Module libdata::column [−]

Column descriptions and values.

A column is a kind of value tagged onto a flow (o part of it). As these can be arbitrary data, this module contains an abstraction allowing to manipulate them.

The basic type is a Value, which represents one opaque tag. The other important type is Ident. That one describes the kind (identity) of a value. In a nutshell, Ident can talk about a remote IP address, while Value holds an actual instance of that IP address. Of course, a Value knows its own identity.

To use a data type as a public tag, two things need to be performed:

Implement the Type trait for it. This allows creation of values out of this type and having an identity for it.
Register it inside a global registry. It can either be done here in the source, if it is globally available (eg. multiple modules might want to use it, like the flow direction), or it can be registered from the outside by register or register_endpoint.

If the column is to be used only as a key for internal use (eg. users won't be able to query for it), the registration is not needed.

There are also some other helpful types that build on top of these.

Structs

FlowTags	A reference counted handle to `Tags`
Headers	A multi-set of tags.
Ident	An identity of a column.
Local	A wrapper for local-endpoint columns.
RefHeaders	Just like `Headers`, but with references instead of owned values.
Remote	A wrapper for remote-endpoint columns.
Tags	Tags of a single entity.
Value	A column value.

Traits

EndpointType	A trait to implement endpoint types.
Type	A trait for the types that can be made into the generic `Value`

Functions

register	Register a type to be used as a column.
register_endpoint	Register a type to be used as endpoint columns.

Type Definitions

Header	A set of values of the same type.
RefHeader	Just like `Header`, but with references instead of owned values.