-# $Id: ZOOM.pod,v 1.16 2005-12-13 14:01:59 mike Exp $
+# $Id: ZOOM.pod,v 1.23 2005-12-19 17:42:15 mike Exp $
use strict;
use warnings;
anyway; but knowing that the same code is running is reassuring.)
The ZOOM module provides two enumerations (C<ZOOM::Error> and
-C<ZOOM::Event>), a single utility function C<diag_str()> in the C<ZOOM>
-package itself, and eight classes:
+C<ZOOM::Event>), two utility functions C<diag_str()> and C<event()> in
+the C<ZOOM> package itself, and eight classes:
C<ZOOM::Exception>,
C<ZOOM::Options>,
C<ZOOM::Connection>,
you don't need to test for success after each call. See the section
below on the Exception class for details.
-=head1 UTILITY FUNCTION
+=head1 UTILITY FUNCTIONS
=head2 ZOOM::diag_str()
irrespective of whether it is a member of the C<ZOOM::Error>
enumeration or drawn from the BIB-1 diagnostic set.
+=head2 ZOOM::event()
+
+B<Warning.>
+Lark's vomit. Do not read this section.
+
+ $which = ZOOM::event([ $conn1, $conn2, $conn3 ]);
+
+Used only in complex asynchronous applications, this function takes a
+reference to a list of Connection objects, waits until an event
+occurs on any one of them, and returns an integer indicating which of
+the connections it occurred on. The return value is a 1-based index
+into the list; 0 is returned if no event occurs within the longest
+timeout specified by the C<timeout> options of all the connections.
+
+B<Warning.>
+This function is not yet implemented.
+
=head1 CLASSES
The eight ZOOM classes are described here in ``sensible order'':
a C<ZOOM::Query::PQF> object. See the documentation of that class for
information about PQF.
-=head4 scan()
+=head4 scan() / scan1()
+
+ ### Code sample needed here!
Many Z39.50 servers allow you to browse their indexes to find terms to
search for. This is done using the C<scan> method, which creates and
but overriding this can be useful to get a high-level overview of the
index.
+The C<scan1()> method is the same as C<scan()> except that it takes a
+Query object as its argument instead of a PQF string. This means
+that it can be used to scan using a CQL term, so long as the
+underlying ZOOM-C library supports this.
+
=back
=head4 package()
Extended Service. An options block may optionally be passed in. See
the C<ZOOM::Package> documentation.
+=head4 last_event()
+
+ if ($conn->last_event() == ZOOM::Event::CONNECT) {
+ print "Connected!\n";
+ }
+
+Returns a C<ZOOM::Event> enumerated value indicating the type of the
+last event that occurred on the connection. This is used only in
+complex asynchronous applications - see the section below on
+C<ZOOM::Event> for more information.
+
+B<Warning.>
+This method has not been tested.
+
=head4 destroy()
$conn->destroy()
=head2 ZOOM::Query
-I<###>
+ $q = new ZOOM::Query::CQL("creator=pike and subject=unix");
+ $q->sortby("1=4 >i 1=21 >s");
+ $rs = $conn->search($q);
+ $q->destroy();
+
+C<ZOOM::Query> is a virtual base class from which various concrete
+subclasses can be derived. Different subclasses implement different
+types of query. The sole purpose of a Query object is to be used in a
+C<search()> on a Connection; because PQF is such a common special
+case, the shortcut Connection method C<search_pqf()> is provided.
+
+The following Query subclasses are provided, both of the providing the
+same set of methods described below:
+
+=over 4
+
+=item ZOOM::Query::PQF
+
+Implements Prefix Query Format (PQF), also sometimes known as Prefix
+Query Notation (PQN). This esoteric but rigorous and expressive
+format is described in the YAZ Manual at
+http://indexdata.com/yaz/doc/tools.tkl#PQF
+
+=item ZOOM::Query::CQL
+
+Implements the Common Query Language (CQL) of SRU, the Search/Retrieve
+URL. CQL is a much friendlier notation than PQF, using a simple infix
+notation. The queries are passed ``as is'' to the server rather than
+being compiled into a Z39.50 Type-1 query, so only CQL-compliant
+servers can support such querier. CQL is described at
+http://www.loc.gov/standards/sru/cql/
+and in a slight out-of-date but nevertheless useful tutorial at
+http://zing.z3950.org/cql/intro.html
+
+=back
+
+See the description of the C<Query> class in the ZOOM Abstract
+API at
+http://zoom.z3950.org/api/zoom-current.html#3.3
+
+=head3 Methods
+
+=head4 new()
+
+ $q = new ZOOM::Query::CQL('title=dinosaur'));
+ $q = new ZOOM::Query::PQF('@attr 1=4 dinosaur'));
+
+Creates a new query object, compiling the query passed as its argument
+according to the rules of the particular query-type being
+instantiated. If compilation fails, an exception is thrown.
+Otherwise, the query may be passed to the C<Connection> method
+<search()>.
+
+=head4 sortby()
+
+ $q->sortby("1=4 >i 1=21 >s");
+
+Sets a sort specification into the query, so that when a C<search()>
+is run on the query, the result is automatically sorted. The sort
+specification language is the same as the C<yaz> sort-specification
+type of the C<ResultSet> method C<sort()>, described above.
+
+B<It ought to be possible to sort by CQL query, too, but at present
+limitations in the underlying ZOOM-C library make this impossible.>
+
+=head4 destroy()
+
+ $p->destroy()
+
+Destroys a Query object, freeing its resources. It is an error to
+reuse a Query that has been C<destroy()>ed.
=head2 ZOOM::Options
-I<###>
+ $o1 = new ZOOM::Options();
+ $o1->option(user => "alf");
+ $o2 = new ZOOM::Options();
+ $o2->option(password => "fruit");
+ $opts = new ZOOM::Options($o1, $o2);
+ $conn = create ZOOM::Connection($opts);
+ $conn->connect($host); # Uses the specified username and password
+
+Several classes of ZOOM objects carry their own sets of options, which
+can be manipulated using their C<option()> method. Sometimes,
+however, it's useful to deal with the option sets directly, and the
+C<ZOOM::Options> class exists to enable this approach.
+
+Option sets are B<not currently described> in the ZOOM
+Abstract API at
+http://zoom.z3950.org/api/zoom-current.html
+They are an extension to that specification.
+
+=head3 Methods
+
+=head4 new()
+
+ $o1 = new ZOOM::Options();
+ $o1and2 = new ZOOM::Options($o1);
+ $o3 = new ZOOM::Options();
+ $o1and3and4 = new ZOOM::Options($o1, $o3);
+
+Creates and returns a new option set. One or two (but no more)
+existing option sets may be passed as arguments, in which case they
+become ``parents'' of the new set, which thereby ``inherits'' their
+options, the values of the first parent overriding those of the second
+when both have a value for the same key. An option set that inherits
+from a parent that has its own parents also inherits the grandparent's
+options, and so on.
+
+=head4 option() / option_binary()
+
+ $o->option(preferredRecordSyntax => "usmarc");
+ $o->option_binary(iconBlob => "foo\0bar");
+ die if length($o->option_binary("iconBlob") != 7);
+
+These methods are used to get and set options within a set, and behave
+the same way as the same-named C<Connection> methods - see above. As
+with the C<Connection> methods, values passed to and retrieved using
+C<option()> are interpreted as NUL-terminated, while those passed to
+and retrieved from C<option_binary()> are binary-clean.
+
+=head4 bool()
+
+ $o->option(x => "T");
+ $o->option(y => "F");
+ assert($o->bool("x", 1));
+ assert(!$o->bool("y", 1));
+ assert($o->bool("z", 1));
+
+The first argument is a key, and the second is a default value.
+Returns the value associated with the specified key as a boolean, or
+the default value if the key has not been set. The values C<T> (upper
+case) and C<1> are considered true; all other values (including C<t>
+(lower case) and non-zero integers other than one) are considered
+false.
+
+This method is provided in ZOOM-C because in a statically typed
+language it's convenient to have the result returned as an
+easy-to-test type. In a dynamically typed language such as Perl, this
+problem doesn't arise, so C<bool()> is nearly useless; but it is made
+available in case applications need to duplicate the idiosyncratic
+interpretation of truth and falsehood and ZOOM-C uses.
+
+=head4 int()
+
+ $o->option(x => "012");
+ assert($o->int("x", 20) == 12);
+ assert($o->int("y", 20) == 20);
+
+Returns the value associated with the specified key as an integer, or
+the default value if the key has not been set. See the description of
+C<bool()> for why you almost certainly don't want to use this.
+
+=head4 set_int()
+
+ $o->set_int(x => "29");
+
+Sets the value of the specified option as an integer. Of course, Perl
+happily converts strings to integers on its own, so you can just use
+C<option()> for this, but C<set_int()> is guaranteed to use the same
+string-to-integer conversion as ZOOM-C does, which might occasionally
+be useful. Though I can't imagine how.
+
+=head4 set_callback()
+
+ sub cb {
+ ($udata, $key) = @;
+ return "$udata-$key-$udata";
+ }
+ $o->set_callback(\&cb, "xyz");
+ assert($o->option("foo") eq "xyz-foo-xyz");
+
+This method allows a callback function to be installed in an option
+set, so that the values of options can be calculated algorithmically
+rather than, as usual, looked up in a table. Along with the callback
+function itself, an additional datum is provided: when an option is
+subsequently looked up, this datum is passed to the callback function
+along with the key; and its return value is returned to the caller as
+the value of the option.
+
+B<Warning.>
+Although it ought to be possible to specify callback function using
+the C<\&name> syntax above, or a literal C<sub { code }> code
+reference, the complexities of the Perl-internal memory management
+system mean that the function must currently be specified as a string
+containing the fully-qualified name, e.g. C<"main::cb">.>
+
+B<Warning.>
+The current implementation of the this method leaks memory, not only
+when the callback is installed, but on every occasion that it is
+consulted to look up an option value.
+
+=head4 destroy()
+
+ $o->destroy()
+
+Destroys an Options object, freeing its resources. It is an error to
+reuse an Options object that has been C<destroy()>ed.
=head1 ENUMERATIONS
projects / ZOOM-Perl-moved-to-github.git / blobdiff