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;# Usage: &look(*FILEHANDLE,$key,$dict,$fold)
;# Sets file position in FILEHANDLE to be first line greater than or equal
;# (stringwise) to $key. Pass flags for dictionary order and case folding.
sub look {
local(*FH,$key,$dict,$fold) = @_;
local($max,$min,$mid,$_);
local($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,
$blksize,$blocks) = stat(FH);
$blksize = 8192 unless $blksize;
$key =~ s/[^\w\s]//g if $dict;
$key =~ y/A-Z/a-z/ if $fold;
$max = int($size / $blksize);
while ($max - $min > 1) {
$mid = int(($max + $min) / 2);
seek(FH,$mid * $blksize,0);
$_ = <FH> if $mid; # probably a partial line
$_ = <FH>;
chop;
s/[^\w\s]//g if $dict;
y/A-Z/a-z/ if $fold;
if ($_ lt $key) {
$min = $mid;
}
else {
$max = $mid;
}
}
$min *= $blksize;
seek(FH,$min,0);
<FH> if $min;
while (<FH>) {
chop;
s/[^\w\s]//g if $dict;
y/A-Z/a-z/ if $fold;
last if $_ ge $key;
$min = tell(FH);
}
seek(FH,$min,0);
$min;
}
1;
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