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Component declaration

A component declaration describes a instance of the genom component model. It is defined by a unique name (an identifier) that also defines an IDL scope for any embedded types.

(5) component ::=

"component" component-name component-body ";"
(6) component-name ::=

identifier
(7) component-body ::=

[ "{" exports "}" ]

Components export objects from the genom component model, namely: IDS, tasks, ports, attributes or services.

Components may also define new types via IDL statements. Any such types are defined within the component scope.

(8) exports ::=

{ export }
(9) export ::=

idl-statement
| property
| ids
| task
| port
| attribute
| service

A number of properties can be attached to a component:

(10) component-property ::=

( "doc" string-literals
| "version" string-literals
| "lang" string-literals
| "email" string-literals
| "requires" string-list
| "codels-require" string-list
| "clock-rate" const-expr time-unit
| "provides" interface-list
| "uses" interface-list ) ";"
doc

A string that describes the functionality of the component.

version

The component version number, as a string.

lang

The programming language of the codels interface. At the moment, only "c" is supported.

email

A string containing the contact e-mail address to reach support for the component.

requires

A list of dependencies of the component (see #pragma requires). Each string should contain a package name in pkg-config format.

codels-requires

A list of dependencies of the codels. Each string should contain a package name in pkg-config format.

clock-rate

The period of the internal component clock. It is usually not necessary to define it explicitly. If the component defines periodic task, the component clock period will be automatically computed as the greatest common divisor of the period of all periodic tasks.

provides

A list of interfaces (see Interface declaration) that the component implements. All objects from the interface are imported as-is into the component description. Ports and services may be further refined once imported, typically by defining codels (see Codel declaration) that implement the services.

uses

A list of interfaces (see Interface declaration) that the component uses. Ports are imported in the opposite direction (e.g. a port out is imported as a port in). Services are imported as remote objects that can be accessed via codel parameters (see Codel declaration). Other objects are imported as-is.

Example

This would define an empty component with no service and no functionality:

component foo {
  version     "1.0";
  email       "me@example.com";
  lang        "c";
  require     "genom3 >= 2.99.20";
};