pub struct Variant { /* private fields */ }
Expand description
A generic immutable value capable of carrying various types.
See the module documentation for more details.
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:
⚠️ The following code is in c ⚠️
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 [type@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 GLib::Variant::ref()
and
GLib::Variant::unref()
. GVariant
also has floating reference counts —
see [ref_sink()
][Self::ref_sink()].
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 [type@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 GLib::Variant::new_from_data()
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 free()
or
even GLib::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 GLib::Variant::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 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.
GLib type: Shared boxed type with reference counted clone semantics.
Implementations§
source§impl Variant
impl Variant
sourcepub fn type_(&self) -> &VariantTy
pub fn type_(&self) -> &VariantTy
Returns the type of the value. Determines the type of @self.
The return value is valid for the lifetime of @self and must not be freed.
§Returns
a #GVariantType
sourcepub fn is<T: StaticVariantType>(&self) -> bool
pub fn is<T: StaticVariantType>(&self) -> bool
Returns true
if the type of the value corresponds to T
.
sourcepub fn is_type(&self, type_: &VariantTy) -> bool
pub fn is_type(&self, type_: &VariantTy) -> bool
Returns true
if the type of the value corresponds to type_
.
This is equivalent to self.type_().is_subtype_of(type_)
.
sourcepub fn classify(&self) -> VariantClass
pub fn classify(&self) -> VariantClass
Returns the classification of the variant. Classifies @self according to its top-level type.
§Returns
the #GVariantClass of @self
sourcepub fn get<T: FromVariant>(&self) -> Option<T>
pub fn get<T: FromVariant>(&self) -> Option<T>
Tries to extract a value of type T
.
Returns Some
if T
matches the variant’s type.
Deconstructs a #GVariant instance.
Think of this function as an analogue to scanf().
The arguments that are expected by this function are entirely determined by @format_string. @format_string also restricts the permissible types of @self. 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.
§format_string
a #GVariant format string
sourcepub fn try_get<T: FromVariant>(&self) -> Result<T, VariantTypeMismatchError>
pub fn try_get<T: FromVariant>(&self) -> Result<T, VariantTypeMismatchError>
Tries to extract a value of type T
.
sourcepub fn from_variant(value: &Variant) -> Self
pub fn from_variant(value: &Variant) -> Self
Boxes value.
sourcepub fn as_variant(&self) -> Option<Variant>
pub fn as_variant(&self) -> Option<Variant>
Unboxes self.
Returns Some
if self contains a Variant
.
sourcepub fn child_value(&self, index: usize) -> Variant
pub fn child_value(&self, index: usize) -> Variant
Reads a child item out of a container Variant
instance.
§Panics
- if
self
is not a container type. - if given
index
is larger than number of children. Reads a child item out of a container #GVariant instance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type of #GVariant.
It is an error if @index_ is greater than the number of child items in the container. See g_variant_n_children().
The returned value is never floating. You should free it with g_variant_unref() when you’re done with it.
Note that values borrowed from the returned child are not guaranteed to still be valid after the child is freed even if you still hold a reference to @self, if @self has not been serialized at the time this function is called. To avoid this, you can serialize @self 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).
§index_
the index of the child to fetch
§Returns
the child at the specified index
sourcepub fn try_child_value(&self, index: usize) -> Option<Variant>
pub fn try_child_value(&self, index: usize) -> Option<Variant>
Try to read a child item out of a container Variant
instance.
It returns None
if self
is not a container type or if the given
index
is larger than number of children.
sourcepub fn try_child_get<T: StaticVariantType + FromVariant>(
&self,
index: usize,
) -> Result<Option<T>, VariantTypeMismatchError>
pub fn try_child_get<T: StaticVariantType + FromVariant>( &self, index: usize, ) -> Result<Option<T>, VariantTypeMismatchError>
Try to read a child item out of a container Variant
instance.
It returns Ok(None)
if self
is not a container type or if the given
index
is larger than number of children. An error is thrown if the
type does not match.
sourcepub fn child_get<T: StaticVariantType + FromVariant>(&self, index: usize) -> T
pub fn child_get<T: StaticVariantType + FromVariant>(&self, index: usize) -> T
Read a child item out of a container Variant
instance.
§Panics
- if
self
is not a container type. - if given
index
is larger than number of children. - if the expected variant type does not match
sourcepub fn str(&self) -> Option<&str>
pub fn str(&self) -> Option<&str>
Tries to extract a &str
.
Returns Some
if the variant has a string type (s
, o
or g
type
strings).
sourcepub fn fixed_array<T: FixedSizeVariantType>(
&self,
) -> Result<&[T], VariantTypeMismatchError>
pub fn fixed_array<T: FixedSizeVariantType>( &self, ) -> Result<&[T], VariantTypeMismatchError>
Tries to extract a &[T]
from a variant of array type with a suitable element type.
Returns an error if the type is wrong. Provides access to the serialized data for an array of fixed-sized items.
@self 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-None
, is set equal to the number of
items in the array.
§element_size
the size of each element
§Returns
a pointer to the fixed array
sourcepub fn array_from_iter<T: StaticVariantType>(
children: impl IntoIterator<Item = Variant>,
) -> Self
pub fn array_from_iter<T: StaticVariantType>( children: impl IntoIterator<Item = Variant>, ) -> Self
Creates a new Variant array from children.
§Panics
This function panics if not all variants are of type T
.
sourcepub fn array_from_iter_with_type(
type_: &VariantTy,
children: impl IntoIterator<Item = impl AsRef<Variant>>,
) -> Self
pub fn array_from_iter_with_type( type_: &VariantTy, children: impl IntoIterator<Item = impl AsRef<Variant>>, ) -> Self
Creates a new Variant array from children with the specified type.
§Panics
This function panics if not all variants are of type type_
.
sourcepub fn array_from_fixed_array<T: FixedSizeVariantType>(array: &[T]) -> Self
pub fn array_from_fixed_array<T: FixedSizeVariantType>(array: &[T]) -> Self
Creates a new Variant array from a fixed array.
sourcepub fn tuple_from_iter(
children: impl IntoIterator<Item = impl AsRef<Variant>>,
) -> Self
pub fn tuple_from_iter( children: impl IntoIterator<Item = impl AsRef<Variant>>, ) -> Self
Creates a new Variant tuple from children.
sourcepub fn from_dict_entry(key: &Variant, value: &Variant) -> Self
pub fn from_dict_entry(key: &Variant, value: &Variant) -> Self
Creates a new dictionary entry Variant.
DictEntry should be preferred over this when the types are known statically.
sourcepub fn from_maybe<T: StaticVariantType>(child: Option<&Variant>) -> Self
pub fn from_maybe<T: StaticVariantType>(child: Option<&Variant>) -> Self
Creates a new maybe Variant.
sourcepub fn as_maybe(&self) -> Option<Variant>
pub fn as_maybe(&self) -> Option<Variant>
Extract the value of a maybe Variant.
Returns the child value, or None
if the value is Nothing.
§Panics
Panics if the variant is not maybe-typed.
sourcepub fn print(&self, type_annotate: bool) -> GString
pub fn print(&self, type_annotate: bool) -> GString
Pretty-print the contents of this variant in a human-readable form.
A variant can be recreated from this output via Variant::parse
.
Pretty-prints @self in the format understood by g_variant_parse().
The format is described here.
If @type_annotate is true
, then type information is included in
the output.
§type_annotate
true
if type information should be included in
the output
§Returns
a newly-allocated string holding the result.
sourcepub fn parse(type_: Option<&VariantTy>, text: &str) -> Result<Self, Error>
pub fn parse(type_: Option<&VariantTy>, text: &str) -> Result<Self, Error>
Parses a GVariant from the text representation produced by print()
.
sourcepub fn from_bytes<T: StaticVariantType>(bytes: &Bytes) -> Self
pub fn from_bytes<T: StaticVariantType>(bytes: &Bytes) -> Self
Constructs a new serialized-mode GVariant instance. Constructs a new serialized-mode #GVariant instance. This is the inner interface for creation of new serialized values that gets called from various functions in gvariant.c.
A reference is taken on @bytes.
The data in @bytes must be aligned appropriately for the @type_ being loaded. Otherwise this function will internally create a copy of the memory (since GLib 2.60) or (in older versions) fail and exit the process.
§type_
a #GVariantType
§bytes
a #GBytes
§trusted
if the contents of @bytes are trusted
§Returns
a new #GVariant with a floating reference
sourcepub unsafe fn from_bytes_trusted<T: StaticVariantType>(bytes: &Bytes) -> Self
pub unsafe fn from_bytes_trusted<T: StaticVariantType>(bytes: &Bytes) -> Self
Constructs a new serialized-mode GVariant instance.
This is the same as from_bytes
, except that checks on the passed
data are skipped.
You should not use this function on data from external sources.
§Safety
Since the data is not validated, this is potentially dangerous if called on bytes which are not guaranteed to have come from serialising another Variant. The caller is responsible for ensuring bad data is not passed in.
sourcepub fn from_data<T: StaticVariantType, A: AsRef<[u8]>>(data: A) -> Self
pub fn from_data<T: StaticVariantType, A: AsRef<[u8]>>(data: A) -> Self
Constructs a new serialized-mode GVariant instance. Creates a new #GVariant instance from serialized data.
@type_ is the type of #GVariant instance that will be constructed. The interpretation of @data depends on knowing the type.
@data is not modified by this function and must remain valid with an unchanging value until such a time as @notify is called with @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. g_variant_byteswap() can be used to recover the original values.
@notify will be called with @user_data when @data is no longer needed. The exact time of this call is unspecified and might even be before this function returns.
Note: @data must be backed by memory that is aligned appropriately for the @type_ being loaded. Otherwise this function will internally create a copy of the memory (since GLib 2.60) or (in older versions) fail and exit the process.
§type_
a definite #GVariantType
§data
the serialized data
§trusted
true
if @data is definitely in normal form
§notify
function to call when @data is no longer needed
§Returns
a new floating #GVariant of type @type_
sourcepub unsafe fn from_data_trusted<T: StaticVariantType, A: AsRef<[u8]>>(
data: A,
) -> Self
pub unsafe fn from_data_trusted<T: StaticVariantType, A: AsRef<[u8]>>( data: A, ) -> Self
Constructs a new serialized-mode GVariant instance.
This is the same as from_data
, except that checks on the passed
data are skipped.
You should not use this function on data from external sources.
§Safety
Since the data is not validated, this is potentially dangerous if called on bytes which are not guaranteed to have come from serialising another Variant. The caller is responsible for ensuring bad data is not passed in.
sourcepub fn from_bytes_with_type(bytes: &Bytes, type_: &VariantTy) -> Self
pub fn from_bytes_with_type(bytes: &Bytes, type_: &VariantTy) -> Self
Constructs a new serialized-mode GVariant instance with a given type.
sourcepub unsafe fn from_bytes_with_type_trusted(
bytes: &Bytes,
type_: &VariantTy,
) -> Self
pub unsafe fn from_bytes_with_type_trusted( bytes: &Bytes, type_: &VariantTy, ) -> Self
Constructs a new serialized-mode GVariant instance with a given type.
This is the same as from_bytes
, except that checks on the passed
data are skipped.
You should not use this function on data from external sources.
§Safety
Since the data is not validated, this is potentially dangerous if called on bytes which are not guaranteed to have come from serialising another Variant. The caller is responsible for ensuring bad data is not passed in.
sourcepub fn from_data_with_type<A: AsRef<[u8]>>(data: A, type_: &VariantTy) -> Self
pub fn from_data_with_type<A: AsRef<[u8]>>(data: A, type_: &VariantTy) -> Self
Constructs a new serialized-mode GVariant instance with a given type.
sourcepub unsafe fn from_data_with_type_trusted<A: AsRef<[u8]>>(
data: A,
type_: &VariantTy,
) -> Self
pub unsafe fn from_data_with_type_trusted<A: AsRef<[u8]>>( data: A, type_: &VariantTy, ) -> Self
Constructs a new serialized-mode GVariant instance with a given type.
This is the same as from_data
, except that checks on the passed
data are skipped.
You should not use this function on data from external sources.
§Safety
Since the data is not validated, this is potentially dangerous if called on bytes which are not guaranteed to have come from serialising another Variant. The caller is responsible for ensuring bad data is not passed in.
sourcepub fn data_as_bytes(&self) -> Bytes
pub fn data_as_bytes(&self) -> Bytes
Returns the serialized form of a GVariant instance. Returns a pointer to the serialized form of a #GVariant instance. The semantics of this function are exactly the same as g_variant_get_data(), except that the returned #GBytes holds a reference to the variant data.
§Returns
A new #GBytes representing the variant data
sourcepub fn data(&self) -> &[u8] ⓘ
pub fn data(&self) -> &[u8] ⓘ
Returns the serialized form of a GVariant instance. Returns a pointer to the serialized form of a #GVariant instance. The returned data may not be in fully-normalised form if read from an untrusted source. The returned data must not be freed; it remains valid for as long as @self exists.
If @self is a fixed-sized value that was deserialized from a
corrupted serialized container then None
may be returned. In this
case, the proper thing to do is typically to use the appropriate
number of nul bytes in place of @self. If @self is not fixed-sized
then None
is never returned.
In the case that @self is already in serialized form, this function is O(1). If the value is not already in serialized form, serialization occurs implicitly and is approximately O(n) in the size of the result.
To deserialize the data returned by this function, in addition to the
serialized data, you must know the type of the #GVariant, and (if the
machine might be different) the endianness of the machine that stored
it. As a result, file formats or network messages that incorporate
serialized #GVariants must include this information either
implicitly (for instance “the file always contains a
G_VARIANT_TYPE_VARIANT
and it is always in little-endian order”) or
explicitly (by storing the type and/or endianness in addition to the
serialized data).
§Returns
the serialized form of @self, or None
sourcepub fn size(&self) -> usize
pub fn size(&self) -> usize
Returns the size of serialized form of a GVariant instance. Determines the number of bytes that would be required to store @self with g_variant_store().
If @self has a fixed-sized type then this function always returned that fixed size.
In the case that @self 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 @self
sourcepub fn store(&self, data: &mut [u8]) -> Result<usize, BoolError>
pub fn store(&self, data: &mut [u8]) -> Result<usize, BoolError>
Stores the serialized form of a GVariant instance into the given slice.
The slice needs to be big enough. Stores the serialized form of @self at @data. @data should be large enough. See g_variant_get_size().
The stored data is in machine native byte order but may not be in fully-normalised form if read from an untrusted source. See g_variant_get_normal_form() for a solution.
As with g_variant_get_data(), to be able to deserialize the serialized variant successfully, its type and (if the destination machine might be different) its endianness must also be available.
This function is approximately O(n) in the size of @data.
sourcepub fn normal_form(&self) -> Self
pub fn normal_form(&self) -> Self
Returns a copy of the variant in normal form. Gets a #GVariant instance that has the same value as @self and is trusted to be in normal form.
If @self is already trusted to be in normal form then a new reference to @self is returned.
If @self 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 @self is found not to be in normal form then a new trusted #GVariant is created with the same value as @self. The non-normal parts of @self 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 @self is already in normal form, a new reference will be returned (which will be floating if @self 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
sourcepub fn byteswap(&self) -> Self
pub fn byteswap(&self) -> Self
Returns a copy of the variant in the opposite endianness. Performs a byteswapping operation on the contents of @self. The result is that all multi-byte numeric data contained in @self 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 @self
sourcepub fn n_children(&self) -> usize
pub fn n_children(&self) -> usize
Determines the number of children in a container GVariant instance. Determines the number of children in a container #GVariant instance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type of #GVariant.
For variants, the return value is always 1. For values with maybe types, it is always zero or one. For arrays, it is the length of the array. For tuples it is the number of tuple items (which depends only on the type). For dictionary entries, it is always 2
This function is O(1).
§Returns
the number of children in the container
sourcepub fn iter(&self) -> VariantIter ⓘ
pub fn iter(&self) -> VariantIter ⓘ
Create an iterator over items in the variant.
Note that this heap allocates a variant for each element, which can be particularly expensive for large arrays.
sourcepub fn array_iter_str(
&self,
) -> Result<VariantStrIter<'_>, VariantTypeMismatchError>
pub fn array_iter_str( &self, ) -> Result<VariantStrIter<'_>, VariantTypeMismatchError>
Create an iterator over borrowed strings from a GVariant of type as
(array of string).
This will fail if the variant is not an array of with the expected child type.
A benefit of this API over Self::iter()
is that it
minimizes allocation, and provides strongly typed access.
let strs = &["foo", "bar"];
let strs_variant: glib::Variant = strs.to_variant();
for s in strs_variant.array_iter_str()? {
println!("{}", s);
}
sourcepub fn is_container(&self) -> bool
pub fn is_container(&self) -> bool
sourcepub fn is_normal_form(&self) -> bool
pub fn is_normal_form(&self) -> bool
Return whether this Variant is in normal form. Checks if @self 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 @self 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 @self is in normal form
sourcepub fn is_object_path(string: &str) -> bool
pub fn is_object_path(string: &str) -> bool
Return whether input string is a valid VariantClass::ObjectPath
.
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.
§string
a normal C nul-terminated string
§Returns
true
if @string is a D-Bus object path
sourcepub fn is_signature(string: &str) -> bool
pub fn is_signature(string: &str) -> bool
Return whether input string is a valid VariantClass::Signature
.
Determines if a given string is a valid D-Bus type signature. You
should ensure that a string is a valid D-Bus type signature before
passing it to g_variant_new_signature().
D-Bus type signatures consist of zero or more definite #GVariantType strings in sequence.
§string
a normal C nul-terminated string
§Returns
true
if @string is a D-Bus type signature
Trait Implementations§
source§impl<T0, T1, T2> From<(T0, T1, T2)> for Variant
impl<T0, T1, T2> From<(T0, T1, T2)> for Variant
source§fn from(t: (T0, T1, T2)) -> Self
fn from(t: (T0, T1, T2)) -> Self
source§impl<T0, T1, T2, T3> From<(T0, T1, T2, T3)> for Variant
impl<T0, T1, T2, T3> From<(T0, T1, T2, T3)> for Variant
source§fn from(t: (T0, T1, T2, T3)) -> Self
fn from(t: (T0, T1, T2, T3)) -> Self
source§impl<T0, T1, T2, T3, T4> From<(T0, T1, T2, T3, T4)> for Variant
impl<T0, T1, T2, T3, T4> From<(T0, T1, T2, T3, T4)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4)) -> Self
fn from(t: (T0, T1, T2, T3, T4)) -> Self
source§impl<T0, T1, T2, T3, T4, T5> From<(T0, T1, T2, T3, T4, T5)> for Variant
impl<T0, T1, T2, T3, T4, T5> From<(T0, T1, T2, T3, T4, T5)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4, T5)) -> Self
fn from(t: (T0, T1, T2, T3, T4, T5)) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6> From<(T0, T1, T2, T3, T4, T5, T6)> for Variant
impl<T0, T1, T2, T3, T4, T5, T6> From<(T0, T1, T2, T3, T4, T5, T6)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4, T5, T6)) -> Self
fn from(t: (T0, T1, T2, T3, T4, T5, T6)) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6, T7> From<(T0, T1, T2, T3, T4, T5, T6, T7)> for Variant
impl<T0, T1, T2, T3, T4, T5, T6, T7> From<(T0, T1, T2, T3, T4, T5, T6, T7)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7)) -> Self
fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7)) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6, T7, T8> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8)> for Variant
impl<T0, T1, T2, T3, T4, T5, T6, T7, T8> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8)) -> Self
fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8)) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9)> for Variant
impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9)) -> Self
fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9)) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10)> for Variant
impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10)) -> Self
fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10)) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11)> for Variant
impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11)) -> Self
fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11)) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12)> for Variant
impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12)) -> Self
fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12)) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13)> for Variant
impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13)> for Variant
source§fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13)) -> Self
fn from(t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13)) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14)> for Variant
impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14)> for Variant
source§fn from(
t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14),
) -> Self
fn from( t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14), ) -> Self
source§impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15)> for Variantwhere
T0: Into<Variant>,
T1: Into<Variant>,
T2: Into<Variant>,
T3: Into<Variant>,
T4: Into<Variant>,
T5: Into<Variant>,
T6: Into<Variant>,
T7: Into<Variant>,
T8: Into<Variant>,
T9: Into<Variant>,
T10: Into<Variant>,
T11: Into<Variant>,
T12: Into<Variant>,
T13: Into<Variant>,
T14: Into<Variant>,
T15: Into<Variant>,
impl<T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15> From<(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15)> for Variantwhere
T0: Into<Variant>,
T1: Into<Variant>,
T2: Into<Variant>,
T3: Into<Variant>,
T4: Into<Variant>,
T5: Into<Variant>,
T6: Into<Variant>,
T7: Into<Variant>,
T8: Into<Variant>,
T9: Into<Variant>,
T10: Into<Variant>,
T11: Into<Variant>,
T12: Into<Variant>,
T13: Into<Variant>,
T14: Into<Variant>,
T15: Into<Variant>,
source§fn from(
t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15),
) -> Self
fn from( t: (T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15), ) -> Self
source§impl<A: AsRef<[T]>, T: FixedSizeVariantType> From<FixedSizeVariantArray<A, T>> for Variant
impl<A: AsRef<[T]>, T: FixedSizeVariantType> From<FixedSizeVariantArray<A, T>> for Variant
source§fn from(a: FixedSizeVariantArray<A, T>) -> Self
fn from(a: FixedSizeVariantArray<A, T>) -> Self
source§impl From<ObjectPath> for Variant
impl From<ObjectPath> for Variant
source§fn from(p: ObjectPath) -> Self
fn from(p: ObjectPath) -> Self
source§impl From<Variant> for VariantDict
impl From<Variant> for VariantDict
source§impl From<VariantDict> for Variant
impl From<VariantDict> for Variant
source§fn from(d: VariantDict) -> Self
fn from(d: VariantDict) -> Self
source§impl<T: Into<Variant> + StaticVariantType> FromIterator<T> for Variant
impl<T: Into<Variant> + StaticVariantType> FromIterator<T> for Variant
source§fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self
fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self
source§impl FromVariant for Variant
impl FromVariant for Variant
source§impl HasParamSpec for Variant
impl HasParamSpec for Variant
source§impl PartialOrd for Variant
impl PartialOrd for Variant
source§impl StaticType for Variant
impl StaticType for Variant
source§fn static_type() -> Type
fn static_type() -> Type
Self
.source§impl StaticVariantType for Variant
impl StaticVariantType for Variant
source§fn static_variant_type() -> Cow<'static, VariantTy>
fn static_variant_type() -> Cow<'static, VariantTy>
VariantType
corresponding to Self
.source§impl ToVariant for Variant
impl ToVariant for Variant
source§fn to_variant(&self) -> Variant
fn to_variant(&self) -> Variant
Variant
clone of self
.impl Eq for Variant
impl Send for Variant
impl Sync for Variant
Auto Trait Implementations§
impl Freeze for Variant
impl RefUnwindSafe for Variant
impl Unpin for Variant
impl UnwindSafe for Variant
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
source§unsafe fn clone_to_uninit(&self, dst: *mut T)
unsafe fn clone_to_uninit(&self, dst: *mut T)
clone_to_uninit
)source§impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GPtrArray> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GPtrArray> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GSList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GSList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GPtrArray> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GPtrArray> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GSList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GSList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GPtrArray> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GPtrArray> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GSList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GSList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GPtrArray> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GPtrArray> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GSList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GSList> for Twhere
T: GlibPtrDefault + FromGlibPtrNone<<T as GlibPtrDefault>::GlibType> + FromGlibPtrFull<<T as GlibPtrDefault>::GlibType>,
source§impl<T> IntoClosureReturnValue for T
impl<T> IntoClosureReturnValue for T
fn into_closure_return_value(self) -> Option<Value>
source§impl<T> PropertyGet for Twhere
T: HasParamSpec,
impl<T> PropertyGet for Twhere
T: HasParamSpec,
source§impl<T> StaticTypeExt for Twhere
T: StaticType,
impl<T> StaticTypeExt for Twhere
T: StaticType,
source§fn ensure_type()
fn ensure_type()
source§impl<T> ToSendValue for T
impl<T> ToSendValue for T
source§fn to_send_value(&self) -> SendValue
fn to_send_value(&self) -> SendValue
SendValue
clone of self
.