system priority is retrieved and returned. If those variables are set,
then the process's priority is changed!
-We'll use Jarkko Hietaniemi <F<Jarkko.Hietaniemi@hut.fi>>'s
-BSD::Resource class (not included) to access the PRIO_PROCESS, PRIO_MIN,
-and PRIO_MAX constants from your system, as well as the getpriority() and
-setpriority() system calls. Here's the preamble of the class.
+We'll use Jarkko Hietaniemi <F<jhi@iki.fi>>'s BSD::Resource class (not
+included) to access the PRIO_PROCESS, PRIO_MIN, and PRIO_MAX constants
+from your system, as well as the getpriority() and setpriority() system
+calls. Here's the preamble of the class.
package Nice;
use Carp;
=head2 Tying Arrays
A class implementing a tied ordinary array should define the following
-methods: TIEARRAY, FETCH, STORE, and perhaps DESTROY.
+methods: TIEARRAY, FETCH, STORE, FETCHSIZE, STORESIZE and perhaps DESTROY.
-B<WARNING>: Tied arrays are I<incomplete>. They are also distinctly lacking
-something for the C<$#ARRAY> access (which is hard, as it's an lvalue), as
-well as the other obvious array functions, like push(), pop(), shift(),
-unshift(), and splice().
+FETCHSIZE and STORESIZE are used to provide C<$#array> and
+equivalent C<scalar(@array)> access.
+
+The methods POP, PUSH, SHIFT, UNSHIFT, SPLICE are required if the perl
+operator with the corresponding (but lowercase) name is to operate on the
+tied array. The B<Tie::Array> class can be used as a base class to implement
+these in terms of the basic five methods above.
+
+In addition EXTEND will be called when perl would have pre-extended
+allocation in a real array.
+
+This means that tied arrays are now I<complete>. The example below needs
+upgrading to illustrate this. (The documentation in B<Tie::Array> is more
+complete.)
For this discussion, we'll implement an array whose indices are fixed at
its creation. If you try to access anything beyond those bounds, you'll
-take an exception. (Well, if you access an individual element; an
-aggregate assignment would be missed.) For example:
+take an exception. For example:
require Bounded_Array;
tie @ary, 'Bounded_Array', 2;
It's probably worth mentioning that if you're going to filetest the
return values out of a readdir, you'd better prepend the directory
in question. Otherwise, because we didn't chdir() there, it would
-have been testing the wrong file.
+have been testing the wrong file.
=item FETCH this, key
This is partially implemented now.
-A class implementing a tied filehandle should define the following methods:
-TIEHANDLE, at least one of PRINT, READLINE, GETC or READ, and possibly DESTROY.
+A class implementing a tied filehandle should define the following
+methods: TIEHANDLE, at least one of PRINT, PRINTF, WRITE, READLINE, GETC,
+READ, and possibly CLOSE and DESTROY.
It is especially useful when perl is embedded in some other program,
where output to STDOUT and STDERR may have to be redirected in some
sub TIEHANDLE { print "<shout>\n"; my $i; bless \$i, shift }
+=item WRITE this, LIST
+
+This method will be called when the handle is written to via the
+C<syswrite> function.
+
+ sub WRITE {
+ $r = shift;
+ my($buf,$len,$offset) = @_;
+ print "WRITE called, \$buf=$buf, \$len=$len, \$offset=$offset";
+ }
+
=item PRINT this, LIST
-This method will be triggered every time the tied handle is printed to.
+This method will be triggered every time the tied handle is printed to
+with the C<print()> function.
Beyond its self reference it also expects the list that was passed to
the print function.
sub PRINT { $r = shift; $$r++; print join($,,map(uc($_),@_)),$\ }
-=item READLINE this
+=item PRINTF this, LIST
-This method will be called when the handle is read from via <HANDLE>.
-The method should return undef when there is no more data.
+This method will be triggered every time the tied handle is printed to
+with the C<printf()> function.
+Beyond its self reference it also expects the format and list that was
+passed to the printf function.
- sub READLINE { $r = shift; "PRINT called $$r times\n"; }
-
-=item READ this LIST
+ sub PRINTF {
+ shift;
+ my $fmt = shift;
+ print sprintf($fmt, @_)."\n";
+ }
+
+=item READ this, LIST
This method will be called when the handle is read from via the C<read>
or C<sysread> functions.
- sub READ {
- $r = shift;
- my($buf,$len,$offset) = @_;
+ sub READ {
+ $r = shift;
+ my($buf,$len,$offset) = @_;
print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset";
}
+=item READLINE this
+
+This method will be called when the handle is read from via <HANDLE>.
+The method should return undef when there is no more data.
+
+ sub READLINE { $r = shift; "PRINT called $$r times\n"; }
+
=item GETC this
This method will be called when the C<getc> function is called.
sub GETC { print "Don't GETC, Get Perl"; return "a"; }
-
+
+=item CLOSE this
+
+This method will be called when the handle is closed via the C<close>
+function.
+
+ sub CLOSE { print "CLOSE called.\n" }
+
=item DESTROY this
As with the other types of ties, this method will be called when the
Berkeley DB have size limitations, but beyond that, you also have problems
with how references are to be represented on disk. One experimental
module that does attempt to address this need partially is the MLDBM
-module. Check your nearest CPAN site as described in L<perlmod> for
+module. Check your nearest CPAN site as described in L<perlmodlib> for
source code to MLDBM.
=head1 AUTHOR
Tom Christiansen
-TIEHANDLE by Sven Verdoolaege <F<skimo@dns.ufsia.ac.be>>
+TIEHANDLE by Sven Verdoolaege <F<skimo@dns.ufsia.ac.be>> and Doug MacEachern <F<dougm@osf.org>>
projects / p5sagit/p5-mst-13.2.git / blobdiff