines if the given @type is a ‘maybe’ type.

      This is true if the type string for @type starts with an `m`.

      This function returns true for any indefinite type for which every
      definite subtype is a ‘maybe’ type — `G_VARIANT_TYPE_MAYBE`, for
      example.
      Gibt zurück:
      true if @type is a ‘maybe’ type Since 2.24

    • isSubtypeOf

      public boolean isSubtypeOf(@Nonnull VariantType supertype)
      Checks if @type is a subtype of @supertype.

      This function returns true if @type is a subtype of @supertype. All
      types are considered to be subtypes of themselves. Aside from that,
      only indefinite types can have subtypes.
      Parameter:
      supertype - type of potential supertype
      Gibt zurück:
      true if @type is a subtype of @supertype Since 2.24

    • isTuple

      public boolean isTuple()
      Determines if the given @type is a tuple type.

      This is true if the type string for @type starts with a `(` or if @type is
      `G_VARIANT_TYPE_TUPLE`.

      This function returns true for any indefinite type for which every
      definite subtype is a tuple type — `G_VARIANT_TYPE_TUPLE`, for
      example.
      Gibt zurück:
      true if @type is a tuple type Since 2.24

    • isVariant

      public boolean isVariant()
      Determines if the given @type is the variant type.
      Gibt zurück:
      true if @type is the variant type Since 2.24

    • key

      public VariantType key()
      Determines the key type of a dictionary entry type.

      This function may only be used with a dictionary entry type. Other
      than the additional restriction, this call is equivalent to
      [method@GLib.VariantType.first].
      Gibt zurück:
      the key type of the dictionary entry Since 2.24

    • nItems

      public long nItems()
      Determines the number of items contained in a tuple or
      dictionary entry type.

      This function may only be used with tuple or dictionary entry types,
      but must not be used with the generic tuple type
      `G_VARIANT_TYPE_TUPLE`.

      In the case of a dictionary entry type, this function will always
      return `2`.
      Gibt zurück:
      the number of items in @type Since 2.24

    • next

      public VariantType next()
      Determines the next item type of a tuple or dictionary entry
      type.

      @type must be the result of a previous call to
      [method@GLib.VariantType.first] or [method@GLib.VariantType.next].

      If called on the key type of a dictionary entry then this call
      returns the value type. If called on the value type of a dictionary
      entry then this call returns `NULL`.

      For tuples, `NULL` is returned when @type is the last item in the tuple.
      Gibt zurück:
      the next type after @type, or `NULL` if there are no further types Since 2.24

    • peekString

      public Str peekString()
      Returns the type string corresponding to the given @type.

      The result is not nul-terminated; in order to determine its length you
      must call [method@GLib.VariantType.get_string_length].

      To get a nul-terminated string, see [method@GLib.VariantType.dup_string].
      Gibt zurück:
      the corresponding type string (not nul-terminated) Since 2.24

    • value

      public VariantType value()
      Determines the value type of a dictionary entry type.

      This function may only be used with a dictionary entry type.
      Gibt zurück:
      the value type of the dictionary entry Since 2.24

    • checked

      public static VariantType checked(@Nonnull Str type_string)
      Parameter:
      type_string -
      Gibt zurück:

    • stringGetDepth

      public static long stringGetDepth(@Nonnull Str type_string)
      Parameter:
      type_string -
      Gibt zurück:

    • stringIsValid

      public static boolean stringIsValid(@Nonnull Str type_string)
      Checks if @type_string is a valid
      [GVariant type string](./struct.VariantType.html#gvariant-type-strings).

      This call is equivalent to calling [func@GLib.VariantType.string_scan] and
      confirming that the following character is a nul terminator.
      Parameter:
      type_string - a pointer to any string
      Gibt zurück:
      true if @type_string is exactly one valid type string Since 2.24

    • getTypeID

      public static long getTypeID()

    • getParentTypeID

      public static long getParentTypeID()

    • getTypeSize

      public static TypeSystem.TypeSize getTypeSize()

    • getParentTypeSize

      public static TypeSystem.TypeSize getParentTypeSize()

    • getInstanceSize

      public static int getInstanceSize()