N-Variant
#------------------------------------------------------------------------------- #--[Class Description]---------------------------------------------------------- #-------------------------------------------------------------------------------
N-Variant
Description
N-Variant is a variant datatype; it can contain one or more values along with information about the type of the values.
A N-Variant may contain simple types, like an integer, or a boolean value; or complex types, like an array of two strings, or a dictionary of key value pairs. A N-Variant 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 N-Variant, you pass the data you want to store in it along with a string representing the type of data you wish to pass to it.
For instance, if you want to create a N-Variant holding an integer value you can use:
my Gnome::Glib::Variant $v .= new-variant( 'u', guint32, 40);
The string "u" in the first argument tells N-Variant that the data passed to the constructor (40) is going to be an unsigned integer.
More advanced examples of N-Variant in use can be found in documentation for GVariant format strings.
The range of possible values is determined by the type.
The type system used by N-Variant is N-VariantType.
N-Variant instances always have a type and a value (which are given at construction time). The type and value of a N-Variant instance can never change other than by the N-Variant itself being destroyed. A N-Variant cannot contain a pointer.
N-Variant is reference counted using .ref() and
.unref(). N-Variant also has floating reference counts --
see .ref-sink().
N-Variant is completely threadsafe. A N-Variant instance can be concurrently accessed in any way from any number of threads without problems.
N-Variant 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 N-Variant data can also be sent over the network.
N-Variant is largely compatible with D-Bus. Almost all types of N-Variant instances can be sent over D-Bus. See N-VariantType for exceptions. (However, N-Variant'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 N-Variant 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 N-Variant's size is limited mainly by any lower level operating
system constraints, such as the number of bits in #gsize. For
example, it is reasonable to have a 2GB file mapped into memory
with Gnome::Glib::N-MappedFile, and call .new-from-data() on it.
For convenience to C programmers, N-Variant 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 N-Variant values. N-Variant includes a printer for this language and a parser with type inferencing.
Memory Use
N-Variant tries to be quite efficient with respect to memory use. This section gives a rough idea of how much memory is used by the current implementation. The information here is subject to change in the future.
The memory allocated by N-Variant can be grouped into 4 broad purposes: memory for serialized data, memory for the type information cache, buffer management memory and memory for the N-Variant 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 byte to store the int32 (so 6 for the variant containing it) and 6 bytes for the string. The variant must be aligned to 8 after the 6 bytes of the string, so that's 2 extra bytes. 6 (string) + 2 (padding) + 6 (variant) is 14 bytes used for the dictionary entry. An additional 1 byte is added to the array as a framing offset making a total of 15 bytes.
If we add another entry, "title" that maps to a nullable string that happens to have a value of null, then we use 0 bytes for the null value (and 3 bytes for the variant to contain it along with its type string) plus 6 bytes for the string. Again, we need 2 padding bytes. That makes a total of 6 + 2 + 3 = 11 bytes.
We now require extra padding between the two items in the array. After the 14 bytes of the first item, that's 2 bytes required. We now require 2 framing offsets for an extra two bytes. 14 + 2 + 11 + 2 = 29 bytes to encode the entire two-item dictionary.
Type Information Cache
For each GVariant type that currently exists in the program a type information structure is kept in the type information cache. The type information structure is required for rapid deserialization.
Continuing with the above example, if a N-Variant exists with the type "a{sv}" then a type information struct will exist for "a{sv}", "{sv}", "s", and "v". Multiple uses of the same type will share the same type information. Additionally, all single-digit types are stored in read-only static memory and do not contribute to the writable memory footprint of a program using N-Variant.
Aside from the type information structures stored in read-only memory, there are two forms of type information. One is used for container types where there is a single element type: arrays and maybe types. The other is used for container types where there are multiple element types: tuples and dictionary entries.
Array type info structures are 6 * sizeof (void *), plus the memory required to store the type string itself. This means that on 32-bit systems, the cache entry for "a{sv}" would require 30 bytes of memory (plus malloc overhead).
Tuple type info structures are 6 * sizeof (void *), plus 4 * sizeof (void *) for each item in the tuple, plus the memory required to store the type string itself. A 2-item tuple, for example, would have a type information structure that consumed writable memory in the size of 14 * sizeof (void *) (plus type string) This means that on 32-bit systems, the cache entry for "{sv}" would require 61 bytes of memory (plus malloc overhead).
This means that in total, for our "a{sv}" example, 91 bytes of type information would be allocated.
The type information cache, additionally, uses a Gnome::Glib::N-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
N-Variant 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 N-Variant. This may involve a g_free() or a g_slice_free() or even g_mapped_file_unref().
One buffer management structure is used for each chunk of 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 N-Variant structure is 6 * (void *). On 32-bit systems, that's 24 bytes.
N-Variant structures only exist if they are explicitly created with API calls. For example, if a N-Variant 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 N-Variant instance exists -- the one referring to the dictionary.
If calls are made to start accessing the other values then
N-Variant 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 N-Variant instance, or a total of 160 bytes, plus
malloc overhead. If we were to use .get-child-value() to
access the two dictionary entries, we would use an additional 48
bytes. If we were to have other dictionaries of the same type, we
would use more memory for the serialized data and buffer
management for those dictionaries, but the type information would
be shared.
#------------------------------------------------------------------------------- #--[Record Structure]----------------------------------------------------------- #-------------------------------------------------------------------------------
Record N-Variant
This is an opaque type of which fields are not available.
class N-Variant:auth<github:MARTIMM>:api<2> is export is repr('CStruct') { }
#------------------------------------------------------------------------------- #--[Class Initialization]------------------------------------------------------- #-------------------------------------------------------------------------------
Class initialization
new
:native-object
Create an object using a native object from elsewhere. See also Gnome::N::TopLevelSupportClass.
multi method new ( N-Object :$native-object! )
#-------------------------------------------------------------------------------
new-variant This function is not yet available
Creates a new N-Variant 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 $format_string. See the section on GVariant format strings. Please note that
the syntax of the format string is very likely to be extended in the
future.
The first character of the format string must not be '*' '?' '@' or 'r'; in essence, a new N-Variant 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 $format_string. This can be achieved by casting them. See
the GVariant varargs documentation.
enum VFlags ( :AAA(1), :BBB(2), :CCC(4), :DDD(8));
my GFlag $some-flags = AAA +| DDD;
my $some-strings = CArray[Str].new( 'a', 'b', 'c', Str);
my Gnome::Glib::N-Variant $v .= new-variant(
'(t^as)', GFlag, $some-flags, CArray[Str], $some-strings
);
method new-variant ( Str $format-string, ā¦ --> Gnome::Glib::Variant )
$format-string; a N-Variant format string.
ā¦; ā¦. Note that each argument must be specified as a type followed by its value!
#-------------------------------------------------------------------------------
new-array
Creates a new N-Variant array from $children.
$child_type must be non-undefined if $n_children is zero. Otherwise, the
child type is determined by inspecting the first element of the $children array. If $child_type is non-undefined then it must be a
definite type.
The items of the array are taken from the $children array. No entry
in the $children array may be undefined.
All items in the array must have the same type, which must be the
same as $child_type, if given.
If the $children are floating references (see .ref-sink()), the
new instance takes ownership of them as if via .ref-sink().
method new-array ( CArray[N-VariantType] $child-type, CArray[N-Variant] $children, Int() $n-children --> Gnome::Glib::Variant )
$child-type; the element type of the new array.
$children; an array of N-Variant pointers, the children.
$n-children; the length of
$children.
#-------------------------------------------------------------------------------
new-boolean
Creates a new boolean N-Variant instance -- either True or False.
method new-boolean ( Bool() $value --> Gnome::Glib::Variant )
$value; a #gboolean value.
#-------------------------------------------------------------------------------
new-byte
Creates a new byte N-Variant instance.
method new-byte ( UInt() $value --> Gnome::Glib::Variant )
$value; a #guint8 value.
#-------------------------------------------------------------------------------
new-bytestring
Creates an array-of-bytes N-Variant with the contents of $string.
This function is just like .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.
method new-bytestring ( Str $string --> Gnome::Glib::Variant )
$string; a normal nul-terminated string in no particular encoding.
#-------------------------------------------------------------------------------
new-bytestring-array
Constructs an array of bytestring N-Variant from the given array of strings.
If $length is -1 then $strv is undefined-terminated.
method new-bytestring-array ( Array[Str] $strv, Int() $length --> Gnome::Glib::Variant )
$strv; an array of strings.
$length; the length of
$strv, or -1.
#-------------------------------------------------------------------------------
new-dict-entry
Creates a new dictionary entry N-Variant. $key and $value must be
non-undefined. $key must be a value of a basic type (ie: not a container).
If the $key or $value are floating references (see .ref-sink()),
the new instance takes ownership of them as if via .ref-sink().
method new-dict-entry ( CArray[N-Variant] $key, CArray[N-Variant] $value --> Gnome::Glib::Variant )
$key; a basic N-Variant, the key.
$value; a N-Variant, the value.
#-------------------------------------------------------------------------------
new-double
Creates a new double N-Variant instance.
method new-double ( Num() $value --> Gnome::Glib::Variant )
$value; a #gdouble floating point value.
#-------------------------------------------------------------------------------
new-fixed-array
Constructs a new array N-Variant instance, where the elements are
of $element_type type.
$elements must be an array with fixed-sized elements. Numeric types are
fixed-size as are tuples containing only other fixed-sized types.
$element_size must be the size of a single element in the array.
For example, if calling this function for an array of 32-bit integers,
you might say sizeof(gint32). This value isn't used except for the purpose
of a double-check that the form of the serialized data matches the caller's
expectation.
$n_elements must be the length of the $elements array.
method new-fixed-array ( CArray[N-VariantType] $element-type, gpointer $elements, Int() $n-elements, Int() $element-size --> Gnome::Glib::Variant )
$element-type; the N-VariantType of each element.
$elements; a pointer to the fixed array of contiguous elements.
$n-elements; the number of elements.
$element-size; the size of each element.
#-------------------------------------------------------------------------------
new-from-bytes This function is not yet available
Constructs a new serialized-mode N-Variant instance. This is the inner interface for creation of new serialized values that gets called from various functions in gvariant.c.
A reference is taken on $bytes.
The data in $bytes must be aligned appropriately for the $type being loaded.
Otherwise this function will internally create a copy of the memory (since
GLib 2.60) or (in older versions) fail and exit the process.
method new-from-bytes ( CArray[N-VariantType] $type, CArray[N-Bytes] $bytes, Bool() $trusted --> Gnome::Glib::Variant )
$type; a N-VariantType.
$bytes; a Gnome::Glib::N-Bytes.
$trusted; if the contents of
$bytesare trusted.
#-------------------------------------------------------------------------------
new-from-data
Creates a new N-Variant instance from serialized data.
$type is the type of N-Variant instance that will be constructed.
The interpretation of $data depends on knowing the type.
$data is not modified by this function and must remain valid with an
unchanging value until such a time as $notify is called with $user_data. If the contents of $data change before that time then
the result is undefined.
If $data is trusted to be serialized data in normal form then $trusted should be True. This applies to serialized data created
within this process or read from a trusted location on the disk (such
as a file installed in /usr/lib alongside your application). You
should set trusted to False if $data is read from the network, a
file in the user's home directory, etc.
If $data was not stored in this machine's native endianness, any multi-byte
numeric values in the returned variant will also be in non-native
endianness. .byteswap() can be used to recover the original values.
$notify will be called with $user_data when $data is no longer
needed. The exact time of this call is unspecified and might even be
before this function returns.
Note: $data must be backed by memory that is aligned appropriately for the $type being loaded. Otherwise this function will internally create a copy of
the memory (since GLib 2.60) or (in older versions) fail and exit the
process.
method new-from-data ( CArray[N-VariantType] $type, gpointer $data, Int() $size, Bool() $trusted, ¬ify, gpointer $user-data --> Gnome::Glib::Variant )
$type; a definite N-VariantType.
$data; the serialized data.
$size; the size of
$data.$trusted;
Trueif$datais definitely in normal form.¬ify; function to call when
$datais no longer needed. Tthe function must be specified with following signature;:( gpointer $data ).$user-data; data for
$notify.
#-------------------------------------------------------------------------------
new-handle
Creates a new handle N-Variant 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.
method new-handle ( Int() $value --> Gnome::Glib::Variant )
$value; a #gint32 value.
#-------------------------------------------------------------------------------
new-int16
Creates a new int16 N-Variant instance.
method new-int16 ( Int() $value --> Gnome::Glib::Variant )
$value; a #gint16 value.
#-------------------------------------------------------------------------------
new-int32
Creates a new int32 N-Variant instance.
method new-int32 ( Int() $value --> Gnome::Glib::Variant )
$value; a #gint32 value.
#-------------------------------------------------------------------------------
new-int64
Creates a new int64 N-Variant instance.
method new-int64 ( Int() $value --> Gnome::Glib::Variant )
$value; a #gint64 value.
#-------------------------------------------------------------------------------
new-maybe
Depending on if $child is undefined, either wraps $child inside of a
maybe container or creates a Nothing instance for the given $type.
At least one of $child_type and $child must be non-undefined.
If $child_type is non-undefined then it must be a definite type.
If they are both non-undefined then $child_type must be the type
of $child.
If $child is a floating reference (see .ref-sink()), the new
instance takes ownership of $child.
method new-maybe ( CArray[N-VariantType] $child-type, CArray[N-Variant] $child --> Gnome::Glib::Variant )
$child-type; the N-VariantType of the child, or undefined.
$child; the child value, or undefined.
#-------------------------------------------------------------------------------
new-object-path
Creates a D-Bus object path N-Variant with the contents of $string. $string must be a valid D-Bus object path. Use
.is-object-path() if you're not sure.
method new-object-path ( Str $object-path --> Gnome::Glib::Variant )
$object-path; a normal C nul-terminated string.
#-------------------------------------------------------------------------------
new-objv
Constructs an array of object paths N-Variant from the given array of strings.
Each string must be a valid N-Variant object path; see
.is-object-path().
If $length is -1 then $strv is undefined-terminated.
method new-objv ( Array[Str] $strv, Int() $length --> Gnome::Glib::Variant )
$strv; an array of strings.
$length; the length of
$strv, or -1.
#-------------------------------------------------------------------------------
new-parsed This function is not yet available
Parses $format and returns the result.
$format must be a text format N-Variant with one extension: at any
point that a value may appear in the text, a '%' character followed
by a GVariant format string (as per .new-variant()) may appear. In
that case, the same arguments are collected from the argument list as
.new-variant() 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:
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
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 .parse().
You may not use this function to return, unmodified, a single
N-Variant pointer from the argument list. ie: $format may not solely
be anything along the lines of "%*", "%?", "\r", or anything starting
with "%@".
method new-parsed ( Str $format, ā¦ --> Gnome::Glib::Variant )
$format; a text format N-Variant.
ā¦; ā¦. Note that each argument must be specified as a type followed by its value!
#-------------------------------------------------------------------------------
new-parsed-va This function is not yet available
Parses $format and returns the result.
This is the version of .new-parsed() intended to be used
from libraries.
The return value will be floating if it was a newly created GVariant
instance. In the case that $format simply specified the collection
of a N-Variant pointer (eg: $format was "%*") then the collected
N-Variant pointer will be returned unmodified, without adding any
additional references.
Note that the arguments in $app must be of the correct width for their types
specified in $format when collected into the #va_list. See
the GVariant varargs documentation.
In order to behave correctly in all cases it is necessary for the
calling function to .ref-sink() the return result before
returning control to the user that originally provided the pointer.
At this point, the caller will have their own full reference to the
result. This can also be done by adding the result to a container,
or by passing it to another .new-variant() call.
method new-parsed-va ( Str $format, ā¦ --> Gnome::Glib::Variant )
$format; a text format N-Variant.
app; a pointer to a #va_list. Note that each argument must be specified as a type followed by its value!
#-------------------------------------------------------------------------------
new-printf This function is not yet available
Creates a string-type GVariant using printf formatting.
This is similar to calling g_strdup_printf() and then
.new-string() but it saves a temporary variable and an
unnecessary copy.
method new-printf ( Str $format-string, ā¦ --> Gnome::Glib::Variant )
$format-string; a printf-style format string.
ā¦; ā¦. Note that each argument must be specified as a type followed by its value!
#-------------------------------------------------------------------------------
new-signature
Creates a D-Bus type signature N-Variant with the contents of $string. $string must be a valid D-Bus type signature. Use
.is-signature() if you're not sure.
method new-signature ( Str $signature --> Gnome::Glib::Variant )
$signature; a normal C nul-terminated string.
#-------------------------------------------------------------------------------
new-string
Creates a string N-Variant with the contents of $string.
$string must be valid UTF-8, and must not be undefined. To encode
potentially-undefined strings, use .new-variant() with ms as the format string.
method new-string ( Str $string --> Gnome::Glib::Variant )
$string; a normal UTF-8 nul-terminated string.
#-------------------------------------------------------------------------------
new-strv
Constructs an array of strings N-Variant from the given array of strings.
If $length is -1 then $strv is undefined-terminated.
method new-strv ( Array[Str] $strv, Int() $length --> Gnome::Glib::Variant )
$strv; an array of strings.
$length; the length of
$strv, or -1.
#-------------------------------------------------------------------------------
new-take-string
Creates a string N-Variant with the contents of $string.
$string must be valid UTF-8, and must not be undefined. To encode
potentially-undefined strings, use this with .new-maybe().
This function consumes $string. g_free() will be called on $string
when it is no longer required.
You must not modify or access $string in any other way after passing
it to this function. It is even possible that $string is immediately
freed.
method new-take-string ( Str $string --> Gnome::Glib::Variant )
$string; a normal UTF-8 nul-terminated string.
#-------------------------------------------------------------------------------
new-tuple
Creates a new tuple N-Variant out of the items in $children. The
type is determined from the types of $children. No entry in the $children array may be undefined.
If $n_children is 0 then the unit tuple is constructed.
If the $children are floating references (see .ref-sink()), the
new instance takes ownership of them as if via .ref-sink().
method new-tuple ( CArray[N-Variant] $children, Int() $n-children --> Gnome::Glib::Variant )
$children; the items to make the tuple out of.
$n-children; the length of
$children.
#-------------------------------------------------------------------------------
new-uint16
Creates a new uint16 N-Variant instance.
method new-uint16 ( UInt() $value --> Gnome::Glib::Variant )
$value; a #guint16 value.
#-------------------------------------------------------------------------------
new-uint32
Creates a new uint32 N-Variant instance.
method new-uint32 ( UInt() $value --> Gnome::Glib::Variant )
$value; a #guint32 value.
#-------------------------------------------------------------------------------
new-uint64
Creates a new uint64 N-Variant instance.
method new-uint64 ( UInt() $value --> Gnome::Glib::Variant )
$value; a #guint64 value.
#-------------------------------------------------------------------------------
new-va This function is not yet available
This function is intended to be used by libraries based on
N-Variant that want to provide .new-variant()-like functionality
to their users.
The API is more general than .new-variant() to allow a wider range
of possible uses.
$format_string must still point to a valid format string, but it only
needs to be nul-terminated if $endptr is undefined. If $endptr is
non-undefined then it is updated to point to the first character past the
end of the format string.
$app is a pointer to a #va_list. The arguments, according to $format_string, are collected from this #va_list and the list is left
pointing to the argument following the last.
Note that the arguments in $app must be of the correct width for their
types specified in $format_string when collected into the #va_list.
See the GVariant varargs documentation.
These two generalisations allow mixing of multiple calls to
.new-va() and .get-va() within a single actual
varargs call by the user.
The return value will be floating if it was a newly created GVariant instance (for example, if the format string was "(ii)"). In the case that the format_string was '*', '?', 'r', or a format starting with '@' then the collected N-Variant pointer will be returned unmodified, without adding any additional references.
In order to behave correctly in all cases it is necessary for the
calling function to .ref-sink() the return result before
returning control to the user that originally provided the pointer.
At this point, the caller will have their own full reference to the
result. This can also be done by adding the result to a container,
or by passing it to another .new-variant() call.
method new-va ( Str $format-string, Array[Str] $endptr, ā¦ --> Gnome::Glib::Variant )
$format-string; a string that is prefixed with a format string.
$endptr; location to store the end pointer, or undefined.
app; a pointer to a #va_list. Note that each argument must be specified as a type followed by its value!
#-------------------------------------------------------------------------------
new-variant
Boxes $value. The result is a N-Variant instance representing a
variant containing the original value.
If $child is a floating reference (see .ref-sink()), the new
instance takes ownership of $child.
method new-variant ( CArray[N-Variant] $value --> Gnome::Glib::Variant )
$value; a N-Variant instance.
#------------------------------------------------------------------------------- #--[Methods]-------------------------------------------------------------------- #-------------------------------------------------------------------------------
Methods
#-------------------------------------------------------------------------------
byteswap
Performs a byteswapping operation on the contents of $value. The
result is that all multi-byte numeric data contained in $value is
byteswapped. That includes 16, 32, and 64bit signed and unsigned
integers as well as file handles and double precision floating point
values.
This function is an identity mapping on any value that does not contain multi-byte numeric data. That include strings, booleans, bytes and containers containing only these things (recursively).
The returned value is always in normal form and is marked as trusted.
method byteswap (--> CArray[N-Variant] )
Return value; the byteswapped form of $value.
#-------------------------------------------------------------------------------
check-format-string
Checks if calling .get() with $format_string on $value would
be valid from a type-compatibility standpoint. $format_string is
assumed to be a valid format string (from a syntactic standpoint).
If $copy_only is True then this function additionally checks that it
would be safe to call .unref() on $value immediately after
the call to .get() without invalidating the result. This is
only possible if deep copies are made (ie: there are no pointers to
the data inside of the soon-to-be-freed N-Variant instance). If this
check fails then a g_critical() is printed and False is returned.
This function is meant to be used by functions that wish to provide
varargs accessors to N-Variant values of uncertain values (eg:
.lookup() or g_menu_model_get_item_attribute()).
method check-format-string ( Str $format-string, Bool() $copy-only --> Bool )
$format-string; a valid N-Variant format string.
$copy-only;
Trueto ensure the format string makes deep copies.
Return value; True if $format_string is safe to use.
#-------------------------------------------------------------------------------
classify This function is not yet available
Classifies $value according to its top-level type.
method classify ( )
#-------------------------------------------------------------------------------
compare
Compares $one and $two.
The types of $one and $two are #gconstpointer only to allow use of
this function with Gnome::Glib::N-Tree, Gnome::Glib::N-PtrArray, etc. They must each be a
N-Variant.
Comparison is only defined for basic types (ie: booleans, numbers,
strings). For booleans, False is less than True. Numbers are
ordered in the usual way. Strings are in ASCII lexographical order.
It is a programmer error to attempt to compare container values or two values that have types that are not exactly equal. For example, you cannot compare a 32-bit signed integer with a 32-bit unsigned integer. Also note that this function is not particularly well-behaved when it comes to comparison of doubles; in particular, the handling of incomparable values (ie: NaN) is undefined.
If you only require an equality comparison, .equal() is more
general.
method compare ( gpointer $two --> Int )
$two; a N-Variant instance of the same type.
Return value; negative value if a < b; zero if a = b; positive value if a > b..
#-------------------------------------------------------------------------------
dup-bytestring
Similar to .get-bytestring() except that instead of
returning a constant string, the string is duplicated.
The return value must be freed using g_free().
method dup-bytestring ( Array[gsize] $length --> Str )
$length; (transfer ownership: full) a pointer to a #gsize, to store the length (not including the nul terminator).
Return value; a newly allocated string.
#-------------------------------------------------------------------------------
dup-bytestring-array
Gets the contents of an array of array of bytes N-Variant. This call makes a deep copy; the return result should be released with g_strfreev().
If $length is non-undefined then the number of elements in the result is
stored there. In any case, the resulting array will be
undefined-terminated.
For an empty array, $length will be set to 0 and a pointer to a
undefined pointer will be returned.
method dup-bytestring-array ( Array[gsize] $length --> Array[Str] )
$length; (transfer ownership: full) the length of the result, or undefined.
Return value; an array of strings.
#-------------------------------------------------------------------------------
dup-objv
Gets the contents of an array of object paths N-Variant. This call makes a deep copy; the return result should be released with g_strfreev().
If $length is non-undefined then the number of elements in the result
is stored there. In any case, the resulting array will be
undefined-terminated.
For an empty array, $length will be set to 0 and a pointer to a
undefined pointer will be returned.
method dup-objv ( Array[gsize] $length --> Array[Str] )
$length; (transfer ownership: full) the length of the result, or undefined.
Return value; an array of strings.
#-------------------------------------------------------------------------------
dup-string
Similar to .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().
method dup-string ( Array[gsize] $length --> Str )
$length; (transfer ownership: full) a pointer to a #gsize, to store the length.
Return value; a newly allocated string, UTF-8 encoded.
#-------------------------------------------------------------------------------
dup-strv
Gets the contents of an array of strings N-Variant. This call makes a deep copy; the return result should be released with g_strfreev().
If $length is non-undefined then the number of elements in the result
is stored there. In any case, the resulting array will be
undefined-terminated.
For an empty array, $length will be set to 0 and a pointer to a
undefined pointer will be returned.
method dup-strv ( Array[gsize] $length --> Array[Str] )
$length; (transfer ownership: full) the length of the result, or undefined.
Return value; an array of strings.
#-------------------------------------------------------------------------------
equal
Checks if $one and $two have the same type and value.
The types of $one and $two are #gconstpointer only to allow use of
this function with Gnome::Glib::N-HashTable. They must each be a N-Variant.
method equal ( gpointer $two --> Bool )
$two; a N-Variant instance.
Return value; True if $one and $two are equal.
#-------------------------------------------------------------------------------
get This function is not yet available
Deconstructs a N-Variant instance.
Think of this function as an analogue to scanf().
The arguments that are expected by this function are entirely
determined by $format_string. $format_string also restricts the
permissible types of $value. It is an error to give a value with
an incompatible type. See the section on GVariant format strings.
Please note that the syntax of the format string is very likely to be
extended in the future.
$format_string determines the C types that are used for unpacking
the values and also determines if the values are copied or borrowed,
see the section on GVariant format strings.
method get ( Str $format-string, ā¦ )
$format-string; a N-Variant format string.
ā¦; ā¦. Note that each argument must be specified as a type followed by its value!
#-------------------------------------------------------------------------------
get-boolean
Returns the boolean value of $value.
It is an error to call this function with a $value of any type
other than G_VARIANT_TYPE_BOOLEAN.
method get-boolean (--> Bool )
Return value; True or False.
#-------------------------------------------------------------------------------
get-byte
Returns the byte value of $value.
It is an error to call this function with a $value of any type
other than G_VARIANT_TYPE_BYTE.
method get-byte (--> UInt )
Return value; a #guint8.
#-------------------------------------------------------------------------------
get-bytestring
Returns the string value of a N-Variant 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-undefined 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.
.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 $value that is not an
array of bytes.
The return value remains valid as long as $value exists.
method get-bytestring (--> Str )
Return value; the constant string.
#-------------------------------------------------------------------------------
get-bytestring-array
Gets the contents of an array of array of bytes N-Variant. 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-undefined then the number of elements in the result is
stored there. In any case, the resulting array will be
undefined-terminated.
For an empty array, $length will be set to 0 and a pointer to a
undefined pointer will be returned.
method get-bytestring-array ( Array[gsize] $length --> Array[Str] )
$length; (transfer ownership: full) the length of the result, or undefined.
Return value; an array of constant strings.
#-------------------------------------------------------------------------------
get-child This function is not yet available
Reads a child item out of a container N-Variant instance and
deconstructs it according to $format_string. This call is
essentially a combination of .get-child-value() and
.get().
$format_string determines the C types that are used for unpacking
the values and also determines if the values are copied or borrowed,
see the section on GVariant format strings.
method get-child ( Int() $index, Str $format-string, ā¦ )
$index; the index of the child to deconstruct.
$format-string; a N-Variant format string.
ā¦; ā¦. Note that each argument must be specified as a type followed by its value!
#-------------------------------------------------------------------------------
get-child-value
Reads a child item out of a container N-Variant instance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type of N-Variant.
It is an error if $index_ is greater than the number of child items
in the container. See .n-children().
The returned value is never floating. You should free it with
.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 $value has not been serialized at the time this function is
called. To avoid this, you can serialize $value by calling
.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. N-Variant is guaranteed to handle nesting up to at least 64 levels.
This function is O(1).
method get-child-value ( Int() $index --> CArray[N-Variant] )
$index; the index of the child to fetch.
Return value; the child at the specified index.
#-------------------------------------------------------------------------------
get-data
Returns a pointer to the serialized form of a N-Variant 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 $value exists.
If $value is a fixed-sized value that was deserialized from a
corrupted serialized container then undefined may be returned. In this
case, the proper thing to do is typically to use the appropriate
number of nul bytes in place of $value. If $value is not fixed-sized
then undefined is never returned.
In the case that $value 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 N-Variant, and (if the
machine might be different) the endianness of the machine that stored
it. As a result, file formats or network messages that incorporate
serialized GVariants must include this information either
implicitly (for instance "the file always contains a
G_VARIANT_TYPE_VARIANT and it is always in little-endian order") or
explicitly (by storing the type and/or endianness in addition to the
serialized data).
method get-data (--> gpointer )
Return value; the serialized form of $value, or undefined.
#-------------------------------------------------------------------------------
get-data-as-bytes This function is not yet available
Returns a pointer to the serialized form of a N-Variant instance.
The semantics of this function are exactly the same as
.get-data(), except that the returned Gnome::Glib::N-Bytes holds
a reference to the variant data.
method get-data-as-bytes (--> CArray[N-Bytes] )
Return value; A new Gnome::Glib::N-Bytes representing the variant data.
#-------------------------------------------------------------------------------
get-double
Returns the double precision floating point value of $value.
It is an error to call this function with a $value of any type
other than G_VARIANT_TYPE_DOUBLE.
method get-double (--> Num )
Return value; a #gdouble.
#-------------------------------------------------------------------------------
get-fixed-array
Provides access to the serialized data for an array of fixed-sized
items.
$value must be an array with fixed-sized elements. Numeric types are
fixed-size, as are tuples containing only other fixed-sized types.
$element_size must be the size of a single element in the array,
as given by the section on serialized data memory.
In particular, arrays of these fixed-sized types can be interpreted
as an array of the given C type, with $element_size set to the size
the appropriate type:
%G_VARIANT_TYPE_INT16 (etc.): #gint16 (etc.)
G_VARIANT_TYPE_BOOLEAN: #guchar (not #gboolean!)G_VARIANT_TYPE_BYTE: #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.
$n_elements, which must be non-undefined, is set equal to the number of
items in the array.
method get-fixed-array ( Array[gsize] $n-elements, Int() $element-size --> gpointer )
$n-elements; (transfer ownership: full) a pointer to the location to store the number of items.
$element-size; the size of each element.
Return value; a pointer to the fixed array.
#-------------------------------------------------------------------------------
get-handle
Returns the 32-bit signed integer value of $value.
It is an error to call this function with a $value of any type other
than G_VARIANT_TYPE_HANDLE.
By convention, handles are indexes into an array of file descriptors that are sent alongside a D-Bus message. If you're not interacting with D-Bus, you probably don't need them.
method get-handle (--> Int )
Return value; a #gint32.
#-------------------------------------------------------------------------------
get-int16
Returns the 16-bit signed integer value of $value.
It is an error to call this function with a $value of any type
other than %G_VARIANT_TYPE_INT16.
method get-int16 (--> Int )
Return value; a #gint16.
#-------------------------------------------------------------------------------
get-int32
Returns the 32-bit signed integer value of $value.
It is an error to call this function with a $value of any type
other than %G_VARIANT_TYPE_INT32.
method get-int32 (--> Int )
Return value; a #gint32.
#-------------------------------------------------------------------------------
get-int64
Returns the 64-bit signed integer value of $value.
It is an error to call this function with a $value of any type
other than %G_VARIANT_TYPE_INT64.
method get-int64 (--> Int )
Return value; a #gint64.
#-------------------------------------------------------------------------------
get-maybe
Given a maybe-typed N-Variant instance, extract its value. If the value is Nothing, then this function returns undefined.
method get-maybe (--> CArray[N-Variant] )
Return value; the contents of $value, or undefined.
#-------------------------------------------------------------------------------
get-normal-form
Gets a N-Variant instance that has the same value as $value and is
trusted to be in normal form.
If $value is already trusted to be in normal form then a new
reference to $value is returned.
If $value is not already trusted, then it is scanned to check if it
is in normal form. If it is found to be in normal form then it is
marked as trusted and a new reference to it is returned.
If $value is found not to be in normal form then a new trusted
N-Variant is created with the same value as $value.
It makes sense to call this function if you've received N-Variant data from untrusted sources and you want to ensure your serialized output is definitely in normal form.
If $value is already in normal form, a new reference will be returned
(which will be floating if $value is floating). If it is not in normal form,
the newly created N-Variant will be returned with a single non-floating
reference. Typically, .take-ref() should be called on the return
value from this function to guarantee ownership of a single non-floating
reference to it.
method get-normal-form (--> CArray[N-Variant] )
Return value; a trusted N-Variant.
#-------------------------------------------------------------------------------
get-objv
Gets the contents of an array of object paths N-Variant. 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-undefined then the number of elements in the result
is stored there. In any case, the resulting array will be
undefined-terminated.
For an empty array, $length will be set to 0 and a pointer to a
undefined pointer will be returned.
method get-objv ( Array[gsize] $length --> Array[Str] )
$length; (transfer ownership: full) the length of the result, or undefined.
Return value; an array of constant strings.
#-------------------------------------------------------------------------------
get-size
Determines the number of bytes that would be required to store $value
with .store().
If $value has a fixed-sized type then this function always returned
that fixed size.
In the case that $value 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.
method get-size (--> Int )
Return value; the serialized size of $value.
#-------------------------------------------------------------------------------
get-string
Returns the string value of a N-Variant instance with a string
type. This includes the types G_VARIANT_TYPE_STRING,
G_VARIANT_TYPE_OBJECT_PATH and G_VARIANT_TYPE_SIGNATURE.
The string will always be UTF-8 encoded, will never be undefined, and will never contain nul bytes.
If $length is non-undefined 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 ā for
G_VARIANT_TYPE_OBJECT_PATH, this is "/", and for other types it is the
empty string.
It is an error to call this function with a $value of any type
other than those three.
The return value remains valid as long as $value exists.
method get-string ( Array[gsize] $length --> Str )
$length; (transfer ownership: full) a pointer to a #gsize, to store the length.
Return value; the constant string, UTF-8 encoded.
#-------------------------------------------------------------------------------
get-strv
Gets the contents of an array of strings N-Variant. 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-undefined then the number of elements in the result
is stored there. In any case, the resulting array will be
undefined-terminated.
For an empty array, $length will be set to 0 and a pointer to a
undefined pointer will be returned.
method get-strv ( Array[gsize] $length --> Array[Str] )
$length; (transfer ownership: full) the length of the result, or undefined.
Return value; an array of constant strings.
#-------------------------------------------------------------------------------
get-type
Determines the type of $value.
The return value is valid for the lifetime of $value and must not
be freed.
method get-type (--> CArray[N-VariantType] )
Return value; a N-VariantType.
#-------------------------------------------------------------------------------
get-type-string
Returns the type string of $value. Unlike the result of calling
.type-peek-string(), this string is nul-terminated. This
string belongs to N-Variant and must not be freed.
method get-type-string (--> Str )
Return value; the type string for the type of $value.
#-------------------------------------------------------------------------------
get-uint16
Returns the 16-bit unsigned integer value of $value.
It is an error to call this function with a $value of any type
other than %G_VARIANT_TYPE_UINT16.
method get-uint16 (--> UInt )
Return value; a #guint16.
#-------------------------------------------------------------------------------
get-uint32
Returns the 32-bit unsigned integer value of $value.
It is an error to call this function with a $value of any type
other than %G_VARIANT_TYPE_UINT32.
method get-uint32 (--> UInt )
Return value; a #guint32.
#-------------------------------------------------------------------------------
get-uint64
Returns the 64-bit unsigned integer value of $value.
It is an error to call this function with a $value of any type
other than %G_VARIANT_TYPE_UINT64.
method get-uint64 (--> UInt )
Return value; a #guint64.
#-------------------------------------------------------------------------------
get-va This function is not yet available
This function is intended to be used by libraries based on N-Variant
that want to provide .get()-like functionality to their
users.
The API is more general than .get() to allow a wider range
of possible uses.
$format_string must still point to a valid format string, but it only
need to be nul-terminated if $endptr is undefined. If $endptr is
non-undefined then it is updated to point to the first character past the
end of the format string.
$app is a pointer to a #va_list. The arguments, according to $format_string, are collected from this #va_list and the list is left
pointing to the argument following the last.
These two generalisations allow mixing of multiple calls to
.new-va() and .get-va() within a single actual
varargs call by the user.
$format_string determines the C types that are used for unpacking
the values and also determines if the values are copied or borrowed,
see the section on GVariant format strings.
method get-va ( Str $format-string, Array[Str] $endptr, ā¦ )
$format-string; a string that is prefixed with a format string.
$endptr; location to store the end pointer, or undefined.
app; a pointer to a #va_list. Note that each argument must be specified as a type followed by its value!
#-------------------------------------------------------------------------------
get-variant
Unboxes $value. The result is the N-Variant instance that was
contained in $value.
method get-variant (--> CArray[N-Variant] )
Return value; the item contained in the variant.
#-------------------------------------------------------------------------------
hash
Generates a hash value for a N-Variant instance.
The output of this function is guaranteed to be the same for a given value only per-process. It may change between different processor architectures or even different versions of GLib. Do not use this function as a basis for building protocols or file formats.
The type of $value is #gconstpointer only to allow use of this
function with Gnome::Glib::N-HashTable. $value must be a N-Variant.
method hash (--> UInt )
Return value; a hash value corresponding to $value.
#-------------------------------------------------------------------------------
is-container
Checks if $value is a container.
method is-container (--> Bool )
Return value; True if $value is a container.
#-------------------------------------------------------------------------------
is-floating
Checks whether $value 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 .ref-sink()
or .take-ref().
See .ref-sink() for more information about floating reference
counts.
method is-floating (--> Bool )
Return value; whether $value is floating.
#-------------------------------------------------------------------------------
is-normal-form
Checks if $value 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 N-Variant
using .new-from-data() and then use this function to
check.
If $value 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.
method is-normal-form (--> Bool )
Return value; True if $value is in normal form.
#-------------------------------------------------------------------------------
is-of-type
Checks if a value has a type matching the provided type.
method is-of-type ( CArray[N-VariantType] $type --> Bool )
$type; a N-VariantType.
Return value; True if the type of $value matches $type.
#-------------------------------------------------------------------------------
iter-new This function is not yet available
Creates a heap-allocated N-VariantIter for iterating over the items
in $value.
Use .iter-free() to free the return value when you no longer
need it.
A reference is taken to $value and will be released only when
.iter-free() is called.
method iter-new (--> CArray[N-VariantIter] )
Return value; a new heap-allocated N-VariantIter.
#-------------------------------------------------------------------------------
lookup This function is not yet available
Looks up a value in a dictionary N-Variant.
This function is a wrapper around .lookup-value() and
.get(). In the case that undefined would have been returned,
this function returns False. Otherwise, it unpacks the returned
value and returns True.
$format_string determines the C types that are used for unpacking
the values and also determines if the values are copied or borrowed,
see the section on GVariant format strings.
This function is currently implemented with a linear scan. If you plan to do many lookups then N-VariantDict may be more efficient.
method lookup ( Str $key, Str $format-string, ā¦ --> Bool )
$key; the key to look up in the dictionary.
$format-string; a GVariant format string.
ā¦; ā¦. Note that each argument must be specified as a type followed by its value!
Return value; True if a value was unpacked.
#-------------------------------------------------------------------------------
lookup-value
Looks up a value in a dictionary N-Variant.
This function works with dictionaries of the type a{s*} (and equally well with type a{o*}, but we only further discuss the string case for sake of clarity).
In the event that $dictionary has the type a{sv}, the $expected_type
string specifies what type of value is expected to be inside of the
variant. If the value inside the variant has a different type then
undefined is returned. In the event that $dictionary has a value type other
than v then $expected_type must directly match the value type and it is
used to unpack the value directly or an error occurs.
In either case, if $key is not found in $dictionary, undefined is returned.
If the key is found and the value has the correct type, it is
returned. If $expected_type was specified then any non-undefined return
value will have this type.
This function is currently implemented with a linear scan. If you plan to do many lookups then N-VariantDict may be more efficient.
method lookup-value ( Str $key, CArray[N-VariantType] $expected-type --> CArray[N-Variant] )
$key; the key to look up in the dictionary.
$expected-type; a N-VariantType, or undefined.
Return value; the value of the dictionary key, or undefined.
#-------------------------------------------------------------------------------
n-children
Determines the number of children in a container N-Variant instance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type of N-Variant.
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).
method n-children (--> Int )
Return value; the number of children in the container.
#-------------------------------------------------------------------------------
Pretty-prints $value in the format understood by .parse().
The format is described here.
If $type_annotate is True, then type information is included in
the output.
method print ( Bool() $type-annotate --> Str )
$type-annotate;
Trueif type information should be included in the output.
Return value; a newly-allocated string holding the result..
#-------------------------------------------------------------------------------
print-string This function is not yet available
Behaves as .print(), but operates on a Gnome::Glib::N-String.
If $string is non-undefined then it is appended to and returned. Else,
a new empty Gnome::Glib::N-String is allocated and it is returned.
method print-string ( CArray[N-String] $string, Bool() $type-annotate --> CArray[N-String] )
$string; a Gnome::Glib::N-String, or undefined.
$type-annotate;
Trueif type information should be included in the output.
Return value; a Gnome::Glib::N-String containing the string.
#-------------------------------------------------------------------------------
ref
Increases the reference count of $value.
method ref (--> CArray[N-Variant] )
Return value; the same $value.
#-------------------------------------------------------------------------------
ref-sink
N-Variant uses a floating reference count system. All functions with names starting with g_variant_new_ return floating references.
Calling .ref-sink() on a N-Variant with a floating reference
will convert the floating reference into a full reference. Calling
.ref-sink() on a non-floating N-Variant results in an
additional normal reference being added.
In other words, if the $value is floating, then this call "assumes
ownership" of the floating reference, converting it to a normal
reference. If the $value is not floating, then this call adds a
new normal reference increasing the reference count by one.
All calls that result in a N-Variant instance being inserted into a
container will call .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.
method ref-sink (--> CArray[N-Variant] )
Return value; the same $value.
#-------------------------------------------------------------------------------
store
Stores the serialized form of $value at $data. $data should be
large enough. See .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
.get-normal-form() for a solution.
As with .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.
method store ( gpointer $data )
$data; the location to store the serialized data at.
#-------------------------------------------------------------------------------
take-ref
If $value is floating, sink it. Otherwise, do nothing.
Typically you want to use .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 N-Variant. 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 N-Variant API makes it likely that for newly-created N-Variant instances, the user can be saved some typing if they are allowed to return a N-Variant 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
.ref-sink() running at the same time in another thread on
the same N-Variant instance. If .ref-sink() runs first then
the result will be that the floating reference is converted to a hard
reference. If .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.
method take-ref (--> CArray[N-Variant] )
Return value; the same $value.
#-------------------------------------------------------------------------------
unref
Decreases the reference count of $value. When its reference count
drops to 0, the memory used by the variant is freed.
method unref ( )
#------------------------------------------------------------------------------- #--[Functions]------------------------------------------------------------------ #-------------------------------------------------------------------------------
Functions
#-------------------------------------------------------------------------------
is-object-path
Determines if a given string is a valid D-Bus object path. You
should ensure that a string is a valid D-Bus object path before
passing it to .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.
method is-object-path ( Str $string --> Bool )
$string; a normal C nul-terminated string.
Return value; True if $string is a D-Bus object path.
#-------------------------------------------------------------------------------
is-signature
Determines if a given string is a valid D-Bus type signature. You
should ensure that a string is a valid D-Bus type signature before
passing it to .new-signature().
D-Bus type signatures consist of zero or more definite N-VariantType strings in sequence.
method is-signature ( Str $string --> Bool )
$string; a normal C nul-terminated string.
Return value; True if $string is a D-Bus type signature.
#-------------------------------------------------------------------------------
parse
Parses a N-Variant from a text representation.
A single N-Variant is parsed from the content of $text.
The format is described here.
The memory at $limit will never be accessed and the parser behaves as
if the character at $limit is the nul terminator. This has the
effect of bounding $text.
If $endptr is non-undefined then $text is permitted to contain data
following the value that this function parses and $endptr will be
updated to point to the first character past the end of the text
parsed by this function. If $endptr is undefined and there is extra data
then an error is returned.
If $type is non-undefined 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 N-Variant
is returned. It is never floating, and must be freed with
.unref().
In case of any error, undefined will be returned. If $error is non-undefined
then it will be set to reflect the error that occurred.
Officially, the language understood by the parser is "any string
produced by .print()".
There may be implementation specific restrictions on deeply nested values,
which would result in a G_VARIANT_PARSE_ERROR_RECURSION error. N-Variant is
guaranteed to handle nesting up to at least 64 levels.
method parse ( CArray[N-VariantType] $type, Str $text, Str $limit, Array[Str] $endptr --> CArray[N-Variant] )
$type; a N-VariantType, or undefined.
$text; a string containing a GVariant in text form.
$limit; a pointer to the end of
$text, or undefined.$endptr; a location to store the end pointer, or undefined.
Return value; a non-floating reference to a N-Variant, or undefined.
#-------------------------------------------------------------------------------
parse-error-print-context
Pretty-prints a message showing the context of a N-Variant 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:
or
The format of the message may change in a future version.
$error must have come from a failed attempt to .parse() and $source_str must be exactly the same string that caused the error.
If $source_str was not nul-terminated when you passed it to
.parse() then you must add nul termination before using this
function.
method parse-error-print-context ( CArray[N-Error] $error, Str $source-str --> Str )
$error; a Gnome::Glib::N-Error from the Gnome::Glib::T-Variant domain.
$source-str; the string that was given to the parser.
Return value; the printed message.
#-------------------------------------------------------------------------------
parse-error-quark
No documentation of method.
method parse-error-quark (--> UInt )
Return value; No documentation about its value and use.