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NAME="REF.IMPLEMENTS"><SPAN
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>implements</SPAN
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><H2
>Name</H2
>Property <SPAN
CLASS="PROPERTY"
>implements</SPAN
> -- Enabling this option provides one instance of a more
general interface.</DIV
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>cdl_option <name> {
implements <interface>
…
}</PRE
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><H2
>Description</H2
><P
>The <SPAN
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>CDL</SPAN
> interface concept provides an abstraction mechanism that can
be useful in many different circumstances. Essentially an interface is
a calculated option whose value is the number of active and enabled
options which implement that interface. For example the interface
<TT
CLASS="VARNAME"
>CYGINT_KERNEL_SCHEDULER</TT
> has a value corresponding
to the number of schedulers in the system, typically just one.</P
><P
>The <SPAN
CLASS="PROPERTY"
>implements</SPAN
> property takes a single argument, which should be the
name of an interface. This interface may be defined in the same
package as the implementor or in some other package. In the latter
case it may sometimes be appropriate for the implementor or the
implementor's package to have a <SPAN
CLASS="PROPERTY"
>requires</SPAN
> property for the package
containing the interface. An option may contain multiple <SPAN
CLASS="PROPERTY"
>implements</SPAN
>
properties. It is possible for an option to implement a given
interface multiple times, and on occasion this is actually useful.</P
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><H2
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><PRE
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>cdl_option CYGSEM_KERNEL_SCHED_MLQUEUE {
display "Multi-level queue scheduler"
default_value 1
implements CYGINT_KERNEL_SCHEDULER
…
}</PRE
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><H2
>See Also</H2
><P
>Command <A
HREF="ref.cdl-interface.html"
><TT
CLASS="LITERAL"
>cdl_interface</TT
></A
>.</P
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