| 1 |
=head1 NAME |
| 2 |
|
| 3 |
Coro::State - create and manage simple coroutines |
| 4 |
|
| 5 |
=head1 SYNOPSIS |
| 6 |
|
| 7 |
use Coro::State; |
| 8 |
|
| 9 |
$new = new Coro::State sub { |
| 10 |
print "in coroutine (called with @_), switching back\n"; |
| 11 |
$new->transfer ($main); |
| 12 |
print "in coroutine again, switching back\n"; |
| 13 |
$new->transfer ($main); |
| 14 |
}, 5; |
| 15 |
|
| 16 |
$main = new Coro::State; |
| 17 |
|
| 18 |
print "in main, switching to coroutine\n"; |
| 19 |
$main->transfer ($new); |
| 20 |
print "back in main, switch to coroutine again\n"; |
| 21 |
$main->transfer ($new); |
| 22 |
print "back in main\n"; |
| 23 |
|
| 24 |
=head1 DESCRIPTION |
| 25 |
|
| 26 |
This module implements coroutines. Coroutines, similar to continuations, |
| 27 |
allow you to run more than one "thread of execution" in parallel. Unlike |
| 28 |
threads, there is no parallelism and only voluntary switching is used so |
| 29 |
locking problems are greatly reduced. |
| 30 |
|
| 31 |
This can be used to implement non-local jumps, exception handling, |
| 32 |
continuations and more. |
| 33 |
|
| 34 |
This module provides only low-level functionality. See L<Coro> and related |
| 35 |
modules for a higher level process abstraction including scheduling. |
| 36 |
|
| 37 |
=head2 MEMORY CONSUMPTION |
| 38 |
|
| 39 |
A newly created coroutine that has not been used only allocates a |
| 40 |
relatively small (a few hundred bytes) structure. Only on the first |
| 41 |
C<transfer> will perl stacks (a few k) and optionally C stack (4-16k) be |
| 42 |
allocated. On systems supporting mmap a 128k stack is allocated, on the |
| 43 |
assumption that the OS has on-demand virtual memory. All this is very |
| 44 |
system-dependent. On my i686-pc-linux-gnu system this amounts to about 10k |
| 45 |
per coroutine, 5k when the experimental context sharing is enabled. |
| 46 |
|
| 47 |
=head2 FUNCTIONS |
| 48 |
|
| 49 |
=over 4 |
| 50 |
|
| 51 |
=cut |
| 52 |
|
| 53 |
package Coro::State; |
| 54 |
|
| 55 |
BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") } |
| 56 |
|
| 57 |
BEGIN { |
| 58 |
$VERSION = 1.31; |
| 59 |
|
| 60 |
require DynaLoader; |
| 61 |
push @ISA, 'DynaLoader'; |
| 62 |
bootstrap Coro::State $VERSION; |
| 63 |
} |
| 64 |
|
| 65 |
use base 'Exporter'; |
| 66 |
|
| 67 |
@EXPORT_OK = qw(SAVE_DEFAV SAVE_DEFSV SAVE_ERRSV SAVE_CURPM SAVE_CCTXT); |
| 68 |
|
| 69 |
=item $coro = new [$coderef] [, @args...] |
| 70 |
|
| 71 |
Create a new coroutine and return it. The first C<transfer> call to this |
| 72 |
coroutine will start execution at the given coderef. If the subroutine |
| 73 |
returns it will be executed again. |
| 74 |
|
| 75 |
If the coderef is omitted this function will create a new "empty" |
| 76 |
coroutine, i.e. a coroutine that cannot be transfered to but can be used |
| 77 |
to save the current coroutine in. |
| 78 |
|
| 79 |
=cut |
| 80 |
|
| 81 |
# this is called (or rather: goto'ed) for each and every |
| 82 |
# new coroutine. IT MUST NEVER RETURN! |
| 83 |
sub initialize { |
| 84 |
my $proc = shift; |
| 85 |
eval { |
| 86 |
&$proc while 1; |
| 87 |
}; |
| 88 |
if ($@) { |
| 89 |
print STDERR "FATAL: uncaught exception\n$@"; |
| 90 |
} |
| 91 |
_exit 255; |
| 92 |
} |
| 93 |
|
| 94 |
sub new { |
| 95 |
my $class = shift; |
| 96 |
my $proc = shift || sub { die "tried to transfer to an empty coroutine" }; |
| 97 |
bless _newprocess [$proc, @_], $class; |
| 98 |
} |
| 99 |
|
| 100 |
=item $prev->transfer ($next, $flags) |
| 101 |
|
| 102 |
Save the state of the current subroutine in C<$prev> and switch to the |
| 103 |
coroutine saved in C<$next>. |
| 104 |
|
| 105 |
The "state" of a subroutine includes the scope, i.e. lexical variables and |
| 106 |
the current execution state (subroutine, stack). The C<$flags> value can |
| 107 |
be used to specify that additional state to be saved (and later restored), by |
| 108 |
oring the following constants together: |
| 109 |
|
| 110 |
Constant Effect |
| 111 |
SAVE_DEFAV save/restore @_ |
| 112 |
SAVE_DEFSV save/restore $_ |
| 113 |
SAVE_ERRSV save/restore $@ |
| 114 |
SAVE_CCTXT save/restore C-stack (you usually want this for coroutines) |
| 115 |
|
| 116 |
These constants are not exported by default. If you don't need any extra |
| 117 |
additional state saved, use C<0> as the flags value. |
| 118 |
|
| 119 |
If you feel that something important is missing then tell me. Also |
| 120 |
remember that every function call that might call C<transfer> (such |
| 121 |
as C<Coro::Channel::put>) might clobber any global and/or special |
| 122 |
variables. Yes, this is by design ;) You can always create your own |
| 123 |
process abstraction model that saves these variables. |
| 124 |
|
| 125 |
The easiest way to do this is to create your own scheduling primitive like |
| 126 |
this: |
| 127 |
|
| 128 |
sub schedule { |
| 129 |
local ($_, $@, ...); |
| 130 |
$old->transfer ($new); |
| 131 |
} |
| 132 |
|
| 133 |
IMPLEMENTORS NOTE: all Coro::State functions/methods expect either the |
| 134 |
usual Coro::State object or a hashref with a key named "_coro_state" that |
| 135 |
contains the real Coro::State object. That is, you can do: |
| 136 |
|
| 137 |
$obj->{_coro_state} = new Coro::State ...; |
| 138 |
Coro::State::transfer (..., $obj); |
| 139 |
|
| 140 |
This exists mainly to ease subclassing (wether through @ISA or not). |
| 141 |
|
| 142 |
=cut |
| 143 |
|
| 144 |
1; |
| 145 |
|
| 146 |
=back |
| 147 |
|
| 148 |
=head1 BUGS |
| 149 |
|
| 150 |
This module has not yet been extensively tested, but works on most |
| 151 |
platforms. Expect segfaults and memleaks (but please don't be surprised if |
| 152 |
it works...) |
| 153 |
|
| 154 |
This module is not thread-safe. You must only ever use this module from |
| 155 |
the same thread (this requirement might be loosened in the future). |
| 156 |
|
| 157 |
=head1 SEE ALSO |
| 158 |
|
| 159 |
L<Coro>. |
| 160 |
|
| 161 |
=head1 AUTHOR |
| 162 |
|
| 163 |
Marc Lehmann <schmorp@schmorp.de> |
| 164 |
http://home.schmorp.de/ |
| 165 |
|
| 166 |
=cut |
| 167 |
|
