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package Search::Dict;
require 5.000;
require Exporter;
use strict;
our $VERSION = '1.03';
our @ISA = qw(Exporter);
our @EXPORT = qw(look);
=head1 NAME
Search::Dict, look - search for key in dictionary file
=head1 SYNOPSIS
use Search::Dict;
look *FILEHANDLE, $key, $dict, $fold;
use Search::Dict;
look *FILEHANDLE, $params;
=head1 DESCRIPTION
Sets file position in FILEHANDLE to be first line greater than or equal
(stringwise) to I<$key>. Returns the new file position, or -1 if an error
occurs.
The flags specify dictionary order and case folding:
If I<$dict> is true, search by dictionary order (ignore anything but word
characters and whitespace). The default is honour all characters.
If I<$fold> is true, ignore case. The default is to honour case.
If there are only three arguments and the third argument is a hash
reference, the keys of that hash can have values C<dict>, C<fold>, and
C<comp> or C<xfrm> (see below), and their corresponding values will be
used as the parameters.
If a comparison subroutine (comp) is defined, it must return less than zero,
zero, or greater than zero, if the first comparand is less than,
equal, or greater than the second comparand.
If a transformation subroutine (xfrm) is defined, its value is used to
transform the lines read from the filehandle before their comparison.
=cut
sub look {
my($fh,$key,$dict,$fold) = @_;
my ($comp, $xfrm);
if (@_ == 3 && ref $dict eq 'HASH') {
my $params = $dict;
$dict = 0;
$dict = $params->{dict} if exists $params->{dict};
$fold = $params->{fold} if exists $params->{fold};
$comp = $params->{comp} if exists $params->{comp};
$xfrm = $params->{xfrm} if exists $params->{xfrm};
}
$comp = sub { $_[0] cmp $_[1] } unless defined $comp;
local($_);
my(@stat) = stat($fh)
or return -1;
my($size, $blksize) = @stat[7,11];
$blksize ||= 8192;
$key =~ s/[^\w\s]//g if $dict;
$key = lc $key if $fold;
# find the right block
my($min, $max) = (0, int($size / $blksize));
my $mid;
while ($max - $min > 1) {
$mid = int(($max + $min) / 2);
seek($fh, $mid * $blksize, 0)
or return -1;
<$fh> if $mid; # probably a partial line
$_ = <$fh>;
$_ = $xfrm->($_) if defined $xfrm;
chomp;
s/[^\w\s]//g if $dict;
$_ = lc $_ if $fold;
if (defined($_) && $comp->($_, $key) < 0) {
$min = $mid;
}
else {
$max = $mid;
}
}
# find the right line
$min *= $blksize;
seek($fh,$min,0)
or return -1;
<$fh> if $min;
for (;;) {
$min = tell($fh);
defined($_ = <$fh>)
or last;
$_ = $xfrm->($_) if defined $xfrm;
chomp;
s/[^\w\s]//g if $dict;
$_ = lc $_ if $fold;
last if $comp->($_, $key) >= 0;
}
seek($fh,$min,0);
$min;
}
1;
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