lib/WebPAC/Input.pm

package WebPAC::Input;

use warnings;
use strict;

use blib;

use WebPAC::Common;
use base qw/WebPAC::Common/;
use Text::Iconv;
use Data::Dumper;

=head1 NAME

WebPAC::Input - read different file formats into WebPAC

=head1 VERSION

Version 0.05

=cut

our $VERSION = '0.05';

=head1 SYNOPSIS

This module implements input as database which have fixed and known
I<size> while indexing and single unique numeric identifier for database
position ranging from 1 to I<size>.

Simply, something that is indexed by unmber from 1 .. I<size>.

Examples of such databases are CDS/ISIS files, MARC files, lines in
text file, and so on.

Specific file formats are implemented using low-level interface modules,
located in C<WebPAC::Input::*> namespace which export C<open_db>,
C<fetch_rec> and optional C<init> functions.

Perhaps a little code snippet.

    use WebPAC::Input;

    my $db = WebPAC::Input->new(
        module => 'WebPAC::Input::ISIS',
                config => $config,
                lookup => $lookup_obj,
                low_mem => 1,
    );

    $db->open('/path/to/database');
        print "database size: ",$db->size,"\n";
        while (my $rec = $db->fetch) {
                # do something with $rec
        }


=head1 FUNCTIONS

=head2 new

Create new input database object.

  my $db = new WebPAC::Input(
        module => 'WebPAC::Input::MARC',
        code_page => 'ISO-8859-2',
        low_mem => 1,
        recode => 'char pairs',
        no_progress_bar => 1,
  );

C<module> is low-level file format module. See L<WebPAC::Input::Isis> and
L<WebPAC::Input::MARC>.

Optional parametar C<code_page> specify application code page (which will be
used internally). This should probably be your terminal encoding, and by
default, it C<ISO-8859-2>.

Default is not to use C<low_mem> options (see L<MEMORY USAGE> below).

C<recode> is optional string constisting of character or words pairs that
should be replaced in input stream.

C<no_progress_bar> disables progress bar output on C<STDOUT>

This function will also call low-level C<init> if it exists with same
parametars.

=cut

sub new {
        my $class = shift;
        my $self = {@_};
        bless($self, $class);

        my $log = $self->_get_logger;

        $log->logconfess("specify low-level file format module") unless ($self->{module});
        my $module = $self->{module};
        $module =~ s#::#/#g;
        $module .= '.pm';
        $log->debug("require low-level module $self->{module} from $module");

        require $module;
        #eval $self->{module} .'->import';

        # check if required subclasses are implemented
        foreach my $subclass (qw/open_db fetch_rec init/) {
                my $n = $self->{module} . '::' . $subclass;
                if (! defined &{ $n }) {
                        my $missing = "missing $subclass in $self->{module}";
                        $self->{$subclass} = sub { $log->logwarn($missing) };
                } else {
                        $self->{$subclass} = \&{ $n };
                }
        }

        if ($self->{init}) {
                $log->debug("calling init");
                $self->{init}->($self, @_);
        }

        $self->{'code_page'} ||= 'ISO-8859-2';

        # running with low_mem flag? well, use DBM::Deep then.
        if ($self->{'low_mem'}) {
                $log->info("running with low_mem which impacts performance (<32 Mb memory usage)");

                my $db_file = "data.db";

                if (-e $db_file) {
                        unlink $db_file or $log->logdie("can't remove '$db_file' from last run");
                        $log->debug("removed '$db_file' from last run");
                }

                require DBM::Deep;

                my $db = new DBM::Deep $db_file;

                $log->logdie("DBM::Deep error: $!") unless ($db);

                if ($db->error()) {
                        $log->logdie("can't open '$db_file' under low_mem: ",$db->error());
                } else {
                        $log->debug("using file '$db_file' for DBM::Deep");
                }

                $self->{'db'} = $db;
        }

        $self ? return $self : return undef;
}

=head2 open

This function will read whole database in memory and produce lookups.

 $input->open(
        path => '/path/to/database/file',
        code_page => '852',
        limit => 500,
        offset => 6000,
        lookup => $lookup_obj,
        stats => 1,
 );

By default, C<code_page> is assumed to be C<852>.

C<offset> is optional parametar to position at some offset before reading from database.

C<limit> is optional parametar to read just C<limit> records from database

C<stats> create optional report about usage of fields and subfields

Returns size of database, regardless of C<offset> and C<limit>
parametars, see also C<size>.

=cut

sub open {
        my $self = shift;
        my $arg = {@_};

        my $log = $self->_get_logger();

        $log->logcroak("need path") if (! $arg->{'path'});
        my $code_page = $arg->{'code_page'} || '852';

        # store data in object
        $self->{'input_code_page'} = $code_page;
        foreach my $v (qw/path offset limit/) {
                $self->{$v} = $arg->{$v} if ($arg->{$v});
        }

        # create Text::Iconv object
        $self->{iconv} = Text::Iconv->new($code_page,$self->{'code_page'});

        my $filter_ref;

        if ($self->{recode}) {
                my @r = split(/\s/, $self->{recode});
                if ($#r % 2 != 1) {
                        $log->logwarn("recode needs even number of elements (some number of valid pairs)");
                } else {
                        my $recode;
                        while (@r) {
                                my $from = shift @r;
                                my $to = shift @r;
                                $recode->{$from} = $to;
                        }

                        my $regex = join '|' => keys %{ $recode };

                        $log->debug("using recode regex: $regex");
                        
                        $filter_ref = sub {
                                my $t = shift;
                                $t =~ s/($regex)/$recode->{$1}/g;
                                return $t;
                        };

                }

        }

        my ($db, $size) = $self->{open_db}->( $self, 
                path => $arg->{path},
                filter => $filter_ref,
        );

        unless (defined($db)) {
                $log->logwarn("can't open database $arg->{path}, skipping...");
                return;
        }

        unless ($size) {
                $log->logwarn("no records in database $arg->{path}, skipping...");
                return;
        }

        my $from_rec = 1;
        my $to_rec = $size;

        if (my $s = $self->{offset}) {
                $log->debug("skipping to MFN $s");
                $from_rec = $s;
        } else {
                $self->{offset} = $from_rec;
        }

        if ($self->{limit}) {
                $log->debug("limiting to ",$self->{limit}," records");
                $to_rec = $from_rec + $self->{limit} - 1;
                $to_rec = $size if ($to_rec > $size);
        }

        # store size for later
        $self->{size} = ($to_rec - $from_rec) ? ($to_rec - $from_rec + 1) : 0;

        $log->info("processing $self->{size}/$size records [$from_rec-$to_rec] convert $code_page -> $self->{code_page}", $self->{stats} ? ' [stats]' : '');

        # read database
        for (my $pos = $from_rec; $pos <= $to_rec; $pos++) {

                $log->debug("position: $pos\n");

                my $rec = $self->{fetch_rec}->($self, $db, $pos );

                $log->debug(sub { Dumper($rec) });

                if (! $rec) {
                        $log->warn("record $pos empty? skipping...");
                        next;
                }

                # store
                if ($self->{low_mem}) {
                        $self->{db}->put($pos, $rec);
                } else {
                        $self->{data}->{$pos} = $rec;
                }

                # create lookup
                $self->{'lookup'}->add( $rec ) if ($rec && $self->{'lookup'});

                # update counters for statistics
                if ($self->{stats}) {
                        map {
                                my $fld = $_;
                                $self->{_stats}->{fld}->{ $fld }++;
                                if (ref($rec->{ $fld }) eq 'ARRAY') {
                                        map {
                                                if (ref($_) eq 'HASH') {
                                                        map {
                                                                $self->{_stats}->{sf}->{ $fld }->{ $_ }++;
                                                        } keys %{ $_ };
                                                } else {
                                                        $self->{_stats}->{repeatable}->{ $fld }++;
                                                }
                                        } @{ $rec->{$fld} };
                                }
                        } keys %{ $rec };
                }

                $self->progress_bar($pos,$to_rec) unless ($self->{no_progress_bar});

        }

        $self->{pos} = -1;
        $self->{last_pcnt} = 0;

        # store max mfn and return it.
        $self->{max_pos} = $to_rec;
        $log->debug("max_pos: $to_rec");

        return $size;
}

=head2 fetch

Fetch next record from database. It will also displays progress bar.

 my $rec = $isis->fetch;

Record from this function should probably go to C<data_structure> for
normalisation.

=cut

sub fetch {
        my $self = shift;

        my $log = $self->_get_logger();

        $log->logconfess("it seems that you didn't load database!") unless ($self->{pos});

        if ($self->{pos} == -1) {
                $self->{pos} = $self->{offset};
        } else {
                $self->{pos}++;
        }

        my $mfn = $self->{pos};

        if ($mfn > $self->{max_pos}) {
                $self->{pos} = $self->{max_pos};
                $log->debug("at EOF");
                return;
        }

        $self->progress_bar($mfn,$self->{max_pos}) unless ($self->{no_progress_bar});

        my $rec;

        if ($self->{low_mem}) {
                $rec = $self->{db}->get($mfn);
        } else {
                $rec = $self->{data}->{$mfn};
        }

        $rec ||= 0E0;
}

=head2 pos

Returns current record number (MFN).

 print $isis->pos;

First record in database has position 1.

=cut

sub pos {
        my $self = shift;
        return $self->{pos};
}


=head2 size

Returns number of records in database

 print $isis->size;

Result from this function can be used to loop through all records

 foreach my $mfn ( 1 ... $isis->size ) { ... }

because it takes into account C<offset> and C<limit>.

=cut

sub size {
        my $self = shift;
        return $self->{size};
}

=head2 seek

Seek to specified MFN in file.

 $isis->seek(42);

First record in database has position 1.

=cut

sub seek {
        my $self = shift;
        my $pos = shift || return;

        my $log = $self->_get_logger();

        if ($pos < 1) {
                $log->warn("seek before first record");
                $pos = 1;
        } elsif ($pos > $self->{max_pos}) {
                $log->warn("seek beyond last record");
                $pos = $self->{max_pos};
        }

        return $self->{pos} = (($pos - 1) || -1);
}

=head2 stats

Dump statistics about field and subfield usage

  print $input->stats;

=cut

sub stats {
        my $self = shift;

        my $log = $self->_get_logger();

        my $s = $self->{_stats};
        if (! $s) {
                $log->warn("called stats, but there is no statistics collected");
                return;
        }

        my $max_fld = 0;

        my $out = join("\n",
                map {
                        my $f = $_ || die "no field";
                        my $v = $s->{fld}->{$f} || die "no s->{fld}->{$f}";
                        $max_fld = $v if ($v > $max_fld);

                        my $o = sprintf("%4s %d ~", $f, $v);

                        if (defined($s->{sf}->{$f})) {
                                map {
                                        $o .= sprintf(" %s:%d", $_, $s->{sf}->{$f}->{$_});
                                } sort keys %{ $s->{sf}->{$f} };
                        }

                        if (my $v_r = $s->{repeatable}->{$f}) {
                                $o .= " ($v_r)" if ($v_r != $v);
                        }

                        $o;
                } sort { $a cmp $b } keys %{ $s->{fld} }
        );

        $log->debug( sub { Dumper($s) } );

        return $out;
}

=head1 MEMORY USAGE

C<low_mem> options is double-edged sword. If enabled, WebPAC
will run on memory constraint machines (which doesn't have enough
physical RAM to create memory structure for whole source database).

If your machine has 512Mb or more of RAM and database is around 10000 records,
memory shouldn't be an issue. If you don't have enough physical RAM, you
might consider using virtual memory (if your operating system is handling it
well, like on FreeBSD or Linux) instead of dropping to L<DBM::Deep> to handle
parsed structure of ISIS database (this is what C<low_mem> option does).

Hitting swap at end of reading source database is probably o.k. However,
hitting swap before 90% will dramatically decrease performance and you will
be better off with C<low_mem> and using rest of availble memory for
operating system disk cache (Linux is particuallary good about this).
However, every access to database record will require disk access, so
generation phase will be slower 10-100 times.

Parsed structures are essential - you just have option to trade RAM memory
(which is fast) for disk space (which is slow). Be sure to have planty of
disk space if you are using C<low_mem> and thus L<DBM::Deep>.

However, when WebPAC is running on desktop machines (or laptops :-), it's
highly undesireable for system to start swapping. Using C<low_mem> option can
reduce WecPAC memory usage to around 64Mb for same database with lookup
fields and sorted indexes which stay in RAM. Performance will suffer, but
memory usage will really be minimal. It might be also more confortable to
run WebPAC reniced on those machines.


=head1 AUTHOR

Dobrica Pavlinusic, C<< <dpavlin@rot13.org> >>

=head1 COPYRIGHT & LICENSE

Copyright 2005 Dobrica Pavlinusic, All Rights Reserved.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.

=cut

1; # End of WebPAC::Input
1	dpavlin	1	package WebPAC::Input;
2
3			use warnings;
4			use strict;
5
6	dpavlin	507	use blib;
7
8	dpavlin	487	use WebPAC::Common;
9	dpavlin	285	use base qw/WebPAC::Common/;
10			use Text::Iconv;
11	dpavlin	308	use Data::Dumper;
12	dpavlin	285
13	dpavlin	1	=head1 NAME
14
15	dpavlin	286	WebPAC::Input - read different file formats into WebPAC
16	dpavlin	1
17			=head1 VERSION
18
19	dpavlin	506	Version 0.05
20	dpavlin	1
21			=cut
22
23	dpavlin	506	our $VERSION = '0.05';
24	dpavlin	1
25			=head1 SYNOPSIS
26
27	dpavlin	286	This module implements input as database which have fixed and known
28			I<size> while indexing and single unique numeric identifier for database
29			position ranging from 1 to I<size>.
30	dpavlin	1
31	dpavlin	286	Simply, something that is indexed by unmber from 1 .. I<size>.
32
33			Examples of such databases are CDS/ISIS files, MARC files, lines in
34			text file, and so on.
35
36			Specific file formats are implemented using low-level interface modules,
37			located in C<WebPAC::Input::*> namespace which export C<open_db>,
38			C<fetch_rec> and optional C<init> functions.
39
40	dpavlin	1	Perhaps a little code snippet.
41
42			use WebPAC::Input;
43
44	dpavlin	3	my $db = WebPAC::Input->new(
45	dpavlin	286	module => 'WebPAC::Input::ISIS',
46			config => $config,
47			lookup => $lookup_obj,
48			low_mem => 1,
49	dpavlin	3	);
50	dpavlin	1
51	dpavlin	3	$db->open('/path/to/database');
52	dpavlin	416	print "database size: ",$db->size,"\n";
53			while (my $rec = $db->fetch) {
54			# do something with $rec
55			}
56	dpavlin	1
57	dpavlin	286
58
59	dpavlin	1	=head1 FUNCTIONS
60
61	dpavlin	3	=head2 new
62	dpavlin	1
63	dpavlin	3	Create new input database object.
64
65	dpavlin	9	my $db = new WebPAC::Input(
66	dpavlin	286	module => 'WebPAC::Input::MARC',
67	dpavlin	9	code_page => 'ISO-8859-2',
68	dpavlin	10	low_mem => 1,
69	dpavlin	416	recode => 'char pairs',
70	dpavlin	483	no_progress_bar => 1,
71	dpavlin	9	);
72	dpavlin	3
73	dpavlin	286	C<module> is low-level file format module. See L<WebPAC::Input::Isis> and
74			L<WebPAC::Input::MARC>.
75
76	dpavlin	9	Optional parametar C<code_page> specify application code page (which will be
77			used internally). This should probably be your terminal encoding, and by
78			default, it C<ISO-8859-2>.
79
80	dpavlin	10	Default is not to use C<low_mem> options (see L<MEMORY USAGE> below).
81
82	dpavlin	483	C<recode> is optional string constisting of character or words pairs that
83			should be replaced in input stream.
84
85			C<no_progress_bar> disables progress bar output on C<STDOUT>
86
87	dpavlin	285	This function will also call low-level C<init> if it exists with same
88			parametars.
89
90	dpavlin	1	=cut
91
92	dpavlin	3	sub new {
93	dpavlin	285	my $class = shift;
94			my $self = {@_};
95	dpavlin	3	bless($self, $class);
96
97	dpavlin	285	my $log = $self->_get_logger;
98
99	dpavlin	286	$log->logconfess("specify low-level file format module") unless ($self->{module});
100			my $module = $self->{module};
101			$module =~ s#::#/#g;
102			$module .= '.pm';
103			$log->debug("require low-level module $self->{module} from $module");
104	dpavlin	289
105	dpavlin	286	require $module;
106	dpavlin	289	#eval $self->{module} .'->import';
107	dpavlin	286
108	dpavlin	285	# check if required subclasses are implemented
109	dpavlin	289	foreach my $subclass (qw/open_db fetch_rec init/) {
110			my $n = $self->{module} . '::' . $subclass;
111			if (! defined &{ $n }) {
112	dpavlin	290	my $missing = "missing $subclass in $self->{module}";
113	dpavlin	301	$self->{$subclass} = sub { $log->logwarn($missing) };
114	dpavlin	286	} else {
115	dpavlin	289	$self->{$subclass} = \&{ $n };
116	dpavlin	286	}
117	dpavlin	285	}
118
119	dpavlin	289	if ($self->{init}) {
120	dpavlin	285	$log->debug("calling init");
121	dpavlin	289	$self->{init}->($self, @_);
122	dpavlin	285	}
123
124	dpavlin	9	$self->{'code_page'} \|\|= 'ISO-8859-2';
125
126	dpavlin	10	# running with low_mem flag? well, use DBM::Deep then.
127			if ($self->{'low_mem'}) {
128			$log->info("running with low_mem which impacts performance (<32 Mb memory usage)");
129
130			my $db_file = "data.db";
131
132			if (-e $db_file) {
133			unlink $db_file or $log->logdie("can't remove '$db_file' from last run");
134			$log->debug("removed '$db_file' from last run");
135			}
136
137			require DBM::Deep;
138
139			my $db = new DBM::Deep $db_file;
140
141			$log->logdie("DBM::Deep error: $!") unless ($db);
142
143			if ($db->error()) {
144			$log->logdie("can't open '$db_file' under low_mem: ",$db->error());
145			} else {
146			$log->debug("using file '$db_file' for DBM::Deep");
147			}
148
149			$self->{'db'} = $db;
150			}
151
152	dpavlin	3	$self ? return $self : return undef;
153	dpavlin	1	}
154
155	dpavlin	285	=head2 open
156
157			This function will read whole database in memory and produce lookups.
158
159	dpavlin	286	$input->open(
160	dpavlin	285	path => '/path/to/database/file',
161			code_page => '852',
162	dpavlin	286	limit => 500,
163			offset => 6000,
164	dpavlin	285	lookup => $lookup_obj,
165	dpavlin	506	stats => 1,
166	dpavlin	285	);
167
168			By default, C<code_page> is assumed to be C<852>.
169
170	dpavlin	286	C<offset> is optional parametar to position at some offset before reading from database.
171	dpavlin	285
172	dpavlin	286	C<limit> is optional parametar to read just C<limit> records from database
173	dpavlin	285
174	dpavlin	506	C<stats> create optional report about usage of fields and subfields
175
176	dpavlin	286	Returns size of database, regardless of C<offset> and C<limit>
177			parametars, see also C<size>.
178	dpavlin	285
179			=cut
180
181			sub open {
182			my $self = shift;
183			my $arg = {@_};
184
185			my $log = $self->_get_logger();
186
187			$log->logcroak("need path") if (! $arg->{'path'});
188			my $code_page = $arg->{'code_page'} \|\| '852';
189
190			# store data in object
191	dpavlin	292	$self->{'input_code_page'} = $code_page;
192	dpavlin	286	foreach my $v (qw/path offset limit/) {
193	dpavlin	285	$self->{$v} = $arg->{$v} if ($arg->{$v});
194			}
195
196			# create Text::Iconv object
197			$self->{iconv} = Text::Iconv->new($code_page,$self->{'code_page'});
198
199	dpavlin	416	my $filter_ref;
200
201			if ($self->{recode}) {
202			my @r = split(/\s/, $self->{recode});
203			if ($#r % 2 != 1) {
204			$log->logwarn("recode needs even number of elements (some number of valid pairs)");
205			} else {
206			my $recode;
207			while (@r) {
208			my $from = shift @r;
209			my $to = shift @r;
210			$recode->{$from} = $to;
211			}
212
213			my $regex = join '\|' => keys %{ $recode };
214
215			$log->debug("using recode regex: $regex");
216
217			$filter_ref = sub {
218			my $t = shift;
219			$t =~ s/($regex)/$recode->{$1}/g;
220			return $t;
221			};
222
223			}
224
225			}
226
227	dpavlin	289	my ($db, $size) = $self->{open_db}->( $self,
228	dpavlin	285	path => $arg->{path},
229	dpavlin	416	filter => $filter_ref,
230	dpavlin	285	);
231
232	dpavlin	496	unless (defined($db)) {
233	dpavlin	285	$log->logwarn("can't open database $arg->{path}, skipping...");
234			return;
235			}
236
237			unless ($size) {
238			$log->logwarn("no records in database $arg->{path}, skipping...");
239			return;
240			}
241
242	dpavlin	339	my $from_rec = 1;
243			my $to_rec = $size;
244	dpavlin	285
245	dpavlin	286	if (my $s = $self->{offset}) {
246	dpavlin	513	$log->debug("skipping to MFN $s");
247	dpavlin	339	$from_rec = $s;
248	dpavlin	285	} else {
249	dpavlin	339	$self->{offset} = $from_rec;
250	dpavlin	285	}
251
252	dpavlin	286	if ($self->{limit}) {
253	dpavlin	301	$log->debug("limiting to ",$self->{limit}," records");
254	dpavlin	339	$to_rec = $from_rec + $self->{limit} - 1;
255			$to_rec = $size if ($to_rec > $size);
256	dpavlin	285	}
257
258			# store size for later
259	dpavlin	339	$self->{size} = ($to_rec - $from_rec) ? ($to_rec - $from_rec + 1) : 0;
260	dpavlin	285
261	dpavlin	506	$log->info("processing $self->{size}/$size records [$from_rec-$to_rec] convert $code_page -> $self->{code_page}", $self->{stats} ? ' [stats]' : '');
262	dpavlin	285
263			# read database
264	dpavlin	339	for (my $pos = $from_rec; $pos <= $to_rec; $pos++) {
265	dpavlin	285
266	dpavlin	286	$log->debug("position: $pos\n");
267	dpavlin	285
268	dpavlin	289	my $rec = $self->{fetch_rec}->($self, $db, $pos );
269	dpavlin	285
270	dpavlin	308	$log->debug(sub { Dumper($rec) });
271
272	dpavlin	285	if (! $rec) {
273	dpavlin	286	$log->warn("record $pos empty? skipping...");
274	dpavlin	285	next;
275			}
276
277			# store
278	dpavlin	286	if ($self->{low_mem}) {
279			$self->{db}->put($pos, $rec);
280	dpavlin	285	} else {
281	dpavlin	286	$self->{data}->{$pos} = $rec;
282	dpavlin	285	}
283
284			# create lookup
285			$self->{'lookup'}->add( $rec ) if ($rec && $self->{'lookup'});
286
287	dpavlin	506	# update counters for statistics
288			if ($self->{stats}) {
289			map {
290			my $fld = $_;
291			$self->{_stats}->{fld}->{ $fld }++;
292			if (ref($rec->{ $fld }) eq 'ARRAY') {
293			map {
294			if (ref($_) eq 'HASH') {
295			map {
296			$self->{_stats}->{sf}->{ $fld }->{ $_ }++;
297			} keys %{ $_ };
298			} else {
299			$self->{_stats}->{repeatable}->{ $fld }++;
300			}
301			} @{ $rec->{$fld} };
302			}
303			} keys %{ $rec };
304			}
305
306	dpavlin	483	$self->progress_bar($pos,$to_rec) unless ($self->{no_progress_bar});
307	dpavlin	285
308			}
309
310	dpavlin	286	$self->{pos} = -1;
311			$self->{last_pcnt} = 0;
312	dpavlin	285
313			# store max mfn and return it.
314	dpavlin	339	$self->{max_pos} = $to_rec;
315			$log->debug("max_pos: $to_rec");
316	dpavlin	285
317			return $size;
318			}
319
320			=head2 fetch
321
322			Fetch next record from database. It will also displays progress bar.
323
324			my $rec = $isis->fetch;
325
326			Record from this function should probably go to C<data_structure> for
327			normalisation.
328
329			=cut
330
331			sub fetch {
332			my $self = shift;
333
334			my $log = $self->_get_logger();
335
336	dpavlin	286	$log->logconfess("it seems that you didn't load database!") unless ($self->{pos});
337	dpavlin	285
338	dpavlin	286	if ($self->{pos} == -1) {
339			$self->{pos} = $self->{offset};
340	dpavlin	285	} else {
341	dpavlin	286	$self->{pos}++;
342	dpavlin	285	}
343
344	dpavlin	286	my $mfn = $self->{pos};
345	dpavlin	285
346	dpavlin	286	if ($mfn > $self->{max_pos}) {
347			$self->{pos} = $self->{max_pos};
348	dpavlin	285	$log->debug("at EOF");
349			return;
350			}
351
352	dpavlin	483	$self->progress_bar($mfn,$self->{max_pos}) unless ($self->{no_progress_bar});
353	dpavlin	285
354			my $rec;
355
356	dpavlin	286	if ($self->{low_mem}) {
357			$rec = $self->{db}->get($mfn);
358	dpavlin	285	} else {
359	dpavlin	286	$rec = $self->{data}->{$mfn};
360	dpavlin	285	}
361
362			$rec \|\|= 0E0;
363			}
364
365			=head2 pos
366
367			Returns current record number (MFN).
368
369			print $isis->pos;
370
371			First record in database has position 1.
372
373			=cut
374
375			sub pos {
376			my $self = shift;
377	dpavlin	286	return $self->{pos};
378	dpavlin	285	}
379
380
381			=head2 size
382
383			Returns number of records in database
384
385			print $isis->size;
386
387			Result from this function can be used to loop through all records
388
389			foreach my $mfn ( 1 ... $isis->size ) { ... }
390
391	dpavlin	286	because it takes into account C<offset> and C<limit>.
392	dpavlin	285
393			=cut
394
395			sub size {
396			my $self = shift;
397	dpavlin	286	return $self->{size};
398	dpavlin	285	}
399
400			=head2 seek
401
402			Seek to specified MFN in file.
403
404			$isis->seek(42);
405
406			First record in database has position 1.
407
408			=cut
409
410			sub seek {
411			my $self = shift;
412			my $pos = shift \|\| return;
413
414			my $log = $self->_get_logger();
415
416			if ($pos < 1) {
417			$log->warn("seek before first record");
418			$pos = 1;
419	dpavlin	286	} elsif ($pos > $self->{max_pos}) {
420	dpavlin	285	$log->warn("seek beyond last record");
421	dpavlin	286	$pos = $self->{max_pos};
422	dpavlin	285	}
423
424	dpavlin	286	return $self->{pos} = (($pos - 1) \|\| -1);
425	dpavlin	285	}
426
427	dpavlin	506	=head2 stats
428	dpavlin	285
429	dpavlin	506	Dump statistics about field and subfield usage
430
431	dpavlin	507	print $input->stats;
432	dpavlin	506
433			=cut
434
435			sub stats {
436			my $self = shift;
437	dpavlin	507
438			my $log = $self->_get_logger();
439
440			my $s = $self->{_stats};
441			if (! $s) {
442			$log->warn("called stats, but there is no statistics collected");
443			return;
444			}
445
446			my $max_fld = 0;
447
448			my $out = join("\n",
449			map {
450			my $f = $_ \|\| die "no field";
451			my $v = $s->{fld}->{$f} \|\| die "no s->{fld}->{$f}";
452			$max_fld = $v if ($v > $max_fld);
453
454	dpavlin	519	my $o = sprintf("%4s %d ~", $f, $v);
455	dpavlin	507
456			if (defined($s->{sf}->{$f})) {
457			map {
458			$o .= sprintf(" %s:%d", $_, $s->{sf}->{$f}->{$_});
459			} sort keys %{ $s->{sf}->{$f} };
460			}
461
462			if (my $v_r = $s->{repeatable}->{$f}) {
463			$o .= " ($v_r)" if ($v_r != $v);
464			}
465
466			$o;
467	dpavlin	519	} sort { $a cmp $b } keys %{ $s->{fld} }
468	dpavlin	507	);
469
470			$log->debug( sub { Dumper($s) } );
471
472			return $out;
473	dpavlin	506	}
474
475	dpavlin	3	=head1 MEMORY USAGE
476	dpavlin	1
477	dpavlin	3	C<low_mem> options is double-edged sword. If enabled, WebPAC
478			will run on memory constraint machines (which doesn't have enough
479			physical RAM to create memory structure for whole source database).
480	dpavlin	1
481	dpavlin	3	If your machine has 512Mb or more of RAM and database is around 10000 records,
482			memory shouldn't be an issue. If you don't have enough physical RAM, you
483			might consider using virtual memory (if your operating system is handling it
484			well, like on FreeBSD or Linux) instead of dropping to L<DBM::Deep> to handle
485			parsed structure of ISIS database (this is what C<low_mem> option does).
486	dpavlin	1
487	dpavlin	3	Hitting swap at end of reading source database is probably o.k. However,
488			hitting swap before 90% will dramatically decrease performance and you will
489			be better off with C<low_mem> and using rest of availble memory for
490			operating system disk cache (Linux is particuallary good about this).
491			However, every access to database record will require disk access, so
492			generation phase will be slower 10-100 times.
493
494			Parsed structures are essential - you just have option to trade RAM memory
495			(which is fast) for disk space (which is slow). Be sure to have planty of
496			disk space if you are using C<low_mem> and thus L<DBM::Deep>.
497
498			However, when WebPAC is running on desktop machines (or laptops :-), it's
499			highly undesireable for system to start swapping. Using C<low_mem> option can
500			reduce WecPAC memory usage to around 64Mb for same database with lookup
501			fields and sorted indexes which stay in RAM. Performance will suffer, but
502			memory usage will really be minimal. It might be also more confortable to
503			run WebPAC reniced on those machines.
504
505
506			=head1 AUTHOR
507
508			Dobrica Pavlinusic, C<< <dpavlin@rot13.org> >>
509
510	dpavlin	1	=head1 COPYRIGHT & LICENSE
511
512			Copyright 2005 Dobrica Pavlinusic, All Rights Reserved.
513
514			This program is free software; you can redistribute it and/or modify it
515			under the same terms as Perl itself.
516
517			=cut
518
519			1; # End of WebPAC::Input