| 1 | ;# Usage: &look(*FILEHANDLE,$key,$dict,$fold) |
| 2 | |
| 3 | ;# Sets file position in FILEHANDLE to be first line greater than or equal |
| 4 | ;# (stringwise) to $key. Pass flags for dictionary order and case folding. |
| 5 | |
| 6 | sub look { |
| 7 | local(*FH,$key,$dict,$fold) = @_; |
| 8 | local($max,$min,$mid,$_); |
| 9 | local($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime, |
| 10 | $blksize,$blocks) = stat(FH); |
| 11 | $blksize = 8192 unless $blksize; |
| 12 | $key =~ s/[^\w\s]//g if $dict; |
| 13 | $key = lc $key if $fold; |
| 14 | $max = int($size / $blksize); |
| 15 | while ($max - $min > 1) { |
| 16 | $mid = int(($max + $min) / 2); |
| 17 | seek(FH,$mid * $blksize,0); |
| 18 | $_ = <FH> if $mid; # probably a partial line |
| 19 | $_ = <FH>; |
| 20 | chop; |
| 21 | s/[^\w\s]//g if $dict; |
| 22 | $_ = lc $_ if $fold; |
| 23 | if ($_ lt $key) { |
| 24 | $min = $mid; |
| 25 | } |
| 26 | else { |
| 27 | $max = $mid; |
| 28 | } |
| 29 | } |
| 30 | $min *= $blksize; |
| 31 | seek(FH,$min,0); |
| 32 | <FH> if $min; |
| 33 | while (<FH>) { |
| 34 | chop; |
| 35 | s/[^\w\s]//g if $dict; |
| 36 | $_ = lc $_ if $fold; |
| 37 | last if $_ ge $key; |
| 38 | $min = tell(FH); |
| 39 | } |
| 40 | seek(FH,$min,0); |
| 41 | $min; |
| 42 | } |
| 43 | |
| 44 | 1; |