Trait DataT

Source

pub trait DataT: 'static {
    type V<'a>: ValT;
    type Data<'a>: Clone + HasLut<'a, Self>;
}

Expand description

Data types that filters operate on.

Types that implement this trait allow to specify which data types a filter processes. In particular, this allows native filters to operate on data types that may live only as long as the filter is executed. For example, this is required by the inputs filter, whose global data — namely the inputs to the main filter — has a lifetime.

§Motivation

If we have data types that are tied to a particular lifetime and we would bake those data types into a native filter type, then native filters could only be used for data of this particular lifetime. For example, suppose that a filter operating on a value type &'a str would have the type Filter<&'a str>. The crucial point is that here, the 'a is fixed, so we could only run the filter with &'a str for one particular 'a. That would mean that if we want to execute the same filter with data having different 'a lifetimes (e.g. for strings coming from different files), we would need to recompile the filter every time (i.e. for every file).

This trait allows us to avoid this problem by separating the actual data from the knowledge that a filter will operate on certain type of data. That allows us to run a filter using data types with a lifetime that depend on the lifetime of the filter execution.