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authorNorbert Preining <norbert@preining.info>2019-09-02 13:46:59 +0900
committerNorbert Preining <norbert@preining.info>2019-09-02 13:46:59 +0900
commite0c6872cf40896c7be36b11dcc744620f10adf1d (patch)
tree60335e10d2f4354b0674ec22d7b53f0f8abee672 /systems/texlive/tlnet/tlpkg/tlperl/lib/threads
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+package threads::shared;
+
+use 5.008;
+
+use strict;
+use warnings;
+
+use Scalar::Util qw(reftype refaddr blessed);
+
+our $VERSION = '1.58'; # Please update the pod, too.
+my $XS_VERSION = $VERSION;
+$VERSION = eval $VERSION;
+
+# Declare that we have been loaded
+$threads::shared::threads_shared = 1;
+
+# Method of complaint about things we can't clone
+$threads::shared::clone_warn = undef;
+
+# Load the XS code, if applicable
+if ($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) {
+ push(@EXPORT, 'bless');
+ }
+
+ # Export subroutine names
+ my $caller = caller();
+ foreach my $sym (@EXPORT) {
+ no strict 'refs';
+ *{$caller.'::'.$sym} = \&{$sym};
+ }
+}
+
+
+# Predeclarations for internal functions
+my ($make_shared);
+
+
+### Methods, etc. ###
+
+sub threads::shared::tie::SPLICE
+{
+ 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->($$item, $cloned);
+ }
+
+ } else {
+ require Carp;
+ if (! defined($threads::shared::clone_warn)) {
+ Carp::croak("Unsupported ref type: ", $ref_type);
+ } elsif ($threads::shared::clone_warn) {
+ Carp::carp("Unsupported ref type: ", $ref_type);
+ }
+ return undef;
+ }
+
+ # If input item is an object, then bless the copy into the same class
+ if (my $class = blessed($item)) {
+ bless($copy, $class);
+ }
+
+ # Clone READONLY flag
+ if ($ref_type eq 'SCALAR') {
+ if (Internals::SvREADONLY($$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 1.58
+
+=head1 SYNOPSIS
+
+ use threads;
+ use threads::shared;
+
+ my $var :shared;
+ my %hsh :shared;
+ my @ary :shared;
+
+ my ($scalar, @array, %hash);
+ share($scalar);
+ share(@array);
+ share(%hash);
+
+ $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, $lockvar);
+
+=head1 DESCRIPTION
+
+By default, variables are private to each thread, and each newly created
+thread gets a private copy of each existing variable. This module allows you
+to share variables across different threads (and pseudo-forks on Win32). It
+is used together with the L<threads> module.
+
+This module supports the sharing of the following data types only: scalars
+and scalar refs, arrays and array refs, and hashes and hash refs.
+
+=head1 EXPORT
+
+The following functions are exported by this module: C<share>,
+C<shared_clone>, C<is_shared>, C<cond_wait>, C<cond_timedwait>, C<cond_signal>
+and C<cond_broadcast>
+
+Note that if this module is imported when L<threads> has not yet been loaded,
+then these functions all become no-ops. This makes it possible to write
+modules that will work in both threaded and non-threaded environments.
+
+=head1 FUNCTIONS
+
+=over 4
+
+=item share VARIABLE
+
+C<share> takes a variable and marks it as shared:
+
+ my ($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):
+
+ my ($var, %hash, @array) :shared;
+ my $bork;
+
+ # Storing scalars
+ $var = 1;
+ $hash{'foo'} = 'bar';
+ $array[0] = 1.5;
+
+ # 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({});
+
+Not all Perl data types can be cloned (e.g., globs, code refs). By default,
+C<shared_clone> will L<croak|Carp> if it encounters such items. To change
+this behaviour to a warning, then set the following:
+
+ $threads::shared::clone_warn = 1;
+
+In this case, C<undef> will be substituted for the item to be cloned. If
+set to zero:
+
+ $threads::shared::clone_warn = 0;
+
+then the C<undef> substitution will be performed silently.
+
+=item is_shared VARIABLE
+
+C<is_shared> checks if the specified variable is shared or not. If shared,
+returns the variable's internal ID (similar to
+C<refaddr()> (see L<Scalar::Util>). Otherwise, returns C<undef>.
+
+ if (is_shared($var)) {
+ print("\$var is shared\n");
+ } else {
+ print("\$var is not shared\n");
+ }
+
+When used on an element of an array or hash, C<is_shared> checks if the
+specified element belongs to a shared array or hash. (It does not check
+the contents of that element.)
+
+ my %hash :shared;
+ if (is_shared(%hash)) {
+ print("\%hash is shared\n");
+ }
+
+ $hash{'elem'} = 1;
+ if (is_shared($hash{'elem'})) {
+ print("\$hash{'elem'} is in a shared hash\n");
+ }
+
+=item lock VARIABLE
+
+C<lock> places a B<advisory> 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.
+
+C<lock> follows references exactly I<one> level:
+
+ my %hash :shared;
+ my $ref = \%hash;
+ lock($ref); # This is equivalent to lock(%hash)
+
+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
+
+As locks are advisory, they do not prevent data access or modification by
+another thread that does not itself attempt to obtain a lock on the variable.
+
+You cannot lock the individual elements of a container variable:
+
+ my %hash :shared;
+ $hash{'foo'} = 'bar';
+ #lock($hash{'foo'}); # Error
+ lock(%hash); # Works
+
+If you need more fine-grained control over shared variable access, see
+L<Thread::Semaphore>.
+
+=item cond_wait VARIABLE
+
+=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 re-locked 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 synchronization, 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($counter); cond_wait($counter) until $counter == 0; }
+
+=item cond_timedwait VARIABLE, ABS_TIMEOUT
+
+=item cond_timedwait CONDVAR, ABS_TIMEOUT, LOCKVAR
+
+In its two-argument form, C<cond_timedwait> takes a B<locked> variable and an
+absolute timeout in I<epoch> seconds (see L<time() in perlfunc|perlfunc/time>
+for more) as parameters, unlocks the variable, and blocks until the
+timeout is reached or another thread signals the variable. A false value is
+returned if the timeout is reached, and a true value otherwise. In either
+case, the variable is re-locked upon return.
+
+Like C<cond_wait>, this function may take a shared, B<locked> variable as an
+additional parameter; in this case the first parameter is an B<unlocked>
+condition variable protected by a distinct lock variable.
+
+Again like C<cond_wait>, waking up and reacquiring the lock are not atomic,
+and you should always check your desired condition after this function
+returns. Since the timeout is an absolute value, however, it does not have to
+be recalculated with each pass:
+
+ lock($var);
+ my $abs = time() + 15;
+ until ($ok = desired_condition($var)) {
+ last if !cond_timedwait($var, $abs);
+ }
+ # we got it if $ok, otherwise we timed out!
+
+=item cond_signal VARIABLE
+
+The C<cond_signal> function takes a B<locked> variable as a parameter and
+unblocks one thread that's C<cond_wait>ing
+on that variable. If more than one
+thread is blocked in a C<cond_wait> on that variable, only one (and which one
+is indeterminate) will be unblocked.
+
+If there are no threads blocked in a C<cond_wait> on the variable, the signal
+is discarded. By always locking before
+signaling, you can (with care), avoid
+signaling before another thread has entered cond_wait().
+
+C<cond_signal> will normally generate a warning if you attempt to use it on an
+unlocked variable. On the rare occasions
+where doing this may be sensible, you
+can suppress the warning with:
+
+ { no warnings 'threads'; cond_signal($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.
+
+=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
+
+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 WARNINGS
+
+=over 4
+
+=item cond_broadcast() called on unlocked variable
+
+=item cond_signal() called on unlocked variable
+
+See L</"cond_signal VARIABLE">, above.
+
+=back
+
+=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., == ());
+
+ # Create a 'foo' object
+ my $foo = { 'data' => 99 };
+ bless($foo, 'foo');
+
+ # Share the object
+ share($foo); # Contents are now wiped out
+ print("ERROR: \$foo is empty\n")
+ if (! exists($foo->{'data'}));
+
+Therefore, populate such variables B<after> declaring them as shared. (Scalar
+and scalar refs are not affected by this problem.)
+
+Blessing a shared item after it has been nested in another shared item does
+not propagate the blessing to the shared reference:
+
+ my $foo = &share({});
+ my $bar = &share({});
+ $bar->{foo} = $foo;
+ bless($foo, 'baz'); # $foo is now of class 'baz',
+ # but $bar->{foo} is unblessed.
+
+Therefore, you should bless objects before sharing them.
+
+It is often not wise to share an object unless the class itself has been
+written to support sharing. For example, a shared object's destructor may
+get called multiple times, once for each thread's scope exit, or may not
+get called at all if it is embedded inside another shared object. Another
+issue 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.
+
+Destructors may not be called on objects if those objects still exist at
+global destruction time. If the destructors must be called, make sure
+there are no circular references and that nothing is referencing the
+objects before the program ends.
+
+Does not support C<splice> on arrays. Does not support explicitly changing
+array lengths via $#array -- use C<push> and C<pop> instead.
+
+Taking references to the elements of shared arrays and hashes does not
+autovivify the elements, and neither does slicing a shared array/hash over
+non-existent indices/keys autovivify the elements.
+
+C<share()> allows you to C<< share($hashref->{key}) >> and
+C<< share($arrayref->[idx]) >> without giving any error message. But the
+C<< $hashref->{key} >> or C<< $arrayref->[idx] >> is B<not> shared, causing
+the error "lock can only be used on shared values" to occur when you attempt
+to C<< lock($hashref->{key}) >> or C<< lock($arrayref->[idx]) >> in another
+thread.
+
+Using C<refaddr()> 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
+ }
+
+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})) {
+ ...
+ }
+
+ foreach my $key (keys(%{$foo{'bar'}})) {
+ my $val = $foo{'bar'}{$key};
+ ...
+ }
+
+This module supports dual-valued variables created using C<dualvar()> from
+L<Scalar::Util>. However, while C<$!> acts
+like a dualvar, it is implemented as a tied SV. To propagate its value, use
+the follow construct, if needed:
+
+ my $errno :shared = dualvar($!,$!);
+
+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
+
+threads::shared on MetaCPAN:
+L<https://metacpan.org/release/threads-shared>
+
+Code repository for CPAN distribution:
+L<https://github.com/Dual-Life/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.perl.org/list/ithreads.html>
+
+Sample code in the I<examples> directory of this distribution on CPAN.
+
+=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