package threads::shared;
-use 5.007_003;
+use 5.008;
+
use strict;
use warnings;
-BEGIN {
- require Exporter;
- our @ISA = qw(Exporter);
- our @EXPORT = qw(share cond_wait cond_broadcast cond_signal);
- our $VERSION = '0.90';
+use Scalar::Util qw(reftype refaddr blessed);
+
+our $VERSION = '1.27';
+my $XS_VERSION = $VERSION;
+$VERSION = eval $VERSION;
+
+# Declare that we have been loaded
+$threads::shared::threads_shared = 1;
+
+# Load the XS code, if applicable
+if ($threads::threads) {
+ require XSLoader;
+ XSLoader::load('threads::shared', $XS_VERSION);
+
+ *is_shared = \&_id;
+
+} else {
+ # String eval is generally evil, but we don't want these subs to
+ # exist at all if 'threads' is not loaded successfully.
+ # Vivifying them conditionally this way saves on average about 4K
+ # of memory per thread.
+ eval <<'_MARKER_';
+ sub share (\[$@%]) { return $_[0] }
+ sub is_shared (\[$@%]) { undef }
+ sub cond_wait (\[$@%];\[$@%]) { undef }
+ sub cond_timedwait (\[$@%]$;\[$@%]) { undef }
+ sub cond_signal (\[$@%]) { undef }
+ sub cond_broadcast (\[$@%]) { undef }
+_MARKER_
+}
+
+
+### Export ###
+
+sub import
+{
+ # Exported subroutines
+ my @EXPORT = qw(share is_shared cond_wait cond_timedwait
+ cond_signal cond_broadcast shared_clone);
if ($threads::threads) {
- *cond_wait = \&cond_wait_enabled;
- *cond_signal = \&cond_signal_enabled;
- *cond_broadcast = \&cond_broadcast_enabled;
- require XSLoader;
- XSLoader::load('threads::shared',$VERSION);
- push @EXPORT,'bless';
+ push(@EXPORT, 'bless');
}
- else {
- *share = \&share_disabled;
- *cond_wait = \&cond_wait_disabled;
- *cond_signal = \&cond_signal_disabled;
- *cond_broadcast = \&cond_broadcast_disabled;
+
+ # Export subroutine names
+ my $caller = caller();
+ foreach my $sym (@EXPORT) {
+ no strict 'refs';
+ *{$caller.'::'.$sym} = \&{$sym};
}
}
-sub cond_wait_disabled (\[$@%]) { undef }
-sub cond_signal_disabled (\[$@%]) { undef }
-sub cond_broadcast_disabled (\[$@%]) { undef }
-sub share_disabled (\[$@%]) { return $_[0] }
+# Predeclarations for internal functions
+my ($make_shared);
-$threads::shared::threads_shared = 1;
+### Methods, etc. ###
sub threads::shared::tie::SPLICE
{
- die "Splice not implemented for shared arrays";
+ require Carp;
+ Carp::croak('Splice not implemented for shared arrays');
}
+
+# Create a thread-shared clone of a complex data structure or object
+sub shared_clone
+{
+ if (@_ != 1) {
+ require Carp;
+ Carp::croak('Usage: shared_clone(REF)');
+ }
+
+ return $make_shared->(shift, {});
+}
+
+
+### Internal Functions ###
+
+# Used by shared_clone() to recursively clone
+# a complex data structure or object
+$make_shared = sub {
+ my ($item, $cloned) = @_;
+
+ # Just return the item if:
+ # 1. Not a ref;
+ # 2. Already shared; or
+ # 3. Not running 'threads'.
+ return $item if (! ref($item) || is_shared($item) || ! $threads::threads);
+
+ # Check for previously cloned references
+ # (this takes care of circular refs as well)
+ my $addr = refaddr($item);
+ if (exists($cloned->{$addr})) {
+ # Return the already existing clone
+ return $cloned->{$addr};
+ }
+
+ # Make copies of array, hash and scalar refs and refs of refs
+ my $copy;
+ my $ref_type = reftype($item);
+
+ # Copy an array ref
+ if ($ref_type eq 'ARRAY') {
+ # Make empty shared array ref
+ $copy = &share([]);
+ # Add to clone checking hash
+ $cloned->{$addr} = $copy;
+ # Recursively copy and add contents
+ push(@$copy, map { $make_shared->($_, $cloned) } @$item);
+ }
+
+ # Copy a hash ref
+ elsif ($ref_type eq 'HASH') {
+ # Make empty shared hash ref
+ $copy = &share({});
+ # Add to clone checking hash
+ $cloned->{$addr} = $copy;
+ # Recursively copy and add contents
+ foreach my $key (keys(%{$item})) {
+ $copy->{$key} = $make_shared->($item->{$key}, $cloned);
+ }
+ }
+
+ # Copy a scalar ref
+ elsif ($ref_type eq 'SCALAR') {
+ $copy = \do{ my $scalar = $$item; };
+ share($copy);
+ # Add to clone checking hash
+ $cloned->{$addr} = $copy;
+ }
+
+ # Copy of a ref of a ref
+ elsif ($ref_type eq 'REF') {
+ # Special handling for $x = \$x
+ if ($addr == refaddr($$item)) {
+ $copy = \$copy;
+ share($copy);
+ $cloned->{$addr} = $copy;
+ } else {
+ my $tmp;
+ $copy = \$tmp;
+ share($copy);
+ # Add to clone checking hash
+ $cloned->{$addr} = $copy;
+ # Recursively copy and add contents
+ $tmp = $make_shared->($$item, $cloned);
+ }
+
+ } else {
+ require Carp;
+ Carp::croak("Unsupported ref type: ", $ref_type);
+ }
+
+ # If input item is an object, then bless the copy into the same class
+ if (my $class = blessed($item)) {
+ bless($copy, $class);
+ }
+
+ # Clone READONLY flag
+ if ($ref_type eq 'SCALAR') {
+ if (Internals::SvREADONLY($$item)) {
+ Internals::SvREADONLY($$copy, 1) if ($] >= 5.008003);
+ }
+ }
+ if (Internals::SvREADONLY($item)) {
+ Internals::SvREADONLY($copy, 1) if ($] >= 5.008003);
+ }
+
+ return $copy;
+};
+
+1;
+
__END__
=head1 NAME
threads::shared - Perl extension for sharing data structures between threads
+=head1 VERSION
+
+This document describes threads::shared version 1.27
+
=head1 SYNOPSIS
use threads;
use threads::shared;
- my $var : shared;
+ my $var :shared;
+ my %hsh :shared;
+ my @ary :shared;
- my($scalar, @array, %hash);
+ my ($scalar, @array, %hash);
share($scalar);
share(@array);
share(%hash);
- my $bar = &share([]);
- $hash{bar} = &share({});
+
+ $var = $scalar_value;
+ $var = $shared_ref_value;
+ $var = shared_clone($non_shared_ref_value);
+ $var = shared_clone({'foo' => [qw/foo bar baz/]});
+
+ $hsh{'foo'} = $scalar_value;
+ $hsh{'bar'} = $shared_ref_value;
+ $hsh{'baz'} = shared_clone($non_shared_ref_value);
+ $hsh{'quz'} = shared_clone([1..3]);
+
+ $ary[0] = $scalar_value;
+ $ary[1] = $shared_ref_value;
+ $ary[2] = shared_clone($non_shared_ref_value);
+ $ary[3] = shared_clone([ {}, [] ]);
{ lock(%hash); ... }
cond_wait($scalar);
+ cond_timedwait($scalar, time() + 30);
cond_broadcast(@array);
cond_signal(%hash);
+ my $lockvar :shared;
+ # condition var != lock var
+ cond_wait($var, $lockvar);
+ cond_timedwait($var, time()+30, $lockvar);
+
=head1 DESCRIPTION
By default, variables are private to each thread, and each newly created
-thread gets a private copy of each existing variable. This module allows
-you to share variables across different threads (and pseudoforks on Win32).
-It is used together with the threads module.
+thread gets a private copy of each existing variable. This module allows you
+to share variables across different threads (and pseudo-forks on Win32). It
+is used together with the L<threads> module.
+
+This module supports the sharing of the following data types only: scalars
+and scalar refs, arrays and array refs, and hashes and hash refs.
=head1 EXPORT
-C<share>, C<cond_wait>, C<cond_signal>, C<cond_broadcast>
+The following functions are exported by this module: C<share>,
+C<shared_clone>, C<is_shared>, C<cond_wait>, C<cond_timedwait>, C<cond_signal>
+and C<cond_broadcast>
-Note that if this module is imported when C<threads> has not yet been
-loaded, then these functions all become no-ops. This makes it possible
-to write modules that will work in both threaded and non-threaded
-environments.
+Note that if this module is imported when L<threads> has not yet been loaded,
+then these functions all become no-ops. This makes it possible to write
+modules that will work in both threaded and non-threaded environments.
=head1 FUNCTIONS
=item share VARIABLE
-C<share> takes a value and marks it as shared. You can share a scalar,
-array, hash, scalar ref, array ref or hash ref. C<share> will return
-the shared rvalue but always as a reference.
+C<share> takes a variable and marks it as shared:
+
+ my ($scalar, @array, %hash);
+ share($scalar);
+ share(@array);
+ share(%hash);
+
+C<share> will return the shared rvalue, but always as a reference.
+
+Variables can also be marked as shared at compile time by using the
+C<:shared> attribute:
+
+ my ($var, %hash, @array) :shared;
+
+Shared variables can only store scalars, refs of shared variables, or
+refs of shared data (discussed in next section):
-C<share> will traverse up references exactly I<one> level.
-C<share(\$a)> is equivalent to C<share($a)>, while C<share(\\$a)> is not.
+ my ($var, %hash, @array) :shared;
+ my $bork;
-A variable can also be marked as shared at compile time by using the
-C<shared> attribute: C<my $var : shared>.
+ # Storing scalars
+ $var = 1;
+ $hash{'foo'} = 'bar';
+ $array[0] = 1.5;
-If you want to share a newly created reference unfortunately you
-need to use C<&share([])> and C<&share({})> syntax due to problems
-with Perl's prototyping.
+ # Storing shared refs
+ $var = \%hash;
+ $hash{'ary'} = \@array;
+ $array[1] = \$var;
+
+ # The following are errors:
+ # $var = \$bork; # ref of non-shared variable
+ # $hash{'bork'} = []; # non-shared array ref
+ # push(@array, { 'x' => 1 }); # non-shared hash ref
+
+=item shared_clone REF
+
+C<shared_clone> takes a reference, and returns a shared version of its
+argument, performing a deep copy on any non-shared elements. Any shared
+elements in the argument are used as is (i.e., they are not cloned).
+
+ my $cpy = shared_clone({'foo' => [qw/foo bar baz/]});
+
+Object status (i.e., the class an object is blessed into) is also cloned.
+
+ my $obj = {'foo' => [qw/foo bar baz/]};
+ bless($obj, 'Foo');
+ my $cpy = shared_clone($obj);
+ print(ref($cpy), "\n"); # Outputs 'Foo'
+
+For cloning empty array or hash refs, the following may also be used:
+
+ $var = &share([]); # Same as $var = shared_clone([]);
+ $var = &share({}); # Same as $var = shared_clone({});
+
+=item is_shared VARIABLE
+
+C<is_shared> checks if the specified variable is shared or not. If shared,
+returns the variable's internal ID (similar to
+L<refaddr()|Scalar::Util/"refaddr EXPR">). Otherwise, returns C<undef>.
+
+ if (is_shared($var)) {
+ print("\$var is shared\n");
+ } else {
+ print("\$var is not shared\n");
+ }
=item lock VARIABLE
-C<lock> places a lock on a variable until the lock goes out of scope.
-If the variable is locked by another thread, the C<lock> call will
-block until it's available. C<lock> is recursive, so multiple calls
-to C<lock> are safe -- the variable will remain locked until the
-outermost lock on the variable goes out of scope.
+C<lock> places a lock on a variable until the lock goes out of scope. If the
+variable is locked by another thread, the C<lock> call will block until it's
+available. Multiple calls to C<lock> by the same thread from within
+dynamically nested scopes are safe -- the variable will remain locked until
+the outermost lock on the variable goes out of scope.
-If a container object, such as a hash or array, is locked, all the
-elements of that container are not locked. For example, if a thread
-does a C<lock @a>, any other thread doing a C<lock($a[12])> won't block.
+Locking a container object, such as a hash or array, doesn't lock the elements
+of that container. For example, if a thread does a C<lock(@a)>, any other
+thread doing a C<lock($a[12])> won't block.
-C<lock> will traverse up references exactly I<one> level.
-C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not.
+C<lock()> follows references exactly I<one> level. C<lock(\$a)> is equivalent
+to C<lock($a)>, while C<lock(\\$a)> is not.
-Note that you cannot explicitly unlock a variable; you can only wait
-for the lock to go out of scope. If you need more fine-grained
-control, see L<Thread::Semaphore>.
+Note that you cannot explicitly unlock a variable; you can only wait for the
+lock to go out of scope. This is most easily accomplished by locking the
+variable inside a block.
+
+ my $var :shared;
+ {
+ lock($var);
+ # $var is locked from here to the end of the block
+ ...
+ }
+ # $var is now unlocked
+
+If you need more fine-grained control over shared variable access, see
+L<Thread::Semaphore>.
=item cond_wait VARIABLE
-The C<cond_wait> function takes a B<locked> variable as a parameter,
-unlocks the variable, and blocks until another thread does a
-C<cond_signal> or C<cond_broadcast> for that same locked variable.
-The variable that C<cond_wait> blocked on is relocked after the
-C<cond_wait> is satisfied. If there are multiple threads
-C<cond_wait>ing on the same variable, all but one will reblock waiting
-to reacquire the lock on the variable. (So if you're only using
-C<cond_wait> for synchronisation, give up the lock as soon as
-possible). The two actions of unlocking the variable and entering the
-blocked wait state are atomic, The two actions of exiting from the
-blocked wait state and relocking the variable are not.
-
-It is important to note that the variable can be notified even if
-no thread C<cond_signal> or C<cond_broadcast> on the variable.
-It is therefore important to check the value of the variable and
-go back to waiting if the requirement is not fulfilled.
+=item cond_wait CONDVAR, LOCKVAR
+
+The C<cond_wait> function takes a B<locked> variable as a parameter, unlocks
+the variable, and blocks until another thread does a C<cond_signal> or
+C<cond_broadcast> for that same locked variable. The variable that
+C<cond_wait> blocked on is relocked after the C<cond_wait> is satisfied. If
+there are multiple threads C<cond_wait>ing on the same variable, all but one
+will re-block waiting to reacquire the lock on the variable. (So if you're only
+using C<cond_wait> for synchronisation, give up the lock as soon as possible).
+The two actions of unlocking the variable and entering the blocked wait state
+are atomic, the two actions of exiting from the blocked wait state and
+re-locking the variable are not.
+
+In its second form, C<cond_wait> takes a shared, B<unlocked> variable followed
+by a shared, B<locked> variable. The second variable is unlocked and thread
+execution suspended until another thread signals the first variable.
+
+It is important to note that the variable can be notified even if no thread
+C<cond_signal> or C<cond_broadcast> on the variable. It is therefore
+important to check the value of the variable and go back to waiting if the
+requirement is not fulfilled. For example, to pause until a shared counter
+drops to zero:
+
+ { lock($counter); cond_wait($count) until $counter == 0; }
+
+=item cond_timedwait VARIABLE, ABS_TIMEOUT
+
+=item cond_timedwait CONDVAR, ABS_TIMEOUT, LOCKVAR
+
+In its two-argument form, C<cond_timedwait> takes a B<locked> variable and an
+absolute timeout as parameters, unlocks the variable, and blocks until the
+timeout is reached or another thread signals the variable. A false value is
+returned if the timeout is reached, and a true value otherwise. In either
+case, the variable is re-locked upon return.
+
+Like C<cond_wait>, this function may take a shared, B<locked> variable as an
+additional parameter; in this case the first parameter is an B<unlocked>
+condition variable protected by a distinct lock variable.
+
+Again like C<cond_wait>, waking up and reacquiring the lock are not atomic,
+and you should always check your desired condition after this function
+returns. Since the timeout is an absolute value, however, it does not have to
+be recalculated with each pass:
+
+ lock($var);
+ my $abs = time() + 15;
+ until ($ok = desired_condition($var)) {
+ last if !cond_timedwait($var, $abs);
+ }
+ # we got it if $ok, otherwise we timed out!
=item cond_signal VARIABLE
-The C<cond_signal> function takes a B<locked> variable as a parameter
-and unblocks one thread that's C<cond_wait>ing on that variable. If
-more than one thread is blocked in a C<cond_wait> on that variable,
-only one (and which one is indeterminate) will be unblocked.
+The C<cond_signal> function takes a B<locked> variable as a parameter and
+unblocks one thread that's C<cond_wait>ing on that variable. If more than one
+thread is blocked in a C<cond_wait> on that variable, only one (and which one
+is indeterminate) will be unblocked.
-If there are no threads blocked in a C<cond_wait> on the variable,
-the signal is discarded. By always locking before signaling, you can
-(with care), avoid signaling before another thread has entered cond_wait().
+If there are no threads blocked in a C<cond_wait> on the variable, the signal
+is discarded. By always locking before signaling, you can (with care), avoid
+signaling before another thread has entered cond_wait().
-C<cond_signal> will normally generate a warning if you attempt to use it
-on an unlocked variable. On the rare occasions where doing this may be
-sensible, you can skip the warning with
+C<cond_signal> will normally generate a warning if you attempt to use it on an
+unlocked variable. On the rare occasions where doing this may be sensible, you
+can suppress the warning with:
- { no warnings 'threads'; cond_signal($foo) }
+ { no warnings 'threads'; cond_signal($foo); }
=item cond_broadcast VARIABLE
The C<cond_broadcast> function works similarly to C<cond_signal>.
-C<cond_broadcast>, though, will unblock B<all> the threads that are
-blocked in a C<cond_wait> on the locked variable, rather than only one.
+C<cond_broadcast>, though, will unblock B<all> the threads that are blocked in
+a C<cond_wait> on the locked variable, rather than only one.
=back
+=head1 OBJECTS
+
+L<threads::shared> exports a version of L<bless()|perlfunc/"bless REF"> that
+works on shared objects such that I<blessings> propagate across threads.
+
+ # Create a shared 'Foo' object
+ my $foo :shared = shared_clone({});
+ bless($foo, 'Foo');
+
+ # Create a shared 'Bar' object
+ my $bar :shared = shared_clone({});
+ bless($bar, 'Bar');
+
+ # Put 'bar' inside 'foo'
+ $foo->{'bar'} = $bar;
+
+ # Rebless the objects via a thread
+ threads->create(sub {
+ # Rebless the outer object
+ bless($foo, 'Yin');
+
+ # Cannot directly rebless the inner object
+ #bless($foo->{'bar'}, 'Yang');
+
+ # Retrieve and rebless the inner object
+ my $obj = $foo->{'bar'};
+ bless($obj, 'Yang');
+ $foo->{'bar'} = $obj;
+
+ })->join();
+
+ print(ref($foo), "\n"); # Prints 'Yin'
+ print(ref($foo->{'bar'}), "\n"); # Prints 'Yang'
+ print(ref($bar), "\n"); # Also prints 'Yang'
+
=head1 NOTES
-threads::shared is designed to disable itself silently if threads are
-not available. If you want access to threads, you must C<use threads>
-before you C<use threads::shared>. threads will emit a warning if you
-use it after threads::shared.
+L<threads::shared> is designed to disable itself silently if threads are not
+available. This allows you to write modules and packages that can be used
+in both threaded and non-threaded applications.
+
+If you want access to threads, you must C<use threads> before you
+C<use threads::shared>. L<threads> will emit a warning if you use it after
+L<threads::shared>.
+
+=head1 BUGS AND LIMITATIONS
+
+When C<share> is used on arrays, hashes, array refs or hash refs, any data
+they contain will be lost.
+
+ my @arr = qw(foo bar baz);
+ share(@arr);
+ # @arr is now empty (i.e., == ());
-=head1 BUGS
+ # Create a 'foo' object
+ my $foo = { 'data' => 99 };
+ bless($foo, 'foo');
-C<bless> is not supported on shared references. In the current version,
-C<bless> will only bless the thread local reference and the blessing
-will not propagate to the other threads. This is expected to be
-implemented in a future version of Perl.
+ # Share the object
+ share($foo); # Contents are now wiped out
+ print("ERROR: \$foo is empty\n")
+ if (! exists($foo->{'data'}));
-Does not support splice on arrays!
+Therefore, populate such variables B<after> declaring them as shared. (Scalar
+and scalar refs are not affected by this problem.)
+
+It is often not wise to share an object unless the class itself has been
+written to support sharing. For example, an object's destructor may get
+called multiple times, once for each thread's scope exit. Another danger is
+that the contents of hash-based objects will be lost due to the above
+mentioned limitation. See F<examples/class.pl> (in the CPAN distribution of
+this module) for how to create a class that supports object sharing.
+
+Does not support C<splice> on arrays!
Taking references to the elements of shared arrays and hashes does not
-autovivify the elements, and neither does slicing a shared array/hash
-over non-existent indices/keys autovivify the elements.
+autovivify the elements, and neither does slicing a shared array/hash over
+non-existent indices/keys autovivify the elements.
-share() allows you to C<< share $hashref->{key} >> without giving any error
-message. But the C<< $hashref->{key} >> is B<not> shared, causing the error
-"locking can only be used on shared values" to occur when you attempt to
-C<< lock $hasref->{key} >>.
+C<share()> allows you to C<< share($hashref->{key}) >> without giving any
+error message. But the C<< $hashref->{key} >> is B<not> shared, causing the
+error "locking can only be used on shared values" to occur when you attempt to
+C<< lock($hasref->{key}) >>.
-=head1 AUTHOR
+Using L<refaddr()|Scalar::Util/"refaddr EXPR">) is unreliable for testing
+whether or not two shared references are equivalent (e.g., when testing for
+circular references). Use L<is_shared()/"is_shared VARIABLE">, instead:
+
+ use threads;
+ use threads::shared;
+ use Scalar::Util qw(refaddr);
+
+ # If ref is shared, use threads::shared's internal ID.
+ # Otherwise, use refaddr().
+ my $addr1 = is_shared($ref1) || refaddr($ref1);
+ my $addr2 = is_shared($ref2) || refaddr($ref2);
+
+ if ($addr1 == $addr2) {
+ # The refs are equivalent
+ }
-Arthur Bergman E<lt>arthur at contiller.seE<gt>
+L<each()|perlfunc/"each HASH"> does not work properly on shared references
+embedded in shared structures. For example:
+
+ my %foo :shared;
+ $foo{'bar'} = shared_clone({'a'=>'x', 'b'=>'y', 'c'=>'z'});
+
+ while (my ($key, $val) = each(%{$foo{'bar'}})) {
+ ...
+ }
+
+Either of the following will work instead:
+
+ my $ref = $foo{'bar'};
+ while (my ($key, $val) = each(%{$ref})) {
+ ...
+ }
-threads::shared is released under the same license as Perl
+ foreach my $key (keys(%{$foo{'bar'}})) {
+ my $val = $foo{'bar'}{$key};
+ ...
+ }
-Documentation borrowed from the old Thread.pm
+View existing bug reports at, and submit any new bugs, problems, patches, etc.
+to: L<http://rt.cpan.org/Public/Dist/Display.html?Name=threads-shared>
=head1 SEE ALSO
-L<threads>, L<perlthrtut>, L<http://www.perl.com/pub/a/2002/06/11/threads.html>
+L<threads::shared> Discussion Forum on CPAN:
+L<http://www.cpanforum.com/dist/threads-shared>
+
+Annotated POD for L<threads::shared>:
+L<http://annocpan.org/~JDHEDDEN/threads-shared-1.27/shared.pm>
+
+Source repository:
+L<http://code.google.com/p/threads-shared/>
+
+L<threads>, L<perlthrtut>
+
+L<http://www.perl.com/pub/a/2002/06/11/threads.html> and
+L<http://www.perl.com/pub/a/2002/09/04/threads.html>
+
+Perl threads mailing list:
+L<http://lists.cpan.org/showlist.cgi?name=iThreads>
+
+=head1 AUTHOR
+
+Artur Bergman E<lt>sky AT crucially DOT netE<gt>
+
+Documentation borrowed from the old Thread.pm.
+
+CPAN version produced by Jerry D. Hedden E<lt>jdhedden AT cpan DOT orgE<gt>.
+
+=head1 LICENSE
+
+threads::shared is released under the same license as Perl.
=cut
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