Package ch.bailu.gtk.glib

Class VariantType

java.lang.Object
ch.bailu.gtk.type.Type
ch.bailu.gtk.type.Pointer
ch.bailu.gtk.type.Record
ch.bailu.gtk.glib.VariantType
All Implemented Interfaces:
PointerInterface
public class VariantType extends Record
This section introduces the GVariant 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 GVariant.

The first major change with respect to the D-Bus type system is the
introduction of maybe (or "nullable") types. Any type in GVariant 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 GVariant 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 GVariant, 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, GVariant 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. GVariant deals with single values directly so GVariant type
strings always describe the type of exactly one value. This means
that a D-Bus signature string is generally not a valid GVariant 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,
g_variant_get_type() will never return an indefinite type, but
calling g_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 #GtkBin can exist (since #GtkBin is an abstract class),
but a #GtkWindow can certainly be instantiated, and you would say
that the #GtkWindow is a #GtkBin (since #GtkWindow is a subclass of
#GtkBin).

## GVariant Type Strings

A GVariant 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
g_variant_type_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, #GVariant
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 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

  • Constructor Details

    • VariantType

      public VariantType(PointerContainer pointer)

    • VariantType

      public VariantType(@Nonnull Str type_string)
      Creates a new #GVariantType corresponding to the type string given
      by @type_string. It is appropriate to call g_variant_type_free() on
      the return value.

      It is a programmer error to call this function with an invalid type
      string. Use g_variant_type_string_is_valid() if you are unsure.
      Parameters:
      type_string - a valid GVariant type string

    • VariantType

      public VariantType(String type_string)
      Creates a new #GVariantType corresponding to the type string given
      by @type_string. It is appropriate to call g_variant_type_free() on
      the return value.

      It is a programmer error to call this function with an invalid type
      string. Use g_variant_type_string_is_valid() if you are unsure.
      Parameters:
      type_string - a valid GVariant type string

  • Method Details

    • 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 g_variant_type_free() on the return value.
      Parameters:
      element - a #GVariantType
      Returns:
      a new array #GVariantType 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 g_variant_type_free() on the return value.
      Parameters:
      key - a basic #GVariantType
      value - a #GVariantType
      Returns:
      a new dictionary entry #GVariantType 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 g_variant_type_free() on the return value.
      Parameters:
      element - a #GVariantType
      Returns:
      a new maybe #GVariantType Since 2.24

    • copy

      public VariantType copy()
      Makes a copy of a #GVariantType. It is appropriate to call
      g_variant_type_free() on the return value. @type may not be %NULL.
      Returns:
      a new #GVariantType 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 g_free() on the return value.
      Returns:
      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.
      Returns:
      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 g_variant_type_is_subtype_of().

      The argument types of @type1 and @type2 are only #gconstpointer to
      allow use with #GHashTable without function pointer casting. For
      both arguments, a valid #GVariantType must be provided.
      Parameters:
      type2 - a #GVariantType
      Returns:
      %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 g_variant_type_next() provides an iterator
      interface over tuple and dictionary entry types.
      Returns:
      the first item type of @type, or %NULL Since 2.24

    • free

      public void free()
      Frees a #GVariantType that was allocated with
      g_variant_type_copy(), g_variant_type_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 g_variant_type_peek_string().
      Returns:
      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
      #GHashTable without function pointer casting. A valid
      #GVariantType must be provided.
      Returns:
      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.
      Returns:
      %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.
      Returns:
      %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.
      Returns:
      %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 #GVariant instance may not have an indefinite type, so calling
      this function on the result of g_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.
      Returns:
      %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.
      Returns:
      %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.
      Returns:
      %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.
      Parameters:
      supertype - a #GVariantType
      Returns:
      %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.
      Returns:
      %TRUE if @type is a tuple type Since 2.24

    • isVariant

      public boolean isVariant()
      Determines if the given @type is the variant type.
      Returns:
      %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
      g_variant_type_first().
      Returns:
      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.
      Returns:
      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
      g_variant_type_first() or g_variant_type_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 a tuple.
      Returns:
      the next #GVariantType after @type, or %NULL 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 g_variant_type_get_string_length().

      To get a nul-terminated string, see g_variant_type_dup_string().
      Returns:
      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.
      Returns:
      the value type of the dictionary entry Since 2.24

    • checked

      public static VariantType checked(@Nonnull Str arg0)
      Parameters:
      arg0 -
      Returns:

    • stringGetDepth

      public static long stringGetDepth(@Nonnull Str type_string)
      Parameters:
      type_string -
      Returns:

    • stringIsValid

      public static boolean stringIsValid(@Nonnull Str type_string)
      Checks if @type_string is a valid GVariant type string. This call is
      equivalent to calling g_variant_type_string_scan() and confirming
      that the following character is a nul terminator.
      Parameters:
      type_string - a pointer to any string
      Returns:
      %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()