NAME
    Coro - coroutine process abstraction

SYNOPSIS
     use Coro;

     async {
        # some asynchronous thread of execution
     };

     # alternatively create an async process like this:

     sub some_func : Coro {
        # some more async code
     }

     cede;

DESCRIPTION
    This module collection manages coroutines. Coroutines are similar to
    threads but don't run in parallel.

    In this module, coroutines are defined as "callchain + lexical variables
    + @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
    callchain, it's own set of lexicals and it's own set of perl's most
    important global variables.

    $main
        This coroutine represents the main program.

    $current (or as function: current)
        The current coroutine (the last coroutine switched to). The initial
        value is $main (of course).

    $idle
        The coroutine to switch to when no other coroutine is running. The
        default implementation prints "FATAL: deadlock detected" and exits.

  STATIC METHODS
    Static methods are actually functions that operate on the current
    process only.

    async { ... } [@args...]
        Create a new asynchronous process and return it's process object
        (usually unused). When the sub returns the new process is
        automatically terminated.

           # create a new coroutine that just prints its arguments
           async {
              print "@_\n";
           } 1,2,3,4;

    schedule
        Calls the scheduler. Please note that the current process will not
        be put into the ready queue, so calling this function usually means
        you will never be called again.

    cede
        "Cede" to other processes. This function puts the current process
        into the ready queue and calls "schedule", which has the effect of
        giving up the current "timeslice" to other coroutines of the same or
        higher priority.

    terminate [arg...]
        Terminates the current process with the given status values (see
        cancel).

    # dynamic methods

  PROCESS METHODS
    These are the methods you can call on process objects.

    new Coro \&sub [, @args...]
        Create a new process and return it. When the sub returns the process
        automatically terminates as if "terminate" with the returned values
        were called. To make the process run you must first put it into the
        ready queue by calling the ready method.

    $process->ready
        Put the given process into the ready queue.

    $process->cancel (arg...)
        Temrinates the given process and makes it return the given arguments
        as status (default: the empty list).

    $process->join
        Wait until the coroutine terminates and return any values given to
        the "terminate" or "cancel" functions. "join" can be called multiple
        times from multiple processes.

    $oldprio = $process->prio($newprio)
        Sets (or gets, if the argument is missing) the priority of the
        process. Higher priority processes get run before lower priority
        processes. Priorities are small signed integers (currently -4 ..
        +3), that you can refer to using PRIO_xxx constants (use the import
        tag :prio to get then):

           PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
               3    >     1     >      0      >    -1    >    -3     >    -4

           # set priority to HIGH
           current->prio(PRIO_HIGH);

        The idle coroutine ($Coro::idle) always has a lower priority than
        any existing coroutine.

        Changing the priority of the current process will take effect
        immediately, but changing the priority of processes in the ready
        queue (but not running) will only take effect after the next
        schedule (of that process). This is a bug that will be fixed in some
        future version.

    $newprio = $process->nice($change)
        Similar to "prio", but subtract the given value from the priority
        (i.e. higher values mean lower priority, just as in unix).

    $olddesc = $process->desc($newdesc)
        Sets (or gets in case the argument is missing) the description for
        this process. This is just a free-form string you can associate with
        a process.

BUGS/LIMITATIONS
     - you must make very sure that no coro is still active on global
       destruction. very bad things might happen otherwise (usually segfaults).

     - this module is not thread-safe. You should only ever use this module
       from the same thread (this requirement might be losened in the future
       to allow per-thread schedulers, but Coro::State does not yet allow
       this).

SEE ALSO
    Coro::Channel, Coro::Cont, Coro::Specific, Coro::Semaphore,
    Coro::Signal, Coro::State, Coro::Timer, Coro::Event, Coro::Handle,
    Coro::RWLock, Coro::Socket.

AUTHOR
     Marc Lehmann <pcg@goof.com>
     http://www.goof.com/pcg/marc/

