Sets our main struct and passes it to the parent class
Creates a new boolean GVariant instance -- either TRUE or FALSE. Since 2.24
This function is intended to be used by libraries based on GVariant that want to provide g_variant_new()-like functionality to their users. The API is more general than g_variant_new() 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 NULL. If endptr is non-NULL 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 g_variant_new_va() and g_variant_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 GVariant 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 g_variant_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 g_variant_new() call. Since 2.24
Creates a new byte GVariant instance. Since 2.24
Creates a new int16 GVariant instance. Since 2.24
Creates a new uint16 GVariant instance. Since 2.24
Creates a new int32 GVariant instance. Since 2.24
Creates a new uint32 GVariant instance. Since 2.24
Creates a new int64 GVariant instance. Since 2.24
Creates a new uint64 GVariant instance. Since 2.24
Creates a new double GVariant instance. Since 2.24
Creates a string GVariant with the contents of string. string must be valid utf8. Since 2.24
Boxes value. The result is a GVariant instance representing a variant containing the original value. If child is a floating reference (see g_variant_ref_sink()), the new instance takes ownership of child. Since 2.24
Constructs an array of strings GVariant from the given array of strings. If length is -1 then strv is NULL-terminated. Since 2.24
Depending on if child is NULL, 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-NULL. If child_type is non-NULL then it must be a definite type. If they are both non-NULL then child_type must be the type of child. If child is a floating reference (see g_variant_ref_sink()), the new instance takes ownership of child. Since 2.24
Creates a new GVariant array from children. child_type must be non-NULL 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-NULL 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 NULL. 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 g_variant_ref_sink()), the new instance takes ownership of them as if via g_variant_ref_sink(). Since 2.24
Creates a new tuple GVariant out of the items in children. The type is determined from the types of children. No entry in the children array may be NULL. If n_children is 0 then the unit tuple is constructed. If the children are floating references (see g_variant_ref_sink()), the new instance takes ownership of them as if via g_variant_ref_sink(). Since 2.24
Creates a new dictionary entry GVariant. key and value must be non-NULL. key must be a value of a basic type (ie: not a container). If the key or value are floating references (see g_variant_ref_sink()), the new instance takes ownership of them as if via g_variant_ref_sink(). Since 2.24
Creates a new GVariant instance from serialised 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 serialised data in normal form then trusted should be TRUE. This applies to serialised 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. 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. Since 2.24
Parses format and returns the result. This is the version of g_variant_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 GVariant pointer (eg: format was "%*") then the collected GVariant 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 g_variant_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 g_variant_new() call.
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. Since 2.24
Classifies value according to its top-level type. Since 2.24
Increases the reference count of value. Since 2.24
Similar to g_variant_get_bytestring() except that instead of returning a constant string, the string is duplicated. The return value must be freed using g_free(). Since 2.26
Gets the contents of an array of array of bytes GVariant. This call makes a deep copy; the return result should be released with g_strfreev(). If length is non-NULL then the number of elements in the result is stored there. In any case, the resulting array will be NULL-terminated. For an empty array, length will be set to 0 and a pointer to a NULL pointer will be returned. Since 2.26
Similar to g_variant_get_string() except that instead of returning a constant string, the string is duplicated. The string will always be utf8 encoded. The return value must be freed using g_free(). Since 2.24
Gets the contents of an array of strings GVariant. This call makes a deep copy; the return result should be released with g_strfreev(). If length is non-NULL then the number of elements in the result is stored there. In any case, the resulting array will be NULL-terminated. For an empty array, length will be set to 0 and a pointer to a NULL pointer will be returned. Since 2.24
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. Since 2.24
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. Since 2.24
Returns the string value of a GVariant instance with an array-of-bytes type. The string has no particular encoding. If the array does not end with a nul terminator character, the empty string is returned. For this reason, you can always trust that a non-NULL nul-terminated string will be returned by this function. If the array contains a nul terminator character somewhere other than the last byte then the returned string is the string, up to the first such nul character. 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. Since 2.26
Gets the contents of an array of array of bytes GVariant. This call makes a shallow copy; the return result should be released with g_free(), but the individual strings must not be modified. If length is non-NULL then the number of elements in the result is stored there. In any case, the resulting array will be NULL-terminated. For an empty array, length will be set to 0 and a pointer to a NULL pointer will be returned. Since 2.26
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(). This function is O(1). Since 2.24
Returns a pointer to the serialised 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 value exists. If value is a fixed-sized value that was deserialised from a corrupted serialised container then NULL may be returned. In this case, the proper thing to do is typically to use the appropriate number of nul bytes in place of value. If value is not fixed-sized then NULL is never returned. In the case that value is already in serialised form, this function is O(1). If the value is not already in serialised form, serialisation occurs implicitly and is approximately O(n) in the size of the result. Since 2.24
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. Since 2.24
Provides access to the serialised 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. 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 seralised data matches the caller's expectation. n_elements, which must be non-NULL is set equal to the number of items in the array. Since 2.24
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. Since 2.24
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. Since 2.24
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. Since 2.24
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. Since 2.24
Given a maybe-typed GVariant instance, extract its value. If the value is Nothing, then this function returns NULL. Since 2.24
Gets a GVariant 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 GVariant is created with the same value as value. It makes sense to call this function if you've received GVariant data from untrusted sources and you want to ensure your serialised output is definitely in normal form. Since 2.24
Determines the number of bytes that would be required to store value with g_variant_store(). If value has a fixed-sized type then this function always returned that fixed size. In the case that value is already in serialised 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. Since 2.24
Returns the string value of a GVariant 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 utf8 encoded. If length is non-NULL then the length of the string (in bytes) is returned there. For trusted values, this information is already known. For untrusted values, a strlen() will be performed. 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. Since 2.24
the main Gtk struct as a void*
Gets the contents of an array of strings GVariant. This call makes a shallow copy; the return result should be released with g_free(), but the individual strings must not be modified. If length is non-NULL then the number of elements in the result is stored there. In any case, the resulting array will be NULL-terminated. For an empty array, length will be set to 0 and a pointer to a NULL pointer will be returned. Since 2.24
Determines the type of value. The return value is valid for the lifetime of value and must not be freed. Since 2.24
Returns the type string of value. Unlike the result of calling g_variant_type_peek_string(), this string is nul-terminated. This string belongs to GVariant and must not be freed. Since 2.24
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. Since 2.24
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. Since 2.24
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. Since 2.24
This function is intended to be used by libraries based on GVariant that want to provide g_variant_get()-like functionality to their users. The API is more general than g_variant_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 NULL. If endptr is non-NULL 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 g_variant_new_va() and g_variant_get_va() within a single actual varargs call by the user. Since 2.24
Unboxes value. The result is the GVariant instance that was contained in value. Since 2.24
Checks if value is a container.
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 g_variant_ref_sink(). See g_variant_ref_sink() for more information about floating reference counts. Since 2.26
Checks if value is in normal form. The main reason to do this is to detect if a given chunk of serialised 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 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. Since 2.24
Checks if a value has a type matching the provided type. Since 2.24
Looks up a value in a dictionary GVariant. 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 NULL is returned. In the event that dictionary has a value type other than v then expected_type must directly match the key type and it is used to unpack the value directly or an error occurs. In either case, if key is not found in dictionary, NULL 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-NULL return value will have this type. Since 2.28
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). Since 2.24
Pretty-prints value 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.
Behaves as g_variant_print(), but operates on a GString. If string is non-NULL then it is appended to and returned. Else, a new empty GString is allocated and it is returned. Since 2.24
GVariant uses a floating reference count system. All functions with names starting with g_variant_new_ return floating references. Calling g_variant_ref_sink() on a GVariant with a floating reference will convert the floating reference into a full reference. Calling g_variant_ref_sink() on a non-floating GVariant 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 GVariant instance being inserted into a container will call g_variant_ref_sink() on the instance. This means that if the value was just created (and has only its floating reference) then the container will assume sole ownership of the value at that point and the caller will not need to unreference it. This makes certain common styles of programming much easier while still maintaining normal refcounting semantics in situations where values are not floating. Since 2.24
Stores the serialised form of value 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. This function is approximately O(n) in the size of data. Since 2.24
Decreases the reference count of value. When its reference count drops to 0, the memory used by the variant is freed. Since 2.24
Compares one and two. The types of one and two are gconstpointer only to allow use of this function with GTree, GPtrArray, etc. They must each be a GVariant. 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 can not compare a 32-bit signed integer with a 32-bit unsigned integer. Also note that this function is not particularly well-behaved when it comes to comparison of doubles; in particular, the handling of incomparable values (ie: NaN) is undefined. If you only require an equality comparison, g_variant_equal() is more general. Since 2.26
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 GHashTable. They must each be a GVariant. Since 2.24
Creates an array-of-bytes GVariant with the contents of string. This function is just like new Variant(string) except that the string need not be valid utf8.
Constructs an array of bytestring GVariant from the given array of strings. If length is -1 then strv is NULL-terminated. Since 2.26
Creates a DBus object path GVariant with the contents of string. string must be a valid DBus object path. Use Variant.isObjectPath() if you're not sure. Since 2.24
Creates a DBus type signature GVariant with the contents of string. string must be a valid DBus type signature. Use Variant.isSignature() if you're not sure. Since 2.24
Generates a hash value for a GVariant 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 GHashTable. value must be a GVariant. Since 2.24
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. Since 2.24
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. Since 2.24
Parses a GVariant from a text representation. A single GVariant 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-NULL 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 NULL and there is extra data then an error is returned. If type is non-NULL then the value will be parsed to have that type. This may result in additional parse errors (in the case that the parsed value doesn't fit the type) but may also result in fewer errors (in the case that the type would have been ambiguous, such as with empty arrays). In the event that the parsing is successful, the resulting GVariant is returned. In case of any error, NULL will be returned. If error is non-NULL then it will be set to reflect the error that occured. Officially, the language understood by the parser is "any string produced by g_variant_print()".
the main Gtk struct
Description GVariant is a variant datatype; it stores a value along with information about the type of that value. The range of possible values is determined by the type. The type system used by GVariant is GVariantType. 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 can not contain a pointer. GVariant is reference counted using g_variant_ref() and g_variant_unref(). GVariant also has floating reference counts -- see g_variant_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 serialised form. It works particularly well with data located in memory-mapped files. It can perform nearly all deserialisation operations in a small constant time, usually touching only a single memory page. Serialised 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 GVariantType for exceptions. 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 serialised data, memory for the type information cache, buffer management memory and memory for the GVariant structure itself. Serialised Data Memory This is the memory that is used for storing GVariant data in serialised form. This is what would be sent over the network or what would end up on disk. 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 serialisation. 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 deserialisation. 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 32bit 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 32bit 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 GHashTable to store and lookup 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 serialised 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 g_free() or a g_slice_free() or even g_mapped_file_unref(). One buffer management structure is used for each chunk of serialised data. The size of the buffer management structure is 4 * (void *). On 32bit 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 serialised 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 refering 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 g_variant_unref()). The type information is shared. The serialised data and the buffer management structure for that serialised 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 byes of memory for the serialised data, 16 bytes for buffer management and 24 bytes for the GVariant instance, or a total of 160 bytes, plus malloc overhead. If we were to use g_variant_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 serialised data and buffer management for those dictionaries, but the type information would be shared.