--- Coro/Coro.pm 2001/07/13 13:05:38 1.7 +++ Coro/Coro.pm 2001/09/24 00:16:30 1.35 @@ -1,134 +1,298 @@ =head1 NAME -Coro - create and manage simple coroutines +Coro - coroutine process abstraction =head1 SYNOPSIS use Coro; - $new = new Coro sub { - print "in coroutine, switching back\n"; - $new->transfer($main); - print "in coroutine again, switching back\n"; - $new->transfer($main); + async { + # some asynchronous thread of execution }; - $main = new Coro; + # alternatively create an async process like this: - print "in main, switching to coroutine\n"; - $main->transfer($new); - print "back in main, switch to coroutine again\n"; - $main->transfer($new); - print "back in main\n"; + sub some_func : Coro { + # some more async code + } + + cede; =head1 DESCRIPTION -This module implements coroutines. Coroutines, similar to continuations, -allow you to run more than one "thread of execution" in parallel. Unlike -threads this, only voluntary switching is used so locking problems are -greatly reduced. - -Although this is the "main" module of the Coro family it provides only -low-level functionality. See L and related modules for a -more useful process abstraction including scheduling. +This module collection manages coroutines. Coroutines are similar to +Threads but don't run in parallel. -=over 4 +This module is still experimental, see the BUGS section below. + +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. =cut package Coro; -BEGIN { - $VERSION = 0.03; +use Coro::State; + +use base Exporter; + +$VERSION = 0.5; + +@EXPORT = qw(async cede schedule terminate current); +%EXPORT_TAGS = ( + prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], +); +@EXPORT_OK = @{$EXPORT_TAGS{prio}}; + +{ + my @async; + my $init; + + # this way of handling attributes simply is NOT scalable ;() + sub import { + Coro->export_to_level(1, @_); + my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; + *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { + my ($package, $ref) = (shift, shift); + my @attrs; + for (@_) { + if ($_ eq "Coro") { + push @async, $ref; + unless ($init++) { + eval q{ + sub INIT { + &async(pop @async) while @async; + } + }; + } + } else { + push @attrs, $_; + } + } + return $old ? $old->($package, $ref, @attrs) : @attrs; + }; + } + +} + +=item $main - require XSLoader; - XSLoader::load Coro, $VERSION; +This coroutine represents the main program. + +=cut + +our $main = new Coro; + +=item $current (or as function: current) + +The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). + +=cut + +# maybe some other module used Coro::Specific before... +if ($current) { + $main->{specific} = $current->{specific}; } -=item $coro = new [$coderef [, @args]] +our $current = $main; + +sub current() { $current } + +=item $idle + +The coroutine to switch to when no other coroutine is running. The default +implementation prints "FATAL: deadlock detected" and exits. + +=cut + +# should be done using priorities :( +our $idle = new Coro sub { + print STDERR "FATAL: deadlock detected\n"; + exit(51); +}; + +# this coroutine is necessary because a coroutine +# cannot destroy itself. +my @destroy; +my $manager = new Coro sub { + while() { + delete ((pop @destroy)->{_coro_state}) while @destroy; + &schedule; + } +}; + +# static methods. not really. + +=head2 STATIC METHODS + +Static methods are actually functions that operate on the current process only. + +=over 4 + +=item 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; + +The coderef you submit MUST NOT be a closure that refers to variables +in an outer scope. This does NOT work. Pass arguments into it instead. + +=cut + +sub async(&@) { + my $pid = new Coro @_; + $manager->ready; # this ensures that the stack is cloned from the manager + $pid->ready; + $pid; +} -Create a new coroutine and return it. The first C call to this -coroutine will start execution at the given coderef. If, the subroutine -returns it will be executed again. +=item schedule -If the coderef is omitted this function will create a new "empty" -coroutine, i.e. a coroutine that cannot be transfered to but can be used -to save the current coroutine in. +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. =cut +=item cede + +"Cede" to other processes. This function puts the current process into the +ready queue and calls C, which has the effect of giving up the +current "timeslice" to other coroutines of the same or higher priority. + +=cut + +=item terminate + +Terminates the current process. + +Future versions of this function will allow result arguments. + +=cut + +sub terminate { + $current->cancel; + &schedule; + die; # NORETURN +} + +=back + +# dynamic methods + +=head2 PROCESS METHODS + +These are the methods you can call on process objects. + +=over 4 + +=item new Coro \&sub [, @args...] + +Create a new process and return it. When the sub returns the process +automatically terminates. To start the process you must first put it into +the ready queue by calling the ready method. + +The coderef you submit MUST NOT be a closure that refers to variables +in an outer scope. This does NOT work. Pass arguments into it instead. + +=cut + +sub _newcoro { + terminate &{+shift}; +} + sub new { - my $class = $_[0]; - my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" }; - bless _newprocess { - do { - eval { &$proc }; - if ($@) { - $error_msg = $@; - $error_coro = _newprocess { }; - &transfer($error_coro, $error); - } - } while (1); + my $class = shift; + bless { + _coro_state => (new Coro::State $_[0] && \&_newcoro, @_), }, $class; } -=item $prev->transfer($next) +=item $process->ready -Save the state of the current subroutine in C<$prev> and switch to the -coroutine saved in C<$next>. +Put the current process into the ready queue. -The "state" of a subroutine only ever includes scope, i.e. lexical -variables and the current execution state. It does not save/restore any -global variables such as C<$_> or C<$@> or any other special or non -special variables. So remember that every function call that might call -C (such as C) might clobber any global -and/or special variables. Yes, this is by design ;) You cna always create -your own process abstraction model that saves these variables. +=cut -The easiest way to do this is to create your own scheduling primitive like this: +=item $process->cancel - sub schedule { - local ($_, $@, ...); - $old->transfer($new); - } +Like C, but terminates the specified process instead. =cut -# I call the _transfer function from a perl function -# because that way perl saves all important things on -# the stack. Actually, I'd do it from within XS, but -# I couldn't get it to work. -sub transfer { - _transfer($_[0], $_[1]); +sub cancel { + push @destroy, $_[0]; + $manager->ready; + &schedule if $current == $_[0]; } -=item $error, $error_msg, $error_coro +=item $oldprio = $process->prio($newprio) -This coroutine will be called on fatal errors. C<$error_msg> and -C<$error_coro> return the error message and the error-causing coroutine -(NOT an object) respectively. This API might change. +Sets the priority of the process. Higher priority processes get run before +lower priority processes. Priorities are smalled signed integer (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 ($Coro::idle) always has a lower priority than any +existing coroutine. + +Changing the priority of the current process will take effect immediately, +but changing the priority of processes in the ready queue (but not +running) will only take effect after the next schedule (of that +process). This is a bug that will be fixed in some future version. =cut -$error_msg = -$error_coro = undef; +sub prio { + my $old = $_[0]{prio}; + $_[0]{prio} = $_[1] if @_ > 1; + $old; +} -$error = _newprocess { - print STDERR "FATAL: $error_msg\nprogram aborted\n"; - exit 50; -}; +=item $newprio = $process->nice($change) -1; +Similar to C, but subtract the given value from the priority (i.e. +higher values mean lower priority, just as in unix). + +=cut + +sub nice { + $_[0]{prio} -= $_[1]; +} =back -=head1 BUGS +=cut + +1; + +=head1 BUGS/LIMITATIONS -This module has not yet been extensively tested. + - 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 must only ever use this module from + the same thread (this requirement might be loosened in the future to + allow per-thread schedulers, but Coro::State does not yet allow this). =head1 SEE ALSO -L, L. +L, L, L, L, +L, L, L, L, +L, L. =head1 AUTHOR