Class Variant
- All Implemented Interfaces:
Proxy
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(org.gnome.glib.VariantType, byte[], boolean, java.lang.foreign.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(java.lang.foreign.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
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Constructor Summary
ConstructorsConstructorDescriptionVariant(MemorySegment address) Create a Variant proxy instance for the provided memory address.Creates a newGVariantinstance. -
Method Summary
Modifier and TypeMethodDescriptionstatic Variantarray(@Nullable VariantType childType, @Nullable Variant @Nullable [] children) Creates a newGVariantarray fromchildren.static Variantboolean_(boolean value) Creates a new booleanGVariantinstance -- eithertrueorfalse.static Variantbyte_(byte value) Creates a new byteGVariantinstance.static Variantbytestring(@org.jspecify.annotations.Nullable byte @Nullable [] string) Creates an array-of-bytesGVariantwith the contents ofstring.This function is just like g_variant_new_string() except that the string need not be valid UTF-8.static VariantbytestringArray(@Nullable String @Nullable [] strv) Constructs an array of bytestringGVariantfrom the given array of strings.byteswap()Performs a byteswapping operation on the contents ofvalue.The result is that all multi-byte numeric data contained in this Variant is byteswapped.booleancheckFormatString(String formatString, boolean copyOnly) Checks if calling g_variant_get() withformatStringon this Variant would be valid from a type-compatibility standpoint.classify()Classifies this Variant according to its top-level type.intCompares this Variant andtwo.static VariantCreates a new dictionary entryGVariant.static Variantdouble_(double value) Creates a new doubleGVariantinstance.byte[]Similar to g_variant_get_bytestring() except that instead of returning a constant string, the string is duplicated.String[]Gets the contents of an array of array of bytesGVariant.String[]dupObjv()Gets the contents of an array of object pathsGVariant.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 stringsGVariant.booleanChecks if this Variant andtwohave the same type and value.static VariantfixedArray(VariantType elementType, @Nullable MemorySegment elements, long nElements, long elementSize) Constructs a new arrayGVariantinstance, where the elements are ofelementTypetype.static VariantfromBytes(VariantType type, byte[] bytes, boolean trusted) Constructs a new serialized-modeGVariantinstance.static VariantfromData(VariantType type, @org.jspecify.annotations.Nullable byte @Nullable [] data, boolean trusted, @Nullable MemorySegment userData) Creates a newGVariantinstance from serialized data.voidDeconstructs aGVariantinstance.booleanReturns the boolean value ofvalue.bytegetByte()Returns the byte value ofvalue.byte[]Returns the string value of aGVariantinstance with an array-of-bytes type.String[]Gets the contents of an array of array of bytesGVariant.voidReads a child item out of a containerGVariantinstance and deconstructs it according toformatString.This call is essentially a combination of g_variant_get_child_value() and g_variant_get().getChildValue(long index) Reads a child item out of a containerGVariantinstance.@Nullable MemorySegmentgetData()Returns a pointer to the serialized form of aGVariantinstance.byte[]Returns a pointer to the serialized form of aGVariantinstance.doubleReturns the double precision floating point value ofvalue.getFixedArray(long elementSize) Provides access to the serialized data for an array of fixed-sized items.intReturns the 32-bit signed integer value ofvalue.shortgetInt16()Returns the 16-bit signed integer value ofvalue.intgetInt32()Returns the 32-bit signed integer value ofvalue.longgetInt64()Returns the 64-bit signed integer value ofvalue.@Nullable VariantgetMaybe()Given a maybe-typedGVariantinstance, extract its value.Gets aGVariantinstance 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 pathsGVariant.longgetSize()Determines the number of bytes that would be required to store this Variant with g_variant_store().Returns the string value of aGVariantinstance with a string type.String[]getStrv()Gets the contents of an array of stringsGVariant.static TypegetType()Get the GType of the GVariant classReturns the type string ofvalue.Unlike the result of calling g_variant_type_peek_string(), this string is nul-terminated.shortReturns the 16-bit unsigned integer value ofvalue.intReturns the 32-bit unsigned integer value ofvalue.longReturns the 64-bit unsigned integer value ofvalue.Unboxesvalue.The result is theGVariantinstance that was contained invalue.Determines the type ofvalue.static Varianthandle_(int value) Creates a new handleGVariantinstance.inthash()Generates a hash value for aGVariantinstance.static Variantint16(short value) Creates a new int16GVariantinstance.static Variantint32(int value) Creates a new int32GVariantinstance.static Variantint64(long value) Creates a new int64GVariantinstance.booleanChecks if this Variant is a container.booleanChecks whether this Variant has a floating reference count.booleanChecks if this Variant is in normal form.static booleanisObjectPath(String string) Determines if a given string is a valid D-Bus object path.booleanisOfType(VariantType type) Checks if a value has a type matching the provided type.static booleanisSignature(String string) Determines if a given string is a valid D-Bus type signature.iterNew()Creates a heap-allocatedGVariantIterfor iterating over the items invalue.booleanLooks up a value in a dictionaryGVariant.lookupValue(String key, @Nullable VariantType expectedType) Looks up a value in a dictionaryGVariant.static Variantmaybe(@Nullable VariantType childType, @Nullable Variant child) Depending on ifchildisnull, either wrapschildinside of a maybe container or creates a Nothing instance for the giventype.longDetermines the number of children in a containerGVariantinstance.static VariantobjectPath(String objectPath) Creates a D-Bus object pathGVariantwith the contents ofobjectPath.objectPathmust be a valid D-Bus object path.static VariantConstructs an array of object pathsGVariantfrom the given array of strings.static VariantCreate a GVariant from a Java Object.static Variantparse(@Nullable VariantType type, String text, @Nullable String limit, @Nullable String[] endptr) Parses aGVariantfrom a text representation.static VariantParsesformatand returns the result.static StringparseErrorPrintContext(GError error, String sourceStr) Pretty-prints a message showing the context of aGVariantparse error within the string for which parsing was attempted.static Quarkstatic QuarkDeprecated.Use g_variant_parse_error_quark() instead.print(boolean typeAnnotate) Pretty-prints this Variant in the format understood by g_variant_parse().static VariantCreates a string-type GVariant using printf formatting.printString(@Nullable String string, boolean typeAnnotate) Behaves as g_variant_print(), but operates on aGString.ref()Increases the reference count ofvalue.refSink()GVariantuses a floating reference count system.static VariantCreates a D-Bus type signatureGVariantwith the contents ofstring.stringmust be a valid D-Bus type signature.voidstore(MemorySegment data) Stores the serialized form of this Variant atdata.datashould be large enough.static VariantCreates a stringGVariantwith the contents ofstring.static VariantConstructs an array of stringsGVariantfrom the given array of strings.takeRef()If this Variant is floating, sink it.static VarianttakeString(String string) Creates a stringGVariantwith the contents ofstring.toString()Returns a string representation of the object.static VariantCreates a new tupleGVariantout of the items inchildren.The type is determined from the types ofchildren.No entry in thechildrenarray may benull.static Variantuint16(short value) Creates a new uint16GVariantinstance.static Variantuint32(int value) Creates a new uint32GVariantinstance.static Variantuint64(long value) Creates a new uint64GVariantinstance.unpack()Unpack a GVariant into a Java Object.Unpack a GVariant into a Java Object.voidunref()Decreases the reference count ofvalue.When its reference count drops to 0, the memory used by the variant is freed.static VariantBoxesvalue.The result is aGVariantinstance representing a variant containing the original value.Methods inherited from class org.javagi.base.ProxyInstance
equals, handle, hashCode
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Constructor Details
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Variant
Create a Variant proxy instance for the provided memory address.- Parameters:
address- the memory address of the native object
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Variant
Creates a newGVariantinstance.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 newGVariantmust 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- aGVariantformat stringvarargs- arguments, as performatString- Since:
- 2.24
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Method Details
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getType
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array
public static Variant array(@Nullable VariantType childType, @Nullable Variant @Nullable [] children) Creates a newGVariantarray fromchildren.childTypemust be non-nullifnChildrenis zero. Otherwise, the child type is determined by inspecting the first element of thechildrenarray. IfchildTypeis non-nullthen it must be a definite type.The items of the array are taken from the
childrenarray. No entry in thechildrenarray may benull.All items in the array must have the same type, which must be the same as
childType,if given.If the
childrenare 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 arraychildren- an array ofGVariantpointers, the children- Returns:
- a floating reference to a new
GVariantarray - Since:
- 2.24
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boolean_
Creates a new booleanGVariantinstance -- eithertrueorfalse.- Parameters:
value- agbooleanvalue- Returns:
- a floating reference to a new boolean
GVariantinstance - Since:
- 2.24
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byte_
Creates a new byteGVariantinstance.- Parameters:
value- aguint8value- Returns:
- a floating reference to a new byte
GVariantinstance - Since:
- 2.24
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bytestring
Creates an array-of-bytesGVariantwith the contents ofstring.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
GVariantinstance - Since:
- 2.26
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bytestringArray
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dictEntry
Creates a new dictionary entryGVariant.keyandvaluemust be non-null.keymust be a value of a basic type (ie: not a container).If the
keyorvalueare floating references (see g_variant_ref_sink()), the new instance takes ownership of them as if via g_variant_ref_sink().- Parameters:
key- a basicGVariant, the keyvalue- aGVariant, the value- Returns:
- a floating reference to a new dictionary entry
GVariant - Since:
- 2.24
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double_
Creates a new doubleGVariantinstance.- Parameters:
value- agdoublefloating point value- Returns:
- a floating reference to a new double
GVariantinstance - Since:
- 2.24
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fixedArray
public static Variant fixedArray(VariantType elementType, @Nullable MemorySegment elements, long nElements, long elementSize) Constructs a new arrayGVariantinstance, where the elements are ofelementTypetype.elementsmust be an array with fixed-sized elements. Numeric types are fixed-size as are tuples containing only other fixed-sized types.elementSizemust 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.nElementsmust be the length of theelementsarray.- Parameters:
elementType- theGVariantTypeof each elementelements- a pointer to the fixed array of contiguous elementsnElements- the number of elementselementSize- the size of each element- Returns:
- a floating reference to a new array
GVariantinstance - Since:
- 2.32
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fromBytes
Constructs a new serialized-modeGVariantinstance. 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
bytesmust be aligned appropriately for thetypebeing 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- aGVariantTypebytes- aGBytestrusted- if the contents ofbytesare trusted- Returns:
- a new
GVariantwith a floating reference - Since:
- 2.36
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fromData
public static Variant fromData(VariantType type, @org.jspecify.annotations.Nullable byte @Nullable [] data, boolean trusted, @Nullable MemorySegment userData) Creates a newGVariantinstance from serialized data.typeis the type ofGVariantinstance that will be constructed. The interpretation ofdatadepends on knowing the type.datais not modified by this function and must remain valid with an unchanging value until such a time asnotifyis called withuserData.If the contents ofdatachange before that time then the result is undefined.If
datais trusted to be serialized data in normal form thentrustedshould betrue. 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 tofalseifdatais read from the network, a file in the user's home directory, etc.If
datawas 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.notifywill be called withuserDatawhendatais no longer needed. The exact time of this call is unspecified and might even be before this function returns.Note:
datamust be backed by memory that is aligned appropriately for thetypebeing 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 definiteGVariantTypedata- the serialized datatrusted-trueifdatais definitely in normal formuserData- data fornotify- Returns:
- a new floating
GVariantof typetype - Since:
- 2.24
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handle_
Creates a new handleGVariantinstance.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- agint32value- Returns:
- a floating reference to a new handle
GVariantinstance - Since:
- 2.24
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int16
Creates a new int16GVariantinstance.- Parameters:
value- agint16value- Returns:
- a floating reference to a new int16
GVariantinstance - Since:
- 2.24
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int32
Creates a new int32GVariantinstance.- Parameters:
value- agint32value- Returns:
- a floating reference to a new int32
GVariantinstance - Since:
- 2.24
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int64
Creates a new int64GVariantinstance.- Parameters:
value- agint64value- Returns:
- a floating reference to a new int64
GVariantinstance - Since:
- 2.24
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maybe
Depending on ifchildisnull, either wrapschildinside of a maybe container or creates a Nothing instance for the giventype.At least one of
childTypeandchildmust be non-null. IfchildTypeis non-nullthen it must be a definite type. If they are both non-nullthenchildTypemust be the type ofchild.If
childis a floating reference (see g_variant_ref_sink()), the new instance takes ownership ofchild.- Parameters:
childType- theGVariantTypeof the child, ornullchild- the child value, ornull- Returns:
- a floating reference to a new
GVariantmaybe instance - Since:
- 2.24
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objectPath
Creates a D-Bus object pathGVariantwith the contents ofobjectPath.objectPathmust 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
GVariantinstance - Since:
- 2.24
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objv
Constructs an array of object pathsGVariantfrom the given array of strings.Each string must be a valid
GVariantobject path; see g_variant_is_object_path().If
lengthis -1 thenstrvisnull-terminated.- Parameters:
strv- an array of strings- Returns:
- a new floating
GVariantinstance - Since:
- 2.30
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parsed
Parsesformatand returns the result.formatmust be a text formatGVariantwith 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
formatas 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
GVariantpointer from the argument list. ie:formatmay not solely be anything along the lines of "%*", "%?", "\\r", or anything starting with "%".- Parameters:
format- a text formatGVariantvarargs- arguments as performat- Returns:
- a new floating
GVariantinstance
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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.
- Parameters:
formatString- a printf-style format stringvarargs- arguments forformatString- Returns:
- a floating reference to a new string
GVariantinstance - Since:
- 2.38
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signature
Creates a D-Bus type signatureGVariantwith the contents ofstring.stringmust 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
GVariantinstance - Since:
- 2.24
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string
Creates a stringGVariantwith the contents ofstring.stringmust be valid UTF-8, and must not benull. To encode potentially-nullstrings, use g_variant_new() withmsas the format string.- Parameters:
string- a normal UTF-8 nul-terminated string- Returns:
- a floating reference to a new string
GVariantinstance - Since:
- 2.24
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strv
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takeString
Creates a stringGVariantwith the contents ofstring.stringmust be valid UTF-8, and must not benull. To encode potentially-nullstrings, use this with g_variant_new_maybe().After this call,
stringbelongs to theGVariantand may no longer be modified by the caller. The memory ofdatahas to be dynamically allocated and will eventually be freed with g_free().You must not modify or access
stringin any other way after passing it to this function. It is even possible thatstringis immediately freed.- Parameters:
string- a normal UTF-8 nul-terminated string- Returns:
- a floating reference to a new string
GVariantinstance - Since:
- 2.38
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tuple
Creates a new tupleGVariantout of the items inchildren.The type is determined from the types ofchildren.No entry in thechildrenarray may benull.If
nChildrenis 0 then the unit tuple is constructed.If the
childrenare 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
GVarianttuple - Since:
- 2.24
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uint16
Creates a new uint16GVariantinstance.- Parameters:
value- aguint16value- Returns:
- a floating reference to a new uint16
GVariantinstance - Since:
- 2.24
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uint32
Creates a new uint32GVariantinstance.- Parameters:
value- aguint32value- Returns:
- a floating reference to a new uint32
GVariantinstance - Since:
- 2.24
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uint64
Creates a new uint64GVariantinstance.- Parameters:
value- aguint64value- Returns:
- a floating reference to a new uint64
GVariantinstance - Since:
- 2.24
-
variant
Boxesvalue.The result is aGVariantinstance representing a variant containing the original value.If
childis a floating reference (see g_variant_ref_sink()), the new instance takes ownership ofchild.- Parameters:
value- aGVariantinstance- Returns:
- a floating reference to a new variant
GVariantinstance - Since:
- 2.24
-
isObjectPath
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:
trueifstringis a D-Bus object path- Since:
- 2.24
-
isSignature
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
GVariantTypestrings in sequence.- Parameters:
string- a normal C nul-terminated string- Returns:
trueifstringis 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 aGVariantfrom a text representation.A single
GVariantis parsed from the content oftext.The format is described here.
The memory at
limitwill never be accessed and the parser behaves as if the character atlimitis the nul terminator. This has the effect of boundingtext.If
endptris non-nullthentextis permitted to contain data following the value that this function parses andendptrwill be updated to point to the first character past the end of the text parsed by this function. Ifendptrisnulland there is extra data then an error is returned.If
typeis non-nullthen 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
GVariantis returned. It is never floating, and must be freed withunref().In case of any error,
nullwill be returned. Iferroris non-nullthen 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 includesg_variant_print()’s annotated types likeint64 -1000.There may be implementation specific restrictions on deeply nested values, which would result in a
VariantParseError.RECURSIONerror.GVariantis guaranteed to handle nesting up to at least 64 levels.- Parameters:
type- aGVariantType, ornulltext- a string containing a GVariant in text formlimit- a pointer to the end oftext,ornullendptr- a location to store the end pointer, ornull- Returns:
- a non-floating reference to a
GVariant, ornull - Throws:
GErrorException- seeGError
-
parseErrorPrintContext
Pretty-prints a message showing the context of aGVariantparse 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.
errormust have come from a failed attempt to g_variant_parse() andsourceStrmust be exactly the same string that caused the error. IfsourceStrwas not nul-terminated when you passed it to g_variant_parse() then you must add nul termination before using this function.- Parameters:
error- aGErrorfrom theGVariantParseErrordomainsourceStr- the string that was given to the parser- Returns:
- the printed message
- Since:
- 2.40
-
parseErrorQuark
-
parserGetErrorQuark
Deprecated.Use g_variant_parse_error_quark() instead.Same as g_variant_error_quark(). -
byteswap
Performs a byteswapping operation on the contents ofvalue.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
Checks if calling g_variant_get() withformatStringon this Variant would be valid from a type-compatibility standpoint.formatStringis assumed to be a valid format string (from a syntactic standpoint).If
copyOnlyistruethen 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-freedGVariantinstance). If this check fails then a g_critical() is printed andfalseis returned.This function is meant to be used by functions that wish to provide varargs accessors to
GVariantvalues of uncertain values (eg: g_variant_lookup() or g_menu_model_get_item_attribute()).- Parameters:
formatString- a validGVariantformat stringcopyOnly-trueto ensure the format string makes deep copies- Returns:
trueifformatStringis safe to use- Since:
- 2.34
-
classify
Classifies this Variant according to its top-level type.- Returns:
- the
GVariantClassof this Variant - Since:
- 2.24
-
compare
Compares this Variant andtwo.The types of this Variant and
twoaregconstpointeronly to allow use of this function withGTree,GPtrArray, etc. They must each be aGVariant.Comparison is only defined for basic types (ie: booleans, numbers, strings). For booleans,
falseis less thantrue. 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- aGVariantinstance 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
Gets the contents of an array of array of bytesGVariant. This call makes a deep copy; the return result should be released with g_strfreev().If
lengthis non-nullthen the number of elements in the result is stored there. In any case, the resulting array will benull-terminated.For an empty array,
lengthwill be set to 0 and a pointer to anullpointer will be returned.- Returns:
- an array of strings
- Since:
- 2.26
-
dupObjv
Gets the contents of an array of object pathsGVariant. This call makes a deep copy; the return result should be released with g_strfreev().If
lengthis non-nullthen the number of elements in the result is stored there. In any case, the resulting array will benull-terminated.For an empty array,
lengthwill be set to 0 and a pointer to anullpointer will be returned.- Returns:
- an array of strings
- Since:
- 2.30
-
dupString
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 agsize, to store the length- Returns:
- a newly allocated string, UTF-8 encoded
- Since:
- 2.24
-
dupStrv
Gets the contents of an array of stringsGVariant. This call makes a deep copy; the return result should be released with g_strfreev().If
lengthis non-nullthen the number of elements in the result is stored there. In any case, the resulting array will benull-terminated.For an empty array,
lengthwill be set to 0 and a pointer to anullpointer will be returned.- Returns:
- an array of strings
- Since:
- 2.24
-
equal
Checks if this Variant andtwohave the same type and value.The types of this Variant and
twoaregconstpointeronly to allow use of this function withGHashTable. They must each be aGVariant.- Parameters:
two- aGVariantinstance- Returns:
trueif this Variant andtwoare equal- Since:
- 2.24
-
get
Deconstructs aGVariantinstance.Think of this function as an analogue to scanf().
The arguments that are expected by this function are entirely determined by
formatString.formatStringalso restricts the permissible types ofvalue.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.formatStringdetermines the C types that are used for unpacking the values and also determines if the values are copied or borrowed, see the section onGVariantformat strings.- Parameters:
formatString- aGVariantformat stringvarargs- arguments, as performatString- Since:
- 2.24
-
getBoolean
public boolean getBoolean()Returns the boolean value ofvalue.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_BOOLEAN.- Returns:
trueorfalse- Since:
- 2.24
-
getByte
public byte getByte()Returns the byte value ofvalue.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 aGVariantinstance 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-
nullnul-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
Gets the contents of an array of array of bytesGVariant. This call makes a shallow copy; the return result should be released with g_free(), but the individual strings must not be modified.If
lengthis non-nullthen the number of elements in the result is stored there. In any case, the resulting array will benull-terminated.For an empty array,
lengthwill be set to 0 and a pointer to anullpointer will be returned.- Returns:
- an array of constant strings
- Since:
- 2.26
-
getChild
Reads a child item out of a containerGVariantinstance and deconstructs it according toformatString.This call is essentially a combination of g_variant_get_child_value() and g_variant_get().formatStringdetermines the C types that are used for unpacking the values and also determines if the values are copied or borrowed, see the section onGVariantformat strings.- Parameters:
index- the index of the child to deconstructformatString- aGVariantformat stringvarargs- arguments, as performatString- Since:
- 2.24
-
getChildValue
Reads a child item out of a containerGVariantinstance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type ofGVariant.It is an error if
indexis 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.
GVariantis 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
Returns a pointer to the serialized form of aGVariantinstance. 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
nullmay be returned. In this case, the proper thing to do is typically to use the appropriate number of nul bytes in place ofvalue.If this Variant is not fixed-sized thennullis 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 serializedGVariantsmust include this information either implicitly (for instance "the file always contains aG_VARIANT_TYPE_VARIANTand 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,ornull - Since:
- 2.24
-
getDataAsBytes
public byte[] getDataAsBytes()Returns a pointer to the serialized form of aGVariantinstance. The semantics of this function are exactly the same as g_variant_get_data(), except that the returnedGBytesholds a reference to the variant data.- Returns:
- A new
GBytesrepresenting the variant data - Since:
- 2.36
-
getDouble
public double getDouble()Returns the double precision floating point value ofvalue.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
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.
elementSizemust 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
elementSizeset to the size the appropriate type:G_VARIANT_TYPE_INT16(etc.):gint16(etc.)G_VARIANT_TYPE_BOOLEAN:guchar(notgboolean!)G_VARIANT_TYPE_BYTE:guint8G_VARIANT_TYPE_HANDLE:guint32G_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 ofvalue.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 ofvalue.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 ofvalue.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 ofvalue.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
Given a maybe-typedGVariantinstance, extract its value. If the value is Nothing, then this function returnsnull.- Returns:
- the contents of
value,ornull - Since:
- 2.24
-
getNormalForm
Gets aGVariantinstance 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
GVariantis created with the same value asvalue.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
GVariantdata 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
GVariantwill 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
Gets the contents of an array of object pathsGVariant. This call makes a shallow copy; the return result should be released with g_free(), but the individual strings must not be modified.If
lengthis non-nullthen the number of elements in the result is stored there. In any case, the resulting array will benull-terminated.For an empty array,
lengthwill be set to 0 and a pointer to anullpointer 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
Returns the string value of aGVariantinstance with a string type. This includes the typesG_VARIANT_TYPE_STRING,G_VARIANT_TYPE_OBJECT_PATHandG_VARIANT_TYPE_SIGNATURE.The string will always be UTF-8 encoded, will never be
null, and will never contain nul bytes.If
lengthis non-nullthen 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 — forG_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 agsize, to store the length- Returns:
- the constant string, UTF-8 encoded
- Since:
- 2.24
-
getStrv
Gets the contents of an array of stringsGVariant. This call makes a shallow copy; the return result should be released with g_free(), but the individual strings must not be modified.If
lengthis non-nullthen the number of elements in the result is stored there. In any case, the resulting array will benull-terminated.For an empty array,
lengthwill be set to 0 and a pointer to anullpointer will be returned.- Returns:
- an array of constant strings
- Since:
- 2.24
-
getVariantType
Determines the type ofvalue.The return value is valid for the lifetime of this Variant and must not be freed.
- Returns:
- a
GVariantType - Since:
- 2.24
-
getTypeString
Returns the type string ofvalue.Unlike the result of calling g_variant_type_peek_string(), this string is nul-terminated. This string belongs toGVariantand 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 ofvalue.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 ofvalue.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 ofvalue.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
Unboxesvalue.The result is theGVariantinstance that was contained invalue.- Returns:
- the item contained in the variant
- Since:
- 2.24
-
hash
public int hash()Generates a hash value for aGVariantinstance.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
gconstpointeronly to allow use of this function withGHashTable. this Variant must be aGVariant.- Returns:
- a hash value corresponding to this Variant
- Since:
- 2.24
-
isContainer
public boolean isContainer()Checks if this Variant is a container.- Returns:
trueif 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
GVariantusing 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:
trueif this Variant is in normal form- Since:
- 2.24
-
isOfType
Checks if a value has a type matching the provided type.- Parameters:
type- aGVariantType- Returns:
trueif the type of this Variant matchestype- Since:
- 2.24
-
iterNew
Creates a heap-allocatedGVariantIterfor iterating over the items invalue.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
Looks up a value in a dictionaryGVariant.This function is a wrapper around g_variant_lookup_value() and g_variant_get(). In the case that
nullwould have been returned, this function returnsfalse. Otherwise, it unpacks the returned value and returnstrue.formatStringdetermines the C types that are used for unpacking the values and also determines if the values are copied or borrowed, see the section onGVariantformat strings.This function is currently implemented with a linear scan. If you plan to do many lookups then
GVariantDictmay be more efficient.- Parameters:
key- the key to look up in the dictionaryformatString- a GVariant format stringvarargs- the arguments to unpack the value into- Returns:
trueif a value was unpacked- Since:
- 2.28
-
lookupValue
Looks up a value in a dictionaryGVariant.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
expectedTypestring specifies what type of value is expected to be inside of the variant. If the value inside the variant has a different type thennullis returned. In the event that this Variant has a value type other than v thenexpectedTypemust directly match the value type and it is used to unpack the value directly or an error occurs.In either case, if
keyis not found indictionary,nullis returned.If the key is found and the value has the correct type, it is returned. If
expectedTypewas specified then any non-nullreturn value will have this type.This function is currently implemented with a linear scan. If you plan to do many lookups then
GVariantDictmay be more efficient.- Parameters:
key- the key to look up in the dictionaryexpectedType- aGVariantType, ornull- Returns:
- the value of the dictionary key, or
null - Since:
- 2.28
-
nChildren
public long nChildren()Determines the number of children in a containerGVariantinstance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type ofGVariant.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
Pretty-prints this Variant in the format understood by g_variant_parse().The format is described here.
If
typeAnnotateistrue, then type information is included in the output.- Parameters:
typeAnnotate-trueif type information should be included in the output- Returns:
- a newly-allocated string holding the result.
- Since:
- 2.24
-
printString
Behaves as g_variant_print(), but operates on aGString.If
stringis non-nullthen it is appended to and returned. Else, a new emptyGStringis allocated and it is returned.- Parameters:
string- aGString, ornulltypeAnnotate-trueif type information should be included in the output- Returns:
- a
GStringcontaining the string - Since:
- 2.24
-
ref
Increases the reference count ofvalue.- Returns:
- the same this Variant
- Since:
- 2.24
-
refSink
GVariantuses a floating reference count system. All functions with names starting withg_variant_new_return floating references.Calling g_variant_ref_sink() on a
GVariantwith a floating reference will convert the floating reference into a full reference. Calling g_variant_ref_sink() on a non-floatingGVariantresults 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
GVariantinstance 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
Stores the serialized form of this Variant atdata.datashould 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
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
GVariantAPI makes it likely that for newly-createdGVariantinstances, the user can be saved some typing if they are allowed to return aGVariantwith 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
GVariantinstance. 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
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unref
public void unref()Decreases the reference count ofvalue.When its reference count drops to 0, the memory used by the variant is freed.- Since:
- 2.24
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toString
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pack
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unpack
Unpack a GVariant into a Java Object.- Returns:
- the unpacked Java Object
- See Also:
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unpackRecursive
Unpack a GVariant into a Java Object. Nested GVariants are recursively unpacked.- Returns:
- the unpacked Java Object
- See Also:
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