factor/extra/io/unix/launcher/launcher.factor

! Copyright (C) 2007, 2008 Slava Pestov.
! See http://factorcode.org/license.txt for BSD license.
USING: io io.backend io.launcher io.unix.backend io.unix.files
io.nonblocking sequences kernel namespaces math system
alien.c-types debugger continuations arrays assocs combinators
unix.process strings threads unix ;
IN: io.unix.launcher

! Search unix first
USE: unix

: get-arguments ( -- seq )
    +command+ get [ tokenize-command ] [ +arguments+ get ] if* ;

: assoc>env ( assoc -- env )
    [ "=" swap 3append ] { } assoc>map ;

: (redirect) ( path mode fd -- )
    >r file-mode open dup io-error dup
    r> dup2 io-error close ;

: redirect ( obj mode fd -- )
    {
        { [ pick not ] [ 2nip F_SETFL 0 fcntl io-error ] }
        { [ pick string? ] [ (redirect) ] }
    } cond ;

: ?closed dup +closed+ eq? [ drop "/dev/null" ] when ;

: setup-redirection ( -- )
    +stdin+ get ?closed read-flags 0 redirect
    +stdout+ get ?closed write-flags 1 redirect
    +stderr+ get dup +stdout+ eq?
    [ drop 1 2 dup2 io-error ] [ ?closed write-flags 2 redirect ] if ;

: spawn-process ( -- )
    [
        setup-redirection
        get-arguments
        pass-environment?
        [ get-environment assoc>env exec-args-with-env ]
        [ exec-args-with-path ] if
        io-error
    ] [ error. :c flush ] recover 1 exit ;

M: unix-io current-process-handle ( -- handle ) getpid ;

M: unix-io run-process* ( desc -- pid )
    [
        [ spawn-process ] [ ] with-fork <process>
    ] with-descriptor ;

M: unix-io kill-process* ( pid -- )
    SIGTERM kill io-error ;

: open-pipe ( -- pair )
    2 "int" <c-array> dup pipe zero?
    [ 2 c-int-array> ] [ drop f ] if ;

: setup-stdio-pipe ( stdin stdout -- )
    2dup first close second close
    >r first 0 dup2 drop r> second 1 dup2 drop ;

: spawn-process-stream ( -- in out pid )
    open-pipe open-pipe [
        setup-stdio-pipe
        spawn-process
    ] [
        -rot 2dup second close first close
    ] with-fork first swap second rot <process> ;

M: unix-io process-stream*
    [
        spawn-process-stream >r handle>duplex-stream r>
    ] with-descriptor ;

: find-process ( handle -- process )
    processes get swap [ nip swap process-handle = ] curry
    assoc-find 2drop ;

! Inefficient process wait polling, used on Linux and Solaris.
! On BSD and Mac OS X, we use kqueue() which scales better.
: wait-for-processes ( -- ? )
    -1 0 <int> tuck WNOHANG waitpid
    dup 0 <= [
        2drop t
    ] [
        find-process dup [
            >r *int WEXITSTATUS r> notify-exit f
        ] [
            2drop f
        ] if
    ] if ;

: start-wait-thread ( -- )
    [ wait-for-processes [ 250 sleep ] when t ]
    "Process reaper" spawn-server drop ;