Strongly typed value datatype

Description

Gnome::Glib::Variant is a variant datatype; it can contain one or more values along with information about the type of the values.

A Gnome::Glib::Variant may contain simple types, like an integer, or a boolean value; or complex types, like an array of two strings, or a dictionary of key value pairs. A Gnome::Glib::Variant is also immutable: once it's been created neither its type nor its content can be modified further.

Gnome::Glib::Variant is useful whenever data needs to be serialized, for example when sending method parameters in DBus, or when saving settings using Gnome::Glib::Settings.

When creating a new Gnome::Glib::Variant, you pass the data you want to store in it along with a string representing the type of data you wish to pass to it.

For instance, if you want to create a Gnome::Glib::Variant holding an integer value you can use:

my Gnome::Glib::Variant $v .= new(
  :type-string<u>, :value(42)
);

The string "u" in the first argument tells Gnome::Glib::Variant that the data passed to the constructor (40) is going to be an unsigned 32 bit integer.

As an alternative you can write

my Gnome::Glib::Variant $v .= new(:parse('-42'));

where the default used type is a signed 32 bit integer. To use an other integer type, write the type with it.

my Gnome::Glib::Variant $v .= new(:parse('uint64 42'));

More advanced examples of Gnome::Glib::Variant in use can be found in documentation for GVariant format strings.

The range of possible values is determined by the type.

The type system used by Gnome::Glib::Variant is Gnome::Glib::VariantType.

Gnome::Glib::Variant instances always have a type and a value (which are given at construction time). The type and value of a Gnome::Glib::Variant instance can never change other than by the Gnome::Glib::Variant itself being destroyed. A Gnome::Glib::Variant cannot contain a pointer.

Gnome::Glib::Variant is completely threadsafe. A Gnome::Glib::Variant instance can be concurrently accessed in any way from any number of threads without problems.

Gnome::Glib::Variant is heavily optimised for dealing with data in serialised form. It works particularly well with data located in memory-mapped files. It can perform nearly all deserialisation operations in a small constant time, usually touching only a single memory page. Serialised Gnome::Glib::Variant data can also be sent over the network.

Gnome::Glib::Variant is largely compatible with D-Bus. Almost all types of Gnome::Glib::Variant instances can be sent over D-Bus. See Gnome::Glib::VariantType for exceptions. (However, Gnome::Glib::Variant's serialisation format is not the same as the serialisation format of a D-Bus message body: use GDBusMessage, in the gio library, for those.)

For space-efficiency, the Gnome::Glib::Variant serialisation format does not automatically include the variant's length, type or endianness, which must either be implied from context (such as knowledge that a particular file format always contains a little-endian G_VARIANT_TYPE_VARIANT which occupies the whole length of the file) or supplied out-of-band (for instance, a length, type and/or endianness indicator could be placed at the beginning of a file, network message or network stream).

A Gnome::Glib::Variant's size is limited mainly by any lower level operating system constraints, such as the number of bits in gsize. For example, it is reasonable to have a 2GB file mapped into memory with GMappedFile, and call g_variant_new_from_data() on it.

For convenience to C programmers, Gnome::Glib::Variant features powerful varargs-based value construction and destruction. This feature is designed to be embedded in other libraries.

Memory Use

Gnome::Glib::Variant tries to be quite efficient with respect to memory use. This section gives a rough idea of how much memory is used by the current implementation. The information here is subject to change in the future.

The memory allocated by Gnome::Glib::Variant can be grouped into 4 broad purposes: memory for serialised data, memory for the type information cache, buffer management memory and memory for the Gnome::Glib::Variant structure itself.

Serialised Data Memory

This is the memory that is used for storing GVariant data in serialised form. This is what would be sent over the network or what would end up on disk, not counting any indicator of the endianness, or of the length or type of the top-level variant.

The amount of memory required to store a boolean is 1 byte. 16, 32 and 64 bit integers and double precision floating point numbers use their "natural" size. Strings (including object path and signature strings) are stored with a nul terminator, and as such use the length of the string plus 1 byte.

Maybe types use no space at all to represent the null value and use the same amount of space (sometimes plus one byte) as the equivalent non-maybe-typed value to represent the non-null case.

Arrays use the amount of space required to store each of their members, concatenated. Additionally, if the items stored in an array are not of a fixed-size (ie: strings, other arrays, etc) then an additional framing offset is stored for each item. The size of this offset is either 1, 2 or 4 bytes depending on the overall size of the container. Additionally, extra padding bytes are added as required for alignment of child values.

Tuples (including dictionary entries) use the amount of space required to store each of their members, concatenated, plus one framing offset (as per arrays) for each non-fixed-sized item in the tuple, except for the last one. Additionally, extra padding bytes are added as required for alignment of child values.

Variants use the same amount of space as the item inside of the variant, plus 1 byte, plus the length of the type string for the item inside the variant.

As an example, consider a dictionary mapping strings to variants. In the case that the dictionary is empty, 0 bytes are required for the serialisation.

If we add an item "width" that maps to the int32 value of 500 then we will use 4 byte to store the int32 (so 6 for the variant containing it) and 6 bytes for the string. The variant must be aligned to 8 after the 6 bytes of the string, so that's 2 extra bytes. 6 (string) + 2 (padding) + 6 (variant) is 14 bytes used for the dictionary entry. An additional 1 byte is added to the array as a framing offset making a total of 15 bytes.

If we add another entry, "title" that maps to a nullable string that happens to have a value of null, then we use 0 bytes for the null value (and 3 bytes for the variant to contain it along with its type string) plus 6 bytes for the string. Again, we need 2 padding bytes. That makes a total of 6 + 2 + 3 = 11 bytes.

We now require extra padding between the two items in the array. After the 14 bytes of the first item, that's 2 bytes required. We now require 2 framing offsets for an extra two bytes. 14 + 2 + 11 + 2 = 29 bytes to encode the entire two-item dictionary.

Type Information Cache

For each GVariant type that currently exists in the program a type information structure is kept in the type information cache. The type information structure is required for rapid deserialisation.

Continuing with the above example, if a Gnome::Glib::Variant exists with the type "a{sv}" then a type information struct will exist for "a{sv}", "{sv}", "s", and "v". Multiple uses of the same type will share the same type information. Additionally, all single-digit types are stored in read-only static memory and do not contribute to the writable memory footprint of a program using Gnome::Glib::Variant.

Aside from the type information structures stored in read-only memory, there are two forms of type information. One is used for container types where there is a single element type: arrays and maybe types. The other is used for container types where there are multiple element types: tuples and dictionary entries.

Array type info structures are 6 * sizeof (void *), plus the memory required to store the type string itself. This means that on 32-bit systems, the cache entry for "a{sv}" would require 30 bytes of memory (plus malloc overhead).

Tuple type info structures are 6 * sizeof (void *), plus 4 * sizeof (void *) for each item in the tuple, plus the memory required to store the type string itself. A 2-item tuple, for example, would have a type information structure that consumed writable memory in the size of 14 * sizeof (void *) (plus type string) This means that on 32-bit systems, the cache entry for "{sv}" would require 61 bytes of memory (plus malloc overhead).

This means that in total, for our "a{sv}" example, 91 bytes of type information would be allocated.

The type information cache, additionally, uses a GHashTable to store and lookup the cached items and stores a pointer to this hash table in static storage. The hash table is freed when there are zero items in the type cache.

Although these sizes may seem large it is important to remember that a program will probably only have a very small number of different types of values in it and that only one type information structure is required for many different values of the same type.

Buffer Management Memory

Gnome::Glib::Variant uses an internal buffer management structure to deal with the various different possible sources of serialised data that it uses. The buffer is responsible for ensuring that the correct call is made when the data is no longer in use by Gnome::Glib::Variant. This may involve a g_free() or a g_slice_free() or even g_mapped_file_unref().

One buffer management structure is used for each chunk of serialised data. The size of the buffer management structure is 4 * (void *). On 32-bit systems, that's 16 bytes.

## GVariant structure

The size of a Gnome::Glib::Variant structure is 6 * (void *). On 32-bit systems, that's 24 bytes.

Gnome::Glib::Variant structures only exist if they are explicitly created with API calls. For example, if a Gnome::Glib::Variant is constructed out of serialised data for the example given above (with the dictionary) then although there are 9 individual values that comprise the entire dictionary (two keys, two values, two variants containing the values, two dictionary entries, plus the dictionary itself), only 1 Gnome::Glib::Variant instance exists -- the one referring to the dictionary.

If calls are made to start accessing the other values then Gnome::Glib::Variant instances will exist for those values only for as long as they are in use (ie: until you call g_variant_unref()). The type information is shared. The serialised data and the buffer management structure for that serialised data is shared by the child.

Summary

To put the entire example together, for our dictionary mapping strings to variants (with two entries, as given above), we are using 91 bytes of memory for type information, 29 bytes of memory for the serialised data, 16 bytes for buffer management and 24 bytes for the Gnome::Glib::Variant instance, or a total of 160 bytes, plus malloc overhead. If we were to use g_variant_get_child_value() to access the two dictionary entries, we would use an additional 48 bytes. If we were to have other dictionaries of the same type, we would use more memory for the serialised data and buffer management for those dictionaries, but the type information would be shared.

See Also

[Gnome::Glib::VariantType](VariantType.html), [variant format strings](https://developer.gnome.org/glib/stable/gvariant-format-strings.html), [variant text format](https://developer.gnome.org/glib/stable/gvariant-text.html).

• Variant dictionaries

• Variant types

• Variant format strings

• Variant text format

Synopsis

Declaration

unit class Gnome::Glib::Variant;
also is Gnome::N::TopLevelClassSupport;

Types

GVariantClass

The range of possible top-level types of GVariant instances.

• G_VARIANT_CLASS_BOOLEAN; The GVariant is a boolean.

• G_VARIANT_CLASS_BYTE; The GVariant is a byte.

• G_VARIANT_CLASS_INT16; The GVariant is a signed 16 bit integer.

• G_VARIANT_CLASS_UINT16; The GVariant is an unsigned 16 bit integer.

• G_VARIANT_CLASS_INT32; The GVariant is a signed 32 bit integer.

• G_VARIANT_CLASS_UINT32; The GVariant is an unsigned 32 bit integer.

• G_VARIANT_CLASS_INT64; The GVariant is a signed 64 bit integer.

• G_VARIANT_CLASS_UINT64; The GVariant is an unsigned 64 bit integer.

• G_VARIANT_CLASS_HANDLE; The GVariant is a file handle index.

• G_VARIANT_CLASS_DOUBLE; The GVariant is a double precision floating point value.

• G_VARIANT_CLASS_STRING; The GVariant is a normal string.

• G_VARIANT_CLASS_OBJECT_PATH; The GVariant is a D-Bus object path string.

• G_VARIANT_CLASS_SIGNATURE; The GVariant is a D-Bus signature string.

• G_VARIANT_CLASS_VARIANT; The GVariant is a variant.

• G_VARIANT_CLASS_MAYBE; The GVariant is a maybe-typed value.

• G_VARIANT_CLASS_ARRAY; The GVariant is an array.

• G_VARIANT_CLASS_TUPLE; The GVariant is a tuple.

• G_VARIANT_CLASS_DICT_ENTRY; The GVariant is a dictionary entry.

Methods

new

:array

Create a new Variant object. The type of the array elements is taken from the first element.

multi method new ( Array :$array! )

Example

Create a Variant array type containing integers;

my Array $array = [];
for 40, 41, 42 -> $value {
  $array.push: Gnome::Glib::Variant.new( :type-string<i>, :$value);
}
my Gnome::Glib::Variant $v .= new(:$array);
say $v.get-type-string;      # ai

:boolean

Creates a new boolean Variant -- either True or False. Note that the value in the variant is stored as an integer. Its type becomes 'b'.

multi method new ( Bool :$boolean! )

:byte

Creates a new byte Variant. Its type becomes 'y'.

multi method new ( Int :$byte! )

:byte-string

Creates a new byte-string Variant. Its type becomes 'ay' which is essentially an array of bytes. This can be an ascii type of string which does not have to be UTF complient.

multi method new ( Str :$byte-string! )

:byte-string-array

Creates a new byte-string-array Variant. Its type becomes 'aay'. which is essentially an array of an array of bytes.

multi method new ( Array :$byte-string-array! )

:dict

Creates a new dictionary Variant. Its type becomes '{}'.

multi method new ( List :$dict! )

The List $dict has two values, a key and a value and must both be valid Gnome::Glib::Variant objects. key must be a value of a basic type (ie: not a container). It will mostly be a string (variant type 's').

Example

my Gnome::Glib::Variant $v .= new(
  :dict(
    Gnome::Glib::Variant.new(:parse<width>),
    Gnome::Glib::Variant.new(:parse<200>)
  )
);

say $v.print; #

:double

Creates a new double Variant. Its type becomes 'd'.

multi method new ( Num :$double! )

:int16

Creates a new int16 Variant. Its type becomes 'n'.

multi method new ( Int :$int16! )

:int32

Creates a new int32 Variant. Its type becomes 'i'.

multi method new ( Int :$int32! )

:int64

Creates a new int64 Variant. Its type becomes 'x'.

multi method new ( Int :$int64! )

:string

Creates a new string Variant. Its type becomes 's'.

multi method new ( Str :$string! )

:strv

Creates a new string array Variant. Its type becomes 'as'.

multi method new ( Array :$strv! )

Example

my Gnome::Glib::Variant $v .= new(:string-array([<abc def ghi αβ ⓒ™⅔>]));
say $v.get-type-string; #    as

:tuple

Creates a new tuple Variant. Its type becomes ''.

multi method new ( Array :$tuple! )

Example

my Array $tuple = [];
$tuple.push: Gnome::Glib::Variant.new( :type-string<i>, :value(40));
$tuple.push: Gnome::Glib::Variant.new( :type-string<s>, :value<fourtyone>);
$tuple.push: Gnome::Glib::Variant.new( :type-string<x>, :value(42));
my Gnome::Glib::Variant $v .= new(:$tuple);
say $v.get-type-string; #    (isx)

:uint16

Creates a new uint16 Variant. Its type becomes 'q'.

multi method new ( UInt :$uint16! )

:uint32

Creates a new uint32 Variant. Its type becomes 'u'.

multi method new ( UInt :$uint32! )

:uint64

Creates a new uint64 Variant. Its type becomes 't'.

multi method new ( UInt :$uint64! )

:variant

Creates a new variant Variant. Its type becomes 'v'.

multi method new ( N-GObject :$variant! )

Example

my Gnome::Glib::Variant $v .= new(
  :variant(Gnome::Glib::Variant.new( :type-string<i>, :value(40)))
);
say $v.get-type-string; #    v

:type-string, :parse

Create a new Variant object by parsing the type and data provided in strings. The format of the parse string is described here.

multi method new ( Str :$type-string?, Str :$parse! )

Example

Create a Variant tuple containing a string, an unsigned integer and a boolean (Note the lowercase 'true'!);

my Gnome::Glib::Variant $v .= new(
  :type-string<(sub)>, :parse('("abc",20,true)')
);

Because the values in the :parse string take the default types you can also leave out the type string;

my Gnome::Glib::Variant $v .= new(:parse('("abc",20,true)'));

:type-string, :value

Create a new Variant object by parsing the type and a provided value. The type strings are simple like (unsigned) integer ('u' or 'i') but no arrays ('a') etc.

multi method new ( Str :$type-string!, Any :$value! )

:native-object

Create a Variant object using a native object from elsewhere. See also Gnome::N::TopLevelClassSupport.

multi method new ( N-GObject :$native-object! )

byteswap

Performs a byteswapping operation on the contents of value. The result is that all multi-byte numeric data contained in value is byteswapped. That includes 16, 32, and 64bit signed and unsigned integers as well as file handles and double precision floating point values. This function is an identity mapping on any value that does not contain multi-byte numeric data. That include strings, booleans, bytes and containers containing only these things (recursively). The returned value is always in normal form and is marked as trusted.

Returns: (transfer full): the byteswapped form of value

method byteswap ( --> N-GObject )

check-format-string

Checks if calling g_variant_get() with format_string on value would be valid from a type-compatibility standpoint. format_string is assumed to be a valid format string (from a syntactic standpoint). If copy_only is 1 then this function additionally checks that it would be safe to call g_variant_unref() on value immediately after the call to g_variant_get() without invalidating the result. This is only possible if deep copies are made (ie: there are no pointers to the data inside of the soon-to-be-freed N-GObject instance). If this check fails then a g_critical() is printed and 0 is returned. This function is meant to be used by functions that wish to provide varargs accessors to N-GObject values of uncertain values (eg: g_variant_lookup() or g_menu_model_get_item_attribute()).

Returns: 1 if format_string is safe to use

method check-format-string (  Str  $format_string, Int $copy_only --> Int )

• Str $format_string; a valid N-GObject format string

• Int $copy_only; 1 to ensure the format string makes deep copies

classify

Classifies value according to its top-level type.

Returns: the GVariantClass of value

method classify ( --> GVariantClass )

compare

Compares one and two. The types of one and two are gconstpointer only to allow use of this function with GTree, GPtrArray, etc. They must each be a N-GObject. Comparison is only defined for basic types (ie: booleans, numbers, strings). For booleans, 0 is less than 1. Numbers are ordered in the usual way. Strings are in ASCII lexographical order. It is a programmer error to attempt to compare container values or two values that have types that are not exactly equal. For example, you cannot compare a 32-bit signed integer with a 32-bit unsigned integer. Also note that this function is not particularly well-behaved when it comes to comparison of doubles; in particular, the handling of incomparable values (ie: NaN) is undefined. If you only require an equality comparison, g_variant_equal() is more general.

Returns: negative value if a < b; zero if a = b; positive value if a > b.

method compare ( Pointer $one, Pointer $two --> Int )

• Pointer $one; (type GVariant): a basic-typed N-GObject instance

• Pointer $two; (type GVariant): a N-GObject instance of the same type

dup-bytestring

Similar to g_variant_get_bytestring() except that instead of returning a constant string, the string is duplicated. The return value must be freed using g_free().

Returns: (transfer full) (array zero-terminated=1 length=length) (element-type guint8): a newly allocated string

method dup-bytestring ( UInt $length -->  Str  )

• UInt $length; (out) (optional) (default NULL): a pointer to a gsize, to store the length (not including the nul terminator)

dup-bytestring-array

Gets the contents of an array of array of bytes N-GObject. This call makes a deep copy; the return result should be released with g_strfreev(). If length is non-Any then the number of elements in the result is stored there. In any case, the resulting array will be Any-terminated. For an empty array, length will be set to 0 and a pointer to a Any pointer will be returned.

Returns: (array length=length) (transfer full): an array of strings

method dup-bytestring-array ( UInt $length -->  CArray[Str]  )

• UInt $length; (out) (optional): the length of the result, or Any

dup-objv

Gets the contents of an array of object paths N-GObject. This call makes a deep copy; the return result should be released with g_strfreev(). If length is non-Any then the number of elements in the result is stored there. In any case, the resulting array will be Any-terminated. For an empty array, length will be set to 0 and a pointer to a Any pointer will be returned.

Returns: (array length=length zero-terminated=1) (transfer full): an array of strings

method dup-objv ( UInt $length -->  CArray[Str]  )

• UInt $length; (out) (optional): the length of the result, or Any

dup-string

Similar to g_variant_get_string() except that instead of returning a constant string, the string is duplicated. The string will always be UTF-8 encoded. The return value must be freed using g_free().

Returns: (transfer full): a newly allocated string, UTF-8 encoded

method dup-string ( UInt $length -->  Str  )

• UInt $length; (out): a pointer to a gsize, to store the length

dup-strv

Gets the contents of an array of strings N-GObject. This call makes a deep copy; the return result should be released with g_strfreev(). If length is non-Any then the number of elements in the result is stored there. In any case, the resulting array will be Any-terminated. For an empty array, length will be set to 0 and a pointer to a Any pointer will be returned.

Returns: (array length=length zero-terminated=1) (transfer full): an array of strings

method dup-strv ( UInt $length -->  CArray[Str]  )

• UInt $length; (out) (optional): the length of the result, or Any

equal

Checks if one and two have the same type and value. The types of one and two are gconstpointer only to allow use of this function with GHashTable. They must each be a N-GObject.

Returns: 1 if one and two are equal

method equal ( Pointer $one, Pointer $two --> Int )

• Pointer $one; (type GVariant): a N-GObject instance

• Pointer $two; (type GVariant): a N-GObject instance

get

Deconstructs a N-GObject instance. Think of this function as an analogue to scanf(). The arguments that are expected by this function are entirely determined by format_string. format_string also restricts the permissible types of value. It is an error to give a value with an incompatible type. See the section on GVariant format strings. Please note that the syntax of the format string is very likely to be extended in the future. format_string determines the C types that are used for unpacking the values and also determines if the values are copied or borrowed

method get (  Str  $format_string )

• Str $format_string; a N-GObject format string @...: arguments, as per format_string

get-boolean

Returns the boolean value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_BOOLEAN.

Returns: True or False

method get-boolean ( --> Bool )

get-byte

Returns the byte value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_BYTE.

Returns: a guint8

method get-byte ( --> UInt )

get-bytestring

Returns the string value of a N-GObject instance with an array-of-bytes type. The string has no particular encoding.

method get-bytestring ( -->  Str  )

get-bytestring-array

Gets the contents of an array of array of bytes N-GObject.

method get-bytestring-array ( -->  Array[Str]  )

get-child

Reads a child item out of a container N-GObject instance and deconstructs it according to format_string. This call is essentially a combination of g_variant_get_child_value() and g_variant_get(). format_string determines the C types that are used for unpacking the values and also determines if the values are copied or borrowed, see the section on [GVariant format strings][gvariant-format-strings-pointers].

method get-child ( UInt $index_,  Str  $format_string )

• UInt $index_; the index of the child to deconstruct

• Str $format_string; a N-GObject format string @...: arguments, as per format_string

get-child-value

method get-child-value ( UInt $index_ --> N-GObject )

• UInt $index_;

get-data

method get-data ( --> Pointer )

get-data-as-bytes

method get-data-as-bytes ( --> N-GBytes )

get-double

Returns the double precision floating point value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_DOUBLE.

Returns: a gdouble

method get-double ( --> Num )

get-fixed-array

Provides access to the serialised data for an array of fixed-sized items. value must be an array with fixed-sized elements. Numeric types are fixed-size, as are tuples containing only other fixed-sized types. element_size must be the size of a single element in the array, as given by the section on [serialized data memory][gvariant-serialised-data-memory]. In particular, arrays of these fixed-sized types can be interpreted as an array of the given C type, with element_size set to the size the appropriate type: - G_VARIANT_TYPE_INT16 (etc.): gint16 (etc.) - G_VARIANT_TYPE_BOOLEAN: guchar (not gboolean!) - G_VARIANT_TYPE_BYTE: guint8 - G_VARIANT_TYPE_HANDLE: guint32 - G_VARIANT_TYPE_DOUBLE: gdouble For example, if calling this function for an array of 32-bit integers, you might say `sizeof(gint32)`. This value isn't used except for the purpose of a double-check that the form of the serialised data matches the caller's expectation. n_elements, which must be non-Any, is set equal to the number of items in the array.

Returns: (array length=n_elements) (transfer none): a pointer to the fixed array

method get-fixed-array ( UInt $n_elements, UInt $element_size --> Pointer )

• UInt $n_elements; (out): a pointer to the location to store the number of items

• UInt $element_size; the size of each element

get-handle

Returns the 32-bit signed integer value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_HANDLE. By convention, handles are indexes into an array of file descriptors that are sent alongside a D-Bus message. If you're not interacting with D-Bus, you probably don't need them.

Returns: a gint32

method get-handle ( --> Int )

get-int16

Returns the 16-bit signed integer value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_INT16.

Returns: a gint16

method get-int16 ( --> Int )

get-int32

Returns the 32-bit signed integer value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_INT32.

Returns: a gint32

method get-int32 ( --> Int )

get-int64

Returns the 64-bit signed integer value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_INT64.

Returns: a gint64

method get-int64 ( --> Int )

get-maybe

Given a maybe-typed N-GObject instance, extract its value. If the value is Nothing, then this function returns Any.

Returns: (nullable) (transfer full): the contents of value, or Any

method get-maybe ( --> N-GObject )

get-normal-form

Gets a N-GObject instance that has the same value as value and is trusted to be in normal form. If value is already trusted to be in normal form then a new reference to value is returned. If value is not already trusted, then it is scanned to check if it is in normal form. If it is found to be in normal form then it is marked as trusted and a new reference to it is returned. If value is found not to be in normal form then a new trusted N-GObject is created with the same value as value. It makes sense to call this function if you've received N-GObject data from untrusted sources and you want to ensure your serialised output is definitely in normal form. If value is already in normal form, a new reference will be returned (which will be floating if value is floating). If it is not in normal form, the newly created N-GObject will be returned with a single non-floating reference. Typically, g_variant_take_ref() should be called on the return value from this function to guarantee ownership of a single non-floating reference to it.

Returns: (transfer full): a trusted N-GObject

method get-normal-form ( --> N-GObject )

get-objv

Gets the contents of an array of object paths N-GObject. This call makes a shallow copy; the return result should be released with g_free(), but the individual strings must not be modified. If length is non-Any then the number of elements in the result is stored there. In any case, the resulting array will be Any-terminated. For an empty array, length will be set to 0 and a pointer to a Any pointer will be returned.

Returns: (array length=length zero-terminated=1) (transfer container): an array of constant strings

method get-objv ( UInt $length -->  CArray[Str]  )

• UInt $length; (out) (optional): the length of the result, or Any

get-size

method get-size ( --> UInt )

get-string

Returns the string value of a N-GObject instance with a string type.

method get-string ( -->  Str  )

get-strv

Gets the contents of an array of strings N-GObject. This call makes a shallow copy.

method get-strv ( --> Array[Str]  )

get-type

Determines the type of value. The return value is valid for the lifetime of value and must not be freed.

Returns: a GVariantType

method get-type ( --> Gnome::Glib::Variant )

get-type-string

Returns the type string of value. Unlike the result of calling g_variant_type_peek_string(), this string is nul-terminated. This string belongs to N-GObject and must not be freed.

Returns: the type string for the type of value

method get-type-string ( -->  Str  )

get-uint16

Returns the 16-bit unsigned integer value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_UINT16.

Returns: a guint16

method get-uint16 ( --> UInt )

get-uint32

Returns the 32-bit unsigned integer value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_UINT32.

Returns: a guint32

method get-uint32 ( --> UInt )

get-uint64

Returns the 64-bit unsigned integer value of value. It is an error to call this function with a value of any type other than G_VARIANT_TYPE_UINT64.

Returns: a guint64

method get-uint64 ( --> UInt )

get-va

This function is intended to be used by libraries based on N-GObject that want to provide g_variant_get()-like functionality to their users. The API is more general than g_variant_get() to allow a wider range of possible uses. format_string must still point to a valid format string, but it only need to be nul-terminated if endptr is Any. If endptr is non-Any then it is updated to point to the first character past the end of the format string. app is a pointer to a va_list. The arguments, according to format_string, are collected from this va_list and the list is left pointing to the argument following the last. These two generalisations allow mixing of multiple calls to g_variant_new_va() and g_variant_get_va() within a single actual varargs call by the user. format_string determines the C types that are used for unpacking the values and also determines if the values are copied or borrowed, see the section on [GVariant format strings][gvariant-format-strings-pointers].

method get-va (  Str  $format_string,  CArray[Str]  $endptr, va_list $app )

• Str $format_string; a string that is prefixed with a format string

• CArray[Str] $endptr; (nullable) (default NULL): location to store the end pointer, or Any

• va_list $app; a pointer to a va_list

get-variant

Unboxes value. The result is the Gnome::Glib::Variant that was contained in value.

Returns: the item contained in the variant

method get-variant ( --> Gnome::Glib::Variant )

hash

Generates a hash value for a N-GObject instance. The output of this function is guaranteed to be the same for a given value only per-process. It may change between different processor architectures or even different versions of GLib. Do not use this function as a basis for building protocols or file formats. The type of value is gconstpointer only to allow use of this function with GHashTable. value must be a N-GObject.

Returns: a hash value corresponding to value

method hash ( Pointer $value --> UInt )

• Pointer $value; (type GVariant): a basic N-GObject value as a gconstpointer

is-container

Checks if value is a container.

Returns: 1 if value is a container

method is-container ( --> Int )

is-floating

method is-floating ( --> Int )

is-normal-form

method is-normal-form ( --> Int )

is-object-path

Determines if a given string is a valid D-Bus object path. You should ensure that a string is a valid D-Bus object path before passing it to g_variant_new_object_path(). A valid object path starts with `/` followed by zero or more sequences of characters separated by `/` characters. Each sequence must contain only the characters `[A-Z][a-z][0-9]_`. No sequence (including the one following the final `/` character) may be empty.

Returns: 1 if string is a D-Bus object path

method is-object-path (  Str  $string --> Int )

• Str $string; a normal C nul-terminated string

is-of-type

Checks if a value has a type matching the provided type.

Returns: True if the type of value matches type

method is-of-type ( N-GObject $type --> Bool )

• N-GObject $type; a GVariantType

is-signature

Determines if a given string is a valid D-Bus type signature. You should ensure that a string is a valid D-Bus type signature before passing it to g_variant_new_signature(). D-Bus type signatures consist of zero or more definite GVariantType strings in sequence.

Returns: 1 if string is a D-Bus type signature

method is-signature (  Str  $string --> Int )

• Str $string; a normal C nul-terminated string

lookup

Looks up a value in a dictionary N-GObject. This function is a wrapper around g_variant_lookup_value() and g_variant_get(). In the case that Any would have been returned, this function returns 0. Otherwise, it unpacks the returned value and returns 1. format_string determines the C types that are used for unpacking the values and also determines if the values are copied or borrowed, see the section on [GVariant format strings][gvariant-format-strings-pointers]. This function is currently implemented with a linear scan. If you plan to do many lookups then N-GObjectDict may be more efficient.

Returns: 1 if a value was unpacked

method lookup (  Str  $key,  Str  $format_string --> Int )

• Str $key; the key to lookup in the dictionary

• Str $format_string; a GVariant format string @...: the arguments to unpack the value into

lookup-value

Looks up a value in a dictionary N-GObject. This function works with dictionaries of the type a{s*} (and equally well with type a{o*}, but we only further discuss the string case for sake of clarity). In the event that dictionary has the type a{sv}, the expected_type string specifies what type of value is expected to be inside of the variant. If the value inside the variant has a different type then undefined is returned. In the event that dictionary has a value type other than v then expected_type must directly match the value type and it is used to unpack the value directly or an error occurs. In either case, if key is not found in dictionary, Any is returned. If the key is found and the value has the correct type, it is returned. If expected_type was specified then any non-Any return value will have this type. This function is currently implemented with a linear scan. If you plan to do many lookups then N-GObjectDict may be more efficient.

Returns: (transfer full): the value of the dictionary key, or Any

method lookup-value (  Str  $key, N-GObject $expected_type --> N-GObject )

• Str $key; the key to lookup in the dictionary

• N-GObject $expected_type; (nullable): a GVariantType, or Any

n-children

method n-children ( --> UInt )

parse

Parses a GVariant from a text representation.

In the event that the parsing is successful, the resulting GVariant is returned.

In case of any error, NULL will be returned. If error is non-NULL then it will be set to reflect the error that occurred.

There may be implementation specific restrictions on deeply nested values, which would result in a G_VARIANT_PARSE_ERROR_RECURSION error. GVariant is guaranteed to handle nesting up to at least 64 levels.

method g_variant_parse ( Str $type-string, Str $text --> List )

• Str $type-string; String like it is used to create a Gnome::Glib::VariantType. May be undefined.

• Str $text; Textual representation of data.

The returned List has members

• N-GObject object. A native variant object

• Gnome::Glib::Error. The error object. Test for .is-valid() ~~ False to see if parsing went ok and that the variant object is defined.

parse-error-print-context

method parse-error-print-context ( N-GError $error,  Str  $source_str -->  Str  )

• N-GError $error;

• Str $source_str;

parse-error-quark

Error domain for GVariant text format parsing. Specific error codes are not currently defined for this domain. See GError for information on error

method parse-error-quark ( --> UInt )

print

Pretty-prints value in the format understood by parse(). If $type_annotate is True, then type information is included in the output.

Returns: a newly-allocated string holding the result.

method print ( Bool $type_annotate = False --> Str )

• Int $type_annotate; True if type information should be included in the output

print-string

Behaves as g_variant_print(), but operates on a GString. If string is non-Any then it is appended to and returned. Else, a new empty GString is allocated and it is returned.

Returns: a GString containing the string

method print-string ( N-GObject $string, Int $type_annotate --> N-GObject )

• N-GObject $string; (nullable) (default NULL): a GString, or Any

• Int $type_annotate; 1 if type information should be included in the output

ref-sink

method ref-sink ( --> N-GObject )

store

method store ( Pointer $data )

• Pointer $data;

take-ref

method take-ref ( --> N-GObject )

_g_variant_new

method _g_variant_new (  Str  $format_string --> N-GObject )

• Str $format_string;

_g_variant_new_array

Creates a new N-GObject array from children. child_type must be non-Any if n_children is zero. Otherwise, the child type is determined by inspecting the first element of the children array. If child_type is non-Any then it must be a definite type. The items of the array are taken from the children array. No entry in the children array may be Any. All items in the array must have the same type, which must be the same as child_type, if given. If the children are floating references (see g_variant_ref_sink()), the new instance takes ownership of them as if via g_variant_ref_sink().

Returns: (transfer none): a floating reference to a new N-GObject array

method _g_variant_new_array ( N-GObject $child_type,  $GVariant * const *children, UInt $n_children --> N-GObject )

• N-GObject $child_type; (nullable): the element type of the new array

• $GVariant * const *children; (nullable) (array length=n_children): an array of N-GObject pointers, the children

• UInt $n_children; the length of children

_g_variant_new_boolean

Creates a new boolean N-GObject instance -- either 1 or 0.

Returns: (transfer none): a floating reference to a new boolean N-GObject instance

method _g_variant_new_boolean ( Int $value --> N-GObject )

• Int $value; a gboolean value

_g_variant_new_byte

Creates a new byte N-GObject instance.

Returns: (transfer none): a floating reference to a new byte N-GObject instance

method _g_variant_new_byte ( UInt $value --> N-GObject )

• UInt $value; a guint8 value

_g_variant_new_bytestring

Creates an array-of-bytes N-GObject with the contents of string. This function is just like g_variant_new_string() except that the string need not be valid UTF-8. The nul terminator character at the end of the string is stored in the array.

Returns: (transfer none): a floating reference to a new bytestring N-GObject instance

method _g_variant_new_bytestring (  Str  $string --> N-GObject )

• Str $string; (array zero-terminated=1) (element-type guint8): a normal nul-terminated string in no particular encoding

_g_variant_new_bytestring_array

Constructs an array of bytestring N-GObject from the given array of strings. If length is -1 then strv is Any-terminated.

Returns: (transfer none): a new floating N-GObject instance

method _g_variant_new_bytestring_array (  CArray[Str]  $strv, Int $length --> N-GObject )

• CArray[Str] $strv; (array length=length): an array of strings

• Int $length; the length of strv, or -1

dict-entry

Creates a new dictionary entry Gnome::Glib::VariantDict. key and value must be defined. key must be a value of a basic type (ie: not a container).

Returns: a floating reference to a new dictionary entry Gnome::Glib::VariantDict

method _g_variant_new_dict_entry ( N-GObject $key, N-GObject $value --> N-GObject )

• N-GObject $value; a Gnome::Glib::VariantDict, the value

_g_variant_new_double

Creates a new double N-GObject instance.

Returns: (transfer none): a floating reference to a new double N-GObject instance

method _g_variant_new_double ( Num $value --> N-GObject )

• Num $value; a gdouble floating point value

_g_variant_new_fixed_array

Constructs a new array N-GObject instance, where the elements are of element_type type. elements must be an array with fixed-sized elements. Numeric types are fixed-size as are tuples containing only other fixed-sized types. element_size must be the size of a single element in the array. For example, if calling this function for an array of 32-bit integers, you might say sizeof(gint32). This value isn't used except for the purpose of a double-check that the form of the serialised data matches the caller's expectation. n_elements must be the length of the elements array.

Returns: (transfer none): a floating reference to a new array N-GObject instance

method _g_variant_new_fixed_array ( N-GObject $element_type, Pointer $elements, UInt $n_elements, UInt $element_size --> N-GObject )

• N-GObject $element_type; the GVariantType of each element

• Pointer $elements; a pointer to the fixed array of contiguous elements

• UInt $n_elements; the number of elements

• UInt $element_size; the size of each element

_g_variant_new_from_bytes

method _g_variant_new_from_bytes ( N-GObject $type, N-GBytes $bytes, Int $trusted --> N-GObject )

• N-GObject $type;

• N-GObject $bytes;

• Int $trusted;

_g_variant_new_from_data

Creates a new N-GObject instance from serialised data. type is the type of N-GObject instance that will be constructed. The interpretation of data depends on knowing the type. data is not modified by this function and must remain valid with an unchanging value until such a time as notify is called with user_data. If the contents of data change before that time then the result is undefined. If data is trusted to be serialised data in normal form then trusted should be 1. This applies to serialised data created within this process or read from a trusted location on the disk (such as a file installed in /usr/lib alongside your application). You should set trusted to 0 if data is read from the network, a file in the user's home directory, etc. If data was not stored in this machine's native endianness, any multi-byte numeric values in the returned variant will also be in non-native endianness. g_variant_byteswap() can be used to recover the original values. notify will be called with user_data when data is no longer needed. The exact time of this call is unspecified and might even be before this function returns. Note: data must be backed by memory that is aligned appropriately for the type being loaded. Otherwise this function will internally create a copy of the memory (since GLib 2.60) or (in older versions) fail and exit the process.

Returns: (transfer none): a new floating N-GObject of type type

method _g_variant_new_from_data ( N-GObject $type, Pointer $data, UInt $size, Int $trusted, GDestroyNotify $notify, Pointer $user_data --> N-GObject )

• N-GObject $type; a definite GVariantType

• Pointer $data; (array length=size) (element-type guint8): the serialised data

• UInt $size; the size of data

• Int $trusted; 1 if data is definitely in normal form

• GDestroyNotify $notify; (scope async): function to call when data is no longer needed

• Pointer $user_data; data for notify

_g_variant_new_handle

Creates a new handle N-GObject instance. By convention, handles are indexes into an array of file descriptors that are sent alongside a D-Bus message. If you're not interacting with D-Bus, you probably don't need them.

Returns: (transfer none): a floating reference to a new handle N-GObject instance

method _g_variant_new_handle ( Int $value --> N-GObject )

• Int $value; a gint32 value

_g_variant_new_int16

Creates a new int16 N-GObject instance.

Returns: (transfer none): a floating reference to a new int16 N-GObject instance

method _g_variant_new_int16 ( Int $value --> N-GObject )

• Int $value; a gint16 value

_g_variant_new_int32

Creates a new int32 N-GObject instance.

Returns: (transfer none): a floating reference to a new int32 N-GObject instance

method _g_variant_new_int32 ( Int $value --> N-GObject )

• Int $value; a gint32 value

_g_variant_new_int64

Creates a new int64 N-GObject instance.

Returns: (transfer none): a floating reference to a new int64 N-GObject instance

method _g_variant_new_int64 ( Int $value --> N-GObject )

• Int $value; a gint64 value

_g_variant_new_maybe

Depending on if child is Any, either wraps child inside of a maybe container or creates a Nothing instance for the given type. At least one of child_type and child must be non-Any. If child_type is non-Any then it must be a definite type. If they are both non-Any then child_type must be the type of child. If child is a floating reference (see g_variant_ref_sink()), the new instance takes ownership of child.

Returns: (transfer none): a floating reference to a new N-GObject maybe instance

method _g_variant_new_maybe ( N-GObject $child_type, N-GObject $child --> N-GObject )

• N-GObject $child_type; (nullable): the GVariantType of the child, or Any

• N-GObject $child; (nullable): the child value, or Any

_g_variant_new_object_path

Creates a D-Bus object path N-GObject with the contents of string. string must be a valid D-Bus object path. Use g_variant_is_object_path() if you're not sure.

Returns: (transfer none): a floating reference to a new object path N-GObject instance

method _g_variant_new_object_path (  Str  $object_path --> N-GObject )

• Str $object_path; a normal C nul-terminated string

_g_variant_new_objv

Constructs an array of object paths N-GObject from the given array of strings. Each string must be a valid N-GObject object path; see g_variant_is_object_path(). If length is -1 then strv is Any-terminated.

Returns: (transfer none): a new floating N-GObject instance

method _g_variant_new_objv (  CArray[Str]  $strv, Int $length --> N-GObject )

• CArray[Str] $strv; (array length=length) (element-type utf8): an array of strings

• Int $length; the length of strv, or -1

_g_variant_new_parsed

method _g_variant_new_parsed (  Str  $format --> N-GObject )

• Str $format;

_g_variant_new_parsed_va

method _g_variant_new_parsed_va (  Str  $format, va_list $app --> N-GObject )

• Str $format;

• va_list $app;

_g_variant_new_printf

Creates a string-type GVariant using printf formatting. This is similar to calling g_strdup_printf() and then g_variant_new_string() but it saves a temporary variable and an unnecessary copy.

Returns: (transfer none): a floating reference to a new string N-GObject instance

method _g_variant_new_printf (  Str  $format_string,  $2 --> N-GObject )

• Str $format_string; a printf-style format string @...: arguments for format_string

• $2;

_g_variant_new_signature

Creates a D-Bus type signature N-GObject with the contents of string. string must be a valid D-Bus type signature. Use g_variant_is_signature() if you're not sure.

Returns: (transfer none): a floating reference to a new signature N-GObject instance

method _g_variant_new_signature (  Str  $signature --> N-GObject )

• Str $signature; a normal C nul-terminated string

_g_variant_new_string

Creates a string N-GObject with the contents of string. string must be valid UTF-8, and must not be Any. To encode potentially-Any strings, use g_variant_new() with `ms` as the [format string][gvariant-format-strings-maybe-types].

Returns: (transfer none): a floating reference to a new string N-GObject instance

method _g_variant_new_string (  Str  $string --> N-GObject )

• Str $string; a normal UTF-8 nul-terminated string

_g_variant_new_strv

Constructs an array of strings N-GObject from the given array of strings. If length is -1 then strv is Any-terminated.

Returns: (transfer none): a new floating N-GObject instance

method _g_variant_new_strv (  CArray[Str]  $strv, Int $length --> N-GObject )

• CArray[Str] $strv; (array length=length) (element-type utf8): an array of strings

• Int $length; the length of strv, or -1

_g_variant_new_take_string

Creates a string N-GObject with the contents of string. string must be valid UTF-8, and must not be Any. To encode potentially-Any strings, use this with g_variant_new_maybe(). This function consumes string. g_free() will be called on string when it is no longer required. You must not modify or access string in any other way after passing it to this function. It is even possible that string is immediately freed.

Returns: (transfer none): a floating reference to a new string N-GObject instance

method _g_variant_new_take_string (  Str  $string --> N-GObject )

• Str $string; a normal UTF-8 nul-terminated string

_g_variant_new_tuple

Creates a new tuple N-GObject out of the items in children. The type is determined from the types of children. No entry in the children array may be Any. If n_children is 0 then the unit tuple is constructed. If the children are floating references (see g_variant_ref_sink()), the new instance takes ownership of them as if via g_variant_ref_sink().

Returns: (transfer none): a floating reference to a new N-GObject tuple

method _g_variant_new_tuple (  $GVariant * const *children, UInt $n_children --> N-GObject )

• $GVariant * const *children; (array length=n_children): the items to make the tuple out of

• UInt $n_children; the length of children

_g_variant_new_uint16

Creates a new uint16 N-GObject instance.

Returns: (transfer none): a floating reference to a new uint16 N-GObject instance

method _g_variant_new_uint16 ( UInt $value --> N-GObject )

• UInt $value; a guint16 value

_g_variant_new_uint32

Creates a new uint32 N-GObject instance.

Returns: (transfer none): a floating reference to a new uint32 N-GObject instance

method _g_variant_new_uint32 ( UInt $value --> N-GObject )

• UInt $value; a guint32 value

_g_variant_new_uint64

Creates a new uint64 N-GObject instance.

Returns: (transfer none): a floating reference to a new uint64 N-GObject instance

method _g_variant_new_uint64 ( UInt $value --> N-GObject )

• UInt $value; a guint64 value

_g_variant_new_va

This function is intended to be used by libraries based on N-GObject that want to provide g_variant_new()-like functionality to their users. The API is more general than g_variant_new() to allow a wider range of possible uses. format_string must still point to a valid format string, but it only needs to be nul-terminated if endptr is Any. If endptr is non-Any then it is updated to point to the first character past the end of the format string. app is a pointer to a va_list. The arguments, according to format_string, are collected from this va_list and the list is left pointing to the argument following the last. Note that the arguments in app must be of the correct width for their types specified in format_string when collected into the va_list. See the [GVariant varargs documentation][gvariant-varargs]. These two generalisations allow mixing of multiple calls to g_variant_new_va() and g_variant_get_va() within a single actual varargs call by the user. The return value will be floating if it was a newly created GVariant instance (for example, if the format string was "(ii)"). In the case that the format_string was '*', '?', 'r', or a format starting with '@' then the collected N-GObject pointer will be returned unmodified, without adding any additional references. In order to behave correctly in all cases it is necessary for the calling function to g_variant_ref_sink() the return result before returning control to the user that originally provided the pointer. At this point, the caller will have their own full reference to the result. This can also be done by adding the result to a container, or by passing it to another g_variant_new() call.

Returns: a new, usually floating, N-GObject

method _g_variant_new_va (  Str  $format_string,  CArray[Str]  $endptr, va_list $app --> N-GObject )

• Str $format_string; a string that is prefixed with a format string

• CArray[Str] $endptr; (nullable) (default NULL): location to store the end pointer, or Any

• va_list $app; a pointer to a va_list

_g_variant_new_variant

Boxes value. The result is a N-GObject instance representing a variant containing the original value. If child is a floating reference (see g_variant_ref_sink()), the new instance takes ownership of child.

Returns: (transfer none): a floating reference to a new variant N-GObject instance

method _g_variant_new_variant ( --> N-GObject )