1package Search::Dict;
2require 5.000;
3require Exporter;
4
5my $fc_available;
6BEGIN {
7  $fc_available = '5.015008';
8  if ( $] ge $fc_available ) {
9    require feature;
10    'feature'->import('fc'); # string avoids warning on old Perls <sigh>
11  }
12}
13
14use strict;
15
16our $VERSION = '1.07';
17our @ISA = qw(Exporter);
18our @EXPORT = qw(look);
19
20=head1 NAME
21
22Search::Dict - look - search for key in dictionary file
23
24=head1 SYNOPSIS
25
26    use Search::Dict;
27    look *FILEHANDLE, $key, $dict, $fold;
28
29    use Search::Dict;
30    look *FILEHANDLE, $params;
31
32=head1 DESCRIPTION
33
34Sets file position in FILEHANDLE to be first line greater than or equal
35(stringwise) to I<$key>.  Returns the new file position, or -1 if an error
36occurs.
37
38The flags specify dictionary order and case folding:
39
40If I<$dict> is true, search by dictionary order (ignore anything but word
41characters and whitespace).  The default is honour all characters.
42
43If I<$fold> is true, ignore case.  The default is to honour case.
44
45If there are only three arguments and the third argument is a hash
46reference, the keys of that hash can have values C<dict>, C<fold>, and
47C<comp> or C<xfrm> (see below), and their corresponding values will be
48used as the parameters.
49
50If a comparison subroutine (comp) is defined, it must return less than zero,
51zero, or greater than zero, if the first comparand is less than,
52equal, or greater than the second comparand.
53
54If a transformation subroutine (xfrm) is defined, its value is used to
55transform the lines read from the filehandle before their comparison.
56
57=cut
58
59sub look {
60    my($fh,$key,$dict,$fold) = @_;
61    my ($comp, $xfrm);
62    if (@_ == 3 && ref $dict eq 'HASH') {
63	my $params = $dict;
64	$dict = 0;
65	$dict = $params->{dict} if exists $params->{dict};
66	$fold = $params->{fold} if exists $params->{fold};
67	$comp = $params->{comp} if exists $params->{comp};
68	$xfrm = $params->{xfrm} if exists $params->{xfrm};
69    }
70    $comp = sub { $_[0] cmp $_[1] } unless defined $comp;
71    local($_);
72    my $fno = fileno $fh;
73    my @stat;
74    if ( defined $fno && $fno >= 0 && ! tied *{$fh} ) { # real, open file
75      @stat = eval { stat($fh) }; # in case fileno lies
76    }
77    my($size, $blksize) = @stat[7,11];
78    $size = do { seek($fh,0,2); my $s = tell($fh); seek($fh,0,0); $s }
79        unless defined $size;
80    $blksize ||= 8192;
81    $key =~ s/[^\w\s]//g if $dict;
82    if ( $fold ) {
83      $key = $] ge $fc_available ? fc($key) : lc($key);
84    }
85    # find the right block
86    my($min, $max) = (0, int($size / $blksize));
87    my $mid;
88    while ($max - $min > 1) {
89	$mid = int(($max + $min) / 2);
90	seek($fh, $mid * $blksize, 0)
91	    or return -1;
92	<$fh> if $mid;			# probably a partial line
93	$_ = <$fh>;
94	$_ = $xfrm->($_) if defined $xfrm;
95	chomp;
96	s/[^\w\s]//g if $dict;
97        if ( $fold ) {
98          $_ = $] ge $fc_available ? fc($_) : lc($_);
99        }
100	if (defined($_) && $comp->($_, $key) < 0) {
101	    $min = $mid;
102	}
103	else {
104	    $max = $mid;
105	}
106    }
107    # find the right line
108    $min *= $blksize;
109    seek($fh,$min,0)
110	or return -1;
111    <$fh> if $min;
112    for (;;) {
113	$min = tell($fh);
114	defined($_ = <$fh>)
115	    or last;
116	$_ = $xfrm->($_) if defined $xfrm;
117	chomp;
118	s/[^\w\s]//g if $dict;
119        if ( $fold ) {
120          $_ = $] ge $fc_available ? fc($_) : lc($_);
121        }
122	last if $comp->($_, $key) >= 0;
123    }
124    seek($fh,$min,0);
125    $min;
126}
127
1281;
129