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44 lines
1020 B
44 lines
1020 B
;# Usage: &look(*FILEHANDLE,$key,$dict,$fold)
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;# Sets file position in FILEHANDLE to be first line greater than or equal
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;# (stringwise) to $key. Pass flags for dictionary order and case folding.
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sub look {
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local(*FH,$key,$dict,$fold) = @_;
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local($max,$min,$mid,$_);
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local($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,
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$blksize,$blocks) = stat(FH);
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$blksize = 8192 unless $blksize;
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$key =~ s/[^\w\s]//g if $dict;
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$key = lc $key if $fold;
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$max = int($size / $blksize);
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while ($max - $min > 1) {
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$mid = int(($max + $min) / 2);
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seek(FH,$mid * $blksize,0);
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$_ = <FH> if $mid; # probably a partial line
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$_ = <FH>;
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chop;
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s/[^\w\s]//g if $dict;
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$_ = lc $_ if $fold;
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if ($_ lt $key) {
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$min = $mid;
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}
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else {
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$max = $mid;
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}
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}
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$min *= $blksize;
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seek(FH,$min,0);
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<FH> if $min;
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while (<FH>) {
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chop;
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s/[^\w\s]//g if $dict;
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$_ = lc $_ if $fold;
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last if $_ ge $key;
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$min = tell(FH);
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}
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seek(FH,$min,0);
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$min;
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}
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1;
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