Class Variant

java.lang.Object

org.javagi.base.ProxyInstance

org.gnome.glib.Variant

All Implemented Interfaces:

Proxy

@Generated("org.javagi.JavaGI")
public class Variant
extends ProxyInstance

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

A GVariant 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 GVariant is also immutable: once it’s been created neither its type nor its content can be modified further.

GVariant is useful whenever data needs to be serialized, for example when sending method parameters in D-Bus, or when saving settings using GSettings.

When creating a new GVariant, 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 GVariant holding an integer value you can use:

GVariant *v = g_variant_new ("u", 40);

The string u in the first argument tells GVariant that the data passed to the constructor (40) is going to be an unsigned integer.

More advanced examples of GVariant 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 GVariant is GLib.VariantType.

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

GVariant is reference counted using ref() and unref(). GVariant also has floating reference counts — see refSink().

GVariant is completely threadsafe. A GVariant instance can be concurrently accessed in any way from any number of threads without problems.

GVariant is heavily optimised for dealing with data in serialized form. It works particularly well with data located in memory-mapped files. It can perform nearly all deserialization operations in a small constant time, usually touching only a single memory page. Serialized GVariant data can also be sent over the network.

GVariant is largely compatible with D-Bus. Almost all types of GVariant instances can be sent over D-Bus. See GLib.VariantType for exceptions. (However, GVariant’s serialization format is not the same as the serialization format of a D-Bus message body: use GDBusMessage, in the GIO library, for those.)

For space-efficiency, the GVariant serialization 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 GVariant’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 GLib.MappedFile, and call fromData(VariantType, byte[], boolean, MemorySegment) on it.

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

There is a Python-inspired text language for describing GVariant values. GVariant includes a printer for this language and a parser with type inferencing.

Memory Use

GVariant 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 GVariant can be grouped into 4 broad purposes: memory for serialized data, memory for the type information cache, buffer management memory and memory for the GVariant structure itself.

Serialized Data Memory

This is the memory that is used for storing GVariant data in serialized 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 serialization.

If we add an item ‘width’ that maps to the int32 value of 500 then we will use 4 bytes 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 deserialization.

Continuing with the above example, if a GVariant 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 GVariant.

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 allocation 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 allocation 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 GLib.HashTable to store and look up 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

GVariant uses an internal buffer management structure to deal with the various different possible sources of serialized 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 GVariant. This may involve a GLib.free(MemorySegment) or even MappedFile.unref().

One buffer management structure is used for each chunk of serialized 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 GVariant structure is 6 * (void *). On 32-bit systems, that’s 24 bytes.

GVariant structures only exist if they are explicitly created with API calls. For example, if a GVariant is constructed out of serialized 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 GVariant instance exists — the one referring to the dictionary.

If calls are made to start accessing the other values then GVariant instances will exist for those values only for as long as they are in use (ie: until you call unref()). The type information is shared. The serialized data and the buffer management structure for that serialized 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 serialized data, 16 bytes for buffer management and 24 bytes for the GVariant instance, or a total of 160 bytes, plus allocation overhead. If we were to use getChildValue(long) 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 serialized data and buffer management for those dictionaries, but the type information would be shared.

Since:

2.24

Constructor Summary

Constructors

Constructor	Description
Variant(MemorySegment address)	Create a Variant proxy instance for the provided memory address.
Variant(String formatString, Object... varargs)	Creates a new GVariant instance.

Method Summary

Modifier and Type	Method	Description
static Variant	array(@Nullable VariantType childType, @Nullable Variant @Nullable [] children)	Creates a new GVariant array from children.
static Variant	boolean_(boolean value)	Creates a new boolean GVariant instance -- either true or false.
static Variant	byte_(byte value)	Creates a new byte GVariant instance.
static Variant	bytestring(@Nullable byte @Nullable [] string)	Creates an array-of-bytes GVariant with the contents of string. This function is just like g_variant_new_string() except that the string need not be valid UTF-8.
static Variant	bytestringArray(@Nullable String @Nullable [] strv)	Constructs an array of bytestring GVariant from the given array of strings.
Variant	byteswap()	Performs a byteswapping operation on the contents of value. The result is that all multi-byte numeric data contained in this Variant is byteswapped.
boolean	checkFormatString(String formatString, boolean copyOnly)	Checks if calling g_variant_get() with formatString on this Variant would be valid from a type-compatibility standpoint.
VariantClass	classify()	Classifies this Variant according to its top-level type.
int	compare(Variant two)	Compares this Variant and two.
static Variant	dictEntry(Variant key, Variant value)	Creates a new dictionary entry GVariant.
static Variant	double_(double value)	Creates a new double GVariant instance.
byte[]	dupBytestring()	Similar to g_variant_get_bytestring() except that instead of returning a constant string, the string is duplicated.
String[]	dupBytestringArray()	Gets the contents of an array of array of bytes GVariant.
String[]	dupObjv()	Gets the contents of an array of object paths GVariant.
String	dupString(Out<Long> length)	Similar to g_variant_get_string() except that instead of returning a constant string, the string is duplicated.
String[]	dupStrv()	Gets the contents of an array of strings GVariant.
boolean	equal(Variant two)	Checks if this Variant and two have the same type and value.
static Variant	fixedArray(VariantType elementType, @Nullable MemorySegment elements, long nElements, long elementSize)	Constructs a new array GVariant instance, where the elements are of elementType type.
static Variant	fromBytes(VariantType type, byte[] bytes, boolean trusted)	Constructs a new serialized-mode GVariant instance.
static Variant	fromData(VariantType type, @Nullable byte @Nullable [] data, boolean trusted, @Nullable MemorySegment userData)	Creates a new GVariant instance from serialized data.
void	get(String formatString, Object... varargs)	Deconstructs a GVariant instance.
boolean	getBoolean()	Returns the boolean value of value.
byte	getByte()	Returns the byte value of value.
byte[]	getBytestring()	Returns the string value of a GVariant instance with an array-of-bytes type.
String[]	getBytestringArray()	Gets the contents of an array of array of bytes GVariant.
void	getChild(long index, String formatString, Object... varargs)	Reads a child item out of a container GVariant instance and deconstructs it according to formatString. This call is essentially a combination of g_variant_get_child_value() and g_variant_get().
Variant	getChildValue(long index)	Reads a child item out of a container GVariant instance.
@Nullable MemorySegment	getData()	Returns a pointer to the serialized form of a GVariant instance.
byte[]	getDataAsBytes()	Returns a pointer to the serialized form of a GVariant instance.
double	getDouble()	Returns the double precision floating point value of value.
MemorySegment[]	getFixedArray(long elementSize)	Provides access to the serialized data for an array of fixed-sized items.
int	getHandle()	Returns the 32-bit signed integer value of value.
short	getInt16()	Returns the 16-bit signed integer value of value.
int	getInt32()	Returns the 32-bit signed integer value of value.
long	getInt64()	Returns the 64-bit signed integer value of value.
@Nullable Variant	getMaybe()	Given a maybe-typed GVariant instance, extract its value.
static MemoryLayout	getMemoryLayout()	The memory layout of the native struct.
Variant	getNormalForm()	Gets a GVariant instance that has the same value as this Variant and is trusted to be in normal form.
String[]	getObjv()	Gets the contents of an array of object paths GVariant.
long	getSize()	Determines the number of bytes that would be required to store this Variant with g_variant_store().
String	getString(@Nullable Out<Long> length)	Returns the string value of a GVariant instance with a string type.
String[]	getStrv()	Gets the contents of an array of strings GVariant.
static Type	getType()	Get the GType of the GVariant class
String	getTypeString()	Returns the type string of value. Unlike the result of calling g_variant_type_peek_string(), this string is nul-terminated.
short	getUint16()	Returns the 16-bit unsigned integer value of value.
int	getUint32()	Returns the 32-bit unsigned integer value of value.
long	getUint64()	Returns the 64-bit unsigned integer value of value.
Variant	getVariant()	Unboxes value. The result is the GVariant instance that was contained in value.
VariantType	getVariantType()	Determines the type of value.
static Variant	handle_(int value)	Creates a new handle GVariant instance.
int	hash()	Generates a hash value for a GVariant instance.
static Variant	int16(short value)	Creates a new int16 GVariant instance.
static Variant	int32(int value)	Creates a new int32 GVariant instance.
static Variant	int64(long value)	Creates a new int64 GVariant instance.
boolean	isContainer()	Checks if this Variant is a container.
boolean	isFloating()	Checks whether this Variant has a floating reference count.
boolean	isNormalForm()	Checks if this Variant is in normal form.
static boolean	isObjectPath(String string)	Determines if a given string is a valid D-Bus object path.
boolean	isOfType(VariantType type)	Checks if a value has a type matching the provided type.
static boolean	isSignature(String string)	Determines if a given string is a valid D-Bus type signature.
VariantIter	iterNew()	Creates a heap-allocated GVariantIter for iterating over the items in value.
boolean	lookup(String key, String formatString, Object... varargs)	Looks up a value in a dictionary GVariant.
Variant	lookupValue(String key, @Nullable VariantType expectedType)	Looks up a value in a dictionary GVariant.
static Variant	maybe(@Nullable VariantType childType, @Nullable Variant child)	Depending on if child is null, either wraps child inside of a maybe container or creates a Nothing instance for the given type.
long	nChildren()	Determines the number of children in a container GVariant instance.
static Variant	objectPath(String objectPath)	Creates a D-Bus object path GVariant with the contents of objectPath. objectPath must be a valid D-Bus object path.
static Variant	objv(@Nullable String @Nullable [] strv)	Constructs an array of object paths GVariant from the given array of strings.
static Variant	pack(Object object)	Create a GVariant from a Java Object.
static Variant	parse(@Nullable VariantType type, String text, @Nullable String limit, @Nullable String[] endptr)	Parses a GVariant from a text representation.
static Variant	parsed(String format, Object... varargs)	Parses format and returns the result.
static String	parseErrorPrintContext(GError error, String sourceStr)	Pretty-prints a message showing the context of a GVariant parse error within the string for which parsing was attempted.
static Quark	parseErrorQuark()
static Quark	parserGetErrorQuark()	Deprecated. Use g_variant_parse_error_quark() instead.
String	print(boolean typeAnnotate)	Pretty-prints this Variant in the format understood by g_variant_parse().
static Variant	printf(String formatString, Object... varargs)	Creates a string-type GVariant using printf formatting.
String	printString(@Nullable String string, boolean typeAnnotate)	Behaves as g_variant_print(), but operates on a GString.
Variant	ref()	Increases the reference count of value.
Variant	refSink()	GVariant uses a floating reference count system.
static Variant	signature(String signature)	Creates a D-Bus type signature GVariant with the contents of string. string must be a valid D-Bus type signature.
void	store(MemorySegment data)	Stores the serialized form of this Variant at data. data should be large enough.
static Variant	string(String string)	Creates a string GVariant with the contents of string.
static Variant	strv(@Nullable String @Nullable [] strv)	Constructs an array of strings GVariant from the given array of strings.
Variant	takeRef()	If this Variant is floating, sink it.
static Variant	takeString(String string)	Creates a string GVariant with the contents of string.
String	toString()	Returns a string representation of the object.
static Variant	tuple(@Nullable Variant @Nullable [] children)	Creates a new tuple GVariant out of the items in children. The type is determined from the types of children. No entry in the children array may be null.
static Variant	uint16(short value)	Creates a new uint16 GVariant instance.
static Variant	uint32(int value)	Creates a new uint32 GVariant instance.
static Variant	uint64(long value)	Creates a new uint64 GVariant instance.
Object	unpack()	Unpack a GVariant into a Java Object.
Object	unpackRecursive()	Unpack a GVariant into a Java Object.
void	unref()	Decreases the reference count of value. When its reference count drops to 0, the memory used by the variant is freed.
static Variant	variant(Variant value)	Boxes value. The result is a GVariant instance representing a variant containing the original value.

Methods inherited from class ProxyInstance

equals, handle, hashCode

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Details

Variant

public Variant(MemorySegment address)

Create a Variant proxy instance for the provided memory address.

Parameters:

address - the memory address of the native object

Variant

public Variant(String formatString,
 Object... varargs)

Creates a new GVariant instance.

Think of this function as an analogue to g_strdup_printf().

The type of the created instance and the arguments that are expected by this function are determined by formatString. 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.

The first character of the format string must not be '*' '?' '' or 'r'; in essence, a new GVariant must always be constructed by this function (and not merely passed through it unmodified).

Note that the arguments must be of the correct width for their types specified in formatString. This can be achieved by casting them. See the GVariant varargs documentation.

MyFlags some_flags = FLAG_ONE | FLAG_TWO;
const gchar *some_strings[] = { "a", "b", "c", NULL };
GVariant *new_variant;

new_variant = g_variant_new ("(t^as)",
                             // This cast is required.
                             (guint64) some_flags,
                             some_strings);

Parameters:

formatString - a GVariant format string

varargs - arguments, as per formatString

Since:

2.24

Method Details

getType

public static Type getType()

Get the GType of the GVariant class

Returns:

the GType

getMemoryLayout

public static MemoryLayout getMemoryLayout()

The memory layout of the native struct.

Returns:

the memory layout

array

public static Variant array(@Nullable VariantType childType,
 @Nullable Variant @Nullable [] children)

Creates a new GVariant array from children.

childType must be non-null if nChildren is zero. Otherwise, the child type is determined by inspecting the first element of the children array. If childType is non-null 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 null.

All items in the array must have the same type, which must be the same as childType, 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().

Parameters:

childType - the element type of the new array

children - an array of GVariant pointers, the children

Returns:

a floating reference to a new GVariant array

Since:

2.24

boolean_

public static Variant boolean_(boolean value)

Creates a new boolean GVariant instance -- either true or false.

Parameters:

value - a gboolean value

Returns:

a floating reference to a new boolean GVariant instance

Since:

2.24

byte_

public static Variant byte_(byte value)

Creates a new byte GVariant instance.

Parameters:

value - a guint8 value

Returns:

a floating reference to a new byte GVariant instance

Since:

2.24

bytestring

public static Variant bytestring(@Nullable byte @Nullable [] string)

Creates an array-of-bytes GVariant 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.

Parameters:

string - a normal nul-terminated string in no particular encoding

Returns:

a floating reference to a new bytestring GVariant instance

Since:

2.26

bytestringArray

public static Variant bytestringArray(@Nullable String @Nullable [] strv)

Constructs an array of bytestring GVariant from the given array of strings.

If length is -1 then strv is null-terminated.

Parameters:

strv - an array of strings

Returns:

a new floating GVariant instance

Since:

2.26

dictEntry

public static Variant dictEntry(Variant key,
 Variant value)

Creates a new dictionary entry GVariant. key and value must be non-null. key must be a value of a basic type (ie: not a container).

If the key or value are floating references (see g_variant_ref_sink()), the new instance takes ownership of them as if via g_variant_ref_sink().

Parameters:

key - a basic GVariant, the key

value - a GVariant, the value

Returns:

a floating reference to a new dictionary entry GVariant

Since:

2.24

double_

public static Variant double_(double value)

Creates a new double GVariant instance.

Parameters:

value - a gdouble floating point value

Returns:

a floating reference to a new double GVariant instance

Since:

2.24

fixedArray

public static Variant fixedArray(VariantType elementType,
 @Nullable MemorySegment elements,
 long nElements,
 long elementSize)

Constructs a new array GVariant instance, where the elements are of elementType type.

elements must be an array with fixed-sized elements. Numeric types are fixed-size as are tuples containing only other fixed-sized types.

elementSize 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 serialized data matches the caller's expectation.

nElements must be the length of the elements array.

Parameters:

elementType - the GVariantType of each element

elements - a pointer to the fixed array of contiguous elements

nElements - the number of elements

elementSize - the size of each element

Returns:

a floating reference to a new array GVariant instance

Since:

2.32

fromBytes

public static Variant fromBytes(VariantType type,
 byte[] bytes,
 boolean trusted)

Constructs a new serialized-mode GVariant instance. This is the inner interface for creation of new serialized values that gets called from various functions in gvariant.c.

A reference is taken on bytes.

The data in bytes must be 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.

Parameters:

type - a GVariantType

bytes - a GBytes

trusted - if the contents of bytes are trusted

Returns:

a new GVariant with a floating reference

Since:

2.36

fromData

public static Variant fromData(VariantType type,
 @Nullable byte @Nullable [] data,
 boolean trusted,
 @Nullable MemorySegment userData)

Creates a new GVariant instance from serialized data.

type is the type of GVariant 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 userData. If the contents of data change before that time then the result is undefined.

If data is trusted to be serialized data in normal form then trusted should be true. This applies to serialized 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 false 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 userData 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.

Parameters:

type - a definite GVariantType

data - the serialized data

trusted - true if data is definitely in normal form

userData - data for notify

Returns:

a new floating GVariant of type type

Since:

2.24

handle_

public static Variant handle_(int value)

Creates a new handle GVariant 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.

Parameters:

value - a gint32 value

Returns:

a floating reference to a new handle GVariant instance

Since:

2.24

int16

public static Variant int16(short value)

Creates a new int16 GVariant instance.

Parameters:

value - a gint16 value

Returns:

a floating reference to a new int16 GVariant instance

Since:

2.24

int32

public static Variant int32(int value)

Creates a new int32 GVariant instance.

Parameters:

value - a gint32 value

Returns:

a floating reference to a new int32 GVariant instance

Since:

2.24

int64

public static Variant int64(long value)

Creates a new int64 GVariant instance.

Parameters:

value - a gint64 value

Returns:

a floating reference to a new int64 GVariant instance

Since:

2.24

maybe

public static Variant maybe(@Nullable VariantType childType,
 @Nullable Variant child)

Depending on if child is null, either wraps child inside of a maybe container or creates a Nothing instance for the given type.

At least one of childType and child must be non-null. If childType is non-null then it must be a definite type. If they are both non-null then childType must be the type of child.

If child is a floating reference (see g_variant_ref_sink()), the new instance takes ownership of child.

Parameters:

childType - the GVariantType of the child, or null

child - the child value, or null

Returns:

a floating reference to a new GVariant maybe instance

Since:

2.24

objectPath

public static Variant objectPath(String objectPath)

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

Parameters:

objectPath - a normal C nul-terminated string

Returns:

a floating reference to a new object path GVariant instance

Since:

2.24

objv

public static Variant objv(@Nullable String @Nullable [] strv)

Constructs an array of object paths GVariant from the given array of strings.

Each string must be a valid GVariant object path; see g_variant_is_object_path().

If length is -1 then strv is null-terminated.

Parameters:

strv - an array of strings

Returns:

a new floating GVariant instance

Since:

2.30

parsed

public static Variant parsed(String format,
 Object... varargs)

Parses format and returns the result.

format must be a text format GVariant with one extension: at any point that a value may appear in the text, a '%' character followed by a GVariant format string (as per g_variant_new()) may appear. In that case, the same arguments are collected from the argument list as g_variant_new() would have collected.

Note that the arguments must be of the correct width for their types specified in format. This can be achieved by casting them. See the GVariant varargs documentation.

Consider this simple example:

 g_variant_new_parsed ("[('one', 1), ('two', %i), (%s, 3)]", 2, "three");

In the example, the variable argument parameters are collected and filled in as if they were part of the original string to produce the result of

[('one', 1), ('two', 2), ('three', 3)]

This function is intended only to be used with format as a string literal. Any parse error is fatal to the calling process. If you want to parse data from untrusted sources, use g_variant_parse().

You may not use this function to return, unmodified, a single GVariant pointer from the argument list. ie: format may not solely be anything along the lines of "%*", "%?", "\r", or anything starting with "%".

Parameters:

format - a text format GVariant

varargs - arguments as per format

Returns:

a new floating GVariant instance

printf

public static Variant printf(String formatString,
 Object... varargs)

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.

Parameters:

formatString - a printf-style format string

varargs - arguments for formatString

Returns:

a floating reference to a new string GVariant instance

Since:

2.38

signature

public static Variant signature(String signature)

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

Parameters:

signature - a normal C nul-terminated string

Returns:

a floating reference to a new signature GVariant instance

Since:

2.24

string

public static Variant string(String string)

Creates a string GVariant with the contents of string.

string must be valid UTF-8, and must not be null. To encode potentially-null strings, use g_variant_new() with ms as the format string.

Parameters:

string - a normal UTF-8 nul-terminated string

Returns:

a floating reference to a new string GVariant instance

Since:

2.24

strv

public static Variant strv(@Nullable String @Nullable [] strv)

Constructs an array of strings GVariant from the given array of strings.

If length is -1 then strv is null-terminated.

Parameters:

strv - an array of strings

Returns:

a new floating GVariant instance

Since:

2.24

takeString

public static Variant takeString(String string)

Creates a string GVariant with the contents of string.

string must be valid UTF-8, and must not be null. To encode potentially-null strings, use this with g_variant_new_maybe().

After this call, string belongs to the GVariant and may no longer be modified by the caller. The memory of data has to be dynamically allocated and will eventually be freed with g_free().

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.

Parameters:

string - a normal UTF-8 nul-terminated string

Returns:

a floating reference to a new string GVariant instance

Since:

2.38

tuple

public static Variant tuple(@Nullable Variant @Nullable [] children)

Creates a new tuple GVariant out of the items in children. The type is determined from the types of children. No entry in the children array may be null.

If nChildren 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().

Parameters:

children - the items to make the tuple out of

Returns:

a floating reference to a new GVariant tuple

Since:

2.24

uint16

public static Variant uint16(short value)

Creates a new uint16 GVariant instance.

Parameters:

value - a guint16 value

Returns:

a floating reference to a new uint16 GVariant instance

Since:

2.24

uint32

public static Variant uint32(int value)

Creates a new uint32 GVariant instance.

Parameters:

value - a guint32 value

Returns:

a floating reference to a new uint32 GVariant instance

Since:

2.24

uint64

public static Variant uint64(long value)

Creates a new uint64 GVariant instance.

Parameters:

value - a guint64 value

Returns:

a floating reference to a new uint64 GVariant instance

Since:

2.24

variant

public static Variant variant(Variant value)

Boxes value. The result is a GVariant 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.

Parameters:

value - a GVariant instance

Returns:

a floating reference to a new variant GVariant instance

Since:

2.24

isObjectPath

public static boolean isObjectPath(String string)

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.

Parameters:

string - a normal C nul-terminated string

Returns:

true if string is a D-Bus object path

Since:

2.24

isSignature

public static boolean isSignature(String string)

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.

Parameters:

string - a normal C nul-terminated string

Returns:

true if string is a D-Bus type signature

Since:

2.24

parse

public static Variant parse(@Nullable VariantType type,
 String text,
 @Nullable String limit,
 @Nullable String[] endptr)
                     throws GErrorException

Parses a GVariant from a text representation.

A single GVariant is parsed from the content of text.

The format is described here.

The memory at limit will never be accessed and the parser behaves as if the character at limit is the nul terminator. This has the effect of bounding text.

If endptr is non-null then text is permitted to contain data following the value that this function parses and endptr will be updated to point to the first character past the end of the text parsed by this function. If endptr is null and there is extra data then an error is returned.

If type is non-null then the value will be parsed to have that type. This may result in additional parse errors (in the case that the parsed value doesn't fit the type) but may also result in fewer errors (in the case that the type would have been ambiguous, such as with empty arrays).

In the event that the parsing is successful, the resulting GVariant is returned. It is never floating, and must be freed with unref().

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.

Officially, the language understood by the parser is “any string produced by print(boolean)”. This explicitly includes g_variant_print()’s annotated types like int64 -1000.

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

Parameters:

type - a GVariantType, or null

text - a string containing a GVariant in text form

limit - a pointer to the end of text, or null

endptr - a location to store the end pointer, or null

Returns:

a non-floating reference to a GVariant, or null

Throws:

GErrorException - see GError

parseErrorPrintContext

public static String parseErrorPrintContext(GError error,
 String sourceStr)

Pretty-prints a message showing the context of a GVariant parse error within the string for which parsing was attempted.

The resulting string is suitable for output to the console or other monospace media where newlines are treated in the usual way.

The message will typically look something like one of the following:

unterminated string constant:
  (1, 2, 3, 'abc
            ^^^^

or

unable to find a common type:
  [1, 2, 3, 'str']
   ^        ^^^^^

The format of the message may change in a future version.

error must have come from a failed attempt to g_variant_parse() and sourceStr must be exactly the same string that caused the error. If sourceStr was not nul-terminated when you passed it to g_variant_parse() then you must add nul termination before using this function.

Parameters:

error - a GError from the GVariantParseError domain

sourceStr - the string that was given to the parser

Returns:

the printed message

Since:

2.40

parseErrorQuark

public static Quark parseErrorQuark()

parserGetErrorQuark

@Deprecated
public static Quark parserGetErrorQuark()

Deprecated.

Use g_variant_parse_error_quark() instead.

Same as g_variant_error_quark().

byteswap

public Variant byteswap()

Performs a byteswapping operation on the contents of value. The result is that all multi-byte numeric data contained in this Variant 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).

While this function can safely handle untrusted, non-normal data, it is recommended to check whether the input is in normal form beforehand, using g_variant_is_normal_form(), and to reject non-normal inputs if your application can be strict about what inputs it rejects.

The returned value is always in normal form and is marked as trusted. A full, not floating, reference is returned.

Returns:

the byteswapped form of this Variant

Since:

2.24

checkFormatString

public boolean checkFormatString(String formatString,
 boolean copyOnly)

Checks if calling g_variant_get() with formatString on this Variant would be valid from a type-compatibility standpoint. formatString is assumed to be a valid format string (from a syntactic standpoint).

If copyOnly is true then this function additionally checks that it would be safe to call g_variant_unref() on this Variant 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 GVariant instance). If this check fails then a g_critical() is printed and false is returned.

This function is meant to be used by functions that wish to provide varargs accessors to GVariant values of uncertain values (eg: g_variant_lookup() or g_menu_model_get_item_attribute()).

Parameters:

formatString - a valid GVariant format string

copyOnly - true to ensure the format string makes deep copies

Returns:

true if formatString is safe to use

Since:

2.34

classify

public VariantClass classify()

Classifies this Variant according to its top-level type.

Returns:

the GVariantClass of this Variant

Since:

2.24

compare

public int compare(Variant two)

Compares this Variant and two.

The types of this Variant and two are gconstpointer only to allow use of this function with GTree, GPtrArray, etc. They must each be a GVariant.

Comparison is only defined for basic types (ie: booleans, numbers, strings). For booleans, false is less than true. 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.

Parameters:

two - a GVariant instance of the same type

Returns:

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

Since:

2.26

dupBytestring

public byte[] dupBytestring()

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:

a newly allocated string

Since:

2.26

dupBytestringArray

public String[] dupBytestringArray()

Gets the contents of an array of array of bytes GVariant. This call makes a deep copy; the return result should be released with g_strfreev().

If length is non-null then the number of elements in the result is stored there. In any case, the resulting array will be null-terminated.

For an empty array, length will be set to 0 and a pointer to a null pointer will be returned.

Returns:

an array of strings

Since:

2.26

dupObjv

public String[] dupObjv()

Gets the contents of an array of object paths GVariant. This call makes a deep copy; the return result should be released with g_strfreev().

If length is non-null then the number of elements in the result is stored there. In any case, the resulting array will be null-terminated.

For an empty array, length will be set to 0 and a pointer to a null pointer will be returned.

Returns:

an array of strings

Since:

2.30

dupString

public String dupString(Out<Long> length)

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().

Parameters:

length - a pointer to a gsize, to store the length

Returns:

a newly allocated string, UTF-8 encoded

Since:

2.24

dupStrv

public String[] dupStrv()

Gets the contents of an array of strings GVariant. This call makes a deep copy; the return result should be released with g_strfreev().

If length is non-null then the number of elements in the result is stored there. In any case, the resulting array will be null-terminated.

For an empty array, length will be set to 0 and a pointer to a null pointer will be returned.

Returns:

an array of strings

Since:

2.24

equal

public boolean equal(Variant two)

Checks if this Variant and two have the same type and value.

The types of this Variant and two are gconstpointer only to allow use of this function with GHashTable. They must each be a GVariant.

Parameters:

two - a GVariant instance

Returns:

true if this Variant and two are equal

Since:

2.24

get

public void get(String formatString,
 Object... varargs)

Deconstructs a GVariant instance.

Think of this function as an analogue to scanf().

The arguments that are expected by this function are entirely determined by formatString. formatString 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.

formatString 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.

Parameters:

formatString - a GVariant format string

varargs - arguments, as per formatString

Since:

2.24

getBoolean

public boolean getBoolean()

Returns the boolean value of value.

It is an error to call this function with a this Variant of any type other than G_VARIANT_TYPE_BOOLEAN.

Returns:

true or false

Since:

2.24

getByte

public byte getByte()

Returns the byte value of value.

It is an error to call this function with a this Variant of any type other than G_VARIANT_TYPE_BYTE.

Returns:

a guint8

Since:

2.24

getBytestring

public byte[] getBytestring()

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

If the array does not end with a nul terminator character, the empty string is returned. For this reason, you can always trust that a non-null nul-terminated string will be returned by this function.

If the array contains a nul terminator character somewhere other than the last byte then the returned string is the string, up to the first such nul character.

g_variant_get_fixed_array() should be used instead if the array contains arbitrary data that could not be nul-terminated or could contain nul bytes.

It is an error to call this function with a this Variant that is not an array of bytes.

The return value remains valid as long as this Variant exists.

Returns:

the constant string

Since:

2.26

getBytestringArray

public String[] getBytestringArray()

Gets the contents of an array of array of bytes GVariant. 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-null then the number of elements in the result is stored there. In any case, the resulting array will be null-terminated.

For an empty array, length will be set to 0 and a pointer to a null pointer will be returned.

Returns:

an array of constant strings

Since:

2.26

getChild

public void getChild(long index,
 String formatString,
 Object... varargs)

Reads a child item out of a container GVariant instance and deconstructs it according to formatString. This call is essentially a combination of g_variant_get_child_value() and g_variant_get().

formatString 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.

Parameters:

index - the index of the child to deconstruct

formatString - a GVariant format string

varargs - arguments, as per formatString

Since:

2.24

getChildValue

public Variant getChildValue(long index)

Reads a child item out of a container GVariant instance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type of GVariant.

It is an error if index is greater than the number of child items in the container. See g_variant_n_children().

The returned value is never floating. You should free it with g_variant_unref() when you're done with it.

Note that values borrowed from the returned child are not guaranteed to still be valid after the child is freed even if you still hold a reference to value, if this Variant has not been serialized at the time this function is called. To avoid this, you can serialize this Variant by calling g_variant_get_data() and optionally ignoring the return value.

There may be implementation specific restrictions on deeply nested values, which would result in the unit tuple being returned as the child value, instead of further nested children. GVariant is guaranteed to handle nesting up to at least 64 levels.

This function is O(1).

Parameters:

index - the index of the child to fetch

Returns:

the child at the specified index

Since:

2.24

getData

public @Nullable MemorySegment getData()

Returns a pointer to the serialized form of a GVariant instance. The returned data may not be in fully-normalised form if read from an untrusted source. The returned data must not be freed; it remains valid for as long as this Variant exists.

If this Variant is a fixed-sized value that was deserialized from a corrupted serialized container then null may be returned. In this case, the proper thing to do is typically to use the appropriate number of nul bytes in place of value. If this Variant is not fixed-sized then null is never returned.

In the case that this Variant is already in serialized form, this function is O(1). If the value is not already in serialized form, serialization occurs implicitly and is approximately O(n) in the size of the result.

To deserialize the data returned by this function, in addition to the serialized data, you must know the type of the GVariant, and (if the machine might be different) the endianness of the machine that stored it. As a result, file formats or network messages that incorporate serialized GVariants must include this information either implicitly (for instance "the file always contains a G_VARIANT_TYPE_VARIANT and it is always in little-endian order") or explicitly (by storing the type and/or endianness in addition to the serialized data).

Returns:

the serialized form of value, or null

Since:

2.24

getDataAsBytes

public byte[] getDataAsBytes()

Returns a pointer to the serialized form of a GVariant instance. The semantics of this function are exactly the same as g_variant_get_data(), except that the returned GBytes holds a reference to the variant data.

Returns:

A new GBytes representing the variant data

Since:

2.36

getDouble

public double getDouble()

Returns the double precision floating point value of value.

It is an error to call this function with a this Variant of any type other than G_VARIANT_TYPE_DOUBLE.

Returns:

a gdouble

Since:

2.24

getFixedArray

public MemorySegment[] getFixedArray(long elementSize)

Provides access to the serialized data for an array of fixed-sized items.

this Variant must be an array with fixed-sized elements. Numeric types are fixed-size, as are tuples containing only other fixed-sized types.

elementSize must be the size of a single element in the array, as given by the section on serialized data memory.

In particular, arrays of these fixed-sized types can be interpreted as an array of the given C type, with elementSize 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 serialized data matches the caller's expectation.

nElements, which must be non-null, is set equal to the number of items in the array.

Parameters:

elementSize - the size of each element

Returns:

a pointer to the fixed array

Since:

2.24

getHandle

public int getHandle()

Returns the 32-bit signed integer value of value.

It is an error to call this function with a this Variant 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

Since:

2.24

getInt16

public short getInt16()

Returns the 16-bit signed integer value of value.

It is an error to call this function with a this Variant of any type other than G_VARIANT_TYPE_INT16.

Returns:

a gint16

Since:

2.24

getInt32

public int getInt32()

Returns the 32-bit signed integer value of value.

It is an error to call this function with a this Variant of any type other than G_VARIANT_TYPE_INT32.

Returns:

a gint32

Since:

2.24

getInt64

public long getInt64()

Returns the 64-bit signed integer value of value.

It is an error to call this function with a this Variant of any type other than G_VARIANT_TYPE_INT64.

Returns:

a gint64

Since:

2.24

getMaybe

public @Nullable Variant getMaybe()

Given a maybe-typed GVariant instance, extract its value. If the value is Nothing, then this function returns null.

Returns:

the contents of value, or null

Since:

2.24

getNormalForm

public Variant getNormalForm()

Gets a GVariant instance that has the same value as this Variant and is trusted to be in normal form.

If this Variant is already trusted to be in normal form then a new reference to this Variant is returned.

If this Variant 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 this Variant is found not to be in normal form then a new trusted GVariant is created with the same value as value. The non-normal parts of this Variant will be replaced with default values which are guaranteed to be in normal form.

It makes sense to call this function if you've received GVariant data from untrusted sources and you want to ensure your serialized output is definitely in normal form.

If this Variant is already in normal form, a new reference will be returned (which will be floating if this Variant is floating). If it is not in normal form, the newly created GVariant 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:

a trusted GVariant

Since:

2.24

getObjv

public String[] getObjv()

Gets the contents of an array of object paths GVariant. 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-null then the number of elements in the result is stored there. In any case, the resulting array will be null-terminated.

For an empty array, length will be set to 0 and a pointer to a null pointer will be returned.

Returns:

an array of constant strings

Since:

2.30

getSize

public long getSize()

Determines the number of bytes that would be required to store this Variant with g_variant_store().

If this Variant has a fixed-sized type then this function always returned that fixed size.

In the case that this Variant is already in serialized form or the size has already been calculated (ie: this function has been called before) then this function is O(1). Otherwise, the size is calculated, an operation which is approximately O(n) in the number of values involved.

Returns:

the serialized size of this Variant

Since:

2.24

getString

public String getString(@Nullable Out<Long> length)

Returns the string value of a GVariant instance with a string type. This includes the types G_VARIANT_TYPE_STRING, G_VARIANT_TYPE_OBJECT_PATH and G_VARIANT_TYPE_SIGNATURE.

The string will always be UTF-8 encoded, will never be null, and will never contain nul bytes.

If length is non-null then the length of the string (in bytes) is returned there. For trusted values, this information is already known. Untrusted values will be validated and, if valid, a strlen() will be performed. If invalid, a default value will be returned — for G_VARIANT_TYPE_OBJECT_PATH, this is "/", and for other types it is the empty string.

It is an error to call this function with a this Variant of any type other than those three.

The return value remains valid as long as this Variant exists.

Parameters:

length - a pointer to a gsize, to store the length

Returns:

the constant string, UTF-8 encoded

Since:

2.24

getStrv

public String[] getStrv()

Gets the contents of an array of strings GVariant. 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-null then the number of elements in the result is stored there. In any case, the resulting array will be null-terminated.

For an empty array, length will be set to 0 and a pointer to a null pointer will be returned.

Returns:

an array of constant strings

Since:

2.24

getVariantType

public VariantType getVariantType()

Determines the type of value.

The return value is valid for the lifetime of this Variant and must not be freed.

Returns:

a GVariantType

Since:

2.24

getTypeString

public String getTypeString()

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 GVariant and must not be freed.

Returns:

the type string for the type of this Variant

Since:

2.24

getUint16

public short getUint16()

Returns the 16-bit unsigned integer value of value.

It is an error to call this function with a this Variant of any type other than G_VARIANT_TYPE_UINT16.

Returns:

a guint16

Since:

2.24

getUint32

public int getUint32()

Returns the 32-bit unsigned integer value of value.

It is an error to call this function with a this Variant of any type other than G_VARIANT_TYPE_UINT32.

Returns:

a guint32

Since:

2.24

getUint64

public long getUint64()

Returns the 64-bit unsigned integer value of value.

It is an error to call this function with a this Variant of any type other than G_VARIANT_TYPE_UINT64.

Returns:

a guint64

Since:

2.24

getVariant

public Variant getVariant()

Unboxes value. The result is the GVariant instance that was contained in value.

Returns:

the item contained in the variant

Since:

2.24

hash

public int hash()

Generates a hash value for a GVariant 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 this Variant is gconstpointer only to allow use of this function with GHashTable. this Variant must be a GVariant.

Returns:

a hash value corresponding to this Variant

Since:

2.24

isContainer

public boolean isContainer()

Checks if this Variant is a container.

Returns:

true if this Variant is a container

Since:

2.24

isFloating

public boolean isFloating()

Checks whether this Variant has a floating reference count.

This function should only ever be used to assert that a given variant is or is not floating, or for debug purposes. To acquire a reference to a variant that might be floating, always use g_variant_ref_sink() or g_variant_take_ref().

See g_variant_ref_sink() for more information about floating reference counts.

Returns:

whether this Variant is floating

Since:

2.26

isNormalForm

public boolean isNormalForm()

Checks if this Variant is in normal form.

The main reason to do this is to detect if a given chunk of serialized data is in normal form: load the data into a GVariant using g_variant_new_from_data() and then use this function to check.

If this Variant is found to be in normal form then it will be marked as being trusted. If the value was already marked as being trusted then this function will immediately return true.

There may be implementation specific restrictions on deeply nested values. GVariant is guaranteed to handle nesting up to at least 64 levels.

Returns:

true if this Variant is in normal form

Since:

2.24

isOfType

public boolean isOfType(VariantType type)

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

Parameters:

type - a GVariantType

Returns:

true if the type of this Variant matches type

Since:

2.24

iterNew

public VariantIter iterNew()

Creates a heap-allocated GVariantIter for iterating over the items in value.

Use g_variant_iter_free() to free the return value when you no longer need it.

A reference is taken to this Variant and will be released only when g_variant_iter_free() is called.

Returns:

a new heap-allocated GVariantIter

Since:

2.24

lookup

public boolean lookup(String key,
 String formatString,
 Object... varargs)

Looks up a value in a dictionary GVariant.

This function is a wrapper around g_variant_lookup_value() and g_variant_get(). In the case that null would have been returned, this function returns false. Otherwise, it unpacks the returned value and returns true.

formatString 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.

This function is currently implemented with a linear scan. If you plan to do many lookups then GVariantDict may be more efficient.

Parameters:

key - the key to look up in the dictionary

formatString - a GVariant format string

varargs - the arguments to unpack the value into

Returns:

true if a value was unpacked

Since:

2.28

lookupValue

public Variant lookupValue(String key,
 @Nullable VariantType expectedType)

Looks up a value in a dictionary GVariant.

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 this Variant has the type a{sv}, the expectedType 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 null is returned. In the event that this Variant has a value type other than v then expectedType 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, null is returned.

If the key is found and the value has the correct type, it is returned. If expectedType was specified then any non-null return value will have this type.

This function is currently implemented with a linear scan. If you plan to do many lookups then VariantDict may be more efficient.

Parameters:

key - the key to look up in the dictionary

expectedType - a GVariantType, or null

Returns:

the value of the dictionary key, or null

Since:

2.28

nChildren

public long nChildren()

Determines the number of children in a container GVariant instance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type of GVariant.

For variants, the return value is always 1. For values with maybe types, it is always zero or one. For arrays, it is the length of the array. For tuples it is the number of tuple items (which depends only on the type). For dictionary entries, it is always 2

This function is O(1).

Returns:

the number of children in the container

Since:

2.24

print

public String print(boolean typeAnnotate)

Pretty-prints this Variant in the format understood by g_variant_parse().

The format is described here.

If typeAnnotate is true, then type information is included in the output.

Parameters:

typeAnnotate - true if type information should be included in the output

Returns:

a newly-allocated string holding the result.

Since:

2.24

printString

public String printString(@Nullable String string,
 boolean typeAnnotate)

Behaves as g_variant_print(), but operates on a GString.

If string is non-null then it is appended to and returned. Else, a new empty GString is allocated and it is returned.

Parameters:

string - a GString, or null

typeAnnotate - true if type information should be included in the output

Returns:

a GString containing the string

Since:

2.24

ref

public Variant ref()

Increases the reference count of value.

Returns:

the same this Variant

Since:

2.24

refSink

public Variant refSink()

GVariant uses a floating reference count system. All functions with names starting with g_variant_new_ return floating references.

Calling g_variant_ref_sink() on a GVariant with a floating reference will convert the floating reference into a full reference. Calling g_variant_ref_sink() on a non-floating GVariant results in an additional normal reference being added.

In other words, if the this Variant is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference. If the this Variant is not floating, then this call adds a new normal reference increasing the reference count by one.

All calls that result in a GVariant instance being inserted into a container will call g_variant_ref_sink() on the instance. This means that if the value was just created (and has only its floating reference) then the container will assume sole ownership of the value at that point and the caller will not need to unreference it. This makes certain common styles of programming much easier while still maintaining normal refcounting semantics in situations where values are not floating.

Returns:

the same this Variant

Since:

2.24

store

public void store(MemorySegment data)

Stores the serialized form of this Variant at data. data should be large enough. See g_variant_get_size().

The stored data is in machine native byte order but may not be in fully-normalised form if read from an untrusted source. See g_variant_get_normal_form() for a solution.

As with g_variant_get_data(), to be able to deserialize the serialized variant successfully, its type and (if the destination machine might be different) its endianness must also be available.

This function is approximately O(n) in the size of data.

Parameters:

data - the location to store the serialized data at

Since:

2.24

takeRef

public Variant takeRef()

If this Variant is floating, sink it. Otherwise, do nothing.

Typically you want to use g_variant_ref_sink() in order to automatically do the correct thing with respect to floating or non-floating references, but there is one specific scenario where this function is helpful.

The situation where this function is helpful is when creating an API that allows the user to provide a callback function that returns a GVariant. We certainly want to allow the user the flexibility to return a non-floating reference from this callback (for the case where the value that is being returned already exists).

At the same time, the style of the GVariant API makes it likely that for newly-created GVariant instances, the user can be saved some typing if they are allowed to return a GVariant with a floating reference.

Using this function on the return value of the user's callback allows the user to do whichever is more convenient for them. The caller will always receives exactly one full reference to the value: either the one that was returned in the first place, or a floating reference that has been converted to a full reference.

This function has an odd interaction when combined with g_variant_ref_sink() running at the same time in another thread on the same GVariant instance. If g_variant_ref_sink() runs first then the result will be that the floating reference is converted to a hard reference. If g_variant_take_ref() runs first then the result will be that the floating reference is converted to a hard reference and an additional reference on top of that one is added. It is best to avoid this situation.

Returns:

the same this Variant

unref

public void unref()

Decreases the reference count of value. When its reference count drops to 0, the memory used by the variant is freed.

Since:

2.24

toString

public String toString()

Returns a string representation of the object.

Overrides:

toString in class Object

Returns:

a string representation of the object

pack

public static Variant pack(Object object)

Create a GVariant from a Java Object.

Parameters:

object - the Java Object to pack into a GVariant

Returns:

the GVariant with the packed Object

See Also:

• Variants.pack(Object)

unpack

public Object unpack()

Unpack a GVariant into a Java Object.

Returns:

the unpacked Java Object

See Also:

• Variants.unpack(Variant, boolean)

unpackRecursive

public Object unpackRecursive()

Unpack a GVariant into a Java Object. Nested GVariants are recursively unpacked.

Returns:

the unpacked Java Object

See Also:

• Variants.unpack(Variant, boolean)