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.
-
Constructor Summary
ConstructorDescriptionVariant
(MemorySegment address) Create a Variant proxy instance for the provided memory address.Creates a newGVariant
instance. -
Method Summary
Modifier and TypeMethodDescriptionstatic Variant
array
(@Nullable VariantType childType, @Nullable Variant[] children) Creates a newGVariant
array fromchildren
.static Variant
boolean_
(boolean value) Creates a new booleanGVariant
instance -- eithertrue
orfalse
.static Variant
byte_
(byte value) Creates a new byteGVariant
instance.static Variant
bytestring
(byte[] string) Creates an array-of-bytesGVariant
with the contents ofstring
.static Variant
bytestringArray
(String[] strv) Constructs an array of bytestringGVariant
from the given array of strings.byteswap()
Performs a byteswapping operation on the contents of this Variant.boolean
checkFormatString
(String formatString, boolean copyOnly) Checks if calling g_variant_get() withformatString
on this Variant would be valid from a type-compatibility standpoint.classify()
Classifies this Variant according to its top-level type.int
Compares this Variant andtwo
.static Variant
Creates a new dictionary entryGVariant
.static Variant
double_
(double value) Creates a new doubleGVariant
instance.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
.boolean
Checks if this Variant andtwo
have the same type and value.static Variant
fixedArray
(VariantType elementType, @Nullable MemorySegment elements, long nElements, long elementSize) Constructs a new arrayGVariant
instance, where the elements are ofelementType
type.static Variant
fromBytes
(VariantType type, Bytes bytes, boolean trusted) Constructs a new serialized-modeGVariant
instance.static Variant
fromData
(VariantType type, byte[] data, boolean trusted, @Nullable MemorySegment userData) Creates a newGVariant
instance from serialized data.void
Deconstructs aGVariant
instance.boolean
Returns the boolean value of this Variant.byte
getByte()
Returns the byte value of this Variant.byte[]
Returns the string value of aGVariant
instance with an array-of-bytes type.String[]
Gets the contents of an array of array of bytesGVariant
.void
Reads a child item out of a containerGVariant
instance and deconstructs it according toformatString
.getChildValue
(long index) Reads a child item out of a containerGVariant
instance.getData()
Returns a pointer to the serialized form of aGVariant
instance.Returns a pointer to the serialized form of aGVariant
instance.double
Returns the double precision floating point value of this Variant.getFixedArray
(long elementSize) Provides access to the serialized data for an array of fixed-sized items.int
Returns the 32-bit signed integer value of this Variant.short
getInt16()
Returns the 16-bit signed integer value of this Variant.int
getInt32()
Returns the 32-bit signed integer value of this Variant.long
getInt64()
Returns the 64-bit signed integer value of this Variant.getMaybe()
Given a maybe-typedGVariant
instance, extract its value.Gets aGVariant
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 pathsGVariant
.long
getSize()
Determines the number of bytes that would be required to store this Variant with g_variant_store().Returns the string value of aGVariant
instance with a string type.String[]
getStrv()
Gets the contents of an array of stringsGVariant
.static Type
getType()
Get the GType of the GVariant classReturns the type string of this Variant.short
Returns the 16-bit unsigned integer value of this Variant.int
Returns the 32-bit unsigned integer value of this Variant.long
Returns the 64-bit unsigned integer value of this Variant.Unboxes this Variant.Determines the type of this Variant.static Variant
handle_
(int value) Creates a new handleGVariant
instance.int
hash()
Generates a hash value for aGVariant
instance.static Variant
int16
(short value) Creates a new int16GVariant
instance.static Variant
int32
(int value) Creates a new int32GVariant
instance.static Variant
int64
(long value) Creates a new int64GVariant
instance.boolean
Checks if this Variant is a container.boolean
Checks whether this Variant has a floating reference count.boolean
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.iterNew()
Creates a heap-allocatedGVariantIter
for iterating over the items in this Variant.boolean
Looks up a value in a dictionaryGVariant
.lookupValue
(String key, @Nullable VariantType expectedType) Looks up a value in a dictionaryGVariant
.static Variant
maybe
(@Nullable VariantType childType, @Nullable Variant child) Depending on ifchild
isnull
, either wrapschild
inside of a maybe container or creates a Nothing instance for the giventype
.long
Determines the number of children in a containerGVariant
instance.static Variant
objectPath
(String objectPath) Creates a D-Bus object pathGVariant
with the contents ofobjectPath
.static Variant
Constructs an array of object pathsGVariant
from the given array of strings.static Variant
parse
(@Nullable VariantType type, String text, @Nullable String limit, @Nullable String[] endptr) Parses aGVariant
from a text representation.static Variant
Parsesformat
and returns the result.static String
parseErrorPrintContext
(GError error, String sourceStr) Pretty-prints a message showing the context of aGVariant
parse error within the string for which parsing was attempted.static Quark
static Quark
Deprecated.Use g_variant_parse_error_quark() instead.print
(boolean typeAnnotate) Pretty-prints this Variant in the format understood by g_variant_parse().static Variant
Creates a string-type GVariant using printf formatting.printString
(@Nullable GString string, boolean typeAnnotate) Behaves as g_variant_print(), but operates on aGString
.ref()
Increases the reference count of this Variant.refSink()
GVariant
uses a floating reference count system.static Variant
Creates a D-Bus type signatureGVariant
with the contents ofstring
.void
store
(MemorySegment data) Stores the serialized form of this Variant atdata
.static Variant
Creates a stringGVariant
with the contents ofstring
.static Variant
Constructs an array of stringsGVariant
from the given array of strings.takeRef()
If this Variant is floating, sink it.static Variant
takeString
(String string) Creates a stringGVariant
with the contents ofstring
.toString()
Return a newly allocated String usingprint(boolean)
, which pretty-prints the value and type information of aVariant
.static Variant
Creates a new tupleGVariant
out of the items inchildren
.static Variant
uint16
(short value) Creates a new uint16GVariant
instance.static Variant
uint32
(int value) Creates a new uint32GVariant
instance.static Variant
uint64
(long value) Creates a new uint64GVariant
instance.void
unref()
Decreases the reference count of this Variant.static Variant
Boxesvalue
.Methods inherited from class io.github.jwharm.javagi.base.ProxyInstance
equals, handle, hashCode
-
Constructor Details
-
Variant
Create a Variant proxy instance for the provided memory address.- Parameters:
address
- the memory address of the native object
-
Variant
Creates a newGVariant
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 newGVariant
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
- aGVariant
format stringvarargs
- arguments, as performatString
-
-
Method Details
-
getType
-
array
public static Variant array(@Nullable @Nullable VariantType childType, @Nullable @Nullable Variant[] children) Creates a newGVariant
array fromchildren
.childType
must be non-null
ifnChildren
is zero. Otherwise, the child type is determined by inspecting the first element of thechildren
array. IfchildType
is non-null
then it must be a definite type.The items of the array are taken from the
children
array. No entry in thechildren
array may benull
.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 arraychildren
- an array ofGVariant
pointers, the children- Returns:
- a floating reference to a new
GVariant
array
-
boolean_
Creates a new booleanGVariant
instance -- eithertrue
orfalse
.- Parameters:
value
- agboolean
value- Returns:
- a floating reference to a new boolean
GVariant
instance
-
byte_
Creates a new byteGVariant
instance.- Parameters:
value
- aguint8
value- Returns:
- a floating reference to a new byte
GVariant
instance
-
bytestring
Creates an array-of-bytesGVariant
with 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
GVariant
instance
-
bytestringArray
-
dictEntry
Creates a new dictionary entryGVariant
.key
andvalue
must be non-null
.key
must be a value of a basic type (ie: not a container).If the
key
orvalue
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 basicGVariant
, the keyvalue
- aGVariant
, the value- Returns:
- a floating reference to a new dictionary entry
GVariant
-
double_
Creates a new doubleGVariant
instance.- Parameters:
value
- agdouble
floating point value- Returns:
- a floating reference to a new double
GVariant
instance
-
fixedArray
public static Variant fixedArray(VariantType elementType, @Nullable @Nullable MemorySegment elements, long nElements, long elementSize) Constructs a new arrayGVariant
instance, where the elements are ofelementType
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 theelements
array.- Parameters:
elementType
- theGVariantType
of 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
GVariant
instance
-
fromBytes
Constructs a new serialized-modeGVariant
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 thetype
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
- aGVariantType
bytes
- aGBytes
trusted
- if the contents ofbytes
are trusted- Returns:
- a new
GVariant
with a floating reference
-
fromData
public static Variant fromData(VariantType type, byte[] data, boolean trusted, @Nullable @Nullable MemorySegment userData) Creates a newGVariant
instance from serialized data.type
is the type ofGVariant
instance that will be constructed. The interpretation ofdata
depends on knowing the type.data
is not modified by this function and must remain valid with an unchanging value until such a time asnotify
is called withuserData
. If the contents ofdata
change before that time then the result is undefined.If
data
is trusted to be serialized data in normal form thentrusted
should 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 tofalse
ifdata
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 withuserData
whendata
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 thetype
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 definiteGVariantType
data
- the serialized datatrusted
-true
ifdata
is definitely in normal formuserData
- data fornotify
- Returns:
- a new floating
GVariant
of typetype
-
handle_
Creates a new handleGVariant
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
- agint32
value- Returns:
- a floating reference to a new handle
GVariant
instance
-
int16
Creates a new int16GVariant
instance.- Parameters:
value
- agint16
value- Returns:
- a floating reference to a new int16
GVariant
instance
-
int32
Creates a new int32GVariant
instance.- Parameters:
value
- agint32
value- Returns:
- a floating reference to a new int32
GVariant
instance
-
int64
Creates a new int64GVariant
instance.- Parameters:
value
- agint64
value- Returns:
- a floating reference to a new int64
GVariant
instance
-
maybe
public static Variant maybe(@Nullable @Nullable VariantType childType, @Nullable @Nullable Variant child) Depending on ifchild
isnull
, either wrapschild
inside of a maybe container or creates a Nothing instance for the giventype
.At least one of
childType
andchild
must be non-null
. IfchildType
is non-null
then it must be a definite type. If they are both non-null
thenchildType
must be the type ofchild
.If
child
is a floating reference (see g_variant_ref_sink()), the new instance takes ownership ofchild
.- Parameters:
childType
- theGVariantType
of the child, ornull
child
- the child value, ornull
- Returns:
- a floating reference to a new
GVariant
maybe instance
-
objectPath
Creates a D-Bus object pathGVariant
with the contents ofobjectPath
.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
-
objv
Constructs an array of object pathsGVariant
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 thenstrv
isnull
-terminated.- Parameters:
strv
- an array of strings- Returns:
- a new floating
GVariant
instance
-
parsed
Parsesformat
and returns the result.format
must be a text formatGVariant
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 formatGVariant
varargs
- arguments as performat
- Returns:
- a new floating
GVariant
instance
-
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
GVariant
instance
-
signature
Creates a D-Bus type signatureGVariant
with the contents ofstring
.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
-
string
Creates a stringGVariant
with the contents ofstring
.string
must be valid UTF-8, and must not benull
. To encode potentially-null
strings, use g_variant_new() withms
as the format string.- Parameters:
string
- a normal UTF-8 nul-terminated string- Returns:
- a floating reference to a new string
GVariant
instance
-
strv
-
takeString
Creates a stringGVariant
with the contents ofstring
.string
must be valid UTF-8, and must not benull
. To encode potentially-null
strings, use this with g_variant_new_maybe().After this call,
string
belongs to theGVariant
and may no longer be modified by the caller. The memory ofdata
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 thatstring
is immediately freed.- Parameters:
string
- a normal UTF-8 nul-terminated string- Returns:
- a floating reference to a new string
GVariant
instance
-
tuple
Creates a new tupleGVariant
out of the items inchildren
. The type is determined from the types ofchildren
. No entry in thechildren
array may benull
.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
-
uint16
Creates a new uint16GVariant
instance.- Parameters:
value
- aguint16
value- Returns:
- a floating reference to a new uint16
GVariant
instance
-
uint32
Creates a new uint32GVariant
instance.- Parameters:
value
- aguint32
value- Returns:
- a floating reference to a new uint32
GVariant
instance
-
uint64
Creates a new uint64GVariant
instance.- Parameters:
value
- aguint64
value- Returns:
- a floating reference to a new uint64
GVariant
instance
-
variant
Boxesvalue
. The result is aGVariant
instance representing a variant containing the original value.If
child
is a floating reference (see g_variant_ref_sink()), the new instance takes ownership ofchild
.- Parameters:
value
- aGVariant
instance- Returns:
- a floating reference to a new variant
GVariant
instance
-
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:
true
ifstring
is a D-Bus object path
-
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
GVariantType
strings in sequence.- Parameters:
string
- a normal C nul-terminated string- Returns:
true
ifstring
is a D-Bus type signature
-
parse
public static Variant parse(@Nullable @Nullable VariantType type, String text, @Nullable @Nullable String limit, @Nullable @Nullable String[] endptr) throws GErrorException Parses aGVariant
from a text representation.A single
GVariant
is parsed from the content oftext
.The format is described here.
The memory at
limit
will never be accessed and the parser behaves as if the character atlimit
is the nul terminator. This has the effect of boundingtext
.If
endptr
is non-null
thentext
is permitted to contain data following the value that this function parses andendptr
will be updated to point to the first character past the end of the text parsed by this function. Ifendptr
isnull
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 withunref()
.In case of any error,
null
will be returned. Iferror
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 includesg_variant_print()
’s annotated types likeint64 -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
- aGVariantType
, ornull
text
- a string containing a GVariant in text formlimit
- a pointer to the end oftext
, ornull
endptr
- 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 aGVariant
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() andsourceStr
must be exactly the same string that caused the error. IfsourceStr
was not nul-terminated when you passed it to g_variant_parse() then you must add nul termination before using this function.- Parameters:
error
- aGError
from theGVariantParseError
domainsourceStr
- the string that was given to the parser- Returns:
- the printed message
-
parseErrorQuark
-
parserGetErrorQuark
Deprecated.Use g_variant_parse_error_quark() instead.Same as g_variant_error_quark(). -
byteswap
Performs a byteswapping operation on the contents of this Variant. 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
-
checkFormatString
Checks if calling g_variant_get() withformatString
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
istrue
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-freedGVariant
instance). If this check fails then a g_critical() is printed andfalse
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 validGVariant
format stringcopyOnly
-true
to ensure the format string makes deep copies- Returns:
true
ifformatString
is safe to use
-
classify
Classifies this Variant according to its top-level type.- Returns:
- the
GVariantClass
of this Variant
-
compare
Compares this Variant andtwo
.The types of this Variant and
two
aregconstpointer
only 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,
false
is 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
- aGVariant
instance of the same type- Returns:
- negative value if a < b; zero if a = b; positive value if a > b.
-
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
-
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
length
is non-null
then the number of elements in the result is stored there. In any case, the resulting array will benull
-terminated.For an empty array,
length
will be set to 0 and a pointer to anull
pointer will be returned.- Returns:
- an array of strings
-
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
length
is non-null
then the number of elements in the result is stored there. In any case, the resulting array will benull
-terminated.For an empty array,
length
will be set to 0 and a pointer to anull
pointer will be returned.- Returns:
- an array of strings
-
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
-
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
length
is non-null
then the number of elements in the result is stored there. In any case, the resulting array will benull
-terminated.For an empty array,
length
will be set to 0 and a pointer to anull
pointer will be returned.- Returns:
- an array of strings
-
equal
Checks if this Variant andtwo
have the same type and value.The types of this Variant and
two
aregconstpointer
only to allow use of this function withGHashTable
. They must each be aGVariant
.- Parameters:
two
- aGVariant
instance- Returns:
true
if this Variant andtwo
are equal
-
get
Deconstructs aGVariant
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 this Variant. 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 onGVariant
format strings.- Parameters:
formatString
- aGVariant
format stringvarargs
- arguments, as performatString
-
getBoolean
public boolean getBoolean()Returns the boolean value of this Variant.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_BOOLEAN
.- Returns:
true
orfalse
-
getByte
public byte getByte()Returns the byte value of this Variant.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_BYTE
.- Returns:
- a
guint8
-
getBytestring
public byte[] getBytestring()Returns the string value of aGVariant
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
-
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
length
is non-null
then the number of elements in the result is stored there. In any case, the resulting array will benull
-terminated.For an empty array,
length
will be set to 0 and a pointer to anull
pointer will be returned.- Returns:
- an array of constant strings
-
getChild
Reads a child item out of a containerGVariant
instance and deconstructs it according toformatString
. 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 onGVariant
format strings.- Parameters:
index
- the index of the child to deconstructformatString
- aGVariant
format stringvarargs
- arguments, as performatString
-
getChildValue
Reads a child item out of a containerGVariant
instance. 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
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 this Variant, 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
-
getData
Returns a pointer to the serialized form of aGVariant
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 this Variant. If this Variant is not fixed-sized thennull
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 serializedGVariants
must include this information either implicitly (for instance "the file always contains aG_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 this Variant, or
null
-
getDataAsBytes
Returns a pointer to the serialized form of aGVariant
instance. The semantics of this function are exactly the same as g_variant_get_data(), except that the returnedGBytes
holds a reference to the variant data.- Returns:
- A new
GBytes
representing the variant data
-
getDouble
public double getDouble()Returns the double precision floating point value of this Variant.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_DOUBLE
.- Returns:
- a
gdouble
-
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.
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
(notgboolean
!)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
-
getHandle
public int getHandle()Returns the 32-bit signed integer value of this Variant.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
-
getInt16
public short getInt16()Returns the 16-bit signed integer value of this Variant.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_INT16
.- Returns:
- a
gint16
-
getInt32
public int getInt32()Returns the 32-bit signed integer value of this Variant.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_INT32
.- Returns:
- a
gint32
-
getInt64
public long getInt64()Returns the 64-bit signed integer value of this Variant.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_INT64
.- Returns:
- a
gint64
-
getMaybe
Given a maybe-typedGVariant
instance, extract its value. If the value is Nothing, then this function returnsnull
.- Returns:
- the contents of this Variant, or
null
-
getNormalForm
Gets aGVariant
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 this Variant. 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
-
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
length
is non-null
then the number of elements in the result is stored there. In any case, the resulting array will benull
-terminated.For an empty array,
length
will be set to 0 and a pointer to anull
pointer will be returned.- Returns:
- an array of constant strings
-
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
-
getString
Returns the string value of aGVariant
instance with a string type. This includes the typesG_VARIANT_TYPE_STRING
,G_VARIANT_TYPE_OBJECT_PATH
andG_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 — 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
-
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
length
is non-null
then the number of elements in the result is stored there. In any case, the resulting array will benull
-terminated.For an empty array,
length
will be set to 0 and a pointer to anull
pointer will be returned.- Returns:
- an array of constant strings
-
getVariantType
Determines the type of this Variant.The return value is valid for the lifetime of this Variant and must not be freed.
- Returns:
- a
GVariantType
-
getTypeString
Returns the type string of this Variant. Unlike the result of calling g_variant_type_peek_string(), this string is nul-terminated. This string belongs toGVariant
and must not be freed.- Returns:
- the type string for the type of this Variant
-
getUint16
public short getUint16()Returns the 16-bit unsigned integer value of this Variant.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_UINT16
.- Returns:
- a
guint16
-
getUint32
public int getUint32()Returns the 32-bit unsigned integer value of this Variant.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_UINT32
.- Returns:
- a
guint32
-
getUint64
public long getUint64()Returns the 64-bit unsigned integer value of this Variant.It is an error to call this function with a this Variant of any type other than
G_VARIANT_TYPE_UINT64
.- Returns:
- a
guint64
-
getVariant
Unboxes this Variant. The result is theGVariant
instance that was contained in this Variant.- Returns:
- the item contained in the variant
-
hash
public int hash()Generates a hash value for aGVariant
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 withGHashTable
. this Variant must be aGVariant
.- Returns:
- a hash value corresponding to this Variant
-
isContainer
public boolean isContainer()Checks if this Variant is a container.- Returns:
true
if this Variant is a container
-
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
-
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
-
isOfType
Checks if a value has a type matching the provided type.- Parameters:
type
- aGVariantType
- Returns:
true
if the type of this Variant matchestype
-
iterNew
Creates a heap-allocatedGVariantIter
for iterating over the items in this Variant.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
-
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
null
would have been returned, this function returnsfalse
. Otherwise, it unpacks the returned value and returnstrue
.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 onGVariant
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 dictionaryformatString
- a GVariant format stringvarargs
- the arguments to unpack the value into- Returns:
true
if a value was unpacked
-
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
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 thennull
is returned. In the event that this Variant has a value type other than v thenexpectedType
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 this Variant,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
GVariantDict
may be more efficient.- Parameters:
key
- the key to look up in the dictionaryexpectedType
- aGVariantType
, ornull
- Returns:
- the value of the dictionary key, or
null
-
nChildren
public long nChildren()Determines the number of children in a containerGVariant
instance. 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
-
print
Pretty-prints this Variant in the format understood by g_variant_parse().The format is described here.
If
typeAnnotate
istrue
, 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.
-
printString
Behaves as g_variant_print(), but operates on aGString
.If
string
is non-null
then it is appended to and returned. Else, a new emptyGString
is allocated and it is returned.- Parameters:
string
- aGString
, ornull
typeAnnotate
-true
if type information should be included in the output- Returns:
- a
GString
containing the string
-
ref
-
refSink
GVariant
uses a floating reference count system. All functions with names starting withg_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-floatingGVariant
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
-
store
Stores the serialized form of this Variant atdata
.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
-
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-createdGVariant
instances, the user can be saved some typing if they are allowed to return aGVariant
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 this Variant. When its reference count drops to 0, the memory used by the variant is freed. -
toString
Return a newly allocated String usingprint(boolean)
, which pretty-prints the value and type information of aVariant
.
-