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161 lines
3.4 KiB
161 lines
3.4 KiB
package Tie::Handle;
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=head1 NAME
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Tie::Handle - base class definitions for tied handles
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=head1 SYNOPSIS
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package NewHandle;
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require Tie::Handle;
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@ISA = (Tie::Handle);
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sub READ { ... } # Provide a needed method
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sub TIEHANDLE { ... } # Overrides inherited method
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package main;
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tie *FH, 'NewHandle';
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=head1 DESCRIPTION
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This module provides some skeletal methods for handle-tying classes. See
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L<perltie> for a list of the functions required in tying a handle to a package.
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The basic B<Tie::Handle> package provides a C<new> method, as well as methods
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C<TIESCALAR>, C<FETCH> and C<STORE>. The C<new> method is provided as a means
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of grandfathering, for classes that forget to provide their own C<TIESCALAR>
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method.
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For developers wishing to write their own tied-handle classes, the methods
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are summarized below. The L<perltie> section not only documents these, but
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has sample code as well:
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=over
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=item TIEHANDLE classname, LIST
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The method invoked by the command C<tie *glob, classname>. Associates a new
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glob instance with the specified class. C<LIST> would represent additional
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arguments (along the lines of L<AnyDBM_File> and compatriots) needed to
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complete the association.
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=item WRITE this, scalar, length, offset
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Write I<length> bytes of data from I<scalar> starting at I<offset>.
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=item PRINT this, LIST
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Print the values in I<LIST>
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=item PRINTF this, format, LIST
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Print the values in I<LIST> using I<format>
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=item READ this, scalar, length, offset
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Read I<length> bytes of data into I<scalar> starting at I<offset>.
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=item READLINE this
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Read a single line
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=item GETC this
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Get a single character
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=item DESTROY this
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Free the storage associated with the tied handle referenced by I<this>.
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This is rarely needed, as Perl manages its memory quite well. But the
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option exists, should a class wish to perform specific actions upon the
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destruction of an instance.
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=back
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=head1 MORE INFORMATION
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The L<perltie> section contains an example of tying handles.
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=cut
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use Carp;
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sub new {
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my $pkg = shift;
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$pkg->TIEHANDLE(@_);
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}
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# "Grandfather" the new, a la Tie::Hash
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sub TIEHANDLE {
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my $pkg = shift;
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if (defined &{"{$pkg}::new"}) {
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carp "WARNING: calling ${pkg}->new since ${pkg}->TIEHANDLE is missing"
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if $^W;
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$pkg->new(@_);
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}
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else {
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croak "$pkg doesn't define a TIEHANDLE method";
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}
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}
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sub PRINT {
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my $self = shift;
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if($self->can('WRITE') != \&WRITE) {
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my $buf = join(defined $, ? $, : "",@_);
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$buf .= $\ if defined $\;
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$self->WRITE($buf,length($buf),0);
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}
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else {
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croak ref($self)," doesn't define a PRINT method";
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}
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}
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sub PRINTF {
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my $self = shift;
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if($self->can('WRITE') != \&WRITE) {
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my $buf = sprintf(@_);
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$self->WRITE($buf,length($buf),0);
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}
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else {
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croak ref($self)," doesn't define a PRINTF method";
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}
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}
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sub READLINE {
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my $pkg = ref $_[0];
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croak "$pkg doesn't define a READLINE method";
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}
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sub GETC {
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my $self = shift;
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if($self->can('READ') != \&READ) {
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my $buf;
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$self->READ($buf,1);
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return $buf;
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}
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else {
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croak ref($self)," doesn't define a GETC method";
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}
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}
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sub READ {
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my $pkg = ref $_[0];
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croak "$pkg doesn't define a READ method";
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}
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sub WRITE {
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my $pkg = ref $_[0];
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croak "$pkg doesn't define a WRITE method";
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}
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sub CLOSE {
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my $pkg = ref $_[0];
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croak "$pkg doesn't define a CLOSE method";
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}
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1;
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