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# You may distribute under the terms of either the GNU General Public License |
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# or the Artistic License (the same terms as Perl itself) |
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# |
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# (C) Paul Evans, 2010-2012 -- leonerd@leonerd.org.uk |
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package overload::substr; |
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use strict; |
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use warnings; |
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use Carp; |
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our $VERSION = '0.03'; |
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require XSLoader; |
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XSLoader::load(__PACKAGE__, $VERSION ); |
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=head1 NAME |
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C - overload Perl's C function |
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=head1 SYNOPSIS |
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package My::Stringlike::Object; |
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use overload::substr; |
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sub _substr |
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{ |
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my $self = shift; |
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if( @_ > 2 ) { |
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$self->replace_substr( @_ ); |
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} |
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else { |
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return $self->get_substr( @_ ); |
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} |
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} |
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... |
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=head1 DESCRIPTION |
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This module allows an object class to overload the C core function, |
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which Perl's C pragma does not allow by itself. |
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It is invoked similarly to the C pragma, being passed a single named |
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argument which should be a code reference or method name to implement the |
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C function. |
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use overload::substr substr => \&SUBSTR; |
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use overload::substr substr => "SUBSTR"; |
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The referred method will be invoked as per core's C; namely, it will |
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take the string to be operated on (which will be an object in this case), an |
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offset, optionally a length, and optionally a replacement. |
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$str->SUBSTR( $offset ); |
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$str->SUBSTR( $offset, $length ); |
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$str->SUBSTR( $offset, $length, $replacement ); |
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In each case, whatever it returns will be the return value of the C |
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function that invoked it. |
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If the C argument is not provided, it defaults to a method called |
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C<_substr>. |
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It is not required that the return value be a plain string; any Perl value may |
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be returned unmodified from the C method, or passed in as the value of |
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the replacement. This allows objects to behave in whatever way is deemed most |
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appropriate. |
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=cut |
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sub import |
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{ |
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my $class = shift; |
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my %args = @_; |
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my $package = caller; |
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my $substr = delete $args{substr}; |
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defined $substr or $substr = "_substr"; |
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keys %args and |
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croak "Unrecognised extra keys to $class: " . join( ", ", sort keys %args ); |
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no strict 'refs'; |
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unless( ref $substr ) { |
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$substr = \&{$package."::$substr"}; |
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} |
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# This somewhat steps on overload.pm 's toes |
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*{$package."::(substr"} = $substr; |
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} |
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=head1 TODO |
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=over 8 |
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=item * |
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More testing - edge cases, especially in LVALUE logic. |
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=item * |
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Test for memory leaks, especially in LVALUE logic. |
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=item * |
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Look into / implement fixup of substr() ops compiled before module is loaded |
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=item * |
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Consider if implementations of split(), and C and C regexps should |
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be done that also uses the overloaded substr() method. |
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=back |
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=head1 ACKNOWLEDGEMENTS |
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With thanks to Matt S Trout for suggesting the |
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possibility, and Joshua ben Jore for the inspiration by way |
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of L. |
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=head1 AUTHOR |
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Paul Evans |
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=cut |
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0x55AA; |