haskell-gi-base-0.15: Foundation for libraries generated by haskell-gi

Safe HaskellNone
LanguageHaskell98

Data.GI.Base.GVariant

Contents

Description

This module contains some helper functions for dealing with GVariant values. The simplest way of dealing with them is by using the IsGVariant typeclass:

str <- fromGVariant variant :: IO (Maybe Text)

assuming that the variant is expected to contain a string in UTF8 encoding. The code becomes even shorter if the type checker can determine the return type for you:

readStringVariant :: GVariant -> IO Text
readStringVariant variant =
  fromGVariant variant >>= \case
     Nothing  -> error "Variant was not a string"
     Just str -> return str

Alternatively, you can use manually the gvariantFrom* and gvariantTo* family of functions.

Synopsis

Documentation

class IsGVariant a where Source

The typeclass for types that can be automatically marshalled into GVariant using toGVariant and fromGVariant.

Methods

toGVariant :: a -> IO GVariant Source

Convert a value of the given type into a GVariant.

fromGVariant :: GVariant -> IO (Maybe a) Source

Try to decode a GVariant into a target type. If the conversion fails we return Nothing. The type that was expected can be obtained by calling toGVariantFormatString, and the actual type as understood by the GVariant code can be obtained by calling gvariantToTypeString.

toGVariantFormatString :: a -> Text Source

The expected format string for this type (the argument is ignored).

Instances

class Ord a => IsGVariantBasicType a Source

The typeclass for basic type GVariant types, i.e. those that are not containers.

Instances

noGVariant :: Maybe GVariant Source

An alias for Nothing :: Maybe GVariant to save some typing.

gvariantGetTypeString :: GVariant -> IO Text Source

Get the expected type of a GVariant, in GVariant notation. See https://developer.gnome.org/glib/stable/glib-GVariantType.html for the meaning of the resulting format string.

Type wrappers

Some GVariant types are isomorphic to Haskell types, but they carry some extra information. For example, there is a tuple singlet type, which is isomorphic to a single Haskell value with the added bit of information that it is wrapped in a tuple container. In order to use these values you can use the following wrappers, which allow the IsGVariant instance to disambiguate the requested type properly.

newtype GVariantSinglet a Source

Haskell has no notion of one element tuples, but GVariants do, so the following allows for marshalling one element tuples properly using fromGVariant and toGVariant. For instance, to construct a single element tuple containing a string, you could do

toGVariant (GVariantSinglet "Test")

Constructors

GVariantSinglet a 

Instances

Eq a => Eq (GVariantSinglet a) 
Show a => Show (GVariantSinglet a) 
IsGVariant a => IsGVariant (GVariantSinglet a)

One element tuples.

data GVariantDictEntry key value Source

A DictEntry GVariant is isomorphic to a two-tuple. Wrapping the values into a GVariantDictentry allows the IsGVariant instance to do the right thing.

Constructors

GVariantDictEntry key value 

Instances

(Eq key, Eq value) => Eq (GVariantDictEntry key value) 
(Show key, Show value) => Show (GVariantDictEntry key value) 
(IsGVariant a, IsGVariantBasicType a, IsGVariant b) => IsGVariant (GVariantDictEntry a b) 

newtype GVariantHandle Source

Constructors

GVariantHandle Int32 

Instances

data GVariantObjectPath Source

An object representing a DBus object path, which is a particular type of GVariant too. (Just a string with some specific requirements.) In order to construct/deconstruct a GVariantObjectPath one can use newGVariantObjectPath and gvariantObjectPathToText.

Instances

newGVariantObjectPath :: Text -> Maybe GVariantObjectPath Source

Try to construct a DBus object path. If the passed string is not a valid object path Nothing will be returned.

gvariantObjectPathToText :: GVariantObjectPath -> Text Source

Return the Text representation of a GVariantObjectPath.

data GVariantSignature Source

An object representing a DBus signature, which is a particular type of GVariant too. (Just a string with some specific requirements.) In order to construct/deconstruct a GVariantSignature one can use newGVariantSignature and gvariantSignatureToText.

Instances

newGVariantSignature :: Text -> Maybe GVariantSignature Source

Try to construct a DBus object path. If the passed string is not a valid DBus signature Nothing will be returned.

gvariantSignatureToText :: GVariantSignature -> Text Source

Return the Text representation of a GVariantSignature.

Manual memory management

wrapGVariantPtr :: Ptr GVariant -> IO GVariant Source

Take ownership of a passed in Ptr (typically created just for us, so if it is floating we sink it).

newGVariantFromPtr :: Ptr GVariant -> IO GVariant Source

Construct a Haskell wrapper for the given GVariant, without assuming ownership.

refGVariant :: GVariant -> IO (Ptr GVariant) Source

Add a reference to the given GVariant.

unrefGVariant :: GVariant -> IO () Source

Remove a reference to the given GVariant.

Manual conversions

Basic types

The use of these should be fairly self-explanatory. If you want to convert a Haskell type into a GVariant, use gvariantTo*. If you want to convert a GVariant into a Haskell type, use gvariantFrom*. The conversion can fail if the GVariant is not of the expected type (if you want to convert a GVariant containing a Int16 into a Text value, say), in which case Nothing will be returned.

gvariantToBool :: GVariant -> IO (Maybe Bool) Source

gvariantFromBool :: Bool -> IO GVariant Source

gvariantToWord8 :: GVariant -> IO (Maybe Word8) Source

gvariantFromWord8 :: Word8 -> IO GVariant Source

gvariantToInt16 :: GVariant -> IO (Maybe Int16) Source

gvariantFromInt16 :: Int16 -> IO GVariant Source

gvariantToWord16 :: GVariant -> IO (Maybe Word16) Source

gvariantFromWord16 :: Word16 -> IO GVariant Source

gvariantToInt32 :: GVariant -> IO (Maybe Int32) Source

gvariantFromInt32 :: Int32 -> IO GVariant Source

gvariantToWord32 :: GVariant -> IO (Maybe Word32) Source

gvariantFromWord32 :: Word32 -> IO GVariant Source

gvariantToInt64 :: GVariant -> IO (Maybe Int64) Source

gvariantFromInt64 :: Int64 -> IO GVariant Source

gvariantToWord64 :: GVariant -> IO (Maybe Word64) Source

gvariantFromWord64 :: Word64 -> IO GVariant Source

gvariantToHandle :: GVariant -> IO (Maybe Int32) Source

Extract the DBus handle (an Int32) inside a GVariant.

gvariantFromHandle :: Int32 -> IO GVariant Source

Convert a DBus handle (an Int32) into a GVariant.

gvariantToDouble :: GVariant -> IO (Maybe Double) Source

gvariantFromDouble :: Double -> IO GVariant Source

gvariantToText :: GVariant -> IO (Maybe Text) Source

Decode an UTF-8 encoded string GVariant into Text.

gvariantFromText :: Text -> IO GVariant Source

Encode a Text into an UTF-8 encoded string GVariant.

gvariantToObjectPath :: GVariant -> IO (Maybe Text) Source

Extract a GVariantObjectPath from a GVariant, represented as its underlying Text representation.

gvariantFromObjectPath :: GVariantObjectPath -> IO GVariant Source

Construct a GVariant containing an object path. In order to build a GVariantObjectPath value see newGVariantObjectPath.

gvariantToSignature :: GVariant -> IO (Maybe Text) Source

Extract a GVariantSignature from a GVariant, represented as Text.

gvariantFromSignature :: GVariantSignature -> IO GVariant Source

Construct a GVariant containing an DBus signature. In order to build a GVariantSignature value see newGVariantSignature.

Container type conversions

gvariantToGVariant :: GVariant -> IO (Maybe GVariant) Source

Unbox a GVariant contained inside another GVariant.

gvariantFromGVariant :: GVariant -> IO GVariant Source

Box a GVariant inside another GVariant.

gvariantToBytestring :: GVariant -> IO (Maybe ByteString) Source

Extract a zero terminated list of bytes into a ByteString.

gvariantFromBytestring :: ByteString -> IO GVariant Source

Encode a ByteString into a list of bytes GVariant.

gvariantFromMaybe :: forall a. IsGVariant a => Maybe a -> IO GVariant Source

Convert a Maybe value into a corresponding GVariant of maybe type.

gvariantToMaybe :: forall a. IsGVariant a => GVariant -> IO (Maybe (Maybe a)) Source

Try to decode a maybe GVariant into the corresponding Maybe type. If the conversion is successful this returns Just x, where x itself is of Maybe type. So, in particular, Just Nothing indicates a successful call, and means that the GVariant of maybe type was empty.

gvariantFromDictEntry :: (IsGVariant key, IsGVariantBasicType key, IsGVariant value) => key -> value -> IO GVariant Source

Construct a GVariant of type DictEntry from the given key and value. The key must be a basic GVariant type, i.e. not a container. This is determined by whether it belongs to the IsGVariantBasicType typeclass. On the other hand value is an arbitrary GVariant, and in particular it can be a container type.

gvariantToDictEntry :: forall key value. (IsGVariant key, IsGVariantBasicType key, IsGVariant value) => GVariant -> IO (Maybe (key, value)) Source

Unpack a DictEntry variant into key and value, which are returned as a two element tuple in case of success.

gvariantFromMap :: (IsGVariant key, IsGVariantBasicType key, IsGVariant value) => Map key value -> IO GVariant Source

Pack a Map into a GVariant for dictionary type, which is just an array of GVariantDictEntry.

gvariantToMap :: forall key value. (IsGVariant key, IsGVariantBasicType key, IsGVariant value) => GVariant -> IO (Maybe (Map key value)) Source

Unpack a GVariant into a Map. Notice that this assumes that all the elements in the GVariant array of GVariantDictEntry are of the same type, which is not necessary for a generic GVariant, so this is somewhat restrictive. For the general case it is necessary to use gvariantToList plus gvariantToDictEntry directly.

gvariantFromList :: forall a. IsGVariant a => [a] -> IO GVariant Source

Given a list of elements construct a GVariant array containing them.

gvariantToList :: forall a. IsGVariant a => GVariant -> IO (Maybe [a]) Source

Unpack a GVariant array into its elements.

gvariantFromTuple :: [GVariant] -> IO GVariant Source

Given a list of GVariant, construct a GVariant tuple containing the elements in the list.

gvariantToTuple :: GVariant -> IO (Maybe [GVariant]) Source

Extract the children of a GVariant tuple into a list.