Make Thread a wrapper for both ithreads and 5005threads.

Needs a lot of work and Arthur's eyeballing (and finishing
few missing odds and ends of threads.pm).  Now Thread
is an extension without its own .pm.

If there are people who have experience working with
either the 5005threads or the ithreads: cleaning up
the documentation (Thread.pm, threads.pm, and perl*thrtut.pod),
and porting the various Thread::* modules, like Thread::Queue,
to work also with ithreads, is needed.

Removed the 5005threads requirement from the 5005 tests
for easier testing (not all of them work yet since
they use the Thread::* modules that have not been made
to work with ithreads).  Leave the 5005 tests named as
*.tx so that they are not run by "make test".

p4raw-id: //depot/perl@13036

1 files changed, 321 insertions, 0 deletions

diff --git a/lib/Thread.pm b/lib/Thread.pm
new file mode 100644
index 0000000000..b6be663166
--- /dev/null
+++ b/lib/Thread.pm
@@ -0,0 +1,321 @@
+package Thread;
+
+$VERSION = '2.00';
+
+BEGIN {
+    use Config;
+    our $ithreads = $Config{useithreads};
+    our $othreads = $Config{use5005threads};
+}
+
+require Exporter;
+use XSLoader ();
+our($VERSION, @ISA, @EXPORT);
+
+@ISA = qw(Exporter);
+
+BEGIN {
+    if ($ithreads) {
+	@EXPORT = qw(share cond_wait cond_broadcast cond_signal unlock)
+    } elsif ($othreads) {
+	@EXPORT_OK = qw(cond_signal cond_broadcast cond_wait);
+    }
+    push @EXPORT_OK, qw(async yield);
+}
+
+=head1 NAME
+
+Thread - manipulate threads in Perl
+
+=head1 CAVEAT
+
+Perl has two thread models.
+
+In Perl 5.005 the thread model was that all data is implicitly shared
+and shared access to data has to be explicitly synchronized.
+This model is called "5005threads".
+
+In Perl 5.6 a new model was introduced in which all is was thread
+local and shared access to data has to be explicitly declared.
+This model is called "ithreads", for "interpreter threads".
+
+In Perl 5.6 the ithreads model was not available as a public API,
+only as an internal API that was available for extension writers,
+and to implement fork() emulation on Win32 platforms.
+
+In Perl 5.8 the ithreads model became available through the C<threads>
+module.
+
+Neither model is configured by default into Perl (except, as mentioned
+above, in Win32 ithreads are always available.)
+
+For backwards compatibility, the Thread module has been reworked
+to function as a frontend for both 5005threads and ithreads.
+Note that the compatibility is not complete: because the data sharing
+models are directly opposed, anything to do with data sharing has to
+be thought differently.  With the ithreads you must explicitly share()
+variables between the threads.
+
+Finally, note that there are many known serious problems with the
+5005threads, one of the least of which is that regular expression
+match variables like $1 are not threadsafe, that is, they easily get
+corrupted by competing threads.  Other problems include more insidious
+data corruption and mysterious crashes.  You are seriously urged to
+use ithreads instead.
+
+=head1 SYNOPSIS
+
+    use Thread;
+
+    my $t = Thread->new(\&start_sub, @start_args);
+
+    $result = $t->join;
+    $result = $t->eval;
+    $t->detach;
+
+    if ($t->done) {
+        $t->join;
+    }
+
+    if($t->equal($another_thread)) {
+    	# ...
+    }
+
+    yield();
+
+    my $tid = Thread->self->tid; 
+
+    lock($scalar);
+    lock(@array);
+    lock(%hash);
+
+    lock(\&sub);	# not available with ithreads
+
+    $flags = $t->flags;	# not available with ithreads
+
+    my @list = Thread->list;	# not available with ithreads
+
+    unlock(...);	# not available with the 5.005 threads
+
+    use Thread 'async';
+
+=head1 DESCRIPTION
+
+The C<Thread> module provides multithreading support for perl.
+
+=head1 FUNCTIONS
+
+=over 8
+
+=item $thread = Thread->new(\&start_sub)
+
+=item $thread = Thread->new(\&start_sub, LIST)
+
+C<new> starts a new thread of execution in the referenced subroutine. The
+optional list is passed as parameters to the subroutine. Execution
+continues in both the subroutine and the code after the C<new> call.
+
+C<Thread-&gt;new> returns a thread object representing the newly created
+thread.
+
+=item lock VARIABLE
+
+C<lock> places a lock on a variable until the lock goes out of scope
+(with ithreads you can also explicitly unlock()).
+
+If the variable is locked by another thread, the C<lock> call will
+block until it's available.  C<lock> is recursive, so multiple calls
+to C<lock> are safe--the variable will remain locked until the
+outermost lock on the variable goes out of scope.
+
+Locks on variables only affect C<lock> calls--they do I<not> affect normal
+access to a variable. (Locks on subs are different, and covered in a bit.)
+If you really, I<really> want locks to block access, then go ahead and tie
+them to something and manage this yourself.  This is done on purpose.
+While managing access to variables is a good thing, Perl doesn't force
+you out of its living room...
+
+If a container object, such as a hash or array, is locked, all the
+elements of that container are not locked. For example, if a thread
+does a C<lock @a>, any other thread doing a C<lock($a[12])> won't
+block.
+
+With 5005threads you may also C<lock> a sub, using C<lock &sub>.
+Any calls to that sub from another thread will block until the lock
+is released. This behaviour is not equivalent to declaring the sub
+with the C<locked> attribute.  The C<locked> attribute serializes
+access to a subroutine, but allows different threads non-simultaneous
+access. C<lock &sub>, on the other hand, will not allow I<any> other
+thread access for the duration of the lock.
+
+Finally, 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.
+
+=item async BLOCK;
+
+C<async> creates a thread to execute the block immediately following
+it.  This block is treated as an anonymous sub, and so must have a
+semi-colon after the closing brace. Like C<Thread-&gt;new>, C<async>
+returns a thread object.
+
+=item Thread->self
+
+The C<Thread-E<gt>self> function returns a thread object that represents
+the thread making the C<Thread-E<gt>self> call.
+
+=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 reaquire the lock on the variable.  (So if you're only using
+C<cond_wait> for synchronization, give up the lock as soon as
+possible.)
+
+=item cond_signal VARIABLE
+
+The C<cond_signal> function takes a 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.
+
+=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.
+
+=item yield
+
+The C<yield> function allows another thread to take control of the
+CPU. The exact results are implementation-dependent.
+
+=back
+
+=head1 METHODS
+
+=over 8
+
+=item join
+
+C<join> waits for a thread to end and returns any values the thread
+exited with.  C<join> will block until the thread has ended, though
+it won't block if the thread has already terminated.
+
+If the thread being C<join>ed C<die>d, the error it died with will
+be returned at this time. If you don't want the thread performing
+the C<join> to die as well, you should either wrap the C<join> in
+an C<eval> or use the C<eval> thread method instead of C<join>.
+
+=item eval
+
+The C<eval> method wraps an C<eval> around a C<join>, and so waits for
+a thread to exit, passing along any values the thread might have returned.
+Errors, of course, get placed into C<$@>.  (Not available with ithreads.)
+
+=item detach
+
+C<detach> tells a thread that it is never going to be joined i.e.
+that all traces of its existence can be removed once it stops running.
+Errors in detached threads will not be visible anywhere - if you want
+to catch them, you should use $SIG{__DIE__} or something like that.
+
+=item equal 
+
+C<equal> tests whether two thread objects represent the same thread and
+returns true if they do.
+
+=item tid
+
+The C<tid> method returns the tid of a thread. The tid is
+a monotonically increasing integer assigned when a thread is
+created. The main thread of a program will have a tid of zero,
+while subsequent threads will have tids assigned starting with one.
+
+=item flags
+
+The C<flags> method returns the flags for the thread. This is the
+integer value corresponding to the internal flags for the thread,
+and the value may not be all that meaningful to you.
+(Not available with ithreads.)
+
+=item done
+
+The C<done> method returns true if the thread you're checking has
+finished, and false otherwise.  (Not available with ithreads.)
+
+=back
+
+=head1 LIMITATIONS
+
+The sequence number used to assign tids is a simple integer, and no
+checking is done to make sure the tid isn't currently in use.  If a
+program creates more than 2**32 - 1 threads in a single run, threads
+may be assigned duplicate tids.  This limitation may be lifted in
+a future version of Perl.
+
+=head1 SEE ALSO
+
+L<threads::shared> (not available with 5005threads)
+
+L<attributes>, L<Thread::Queue>, L<Thread::Semaphore>,
+L<Thread::Specific> (not available with ithreads)
+
+=cut
+
+#
+# Methods
+#
+
+#
+# Exported functions
+#
+
+sub async (&) {
+    return Thread->new($_[0]);
+}
+
+sub eval {
+    return eval { shift->join; };
+}
+
+sub unimplemented {
+    print $_[0], " unimplemented with ",
+          $Config{useithreads} ? "ithreads" : "5005threads", "\n";
+
+}
+
+sub unimplement {
+    for my $m (@_) {
+	*{"Thread::$m"} = sub { unimplemented $m };
+    }
+}
+
+BEGIN {
+    if ($ithreads) {
+	XSLoader::load 'threads';
+	for my $m (qw(new join detach yield self tid equal)) {
+	    *{"Thread::$m"} = \&{"threads::$m"};
+	}
+	XSLoader::load 'threads::shared';
+	for my $m (qw(cond_signal cond_broadcast cond_wait unlock share)) {
+	    *{"Thread::$m"} = \&{"threads::shared::${m}_enabled"};
+	}
+	unimplement(qw(list done eval flags));
+    } elsif ($othreads) {
+	XSLoader::load 'Thread';
+	unimplement(qw(unlock));
+    } else {
+	require Carp;
+	Carp::croak("This Perl has neither ithreads not 5005threads");
+    }
+}
+
+1;