Tie::Handle, Tie::StdHandle - base class definitions for tied handles
sub READ { ... } # Provide a needed method
sub TIEHANDLE { ... } # Overrides inherited method
This module provides some skeletal methods for handle-tying classes. See
L<perltie> for a list of the functions required in tying a handle to a package.
The basic B<Tie::Handle> package provides a C<new> method, as well as methods
C<TIEHANDLE>, C<PRINT>, C<PRINTF> and C<GETC>.
For developers wishing to write their own tied-handle classes, the methods
are summarized below. The L<perltie> section not only documents these, but
=item TIEHANDLE classname, LIST
The method invoked by the command C<tie *glob, classname>. Associates a new
glob instance with the specified class. C<LIST> would represent additional
arguments (along the lines of L<AnyDBM_File> and compatriots) needed to
complete the association.
=item WRITE this, scalar, length, offset
Write I<length> bytes of data from I<scalar> starting at I<offset>.
Print the values in I<LIST>
=item PRINTF this, format, LIST
Print the values in I<LIST> using I<format>
=item READ this, scalar, length, offset
Read I<length> bytes of data into I<scalar> starting at I<offset>.
=item OPEN this, filename
Specify content is binary
Return position in the file.
=item SEEK this, offset, whence
Free the storage associated with the tied handle referenced by I<this>.
This is rarely needed, as Perl manages its memory quite well. But the
option exists, should a class wish to perform specific actions upon the
destruction of an instance.
The L<perltie> section contains an example of tying handles.
This version of Tie::Handle is neither related to nor compatible with
the Tie::Handle (3.0) module available on CPAN. It was due to an
accident that two modules with the same name appeared. The namespace
clash has been cleared in favor of this module that comes with the
perl core in September 2000 and accordingly the version number has
# "Grandfather" the new, a la Tie::Hash
if (defined &{"{$pkg}::new"}) {
warnings
::warnif
("WARNING: calling ${pkg}->new since ${pkg}->TIEHANDLE is missing");
croak
"$pkg doesn't define a TIEHANDLE method";
if($self->can('WRITE') != \
&WRITE
) {
my $buf = join(defined $, ?
$, : "",@_);
$buf .= $\
if defined $\
;
$self->WRITE($buf,length($buf),0);
croak
ref($self)," doesn't define a PRINT method";
if($self->can('WRITE') != \
&WRITE
) {
my $buf = sprintf(shift,@_);
$self->WRITE($buf,length($buf),0);
croak
ref($self)," doesn't define a PRINTF method";
croak
"$pkg doesn't define a READLINE method";
if($self->can('READ') != \
&READ
) {
croak
ref($self)," doesn't define a GETC method";
croak
"$pkg doesn't define a READ method";
croak
"$pkg doesn't define a WRITE method";
croak
"$pkg doesn't define a CLOSE method";
our @ISA = 'Tie::Handle';
my $fh = \
do { local *HANDLE
};
sub FILENO
{ fileno($_[0]) }
sub SEEK
{ seek($_[0],$_[1],$_[2]) }
sub CLOSE
{ close($_[0]) }
sub BINMODE
{ binmode($_[0]) }
$_[0]->CLOSE if defined($_[0]->FILENO);
@_ == 2 ?
open($_[0], $_[1]) : open($_[0], $_[1], $_[2]);
sub READ
{ read($_[0],$_[1],$_[2]) }
sub READLINE
{ my $fh = $_[0]; <$fh> }
print $fh substr($_[1],0,$_[2])