/usr/share/perl5/FaSlice.pm is in vcftools 0.1.15-1.
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#
=head1 NAME
FaSlice.pm. Module for cached access to fasta sequences, employs samtools faidx.
=head1 SYNOPSIS
use FaSlice;
my $fa = FaSlice->new(file=>'ref.fa');
$fa->get_base(1,12345);
$fa->get_slice(1,12345,54321);
=cut
package FaSlice;
use strict;
use warnings;
use Carp;
=head2 new
About : Creates new FaSlice object.
Usage : my $fa = FaSlice->new(file=>'ref.fa');
Args : file .. the fasta file
oob .. out-of-bounds requests: one of 'throw' (throws), 'N' (fills the missing bases with Ns), or '' (returns empty string, default)
size .. size of the cached chunk read by samtools faidx (1_000_000)
=cut
sub new
{
my ($class,@args) = @_;
my $self = @args ? {@args} : {};
bless $self, ref($class) || $class;
if ( !$$self{file} ) { $self->throw("Missing the parameter file\n"); }
$$self{chr} = undef;
$$self{from} = undef;
$$self{to} = undef;
if ( !$$self{size} ) { $$self{size}=1_000_000; }
$$self{ncache_missed} = 0;
$$self{nqueries} = 0;
if ( !exists($$self{oob}) ) { $$self{oob}=''; }
if ( $$self{oob} ne '' && $$self{oob} ne 'throw' && $$self{oob} ne 'N' ) { $self->throw("The value of oob not recognised: [$$self{oob}]"); }
$self->chromosome_naming($$self{file});
return $self;
}
sub throw
{
my ($self,@msg) = @_;
confess(@msg);
}
sub cmd
{
my ($self,$cmd) = @_;
my @out = `$cmd`;
if ( $? )
{
my @msg = ();
push @msg, qq[The command "$cmd" returned non-zero status $?];
if ( $! )
{
push @msg, ": $!\n";
}
else
{
push @msg, ".\n";
}
if ( scalar @out )
{
push @msg, @out;
}
$self->throw(@msg);
}
return (@out);
}
# Read the first file of the fasta file and make a guess: Are all chromosomes
# names as 'chr1','chr2',etc or just '1','2',...?
# Future TODO: more robust chromosome name mapping?
sub chromosome_naming
{
my ($self,$fa_file) = @_;
open(my $fh,'<',"$fa_file.fai") or $self->throw("$fa_file.fai: $!");
my $line=<$fh>;
if ( !($line=~/^(chr)?\S+\t/) ) { chomp($line); $self->throw("FIXME: the sequence names not in '>(chr)?\\S+' format [$line] ... $fa_file.fai\n"); }
close($fh);
$$self{chr_naming} = defined $1 ? $1 : '';
}
sub cache_chr_lengths
{
my ($self) = @_;
if ( exists($$self{chr_lengths}) ) { return; }
open(my $fh,'<',"$$self{file}.fai") or $self->throw("$$self{file}.fai: $!");
while (my $line=<$fh>)
{
my @items = split(/\t/,$line);
my $chr = $$self{chr_naming}.$items[0];
$$self{chr_lengths}{$chr} = $items[1];
}
close($fh) or $self->throw("close $$self{file}.fai");
}
sub read_chunk
{
my ($self,$chr,$pos) = @_;
$$self{chr} = $chr;
$chr =~ s/^chr//;
$chr = $$self{chr_naming}.$chr;
if ( exists($$self{chr_lengths}) && (!exists($$self{chr_lengths}{$chr}) or $$self{chr_lengths}{$chr} < $pos ) )
{
$$self{to} = $$self{from} - 1;
$$self{chunk} = '';
return;
}
my $to = $pos + $$self{size};
my $cmd = "samtools faidx \Q$$self{file}\E \Q$chr:$pos-$to\E";
my @out = $self->cmd($cmd) or $self->throw("$cmd: $!");
my $line = shift(@out);
if ( !($line=~/^>\Q$chr\E:(\d+)-(\d+)/) ) { $self->throw("Could not parse: $line"); }
$$self{from} = $1;
my $chunk = '';
while ($line=shift(@out))
{
chomp($line);
$chunk .= $line;
}
$$self{to} = $$self{from} + length($chunk) - 1;
$$self{chunk} = $chunk;
$self->cache_chr_lengths();
return;
}
=head2 get_base
About : Retrieves base at the given chromosome and position
Usage : my $fa = FaSlice->new(file=>'ref.fa'); $fa->get_base(1,12345);
Args : chromosome
1-based coordinate
=cut
sub get_base
{
my ($self,$chr,$pos) = @_;
if ( !$$self{chr} || $chr ne $$self{chr} || $pos<$$self{from} || $pos>$$self{to} )
{
$self->read_chunk($chr,$pos);
}
$$self{nqueries}++;
my $idx = $pos - $$self{from};
if ( $$self{from}>$$self{to} )
{
if ( $$self{oob} eq '' ) { return ''; }
elsif ( $$self{oob} eq 'N' ) { return 'N'; }
$self->throw("No such site $chr:$pos in $$self{file}\n");
}
return substr($$self{chunk},$idx,1);
}
=head2 get_slice
About : Retrieves region
Usage : my $fa = FaSlice->new(file=>'ref.fa'); $fa->get_base(1,12345,54321);
Args : chromosome
1-based coordinate
=cut
sub get_slice
{
my ($self,$chr,$from,$to) = @_;
if ( $to-$from >= $$self{size} ) { $$self{size} = $to-$from+1; }
if ( $from>$to ) { $self->throw("Expected $from>$to\n"); }
if ( !$$self{chr} || $chr ne $$self{chr} || $from<$$self{from} || $to>$$self{to} )
{
$self->read_chunk($chr,$from);
}
$$self{nqueries}++;
if ( $$self{from}>$$self{to} || $$self{from}>$from || $$self{to}<$to )
{
if ( $$self{oob} eq 'throw' ) { $self->throw("The region out of bounds $chr:$from-$to in $$self{file}\n"); }
elsif ( $$self{oob} eq '' ) { return ''; }
if ( $$self{from}>$$self{to} ) { return 'N' x ($to-$from+1); }
if ( $$self{from}>$to ) { $self->throw("FIXME: this shouldn't happen $chr:$from-$to .. $$self{from},$$self{to} .. $$self{file}"); }
my $lfill = '';
my $rfill = '';
if ( $$self{from}>$from ) { $lfill = 'N' x ($$self{from}-$from); $from=$$self{from}; }
if ( $$self{to}<$to ) { $rfill = 'N' x ($to-$$self{to}); $to=$$self{to}; }
return $lfill . substr($$self{chunk},$from-$$self{from},$to-$from+1) . $rfill;
}
return substr($$self{chunk},$from-$$self{from},$to-$from+1);
}
# http://www.illumina.com/documents/products/technotes/technote_topbot.pdf
sub illumina_alleles_TOP_to_ref
{
my ($self,$a1,$a2,$chr,$pos,$ref) = @_;
my %map = (A=>'T', C=>'G', G=>'C', T=>'A');
my %top = (
A=>{A=>-2,C=> 1,G=> 1,T=>-1},
C=>{A=> 1,C=>-2,G=>-1,T=> 0},
G=>{A=> 1,C=>-1,G=>-2,T=> 0},
T=>{A=>-1,C=> 0,G=> 0,T=>-2} );
my $stat = $top{$a1}{$a2};
if ( $stat==-2 ) { $self->throw("Expected two different bases, got $a1 and $a2.\n"); }
if ( $stat==-1 )
{
# Now we should do the sequence walking to see if the reference is TOP or BOT,
# but we do not this in ill-to-vcf: C/G would become G/C and A/T would become T/A.
return ($a1,$a2);
}
if ( $stat==0 ) { $self->throw("Expected Illumina TOP, got $a1 and $a2.\n"); }
if ( $ref eq $a1 or $ref eq $a2 ) { return ($a1,$a2); }
return ($map{$a1},$map{$a2});
}
1;
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