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=head1 NAME |
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|
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Coro::State - create and manage simple coroutines |
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|
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=head1 SYNOPSIS |
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|
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use Coro::State; |
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|
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$new = new Coro::State sub { |
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print "in coroutine (called with @_), switching back\n"; |
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$new->transfer($main); |
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print "in coroutine again, switching back\n"; |
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$new->transfer($main); |
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}, 5; |
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|
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$main = new Coro::State; |
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|
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print "in main, switching to coroutine\n"; |
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$main->transfer($new); |
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print "back in main, switch to coroutine again\n"; |
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$main->transfer($new); |
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print "back in main\n"; |
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|
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=head1 DESCRIPTION |
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|
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This module implements coroutines. Coroutines, similar to continuations, |
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allow you to run more than one "thread of execution" in parallel. Unlike |
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threads this, only voluntary switching is used so locking problems are |
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greatly reduced. |
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|
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This module provides only low-level functionality. See L<Coro> and related |
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modules for a more useful process abstraction including scheduling. |
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|
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=head2 MEMORY CONSUMPTION |
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|
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A newly created coroutine that has not been used only allocates a |
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relatively small (a few hundred bytes) structure. Only on the first |
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C<transfer> will perl stacks (a few k) and optionally C stack (4-16k) be |
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allocated. On systems supporting mmap a 128k stack is allocated, on the |
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assumption that the OS has on-demand virtual memory. All this is very |
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system-dependent. On my i686-pc-linux-gnu system this amounts to about 10k |
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per coroutine, 5k when the experimental context sharing is enabled. |
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|
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=over 4 |
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|
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=cut |
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|
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package Coro::State; |
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|
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BEGIN { |
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$VERSION = 0.13; |
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|
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require XSLoader; |
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XSLoader::load Coro::State, $VERSION; |
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} |
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|
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use base 'Exporter'; |
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|
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@EXPORT_OK = qw(SAVE_DEFAV SAVE_DEFSV SAVE_ERRSV SAVE_CCTXT); |
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|
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=item $coro = new [$coderef] [, @args...] |
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|
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Create a new coroutine and return it. The first C<transfer> call to this |
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coroutine will start execution at the given coderef. If the subroutine |
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returns it will be executed again. |
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|
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If the coderef is omitted this function will create a new "empty" |
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coroutine, i.e. a coroutine that cannot be transfered to but can be used |
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to save the current coroutine in. |
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|
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=cut |
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|
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# this is called (or rather: goto'ed) for each and every |
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# new coroutine. IT MUST NEVER RETURN and should not call |
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# anything that changes the stacklevel (like eval). |
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sub initialize { |
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my $proc = shift; |
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&$proc while 1; |
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} |
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|
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sub new { |
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my $class = shift; |
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my $proc = shift || sub { die "tried to transfer to an empty coroutine" }; |
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bless _newprocess [$proc, @_], $class; |
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} |
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|
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=item $prev->transfer($next,$flags) |
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|
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Save the state of the current subroutine in C<$prev> and switch to the |
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coroutine saved in C<$next>. |
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|
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The "state" of a subroutine includes the scope, i.e. lexical variables and |
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the current execution state. The C<$flags> value can be used to specify |
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that additional state be saved (and later restored), by C<||>-ing the |
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following constants together: |
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|
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Constant Effect |
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SAVE_DEFAV save/restore @_ |
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SAVE_DEFSV save/restore $_ |
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SAVE_ERRSV save/restore $@ |
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SAVE_CCTXT save/restore C-stack (you usually want this) |
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|
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These constants are not exported by default. |
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|
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If you feel that something important is missing then tell me. Also |
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remember that every function call that might call C<transfer> (such |
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as C<Coro::Channel::put>) might clobber any global and/or special |
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variables. Yes, this is by design ;) You can always create your own |
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process abstraction model that saves these variables. |
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|
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The easiest way to do this is to create your own scheduling primitive like |
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this: |
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|
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sub schedule { |
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local ($_, $@, ...); |
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$old->transfer($new); |
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} |
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|
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IMPLEMENTORS NOTE: all Coro::State functions/methods expect either the |
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usual Coro::State object or a hashref with a key named "_coro_state" that |
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contains the real Coro::State object. That is, you can do: |
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|
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$obj->{_coro_state} = new Coro::State ...; |
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Coro::State::transfer(..., $obj); |
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|
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This exists mainly to ease subclassing (wether through @ISA or not). |
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|
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=cut |
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|
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=item Coro::State::flush |
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|
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To be efficient (actually, to not be abysmaly slow), this module does |
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some fair amount of caching (a possibly complex structure for every |
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subroutine in use). If you don't use coroutines anymore or you want to |
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reclaim some memory then you can call this function which will flush all |
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internal caches. The caches will be rebuilt when needed so this is a safe |
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operation. |
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|
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=cut |
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|
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1; |
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|
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=back |
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|
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=head1 BUGS |
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|
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This module has not yet been extensively tested. Expect segfaults and |
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specially memleaks. |
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|
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This module is not thread-safe. You must only ever use this module from |
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the same thread (this requirenmnt might be loosened in the future). |
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|
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=head1 SEE ALSO |
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|
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L<Coro>. |
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|
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=head1 AUTHOR |
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|
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Marc Lehmann <pcg@goof.com> |
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http://www.goof.com/pcg/marc/ |
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|
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=cut |
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