Bio::SeqIO swiss
SummaryIncluded librariesPackage variablesSynopsisDescriptionGeneral documentationMethods
Summary
Bio::SeqIO::swiss - Swissprot sequence input/output stream
Package variables
No package variables defined.
Included modules
Bio::Annotation::Collection
Bio::Annotation::Comment
Bio::Annotation::DBLink
Bio::Annotation::Reference
Bio::Annotation::SimpleValue
Bio::Annotation::StructuredValue
Bio::Seq::SeqFactory
Bio::SeqFeature::Generic
Bio::SeqIO
Bio::SeqIO::FTHelper
Bio::Species
Bio::Tools::SeqStats
Inherit
Bio::SeqIO
Synopsis
It is probably best not to use this object directly, but
rather go through the SeqIO handler system. Go:
    $stream = Bio::SeqIO->new(-file => $filename, -format => 'swiss');

    while ( my $seq = $stream->next_seq() ) {
	# do something with $seq
    }
Description
This object can transform Bio::Seq objects to and from swissprot flat
file databases.
There is a lot of flexibility here about how to dump things which I need
to document fully.
   _show_dna()
   (output only) shows the dna or not
   _post_sort()
   (output only) provides a sorting func which is applied to the FTHelpers
before printing
   _id_generation_func()
   This is function which is called as 
   print "ID   ", $func($seq), "\n";
   To generate the ID line. If it is not there, it generates a sensible ID
line using a number of tools.
   If you want to output annotations in swissprot format they need to be
stored in a Bio::Annotation::Collection object which is accessible
through the Bio::SeqI interface method annotation().
   The following are the names of the keys which are polled from a
Bio::Annotation::Collection object.
   reference - Should contain Bio::Annotation::Reference objects
comment - Should contain Bio::Annotation::Comment objects
dblink - Should contain Bio::Annotation::DBLink objects
gene_name - Should contain Bio::Annotation::SimpleValue object
Methods
_initialize
No description
Code
next_seqDescriptionCode
write_seqDescriptionCode
_generateCRCTableDescriptionCode
_crc32DescriptionCode
_crc64DescriptionCode
_print_swissprot_FTHelperDescriptionCode
_read_swissprot_ReferencesDescriptionCode
_read_swissprot_SpeciesDescriptionCode
_read_FTHelper_swissprotDescriptionCode
_write_line_swissprotDescriptionCode
_write_line_swissprot_regexDescriptionCode
_post_sortDescriptionCode
_show_dnaDescriptionCode
_id_generation_funcDescriptionCode
_ac_generation_funcDescriptionCode
_sv_generation_funcDescriptionCode
_kw_generation_funcDescriptionCode
Methods description
next_seqcode    nextTop
 Title   : next_seq
 Usage   : $seq = $stream->next_seq()
 Function: returns the next sequence in the stream
 Returns : Bio::Seq object
 Args    :
write_seqcodeprevnextTop
 Title   : write_seq
 Usage   : $stream->write_seq($seq)
 Function: writes the $seq object (must be seq) to the stream
 Returns : 1 for success and 0 for error
 Args    : array of 1 to n Bio::SeqI objects
_generateCRCTablecodeprevnextTop
 Title   : _generateCRCTable
 Usage   :
 Function:
 Example :
 Returns : 
 Args    :
_crc32codeprevnextTop
 Title   : _crc32
 Usage   :
 Function:
 Example :
 Returns : 
 Args    :
_crc64codeprevnextTop
 Title   : _crc64
 Usage   :
 Function:
 Example :
 Returns : 
 Args    :
_print_swissprot_FTHelpercodeprevnextTop
 Title   : _print_swissprot_FTHelper
 Usage   :
 Function:
 Example :
 Returns : 
 Args    :
_read_swissprot_ReferencescodeprevnextTop
 Title   : _read_swissprot_References
 Usage   :
 Function: Reads references from swissprot format. Internal function really
 Example :
 Returns : 
 Args    :
_read_swissprot_SpeciescodeprevnextTop
 Title   : _read_swissprot_Species
 Usage   :
 Function: Reads the swissprot Organism species and classification
           lines.
 Example :
 Returns : A Bio::Species object
 Args    :
_read_FTHelper_swissprotcodeprevnextTop
 Title   : _read_FTHelper_swissprot
 Usage   : _read_FTHelper_swissprot(\$buffer)
 Function: reads the next FT key line
 Example :
 Returns : Bio::SeqIO::FTHelper object 
 Args    : filehandle and reference to a scalar
_write_line_swissprotcodeprevnextTop
 Title   : _write_line_swissprot
 Usage   :
 Function: internal function
 Example :
 Returns : 
 Args    :
_write_line_swissprot_regexcodeprevnextTop
 Title   : _write_line_swissprot_regex
 Usage   :
 Function: internal function for writing lines of specified
           length, with different first and the next line 
           left hand headers and split at specific points in the
           text
 Example :
 Returns : nothing
 Args    : file handle, first header, second header, text-line, regex for line breaks, total line length
_post_sortcodeprevnextTop
 Title   : _post_sort
 Usage   : $obj->_post_sort($newval)
 Function: 
 Returns : value of _post_sort
 Args    : newvalue (optional)
_show_dnacodeprevnextTop
 Title   : _show_dna
 Usage   : $obj->_show_dna($newval)
 Function: 
 Returns : value of _show_dna
 Args    : newvalue (optional)
_id_generation_funccodeprevnextTop
 Title   : _id_generation_func
 Usage   : $obj->_id_generation_func($newval)
 Function: 
 Returns : value of _id_generation_func
 Args    : newvalue (optional)
_ac_generation_funccodeprevnextTop
 Title   : _ac_generation_func
 Usage   : $obj->_ac_generation_func($newval)
 Function: 
 Returns : value of _ac_generation_func
 Args    : newvalue (optional)
_sv_generation_funccodeprevnextTop
 Title   : _sv_generation_func
 Usage   : $obj->_sv_generation_func($newval)
 Function: 
 Returns : value of _sv_generation_func
 Args    : newvalue (optional)
_kw_generation_funccodeprevnextTop
 Title   : _kw_generation_func
 Usage   : $obj->_kw_generation_func($newval)
 Function: 
 Returns : value of _kw_generation_func
 Args    : newvalue (optional)
Methods code
_initializedescriptionprevnextTop
sub _initialize {
  my($self,@args) = @_;
  $self->SUPER::_initialize(@args);
   
  # hash for functions for decoding keys.
  $self->{'_func_ftunit_hash'} = {};
  $self->_show_dna(1); # sets this to one by default. People can change it
  if( ! defined $self->sequence_factory ) {
      $self->sequence_factory(new Bio::Seq::SeqFactory
			      (-verbose => $self->verbose(), 
			       -type => 'Bio::Seq::RichSeq'));      
  }
}
next_seqdescriptionprevnextTop
sub next_seq {
   my ($self,@args) = @_;
   my ($pseq,$c,$line,$name,$desc,$acc,$seqc,$mol,$div,
       $date,$comment,@date_arr);
   
   my $genename = "";
   my ($annotation, %params, @features) = ( new Bio::Annotation::Collection);

   $line = $self->_readline;

   if( !defined $line) {
       return undef; # no throws - end of file
   }

   if( $line =~ /^\s+$/ ) {
       while( defined ($line = $self->_readline) ) {
   	   $line =~ /\S/ && last;
       }
   }
   if( !defined $line ) {
       return undef; # end of file
   }
   
   # fixed to allow _DIVISION to be optional for bug #946
   # see bug report for more information
   if( !($line =~ /^ID\s+([^\s_]+)(_([^\s_]+))?\s+([^\s;]+);\s+([^\s;]+);/)
       && !($line =~ /^ID\s+([^\s_]+)(_([^\s_]+))?/ ) )  {
       $self->throw("swissprot stream with no ID. Not swissprot in my book");
   }

   if( $3 ) {
       $name = "$1$2";
       $params{'-division'} = $3;
   } else {
       $name = $1;
       $params{'-division'} = 'UNK';
       $params{'-primary_id'} = $1;
   }
   $params{'-alphabet'} = 'protein';
    # this is important to have the id for display in e.g. FTHelper, otherwise
    # you won't know which entry caused an error
   $params{'-display_id'} = $name;
   
   my $buffer = $line;

   BEFORE_FEATURE_TABLE :
   until( !defined ($buffer) ) {
       $_ = $buffer;
       
       # Exit at start of Feature table
       last if /^FT/;
       # and at the sequence at the latest HL 05/11/2000
       last if /^SQ/;

       # Description line(s)
       if (/^DE\s+(\S.*\S)/) {
           $desc .= $desc ? " $1" : $1;
       }
       #Gene name
       elsif(/^GN\s+(.*)/) {
	   $genename .= " " if $genename;
	   $genename .= $1;
	   # has GN terminated yet?
	   if($genename =~ s/[\. ]+$//) {
	       my $gn = Bio::Annotation::StructuredValue->new();
	       foreach my $gene (split(/ AND /, $genename)) {
		   $gene =~ s/^\(//;
		   $gene =~ s/\)$//;
		   $gn->add_value([-1,-1], split(/ OR /, $gene));
               }
	       $annotation->add_Annotation('gene_name',$gn,
					   "Bio::Annotation::SimpleValue");
           }
       }
       #accession number(s)
       elsif( /^AC\s+(.+)/) {
	   my @accs = split(/[; ]+/, $1); # allow space in addition
	   $params{'-accession_number'} = shift @accs 
	       unless defined $params{'-accession_number'};
	   push @{$params{'-secondary_accessions'}}, @accs;
       }
       #version number
       elsif( /^SV\s+(\S+);?/ ) {
	   my $sv = $1;
	   $sv =~ s/\;//;
	   $params{'-seq_version'} = $sv;
       }
       #date
       elsif( /^DT\s+(.*)/ ) {
	   my $date = $1;
	   $date =~ s/\;//;
	   $date =~ s/\s+$//;
	   push @{$params{'-dates'}}, $date;
       }
       # Organism name and phylogenetic information
       elsif (/^O[SCG]/) {
           my $species = $self->_read_swissprot_Species(\$buffer);
           $params{'-species'}= $species;
	   # now we are one line ahead -- so continue without reading the next
	   # line   HL 05/11/2000
	   next;
       }
       # References
       elsif (/^R/) {
	   my $refs = $self->_read_swissprot_References(\$buffer);

	   foreach my $r (@$refs) {
	       $annotation->add_Annotation('reference',$r);
	   }
	   # now we are one line ahead -- so continue without reading the next
	   # line   HL 05/11/2000
	   next;
       }
       #Comments
       elsif (/^CC\s{3}(.*)/) {
	   $comment .= $1;
	   $comment .= "\n";
	   while (defined ($buffer = $self->_readline)) {
	       if ($buffer =~ /^CC\s{3}(.*)/) {
		   $comment .= $1;
		   $comment .= "\n";
	       }
	       else {
		   last;
	       }
	   }
	   my $commobj = Bio::Annotation::Comment->new();
	   # note: don't try to process comments here -- they may contain
           # structure. LP 07/30/2000
	   $commobj->text($comment);
	   $annotation->add_Annotation('comment',$commobj);
	   $comment = "";
	   # now we are one line ahead -- so continue without reading the next
	   # line   HL 05/11/2000
	   next;
       }
       #DBLinks
       elsif (/^DR\s+(\S+)\;\s+(\S+)\;\s+(\S+)[\;\.](.*)$/) {
	   my $dblinkobj =  Bio::Annotation::DBLink->new();
	   $dblinkobj->database($1);
	   $dblinkobj->primary_id($2);
	   $dblinkobj->optional_id($3);
	   my $comment = $4;
	   if(length($comment) > 0) {
	       # edit comment to get rid of leading space and trailing dot
	       if( $comment =~ /^\s*(\S+)\./ ) {
		   $dblinkobj->comment($1);
	       } else {
		   $dblinkobj->comment($comment);
	       }
	   }
	   $annotation->add_Annotation('dblink',$dblinkobj);
       }
       #keywords
       elsif( /^KW\s+(.*)$/ ) {
	   my @kw = split(/\s*\;\s*/,$1);
	   defined $kw[-1] && $kw[-1] =~ s/\.$//;
	   push @{$params{'-keywords'}}, @kw;   
       }

       # Get next line. Getting here assumes that we indeed need to read the
       # line.
       $buffer = $self->_readline;
   }
   
   $buffer = $_;
      
   FEATURE_TABLE :
   # if there is no feature table, or if we've got beyond, exit loop or don't
   # even enter    HL 05/11/2000
   while (defined ($buffer) && ($buffer =~ /^FT/)) {
       my $ftunit = $self->_read_FTHelper_swissprot(\$buffer);
       
       # process ftunit
       # when parsing of the line fails we get undef returned
       if($ftunit) {
	   push(@features,
		$ftunit->_generic_seqfeature($self->location_factory(),
					     $params{'-seqid'}, "SwissProt"));
       } else {
	   $self->warn("failed to parse feature table line for seq " .
		       $params{'-display_id'});
       }
   }
   if( $buffer !~ /^SQ/  ) {
       while( defined($_ = $self->_readline) ) {
	   /^SQ/ && last;
       }
   }
   $seqc = "";	
   while( defined ($_ = $self->_readline) ) {
       /^\/\// && last;
       $_ = uc($_);
       s/[^A-Za-z]//g;
       $seqc .= $_;
   }

   my $seq=  $self->sequence_factory->create
       (-verbose  => $self->verbose,
	%params,
	-seq      => $seqc,
	-desc     => $desc,
	-features =>\@ features,
	-annotation => $annotation,
	);

   # The annotation doesn't get added by the contructor
   $seq->annotation($annotation);

   return $seq;
}
write_seqdescriptionprevnextTop
sub write_seq {
    my ($self,@seqs) = @_;
    foreach my $seq ( @seqs ) {
	$self->throw("Attempting to write with no seq!") unless defined $seq;

	if( ! ref $seq || ! $seq->isa('Bio::SeqI') ) {
	    $self->warn(" $seq is not a SeqI compliant module. Attempting to dump, but may fail!");
	}

	my $i;
	my $str = $seq->seq;

	my $mol;
	my $div;
	my $len = $seq->length();

	if ( !$seq->can('division') || ! defined ($div = $seq->division()) ) {
	    $div = 'UNK';
	}

	if( ! $seq->can('alphabet') || ! defined ($mol = $seq->alphabet) ) {
	    $mol = 'XXX';
	}

        $self->warn("No whitespace allowed in SWISS-PROT display id [". $seq->display_id. "]")
            if $seq->display_id =~ /\s/;

	my $temp_line;
	if( $self->_id_generation_func ) {
	    $temp_line = &{$self->_id_generation_func}($seq);
	} else {
	    #$temp_line = sprintf ("%10s     STANDARD;      %3s;   %d AA.",
	    #		     $seq->primary_id()."_".$div,$mol,$len);
	    # Reconstructing the ID relies heavily upon the input source having
	    # been in a format that is parsed as this routine expects it -- that is,
	    # by this module itself. This is bad, I think, and immediately breaks
	    # if e.g. the Bio::DB::GenPept module is used as input.
	    # Hence, switch to display_id(); _every_ sequence is supposed to have
	    # this. HL 2000/09/03
	    $mol =~ s/protein/PRT/;
	    $temp_line = sprintf ("%-10s     STANDARD;      %3s;   %d AA.",
				  $seq->display_id(), $mol, $len);
	}

	$self->_print( "ID   $temp_line\n");

	# if there, write the accession line
	local($^W) = 0;	# supressing warnings about uninitialized fields

	if( $self->_ac_generation_func ) {
	    $temp_line = &{$self->_ac_generation_func}($seq);
	    $self->_print( "AC   $temp_line\n");
	} else {
	    if ($seq->can('accession_number') ) {
		$self->_print("AC   ",$seq->accession_number,";");
		if ($seq->can('get_secondary_accessions') ) {
		    foreach my $sacc ($seq->get_secondary_accessions) {
			$self->_print(" ",$sacc,";");
		    }
		    $self->_print("\n");
		}
		else {
		    $self->_print("\n");
		}
	    }
	    # otherwise - cannot print <sigh>
	}

	# Date lines

	if( $seq->can('get_dates') ) {
	    foreach my $dt ( $seq->get_dates() ) {
		$self->_write_line_swissprot_regex("DT   ","DT   ",
						   $dt,"\\s\+\|\$",80);
	    }
	}

	#Definition lines
	$self->_write_line_swissprot_regex("DE   ","DE   ",$seq->desc(),"\\s\+\|\$",80);

	#Gene name
	if ((my @genes = $seq->annotation->get_Annotations('gene_name') ) ) {
	    $self->_print("GN   ",
			  join(' OR ',
			       map {
				   $_->isa("Bio::Annotation::StructuredValue") ?
				       $_->value(-joins => [" AND ", " OR "]) :
				       $_->value();
			       } @genes),
			  ".\n");
	}

	# Organism lines
	if ($seq->can('species') && (my $spec = $seq->species)) {
	    my($species, @class) = $spec->classification();
	    my $genus = $class[0];
	    my $OS = "$genus $species";
            if ($class[-1] eq 'Viruses') {
                $OS = $species;
                $OS .=  " ". $spec->sub_species if $spec->sub_species;
            } else {
                if ($class[$#class] =~ /viruses/i) {
                    # different OS / OC syntax for viruses LP 09/16/2000
                    shift @class;
                }
                if (my $ssp = $spec->sub_species) {
                    $OS .= " $ssp";
                }
                foreach (($spec->variant, $spec->common_name)) {
                    $OS .= " ($_)" if $_;
                }
            }
	    $self->_print( "OS   $OS.\n");
	    my $OC = join('; ', reverse(@class)) .'.';
	    $self->_write_line_swissprot_regex("OC   ","OC   ",$OC,"\;\|\$ ",80);
	    if ($spec->organelle) {
		$self->_write_line_swissprot_regex("OG   ","OG   ",$spec->organelle,"\;\|\$ ",80);
	    }
	    if ($spec->ncbi_taxid) {
		$self->_print("OX   NCBI_TaxID=".$spec->ncbi_taxid.";\n");
	    }
	}

	# Reference lines
	my $t = 1;
	foreach my $ref ( $seq->annotation->get_Annotations('reference') ) {
	    $self->_print( "RN   [$t]\n");
	    # changed by lorenz 08/03/00
	    # j.gilbert and h.lapp agreed that the rp line in swissprot seems 
	    # more like a comment than a parseable value, so print it as is
	    if ($ref->rp) {
		$self->_write_line_swissprot_regex("RP   ","RP   ",$ref->rp,
						   "\\s\+\|\$",80);
	    }
	    if ($ref->comment) {
		$self->_write_line_swissprot_regex("RC   ","RC   ",$ref->comment,
						   "\\s\+\|\$",80);
	    }
	    if ($ref->medline) {
		# new RX format in swissprot LP 09/17/00
		if ($ref->pubmed) {
		    $self->_write_line_swissprot_regex("RX   ","RX   ",
						       "MEDLINE=".$ref->medline.
						       "; PubMed=".$ref->pubmed.";",
						       "\\s\+\|\$",80);
		} else {
		    $self->_write_line_swissprot_regex("RX   MEDLINE; ","RX   MEDLINE; ",
						       $ref->medline.".","\\s\+\|\$",80);
		}
	    }
	    my $author = $ref->authors .';' if($ref->authors);
	    my $title = $ref->title .';' if( $ref->title);

	    $self->_write_line_swissprot_regex("RA   ","RA   ",$author,"\\s\+\|\$",80);
	    $self->_write_line_swissprot_regex("RT   ","RT   ",$title,"\\s\+\|\$",80);
	    $self->_write_line_swissprot_regex("RL   ","RL   ",$ref->location,"\\s\+\|\$",80);
	    $t++;
	}

	# Comment lines

	foreach my $comment ( $seq->annotation->get_Annotations('comment') ) {
	    foreach my $cline (split ("\n", $comment->text)) {
		while (length $cline > 74) {
		    $self->_print("CC   ",(substr $cline,0,74),"\n");
		    $cline = substr $cline,74;
		}
		$self->_print("CC   ",$cline,"\n");
	    }
	}

	foreach my $dblink ( $seq->annotation->get_Annotations('dblink') ) 
	{
	    if (defined($dblink->comment)&&($dblink->comment)) {
		$self->_print("DR   ",$dblink->database,"; ",$dblink->primary_id,"; ",
			      $dblink->optional_id,"; ",$dblink->comment,".\n");
	    } elsif($dblink->optional_id) {
		$self->_print("DR   ",$dblink->database,"; ",
			      $dblink->primary_id,"; ",
			      $dblink->optional_id,".\n");
	    }
	    else {
		$self->_print("DR   ",$dblink->database,
			      "; ",$dblink->primary_id,"; ","-.\n");
	    }
	}   

	# if there, write the kw line
	{
	    my( $kw );
	    if( my $func = $self->_kw_generation_func ) {
		$kw = &{$func}($seq);
	    } elsif( $seq->can('keywords') ) {		
		$kw = $seq->keywords;
		if( ref($kw) =~ /ARRAY/i ) {
		    $kw = join("; ", @$kw);
		}
		$kw .= '.' if( $kw !~ /\.$/ );
	    }	    
	    $self->_write_line_swissprot_regex("KW   ","KW   ",
					       $kw, "\\s\+\|\$",80);           
	}

        #Check if there is seqfeatures before printing the FT line
	my @feats = $seq->can('top_SeqFeatures') ? $seq->top_SeqFeatures : ();
	if ($feats[0]) {
	    if( defined $self->_post_sort ) {

		# we need to read things into an array. Process. Sort them. Print 'em
		
		my $post_sort_func = $self->_post_sort();
		my @fth;

		foreach my $sf ( @feats ) {
		    push(@fth,Bio::SeqIO::FTHelper::from_SeqFeature($sf,$seq));
		}
		@fth = sort { &$post_sort_func($a,$b) } @fth;

		foreach my $fth ( @fth ) {
		    $self->_print_swissprot_FTHelper($fth);
		}
	    } else {
		# not post sorted. And so we can print as we get them.
		# lower memory load...

		foreach my $sf ( @feats ) {
		    my @fth = Bio::SeqIO::FTHelper::from_SeqFeature($sf,$seq);
		    foreach my $fth ( @fth ) {
			if( ! $fth->isa('Bio::SeqIO::FTHelper') ) {
			    $sf->throw("Cannot process FTHelper... $fth");
			}

			$self->_print_swissprot_FTHelper($fth);
		    }
		}
	    }

	    if( $self->_show_dna() == 0 ) {
		return;
	    }
	}
	# finished printing features.

	# molecular weight
	my $mw = ${Bio::Tools::SeqStats->get_mol_wt($seq->primary_seq)}[0];
	# checksum
	# was crc32 checksum, changed it to crc64 
	my $crc64 = $self->_crc64(\$str); 
	$self->_print( sprintf("SQ   SEQUENCE  %4d AA;  %d MW;  %16s CRC64;\n",
			       $len,$mw,$crc64));
	$self->_print( "     ");
	my $linepos;
	for ($i = 0; $i < length($str); $i += 10) {
	    $self->_print( substr($str,$i,10), " ");
	    $linepos += 11;
	    if( ($i+10)%60 == 0 && (($i+10) < length($str))) {
		$self->_print( "\n     ");
	    }
	}
	$self->_print( "\n//\n");

	$self->flush if $self->_flush_on_write && defined $self->_fh;
	return 1;
    }
}
_generateCRCTabledescriptionprevnextTop
sub _generateCRCTable {
  # 10001000001010010010001110000100
  # 32
  my $poly = 0xEDB88320;
  my ($self) = shift;
        
  $self->{'_crcTable'} = [];
  foreach my $i (0..255) {
    my $crc = $i;
    for (my $j=8; $j > 0; $j--) {
      if ($crc & 1) {
	$crc = ($crc >> 1) ^ $poly;
      }
      else {
	$crc >>= 1;
      }
    }
    ${$self->{'_crcTable'}}[$i] = $crc;
  }
}
_crc32descriptionprevnextTop
sub _crc32 {
  my( $self, $str ) = @_;
  
  $self->throw("Argument to crc32() must be ref to scalar")
    unless ref($str) eq 'SCALAR';
  
  $self->_generateCRCTable() unless exists $self->{'_crcTable'};
  
  my $len = length($$str);
  
  my $crc = 0xFFFFFFFF;
  for (my $i = 0; $i < $len; $i++) {
    # Get upper case value of each letter
    my $int = ord uc substr $$str, $i, 1;
    $crc = (($crc >> 8) & 0x00FFFFFF) ^ 
      ${$self->{'_crcTable'}}[ ($crc ^ $int) & 0xFF ];
  }
  return $crc;
}
_crc64descriptionprevnextTop
sub _crc64 {
    my ($self, $sequence) = @_;
    my $POLY64REVh = 0xd8000000;
    my @CRCTableh = 256;
    my @CRCTablel = 256;
    my $initialized;       
    

    my $seq = $$sequence;
      
    my $crcl = 0;
    my $crch = 0;
    if (!$initialized) {
	$initialized = 1;
	for (my $i=0; $i<256; $i++) {
	    my $partl = $i;
	    my $parth = 0;
	    for (my $j=0; $j<8; $j++) {
		my $rflag = $partl & 1;
		$partl >>= 1;
		$partl |= (1 << 31) if $parth & 1;
		$parth >>= 1;
		$parth ^= $POLY64REVh if $rflag;
	    }
	    $CRCTableh[$i] = $parth;
	    $CRCTablel[$i] = $partl;
	}
    }
    
    foreach (split '', $seq) {
	my $shr = ($crch & 0xFF) << 24
	my $temp1h = $crch >> 8;
	my $temp1l = ($crcl >> 8) | $shr;
	my $tableindex = ($crcl ^ (unpack "C", $_)) & 0xFF;
	$crch = $temp1h ^ $CRCTableh[$tableindex];
	$crcl = $temp1l ^ $CRCTablel[$tableindex];
    }
    my $crc64 = sprintf("%08X%08X", $crch, $crcl);
        
    return $crc64;
}
_print_swissprot_FTHelperdescriptionprevnextTop
sub _print_swissprot_FTHelper {
   my ($self,$fth,$always_quote) = @_;
   $always_quote ||= 0;
   my ($start,$end) = ('?', '?');
   
   if( ! ref $fth || ! $fth->isa('Bio::SeqIO::FTHelper') ) {
       $fth->warn("$fth is not a FTHelper class. ".
		  "Attempting to print, but there could be tears!");
   }

   if( $fth->loc =~ /(\?|\d+|\>\d+|<\d+)?\.\.(\?|\d+|<\d+|>\d+)?/ ) {
       $start = $1 if defined $1;
       $end = $2 if defined $2;

       # to_FTString only returns one value when start == end, #JB955
       # so if no match is found, assume it is both start and end #JB955
   } else {
       $start = $end = $fth->loc; 
   }
   
   my $desc = "";
   $desc = @{$fth->field->{"description"}}[0]."." 
       if exists $fth->field->{"description"};
   $self->_write_line_swissprot_regex(sprintf("FT   %-8s %6s %6s       ",
					      substr($fth->key,0,8),
					      $start,$end),
				      "FT                                ",
				      $desc.'.','\s+|$',80);
}
_read_swissprot_ReferencesdescriptionprevnextTop
sub _read_swissprot_References {
   my ($self,$buffer) = @_;
   my (@refs);
   my ($b1, $b2, $rp, $title, $loc, $au, $med, $com, $pubmed);
   
   if ($$buffer !~ /^RP/) {
       $$buffer = $self->_readline;
   }
   if( !defined $$buffer ) { return undef; }
   if( $$buffer =~ /^RP/ ) {
       if ($$buffer =~ /^RP   (SEQUENCE OF (\d+)-(\d+).*)/) { 
	   $rp=$1;
	   $b1=$2;
	   $b2=$3; 
       }
       elsif ($$buffer =~ /^RP   (.*)/) {
	   $rp=$1;
       }
       
   }
   while( defined ($_ = $self->_readline) ) {
       #/^CC/ && last;
       /^RN/ && last; # separator between references ! LP 07/25/2000
       #/^SQ/ && last; # there may be sequences without CC lines! HL 05/11/2000
       /^[^R]/ && last; # may be the safest exit point HL 05/11/2000
       /^RX   MEDLINE;\s+(\d+)/ && do {$med=$1};
       /^RX   MEDLINE=(\d+);\s+PubMed=(\d+);/ && do {$med=$1;$pubmed=$2};
       /^RA   (.*)/ && do { $au .= $au ? " $1" : $1;   next;};
       /^RT   (.*)/ && do { $title .= $title ? " $1" : $1; next;};
       /^RL   (.*)/ && do { $loc .= $loc ? " $1" : $1; next;};
       /^RC   (.*)/ && do { $com .= $com ? " $1" : $1; next;};
   }
   
   my $ref = new Bio::Annotation::Reference;
   $au =~ s/;\s*$//g;
   if( defined $title ) {
       $title =~ s/;\s*$//g;
   }
   
   $ref->start($b1);
   $ref->end($b2);
   $ref->authors($au);
   $ref->title($title);
   $ref->location($loc);
   $ref->medline($med);
   $ref->pubmed($pubmed) if (defined $pubmed);
   $ref->comment($com);
   $ref->rp($rp);

   push(@refs,$ref);
   $$buffer = $_;
   return\@ refs;
}
_read_swissprot_SpeciesdescriptionprevnextTop
sub _read_swissprot_Species {
    my( $self, $buffer ) = @_;
    my $org;

    $_ = $$buffer;
    my( $subspecies, $species, $genus, $common, $variant, $ncbi_taxid, $ns_name );
    my @class;
    my ($binomial, $descr);
    my $osline = "";

    while (defined( $_ ||= $self->_readline )) {
	last unless /^O[SCGX]/;
	# believe it or not, but OS may come multiple times -- at this time
	# we can't capture multiple species
	if(/^OS\s+(\S.+)/ && (! defined($binomial))) {
	    $osline .= " " if $osline;
	    $osline .= $1;
	    if($osline =~ s/(,|, and|\.)$//) {
		($binomial, $descr) = $osline =~ /(\S[^\(]+)(.*)/;
                ($ns_name) = $binomial;
                $ns_name =~ s/\s+$//; #####
		($genus, $species, $subspecies) = split(/\s+/, $binomial);
		$species = "sp." unless $species;
		while($descr =~ /\(([^\)]+)\)/g) {
		    my $item = $1;
		    # strain etc may not necessarily come first (yes, swissprot
		    # is messy)
		    if((! defined($variant)) &&
		       (($item =~ /(^|[^\(\w])([Ss]train|isolate|serogroup|serotype|subtype|clone)\b/) ||
			($item =~ /^(biovar|pv\.|type\s+)/))) {
			$variant = $item;
		    } elsif($item =~ s/^subsp\.\s+//) {
			if(! $subspecies) {
			    $subspecies = $item;
			} elsif(! $variant) {
			    $variant = $item;
			}
		    } elsif(! defined($common)) {
			# we're only interested in the first common name
			$common = $item;
			if((index($common, '(') >= 0) &&
			   (index($common, ')') < 0)) {
			    $common .= ')';
			}
		    }
		}
	    }
        }
        elsif (s/^OC\s+//) {
            push(@class, split /[\;\.]\s*/);
	    if($class[0] =~ /viruses/i) { 
		# viruses have different OS/OC syntax
		my @virusnames = split(/\s+/, $binomial);
		$species = (@virusnames > 1) ? pop(@virusnames) : '';
		$genus = join(" ", @virusnames);
		$subspecies = $descr;
	    }
        }
	elsif (/^OG\s+(.*)/) {
	    $org = $1;
	}
	elsif (/^OX\s+(.*)/ && (! defined($ncbi_taxid))) {
            my $taxstring = $1;
	    # we only keep the first one and ignore all others
            if ($taxstring =~ /NCBI_TaxID=([\w\d]+)/) {
                $ncbi_taxid = $1;
            } else {
                $self->throw("$taxstring doesn't look like NCBI_TaxID");
            }
	}
        
        $_ = undef; # Empty $_ to trigger read of next line
    }
    
    $$buffer = $_;
    
    # Don't make a species object if it is "Unknown" or "None"
    return if $genus =~ /^(Unknown|None)$/i;

    if ($class[0] eq 'Viruses') {
        push( @class, $ns_name );
    }
    elsif ($class[0] eq 'Viruses') {
        push( @class, $ns_name );
    }
    elsif ($class[$#class] eq $genus) {
        push( @class, $species );
    } else {
        push( @class, $genus, $species );
    }

    @class = reverse @class;
    
    my $taxon = Bio::Species->new();
    $taxon->classification(\@ class, "FORCE" ); # no name validation please
    $taxon->common_name( $common      ) if $common;
    $taxon->sub_species( $subspecies ) if $subspecies;
    $taxon->organelle  ( $org         ) if $org;
    $taxon->ncbi_taxid ( $ncbi_taxid  ) if $ncbi_taxid;
    $taxon->variant($variant)           if $variant;

    # done
    return $taxon;
}
_read_FTHelper_swissprotdescriptionprevnextTop
sub _read_FTHelper_swissprot {
    # initial version implemented by HL 05/10/2000
    # FIXME this may not be perfect, so please review 
    my ($self,$buffer) = @_;
    my ($key,   # The key of the feature
        $loc,   # The location line from the feature
        $desc,  # The descriptive text
        );
    
    if ($$buffer =~ /^FT   (\w+)\s+([\d\?\<]+)\s+([\d\?\>]+)\s*(.*)$/) {
        $key = $1;
        my $loc1 = $2;
        my $loc2 = $3;
	$loc = "$loc1..$loc2";
	if($4 && (length($4) > 0)) {
	    $desc = $4;
	    chomp($desc);
	} else {
	    $desc = "";
	}
	# Read all the continuation lines up to the next feature
	while (defined($_ = $self->_readline) && /^FT\s{20,}(\S.*)$/) {
	    $desc .= $1;
	    chomp($desc);
	}
	$desc =~ s/\.$//;
    } else {
        # No feature key. What's this?
	$self->warn("No feature key in putative feature table line: $_");
        return;
    } 
    
    # Put the first line of the next feature into the buffer
    $$buffer = $_;

    # Make the new FTHelper object
    my $out = new Bio::SeqIO::FTHelper(-verbose => $self->verbose());
    $out->key($key);
    $out->loc($loc);
    
    # store the description if there is one
    if($desc && (length($desc) > 0)) {
	$out->field->{"description"} ||= [];
	push(@{$out->field->{"description"}}, $desc);
    }
    return $out;
}
_write_line_swissprotdescriptionprevnextTop
sub _write_line_swissprot {
   my ($self,$pre1,$pre2,$line,$length) = @_;

   $length || die "Miscalled write_line_swissprot without length. Programming error!";
   my $subl = $length - length $pre2;
   my $linel = length $line;
   my $i;

   my $sub = substr($line,0,$length - length $pre1);

   $self->_print( "$pre1$sub\n");
   
   for($i= ($length - length $pre1);$i < $linel;) {
       $sub = substr($line,$i,($subl));
       $self->_print( "$pre2$sub\n");
       $i += $subl;
   }
}
_write_line_swissprot_regexdescriptionprevnextTop
sub _write_line_swissprot_regex {
   my ($self,$pre1,$pre2,$line,$regex,$length) = @_;
   
   #print STDOUT "Going to print with $line!\n";

   $length || die "Miscalled write_line_swissprot without length. Programming error!";

   if( length $pre1 != length $pre2 ) {
       print STDERR "len 1 is ", length $pre1, " len 2 is ", length $pre2, "\n";
       die "Programming error - cannot called write_line_swissprot_regex with different length\n pre1 ($pre1) and\n pre2 ($pre2) tags!";
   }

   my $subl = $length - (length $pre1) -1 ;
   my @lines;

   while($line =~ m/(.{1,$subl})($regex)/g) {
       push(@lines, $1.$2);
   }
   
   my $s = shift @lines;
   $self->_print( "$pre1$s\n");
   foreach my $s ( @lines ) {
       $self->_print( "$pre2$s\n");
   }
}
_post_sortdescriptionprevnextTop
sub _post_sort {
   my $obj = shift;
   if( @_ ) {
      my $value = shift;
      $obj->{'_post_sort'} = $value;
    }
    return $obj->{'_post_sort'};
}
_show_dnadescriptionprevnextTop
sub _show_dna {
   my $obj = shift;
   if( @_ ) {
      my $value = shift;
      $obj->{'_show_dna'} = $value;
    }
    return $obj->{'_show_dna'};
}
_id_generation_funcdescriptionprevnextTop
sub _id_generation_func {
   my $obj = shift;
   if( @_ ) {
      my $value = shift;
      $obj->{'_id_generation_func'} = $value;
    }
    return $obj->{'_id_generation_func'};
}
_ac_generation_funcdescriptionprevnextTop
sub _ac_generation_func {
   my $obj = shift;
   if( @_ ) {
      my $value = shift;
      $obj->{'_ac_generation_func'} = $value;
    }
    return $obj->{'_ac_generation_func'};
}
_sv_generation_funcdescriptionprevnextTop
sub _sv_generation_func {
   my $obj = shift;
   if( @_ ) {
      my $value = shift;
      $obj->{'_sv_generation_func'} = $value;
    }
    return $obj->{'_sv_generation_func'};
}
_kw_generation_funcdescriptionprevnextTop
sub _kw_generation_func {
   my $obj = shift;
   if( @_ ) {
      my $value = shift;
      $obj->{'_kw_generation_func'} = $value;
    }
    return $obj->{'_kw_generation_func'};
}
General documentation
FEEDBACKTop
Mailing ListsTop
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
  http://bio.perl.org/MailList.html             - About the mailing lists
Reporting BugsTop
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/
AUTHOR - Elia StupkaTop
Email elia@tll.org.sg
Describe contact details here
APPENDIXTop
The rest of the documentation details each of the object methods. Internal methods are usually preceded with a _
_filehandleTop
 Title   : _filehandle
 Usage   : $obj->_filehandle($newval)
 Function: 
 Example : 
 Returns : value of _filehandle
 Args    : newvalue (optional)