[−][src]Struct gstreamer::structure::Structure

pub struct Structure(_);

A Structure is a collection of key/value pairs. The keys are expressed as GQuarks and the values can be of any GType.

In addition to the key/value pairs, a Structure also has a name. The name starts with a letter and can be filled by letters, numbers and any of "/-_.:".

Structure is used by various GStreamer subsystems to store information in a flexible and extensible way. A Structure does not have a refcount because it usually is part of a higher level object such as Caps, Message, Event, Query. It provides a means to enforce mutability using the refcount of the parent with the Structure::set_parent_refcount method.

A Structure can be created with Structure::new_empty or Structure::new, which both take a name and an optional set of key/value pairs along with the types of the values.

Field values can be changed with Structure::set_value or Structure::set.

Field values can be retrieved with Structure::get_value or the more convenient gst_structure_get_*() functions.

Fields can be removed with Structure::remove_field or Structure::remove_fields.

Strings in structures must be ASCII or UTF-8 encoded. Other encodings are not allowed. Strings may be None however.

The serialization format

GstStructure serialization format serialize the GstStructure name, keys/GType/values in a comma separated list with the structure name as first field without value followed by separated key/value pairs in the form key=value, for example:

a-structure, key=value

The values type will be inferred if not explicitly specified with the (GTypeName)value syntax, for example the following struct will have one field called 'is-string' which has the string 'true' as a value:

a-struct, field-is-string=(string)true, field-is-boolean=true

Note: without specifying (string), field-is-string` type would have been inferred as boolean.

Note: we specified (string) as a type even if gchararray is the actual GType name as for convenience some well known types have been aliased or abbreviated.

To avoid specifying the type, you can give some hints to the "type system". For example to specify a value as a double, you should add a decimal (ie. 1 is an int while 1.0 is a double).

Note: when a structure is serialized with Structure::to_string, all values are explicitly typed.

Some types have special delimiters:

GstValueArray are inside curly brackets ({ and }). For example a-structure, array={1, 2, 3}
Ranges are inside brackets ([ and ]). For example a-structure, range=[1, 6, 2] 1 being the min value, 6 the maximum and 2 the step. To specify a GST_TYPE_INT64_RANGE you need to explicitly specify it like: a-structure, a-int64-range=(gint64) [1, 5]
GstValueList are inside "less and greater than" (< and >). For example `a-structure, list=<1, 2, 3>

Structures are delimited either by a null character \0 or a semicolumn ; the latter allowing to store multiple structures in the same string (see #GstCaps).

Quotes are used as "default" delimiters and can be used around any types that don't use other delimiters (for example a-struct, i=(int)"1"). They are use to allow adding spaces or special characters (such as delimiters, semicolumns, etc..) inside strings and you can use backslashes \ to escape characters inside them, for example:

a-struct, special="\"{[(;)]}\" can be used inside quotes"

They also allow for nested structure, such as:

a-struct, nested=(GstStructure)"nested-struct, nested=true"

Note: Be aware that the current #GstCaps / #GstStructure serialization into string has limited support for nested #GstCaps / #GstStructure fields. It can only support one level of nesting. Using more levels will lead to unexpected behavior when using serialization features, such as gst_caps_to_string() or gst_value_serialize() and their counterparts.

Implementations

`impl Structure`[src]

`pub fn builder(name: &str) -> Builder`[src]

`pub fn new_empty(name: &str) -> Structure`[src]

Creates a new, empty Structure with the given name.

See Structure::set_name for constraints on the name parameter.

Free-function: gst_structure_free

`name`

name of new structure

Returns

a new, empty Structure

`pub fn new(name: &str, values: &[(&str, &dyn ToSendValue)]) -> Structure`[src]

Creates a new Structure with the given name. Parses the list of variable arguments and sets fields to the values listed. Variable arguments should be passed as field name, field type, and value. Last variable argument should be None.

Free-function: gst_structure_free