lib/perl5/5.6.1/look.pl

   1 ;# Usage: &look(*FILEHANDLE,$key,$dict,$fold)
   2 #
   3 # This library is no longer being maintained, and is included for backward
   4 # compatibility with Perl 4 programs which may require it.
   5 #
   6 # In particular, this should not be used as an example of modern Perl
   7 # programming techniques.
   8 #
   9 ;# Sets file position in FILEHANDLE to be first line greater than or equal
  10 ;# (stringwise) to $key.  Pass flags for dictionary order and case folding.
  11
  12 sub look {
  13     local(*FH,$key,$dict,$fold) = @_;
  14     local($max,$min,$mid,$_);
  15     local($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,
  16        $blksize,$blocks) = stat(FH);
  17     $blksize = 8192 unless $blksize;
  18     $key =~ s/[^\w\s]//g if $dict;
  19     $key = lc $key if $fold;
  20     $max = int($size / $blksize);
  21     while ($max - $min > 1) {
  22         $mid = int(($max + $min) / 2);
  23         seek(FH,$mid * $blksize,0);
  24         $_ = <FH> if $mid;              # probably a partial line
  25         $_ = <FH>;
  26         chop;
  27         s/[^\w\s]//g if $dict;
  28         $_ = lc $_ if $fold;
  29         if ($_ lt $key) {
  30             $min = $mid;
  31         }
  32         else {
  33             $max = $mid;
  34         }
  35     }
  36     $min *= $blksize;
  37     seek(FH,$min,0);
  38     <FH> if $min;
  39     while (<FH>) {
  40         chop;
  41         s/[^\w\s]//g if $dict;
  42         $_ = lc $_ if $fold;
  43         last if $_ ge $key;
  44         $min = tell(FH);
  45     }
  46     seek(FH,$min,0);
  47     $min;
  48 }
  49
  50 1;