exchange ( obj exchanger -- newobj )
Object exchange points

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<exchanger> ( -- exchanger )

Vocabulary
concurrency.exchangers

Inputs

obj	an object
exchanger	an exchanger

Outputs

newobj

an object

Word description
Waits for another thread to call exchange on the same exchanger. The thread's call to exchange returns with obj on the stack, and the object passed to exchange by the other thread is left on the current's thread stack as newobj.

Definition

USING: accessors boxes kernel threads ;

IN: concurrency.exchangers

: exchange ( obj exchanger -- newobj )
    dup thread>> occupied>>
    [ dup object>> box> [ thread>> box> resume-with ] dip ] [
        [ object>> >box ] keep [ self ] dip thread>> >box
        "exchange" suspend
    ] if ;