! Copyright (C) 2008 Slava Pestov.

! See http://factorcode.org/license.txt for BSD license.

USING: dlists kernel threads math concurrency.conditions

continuations accessors summary locals fry ;

IN: concurrency.semaphores



TUPLE: semaphore count threads ;



ERROR: negative-count-semaphore ;



M: negative-count-semaphore summary

    drop "Cannot have semaphore with negative count" ;



: <semaphore> ( n -- semaphore )

    dup 0 < [ negative-count-semaphore ] when

    <dlist> semaphore boa ;



: wait-to-acquire ( semaphore timeout -- )

    [ threads>> ] dip "semaphore" wait ;



: acquire-timeout ( semaphore timeout -- )

    over count>> zero?

    [ dupd wait-to-acquire ] [ drop ] if

    [ 1 - ] change-count drop ;



: acquire ( semaphore -- )

    f acquire-timeout ;



: release ( semaphore -- )

    [ 1 + ] change-count

    threads>> notify-1 ;



:: with-semaphore-timeout ( semaphore timeout quot -- )

    semaphore timeout acquire-timeout

    quot [ semaphore release ] [ ] cleanup ; inline



: with-semaphore ( semaphore quot -- )

    swap dup acquire '[ _ release ] [ ] cleanup ; inline