lib/Bio/DB/GFF/Adaptor/dbi/iterator.pm

   1 =head1 NAME
   2
   3 Bio::DB::GFF::Adaptor::dbi::iterator - iterator for Bio::DB::GFF::Adaptor::dbi
   4
   5 =head1 SYNOPSIS
   6
   7 For internal use only
   8
   9 =head1 DESCRIPTION
  10
  11 This is an internal module that is used by the Bio::DB::GFF DBI
  12 adaptor to return an iterator across a sequence feature query.  The
  13 object has a single method, next_feature(), that returns the next
  14 feature from the query.  The method next_seq() is an alias for
  15 next_feature().
  16
  17 =head1 BUGS
  18
  19 None known yet.
  20
  21 =head1 SEE ALSO
  22
  23 L<Bio::DB::GFF>,
  24
  25 =head1 AUTHOR
  26
  27 Lincoln Stein E<lt>lstein@cshl.orgE<gt>.
  28
  29 Copyright (c) 2001 Cold Spring Harbor Laboratory.
  30
  31 This library is free software; you can redistribute it and/or modify
  32 it under the same terms as Perl itself.
  33
  34 =cut
  35
  36 package Bio::DB::GFF::Adaptor::dbi::iterator;
  37 use strict;
  38 use Bio::Root::Version;
  39
  40 use constant STH         => 0;
  41 use constant CALLBACK    => 1;
  42 use constant CACHE       => 2;
  43
  44 *next_seq = \&next_feature;
  45
  46 sub new {
  47   my $class = shift;
  48   my ($sth,$callback) = @_;
  49   return bless [$sth,$callback,[]],$class;
  50 }
  51
  52 sub next_feature {
  53   my $self = shift;
  54   return shift @{$self->[CACHE]} if @{$self->[CACHE]};
  55   my $sth = $self->[STH] or return;
  56   my $callback = $self->[CALLBACK];
  57
  58   my $features;
  59   while (1) {
  60     if (my @row = $sth->fetchrow_array) {
  61       $features = $callback->(@row);
  62       last if $features;
  63     } else {
  64       $sth->finish;
  65       undef $self->[STH];
  66       $features = $callback->();
  67       last;
  68     }
  69   }
  70   $self->[CACHE] = $features or return;
  71   shift @{$self->[CACHE]};
  72 }
  73
  74 1;