Summary

Bio::SeqIO::gcg - GCG sequence input/output stream

Package variables

Included modules

Inherit

Bio::SeqIO

Synopsis

Do not use this module directly. Use it via the Bio::SeqIO class.

Description

This object can transform Bio::Seq objects to and from GCG flat
file databases.

Methods

Methods description

 Title   : next_seq
 Usage   : $seq = $stream->next_seq()
 Function: returns the next sequence in the stream
 Returns : Bio::Seq object
 Args    :

 Title   : write_seq
 Usage   : $stream->write_seq(@seq)
 Function: writes the formatted $seq object into the stream
 Returns : 1 for success and 0 for error
 Args    : array of Bio::PrimarySeqI object

 Title     : GCG_checksum
 Usage     : $cksum = $gcgio->GCG_checksum($seq);
 Function  : returns a gcg checksum for the sequence specified

             This method can also be called as a class method.
 Example   : 
 Returns   : a GCG checksum string
 Argument  : a Bio::PrimarySeqI implementing object

 Title   : _validate_checksum
 Usage   : n/a - internal method
 Function: if parsed gcg sequence contains a checksum field
         : we compare it to a value computed here on the parsed
         : sequence. A checksum mismatch would indicate some
         : type of parsing failure occured.
         :
 Returns : 1 for success, 0 for failure
 Args    : string containing parsed seq, value of parsed cheksum

Methods code

sub _initialize {

  my($self,@args) = @_;
  $self->SUPER::_initialize(@args);    
  if( ! defined $self->sequence_factory ) {
      $self->sequence_factory(new Bio::Seq::SeqFactory
			      (-verbose => $self->verbose(), 
			       -type => 'Bio::Seq::RichSeq'));      
   }

}

sub next_seq {

   my ($self,@args)    = @_;
   my($id,$type,$desc,$line,$chksum,$sequence,$date,$len);

   while( defined($_ = $self->_readline()) ) {

       ## Get the descriptive info (anything before the line with '..')
       unless( /\.\.$/ ) { $desc.= $_; }
       ## Pull ID, Checksum & Type from the line containing '..'
       /\.\.$/ && do     { $line = $_; chomp; 
                           if(/Check\:\s(\d+)\s/) { $chksum = $1; }
                           if(/Type:\s(\w)\s/)    { $type   = $1; }
                           if(/(\S+)\s+Length/) 
			   { $id     = $1; }
			   if(/Length:\s+(\d+)\s+(\S.+\S)\s+Type/ )
			   { $len = $1; $date = $2;}
                           last; 
                         }
   }   
   return if ( !defined $_);
   chomp($desc);  # remove last "\n"

   while( defined($_ = $self->_readline()) ) {

       ## This is where we grab the sequence info.

       if( /\.\.$/ ) { 
        $self->throw("Looks like start of another sequence. See documentation. "); 
       }

       next if($_ eq "\n");       ## skip whitespace lines in formatted seq
       s/[^a-zA-Z]//g;            ## remove anything that is not alphabet char
       # $_ = uc($_);               ## uppercase sequence: NO. Keep the case. HL
       $sequence .= $_;
   }
   ##If we parsed out a checksum, we might as well test it

   if(defined $chksum) { 
       unless(_validate_checksum($sequence,$chksum)) {
	   $self->throw("Checksum failure on parsed sequence.");
       }
   }

   ## Remove whitespace from identifier because the constructor
   ## will throw a warning otherwise...
   if(defined $id) { $id =~ s/\s+//g;}

   ## Turn our parsed "Type: N" or "Type: P" (if found) into the appropriate
   ## keyword that the constructor expects...
   if(defined $type) {
       if($type eq "N") { $type = "dna";      }
       if($type eq "P") { $type = "prot";    }
   }

   return $self->sequence_factory->create(-seq  => $sequence, 
					  -id   => $id, 
					  -desc => $desc, 
					  -type => $type,
					  -dates => [ $date ]
					  );

}

sub write_seq {

    my ($self,@seq) = @_;
    for my $seq (@seq) {
	$self->throw("Did not provide a valid Bio::PrimarySeqI object") 
	    unless defined $seq && ref($seq) && $seq->isa('Bio::PrimarySeqI');

	my $str         = $seq->seq;
	my $comment     = $seq->desc; 
	my $id          = $seq->id;
	my $type        = ( $seq->alphabet() =~ /[dr]na/i ) ? 'N' : 'P';
	my $timestamp;

	if( $seq->can('get_dates') ) {
	    ($timestamp) = $seq->get_dates;
	} else { 
	    $timestamp = localtime(time);
	}
	my($sum,$offset,$len,$i,$j,$cnt,@out);

	$len = length($str);
	## Set the offset if we have any non-standard numbering going on
	$offset=1;
	# checksum
	$sum = $self->GCG_checksum($seq);

	#Output the sequence header info
	push(@out,"$comment\n");                        
	push(@out,"$id  Length: $len  $timestamp  Type: $type  Check: $sum  ..\n\n");

	#Format the sequence
	$i = $#out + 1;
	for($j = 0 ; $j < $len ; ) {
	    if( $j % 50 == 0) {
		$out[$i] = sprintf("%8d  ",($j+$offset)); #numbering 
	    }
	    $out[$i] .= sprintf("%s",substr($str,$j,10));
	    $j += 10;
	    if( $j < $len && $j % 50 != 0 ) {
		$out[$i] .= " ";
	    }elsif($j % 50 == 0 ) {
		$out[$i++] .= "\n\n";
	    }                           
	}
	local($^W) = 0;
	if($j % 50 != 0 ) {
	    $out[$i] .= "\n";
	}
	$out[$i] .= "\n";
	return unless $self->_print(@out);
    }

    $self->flush if $self->_flush_on_write && defined $self->_fh;
    return 1;

}

sub GCG_checksum {

    my ($self,$seqobj) = @_;
    my $index = 0;
    my $checksum = 0;
    my $char;

    my $seq = $seqobj->seq();
    $seq =~ tr/a-z/A-Z/;
    
    foreach $char ( split(/[\.\-]*/, $seq)) {
	$index++;
	$checksum += ($index * (unpack("c",$char) || 0) );
	if( $index ==  57 ) {
	    $index = 0;
	}
    }

    return ($checksum % 10000);

}

sub _validate_checksum {

    my($seq,$parsed_sum) = @_;
    my($i,$len,$computed_sum,$cnt);

    $len = length($seq);

    #Generate the GCG Checksum value

    for($i=0; $i<$len ;$i++) {             
	$cnt++;
	$computed_sum += $cnt * ord(substr($seq,$i,1));
	($cnt == 57) && ($cnt=0);
    }
    $computed_sum %= 10000;

    ## Compare and decide if success or failure

    if($parsed_sum == $computed_sum) {
	return 1;
    } else { return 0; }

}

General documentation

User feedback is an integral part of the evolution of this
and other Bioperl modules. Send your comments and suggestions preferably
to one of the Bioperl mailing lists.
Your participation is much appreciated.

  bioperl-l@bioperl.org                 - General discussion
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Report bugs to the Bioperl bug tracking system to help us keep track
the bugs and their resolution. Bug reports can be submitted via email
or the web:

  bioperl-bugs@bio.perl.org
  http://bugzilla.bioperl.org/

Email: <birney@ebi.ac.uk>
<lstein@cshl.org>

Jason Stajich, jason@bioperl.org

The rest of the documentation details each of the object
methods. Internal methods are usually preceded with a _