1 <!-- $Id: zoom.xml,v 1.35 2003-11-24 11:27:57 mike Exp $ -->
2 <chapter id="zoom"><title>ZOOM</title>
4 &zoom; is an acronym for 'Z39.50 Object-Orientation Model' and is
5 an initiative started by Mike Taylor (Mike is from the UK, which
6 explains the peculiar name of the model). The goal of &zoom; is to
7 provide a common Z39.50 client API not bound to a particular
8 programming language or toolkit.
13 A recent addition to &yaz; is SRW support. You can now make
14 SRW ZOOM connections by specifying scheme <literal>http://</literal>
15 for the hostname for a connection.
20 The lack of a simple Z39.50 client API for &yaz; has become more
21 and more apparent over time. So when the first &zoom; specification
23 an implementation for &yaz; was quickly developed. For the first time, it is
24 now as easy (or easier!) to develop clients than servers with &yaz;. This
25 chapter describes the &zoom; C binding. Before going further, please
26 reconsider whether C is the right programming language for the job.
27 There are other language bindings available for &yaz;, and still
29 are in active development. See the
30 <ulink url="http://zoom.z3950.org/">ZOOM web-site</ulink> for
35 In order to fully understand this chapter you should read and
36 try the example programs <literal>zoomtst1.c</literal>,
37 <literal>zoomtst2.c</literal>, .. in the <literal>zoom</literal>
42 The C language misses features found in object oriented languages
43 such as C++, Java, etc. For example, you'll have to manually,
44 destroy all objects you create, even though you may think of them as
45 temporary. Most objects has a <literal>_create</literal> - and a
46 <literal>_destroy</literal> variant.
47 All objects are in fact pointers to internal stuff, but you don't see
48 that because of typedefs. All destroy methods should gracefully ignore a
49 <literal>NULL</literal> pointer.
52 In each of the sections below you'll find a sub section called
53 protocol behavior, that describes how the API maps to the Z39.50
56 <sect1 id="zoom.connections"><title>Connections</title>
58 <para>The Connection object is a session with a target.
61 #include <yaz/zoom.h>
63 ZOOM_connection ZOOM_connection_new (const char *host, int portnum);
65 ZOOM_connection ZOOM_connection_create (ZOOM_options options);
67 void ZOOM_connection_connect(ZOOM_connection c, const char *host,
69 void ZOOM_connection_destroy (ZOOM_connection c);
72 Connection objects are created with either function
73 <function>ZOOM_connection_new</function> or
74 <function>ZOOM_connection_create</function>.
75 The former creates and automatically attempts to establish a network
76 connection with the target. The latter doesn't establish
77 a connection immediately, thus allowing you to specify options
78 before establishing network connection using the function
79 <function>ZOOM_connection_connect</function>.
80 If the port number, <literal>portnum</literal>, is zero, the
81 <literal>host</literal> is consulted for a port specification.
82 If no port is given, 210 is used. A colon denotes the beginning of
83 a port number in the host string. If the host string includes a
84 slash, the following part specifies a database for the connection.
87 You can prefix the host with a scheme followed by colon. The
88 default scheme is <literal>tcp</literal> (Z39.50 protocol).
89 The scheme <literal>http</literal> selects SRW over HTTP.
92 Connection objects should be destroyed using the function
93 <function>ZOOM_connection_destroy</function>.
96 void ZOOM_connection_option_set (ZOOM_connection c,
100 const char *ZOOM_connection_option_get (ZOOM_connection c,
104 The <function>ZOOM_connection_option_set</function> allows you to
105 set an option given by <parameter>key</parameter> to the value
106 <parameter>value</parameter> for the connection.
107 Function <function>ZOOM_connection_option_get</function> returns
108 the value for an option given by <parameter>key</parameter>.
110 <table frame="top"><title>ZOOM Connection Options</title>
112 <colspec colwidth="4*" colname="name"></colspec>
113 <colspec colwidth="7*" colname="description"></colspec>
114 <colspec colwidth="3*" colname="default"></colspec>
117 <entry>Option</entry>
118 <entry>Description</entry>
119 <entry>Default</entry>
124 implementationName</entry><entry>Name of Your client
125 </entry><entry>none</entry></row>
127 user</entry><entry>Authentication user name
128 </entry><entry>none</entry></row>
130 group</entry><entry>Authentication group name
131 </entry><entry>none</entry></row>
133 pass</entry><entry>Authentication password
134 </entry><entry>none</entry></row>
136 host</entry><entry>Target host. This setting is "read-only".
137 It's automatically set internally when connecting to a target.
138 </entry><entry>none</entry></row>
140 proxy</entry><entry>Proxy host
141 </entry><entry>none</entry></row>
143 async</entry><entry>If true (1) the connection operates in
144 asynchronous operation which means that all calls are non-blocking
146 <link linkend="zoom.events"><function>ZOOM_event</function></link>.
147 </entry><entry>0</entry></row>
149 maximumRecordSize</entry><entry> Maximum size of single record.
150 </entry><entry>1 MB</entry></row>
152 preferredMessageSize</entry><entry> Maximum size of multiple records.
153 </entry><entry>1 MB</entry></row>
155 lang</entry><entry> Language for negotiation.
156 </entry><entry>none</entry></row>
158 charset</entry><entry> Character set for negotiation.
159 </entry><entry>none</entry></row>
161 serverImplementationId</entry><entry>
162 Implementation ID of server. (The old targetImplementationId
163 option is also supported for the benefit of old applications.)
164 </entry><entry>none</entry></row>
166 targetImplementationName</entry><entry>
167 Implementation Name of server. (The old
168 targetImplementationName option is also supported for the
169 benefit of old applications.)
170 </entry><entry>none</entry></row>
172 serverImplementationVersion</entry><entry>
173 Implementation Version of server. (the old
174 targetImplementationVersion option is also supported for the
175 benefit of old applications.)
176 </entry><entry>none</entry></row>
178 databaseName</entry><entry>One or more database names
179 separated by character plus (<literal>+</literal>), which to
180 be used by subsequent search requests on this Connection.
181 </entry><entry>Default</entry></row>
183 piggyback</entry><entry>True (1) if piggyback should be
184 used in searches; false (0) if not.
185 </entry><entry>1</entry></row>
187 smallSetUpperBound</entry><entry>If hits is less than or equal to this
188 value, then target will return all records using small element set name
189 </entry><entry>0</entry></row>
191 largeSetLowerBound</entry><entry>If hits is greater than this
192 value, the target will return no records.
193 </entry><entry>1</entry></row>
195 mediumSetPresentNumber</entry><entry>This value represents
196 the number of records to be returned as part of a search when when
197 hits is less than or equal to large set lower bound and if hits
198 is greater than small set upper bound.
199 </entry><entry>0</entry></row>
201 smallSetElementSetName</entry><entry>
202 The element set name to be used for small result sets.
203 </entry><entry>none</entry></row>
205 mediumSetElementSetName</entry><entry>
206 The element set name to be for medium-sized result sets.
207 </entry><entry>none</entry></row>
212 If either option <literal>lang</literal> or <literal>charset</literal>
214 <ulink url="http://lcweb.loc.gov/z3950/agency/defns/charneg-3.html">
215 Character Set and Language Negotiation</ulink> is in effect.
218 int ZOOM_connection_error (ZOOM_connection c, const char **cp,
219 const char **addinfo);
220 int ZOOM_connection_error_x (ZOOM_connection c, const char **cp,
221 const char **addinfo, const char **dset);
224 Function <function>ZOOM_connection_error</function> checks for
225 errors for the last operation(s) performed. The function returns
226 zero if no errors occurred; non-zero otherwise indicating the error.
227 Pointers <parameter>cp</parameter> and <parameter>addinfo</parameter>
228 holds messages for the error and additional-info if passed as
229 non-<literal>NULL</literal>. Function
230 <function>ZOOM_connection_error_x</function> is an extended version
231 of <function>ZOOM_connection_error</function> that is capable of
232 returning name of diagnostic set in <parameter>dset</parameter>.
234 <sect2><title>Z39.50 Protocol behavior</title>
236 The calls <function>ZOOM_connection_new</function> and
237 <function>ZOOM_connection_connect</function> establishes a TCP/IP
238 connection and sends an Initialize Request to the target if
239 possible. In addition, the calls waits for an Initialize Response
240 from the target and the result is inspected (OK or rejected).
243 If <literal>proxy</literal> is set then the client will establish
244 a TCP/IP connection with the peer as specified by the
245 <literal>proxy</literal> host and the hostname as part of the
246 connect calls will be set as part of the Initialize Request.
247 The proxy server will then "forward" the PDU's transparently
248 to the target behind the proxy.
251 For the authentication parameters, if option <literal>user</literal>
252 is set and both options <literal>group</literal> and
253 <literal>pass</literal> are unset, then Open style
254 authentication is used (Version 2/3) in which case the username
255 is usually followed by a slash, then by a password.
256 If either <literal>group</literal>
257 or <literal>pass</literal> is set then idPass authentication
258 (Version 3 only) is used. If none of the options are set, no
259 authentication parameters are set as part of the Initialize Request
263 When option <literal>async</literal> is 1, it really means that
264 all network operations are postponed (and queued) until the
265 function <literal>ZOOM_event</literal> is invoked. When doing so
266 it doesn't make sense to check for errors after
267 <literal>ZOOM_connection_new</literal> is called since that
268 operation "connecting - and init" is still incomplete and the
269 API cannot tell the outcome (yet).
272 <sect2><title>SRW Protocol behavior</title>
274 The SRW protocol doesn't feature an Inititialize Request, so
275 the connection phase merely establishes a TCP/IP connection
276 with the SOAP service.
278 <para>Most of the ZOOM connection options do not
279 affect SRW and they are ignored. However, future versions
280 of &yaz; might honor <literal>implementationName</literal> and
281 put that as part of User-Agent header for HTTP requests.
284 The <literal>charset</literal> is used in the Content-Type header
289 <sect1 id="zoom.query"><title>Queries</title>
291 Query objects represents queries.
294 ZOOM_query ZOOM_query_create(void);
296 void ZOOM_query_destroy(ZOOM_query q);
298 int ZOOM_query_prefix(ZOOM_query q, const char *str);
300 int ZOOM_query_cql(ZOOM_query s, const char *str);
302 int ZOOM_query_sortby(ZOOM_query q, const char *criteria);
305 Create query objects using <function>ZOOM_query_create</function>
306 and destroy them by calling <function>ZOOM_query_destroy</function>.
307 RPN-queries can be specified in <link linkend="PQF">PQF</link>
308 notation by using the
309 function <function>ZOOM_query_prefix</function>.
310 The <function>ZOOM_query_cql</function> specifies a CQL
311 query to be sent to the server/target.
312 More query types will be added in future versions of &yaz;, such as
313 <link linkend="CCL">CCL</link> to RPN-mapping, native CCL query,
314 etc. In addition to a search, a sort criteria may be set. Function
315 <function>ZOOM_query_sortby</function> specifies a
316 sort criteria using the same string notation for sort as offered by
317 the <link linkend="sortspec">YAZ client</link>.
319 <sect2><title>Protocol behavior</title>
321 The query object is just an interface for the member Query
322 in the SearchRequest. The sortby-function is an interface to the
323 sortSequence member of the SortRequest.
327 <sect1 id="zoom.resultsets"><title>Result sets</title>
329 The result set object is a container for records returned from
333 ZOOM_resultset ZOOM_connection_search(ZOOM_connection,
336 ZOOM_resultset ZOOM_connection_search_pqf(ZOOM_connection c,
339 void ZOOM_resultset_destroy(ZOOM_resultset r);
342 Function <function>ZOOM_connection_search</function> creates
343 a result set given a connection and query.
344 Destroy a result set by calling
345 <function>ZOOM_resultset_destroy</function>.
346 Simple clients may using PQF only may use function
347 <function>ZOOM_connection_search_pqf</function> in which case
348 creating query objects is not necessary.
351 void ZOOM_resultset_option_set (ZOOM_resultset r,
355 const char *ZOOM_resultset_option_get (ZOOM_resultset r,
358 size_t ZOOM_resultset_size (ZOOM_resultset r);
361 Functions <function>ZOOM_resultset_options_set</function> and
362 <function>ZOOM_resultset_get</function> sets and gets an option
363 for a result set similar to <function>ZOOM_connection_option_get</function>
364 and <function>ZOOM_connection_option_set</function>.
367 The number of hits also called result-count is returned by
368 function <function>ZOOM_resultset_size</function>.
370 <table frame="top"><title>ZOOM Result set Options</title>
372 <colspec colwidth="4*" colname="name"></colspec>
373 <colspec colwidth="7*" colname="description"></colspec>
374 <colspec colwidth="2*" colname="default"></colspec>
377 <entry>Option</entry>
378 <entry>Description</entry>
379 <entry>Default</entry>
384 start</entry><entry>Offset of first record to be
385 retrieved from target. First record has offset 0 unlike the
386 protocol specifications where first record has position 1.
387 </entry><entry>0</entry></row>
389 count</entry><entry>Number of records to be retrieved.
390 </entry><entry>0</entry></row>
392 step</entry><entry>Number of records to be retrieved in
393 one chunk. The value, 0 means unchunked.
394 </entry><entry>0</entry></row>
396 elementSetName</entry><entry>Element-Set name of records.
397 Most targets should honor element set name <literal>B</literal>
398 and <literal>F</literal> for brief and full respectively.
399 </entry><entry>none</entry></row>
401 preferredRecordSyntax</entry><entry>Preferred Syntax, such as
402 <literal>USMARC</literal>, <literal>SUTRS</literal>, etc.
403 </entry><entry>none</entry></row>
405 schema</entry><entry>Schema for retrieval, such as
406 <literal>Gils-schema</literal>, <literal>Geo-schema</literal>, etc.
407 </entry><entry>none</entry></row>
409 setname</entry><entry>Name of Result Set (Result Set ID).
410 If this option isn't set, the ZOOM module will automatically
411 allocate a result set name.
412 </entry><entry>default</entry></row>
417 <title>Z39.50 Protocol behavior</title>
419 The creation of a result set involves at least a SearchRequest
420 - SearchResponse protocol handshake. Following that, if a sort
421 criteria was specified as part of the query, a SortRequest -
422 SortResponse handshake takes place. Note that it is necessary to
423 perform sorting before any retrieval takes place, so no records will
424 be returned from the target as part of the SearchResponse because these
425 would be unsorted. Hence, piggyback is disabled when sort criteria
426 are set. Following Search - and a possible sort - Retrieval takes
427 place - as one or more Present Requests/Response pairs being
431 The API allows for two different modes for retrieval. A high level
432 mode which is somewhat more powerful and a low level one.
433 The low level is enabled when searching on a Connection object
434 for which the settings
435 <literal>smallSetUpperBound</literal>,
436 <literal>mediumSetPresentNumber</literal> and
437 <literal>largeSetLowerBound</literal> are set. The low level mode
438 thus allows you to precisely set how records are returned as part
439 of a search response as offered by the Z39.50 protocol.
440 Since the client may be retrieving records as part of the
441 search response, this mode doesn't work well if sorting is used.
444 The high-level mode allows you to fetch a range of records from
445 the result set with a given start offset. When you use this mode
446 the client will automatically use piggyback if that is possible
447 with the target and perform one or more present requests as needed.
448 Even if the target returns fewer records as part of a present response
449 because of a record size limit, etc. the client will repeat sending
450 present requests. As an example, if option <literal>start</literal>
451 is 0 (default) and <literal>count</literal> is 4, and
452 <literal>piggyback</literal> is 1 (default) and no sorting criteria
453 is specified, then the client will attempt to retrieve the 4
454 records as part the search response (using piggyback). On the other
455 hand, if either <literal>start</literal> is positive or if
456 a sorting criteria is set, or if <literal>piggyback</literal>
457 is 0, then the client will not perform piggyback but send Present
461 If either of the options <literal>mediumSetElementSetName</literal> and
462 <literal>smallSetElementSetName</literal> are unset, the value
463 of option <literal>elementSetName</literal> is used for piggyback
464 searches. This means that for the high-level mode you only have
465 to specify one elementSetName option rather than three.
469 <title>SRW Protocol behavior</title>
471 Current version of &yaz; does not take advantage of a result set id
472 returned by the SRW server. Future versions might do, however.
473 Since, the ZOOM driver does not save result set IDs any
474 present (retrieval) is transformed to a SRW SearchRetrieveRequest
475 with same query but, possibly, different offsets.
478 Option <literal>schema</literal> specifies SRW schema
479 for retrieval. However, options <literal>elementSetName</literal> and
480 <literal>preferredRecordSyntax</literal> are ignored.
483 Options <literal>start</literal> and <literal>count</literal>
484 are supported by SRW.
485 The remaining options
486 <literal>piggyback</literal>,
487 <literal>smallSetUpperBound</literal>,
488 <literal>largeSetLowerBound</literal>,
489 <literal>mediumSetPresentNumber</literal>,
490 <literal>mediumSetElementSetName</literal>,
491 <literal>smallSetElementSetName</literal> are
495 SRW supports CQL queries, <emphasis>not</emphasis> PQF.
496 If PQF is used, however, the PQF query is transferred anyway
497 using non-standard element <literal>pQuery</literal> in
498 SRW SearchRetrieveRequest.
501 Unfortunately, SRW does not define a database setting. Hence,
502 <literal>databaseName</literal> is unsupported and ignored.
503 However, the path part in host parameter for functions
504 <function>ZOOM_connecton_new</function> and
505 <function>ZOOM_connection_connect</function> acts as a
506 database (at least for the &yaz; SRW server).
510 <sect1 id="zoom.records"><title>Records</title>
512 A record object is a retrieval record on the client side -
513 created from result sets.
516 void ZOOM_resultset_records (ZOOM_resultset r,
518 size_t start, size_t count);
519 ZOOM_record ZOOM_resultset_record (ZOOM_resultset s, size_t pos);
521 const char *ZOOM_record_get (ZOOM_record rec, const char *type,
524 ZOOM_record ZOOM_record_clone (ZOOM_record rec);
526 void ZOOM_record_destroy (ZOOM_record rec);
529 References to temporary records are returned by functions
530 <function>ZOOM_resultset_records</function> or
531 <function>ZOOM_resultset_record</function>.
534 If a persistent reference to a record is desired
535 <function>ZOOM_record_clone</function> should be used.
536 It returns a record reference that should be destroyed
537 by a call to <function>ZOOM_record_destroy</function>.
540 A single record is returned by function
541 <function>ZOOM_resultset_record</function> that takes a
542 position as argument. First record has position zero.
543 If no record could be obtained <literal>NULL</literal> is returned.
546 Function <function>ZOOM_resultset_records</function> retrieves
547 a number of records from a result set. Parameter <literal>start</literal>
548 and <literal>count</literal> specifies the range of records to
549 be returned. Upon completion array
550 <literal>recs[0], ..recs[count-1]</literal>
551 holds record objects for the records. The array of records
552 <literal>recs</literal> should be allocated prior the call
553 <function>ZOOM_resultset_records</function>. Note that for those
554 records that couldn't be retrieved from the target
555 <literal>recs[ ..]</literal> is set to <literal>NULL</literal>.
557 <para id="zoom.record.get">
558 In order to extract information about a single record,
559 <function>ZOOM_record_get</function> is provided. The
560 function returns a pointer to certain record information. The
561 nature (type) of the pointer depends on the parameter,
562 <parameter>type</parameter>.
565 The <parameter>type</parameter> is a string of the format:
568 <replaceable>form</replaceable>[; charset=<replaceable>from</replaceable>[,<replaceable>to</replaceable>]]
571 where <replaceable>form</replaceable> specifies the format of the
572 returned record, <replaceable>from</replaceable>
573 specifies the character set of the record in its original form
574 (as returned by the server), <replaceable>to</replaceable> specifies
575 the output (returned)
576 character set encoding.
577 If charset is not given, then no character set conversion takes place.
578 If <replaceable>to</replaceable> is omitted UTF-8 is assumed.
581 In addition, for certain types, the length
582 <literal>len</literal> passed will be set to the size in bytes of
583 the returned information.
586 The following are the supported values for <replaceable>form</replaceable>.
588 <varlistentry><term><literal>database</literal></term>
589 <listitem><para>Database of record is returned
590 as a C null-terminated string. Return type
591 <literal>const char *</literal>.
594 <varlistentry><term><literal>syntax</literal></term>
595 <listitem><para>The transfer syntax of the record is returned
596 as a C null-terminated string containing the symbolic name of
597 the record syntax, e.g. <literal>Usmarc</literal>. Return type
599 <literal>const char *</literal>.
602 <varlistentry><term><literal>render</literal></term>
603 <listitem><para>The record is returned in a display friendly
604 format. Upon completion buffer is returned
605 (type <literal>const char *</literal>) and length is stored in
606 <literal>*len</literal>.
609 <varlistentry><term><literal>raw</literal></term>
610 <listitem><para>The record is returned in the internal
611 YAZ specific format. For GRS-1, Explain, and others, the
612 raw data is returned as type
613 <literal>Z_External *</literal> which is just the type for
614 the member <literal>retrievalRecord</literal> in
615 type <literal>NamePlusRecord</literal>.
616 For SUTRS and octet aligned record (including all MARCs) the
617 octet buffer is returned and the length of the buffer.
620 <varlistentry><term><literal>xml</literal></term>
621 <listitem><para>The record is returned in XML if possible.
622 SRW/SRU and Z39.50 records with transfer syntax XML are
623 returned verbatim. MARC records are returned in
624 <ulink url="http://www.loc.gov/standards/marcxml/">
627 (converted from ISO2709 to MARCXML by YAZ).
628 GRS-1 and OPAC records are not supported for this form.
629 Upon completion, the XML buffer is returned
630 (type <literal>const char *</literal>) and length is stored in
631 <literal>*len</literal>.
634 <varlistentry><term><literal>opac</literal></term>
635 <listitem><para>OPAC for record is returned in XML.
642 <ulink url="http://www.loc.gov/marc/">
646 <ulink url="http://www.loc.gov/marc/specifications/speccharmarc8.html">
649 character set encoding.
650 An application that wishes to display in Latin-1 would use
652 render; charset=marc8,iso-8859-1
655 <sect2><title>Z39.50 Protocol behavior</title>
657 The functions <function>ZOOM_resultset_record</function> and
658 <function>ZOOM_resultset_records</function> inspects the client-side
659 record cache. Records not found in cache are fetched using
661 The functions may block (and perform network I/O) - even though option
662 <literal>async</literal> is 1, because they return records objects.
663 (and there's no way to return records objects without retrieving them!).
666 There is a trick, however, in the usage of function
667 <function>ZOOM_resultset_records</function> that allows for
668 delayed retrieval (and makes it non-blocking). By using
669 a null pointer for <parameter>recs</parameter> you're indicating
670 you're not interested in getting records objects
671 <emphasis>now</emphasis>.
674 <sect2><title>SRW Protocol behavior</title>
676 The ZOOM driver for SRW treats records returned by a SRW server
677 as if they where Z39.50 records with transfer syntax XML and
678 no element set name or database name.
682 <sect1 id="zoom.scan"><title>Scan</title>
684 This section describes an interface for Scan. Scan is not an
685 official part of the ZOOM model yet. The result of a scan operation
686 is the <literal>ZOOM_scanset</literal> which is a set of terms
687 returned by a target.
691 The Scan interface is Z39.50 only. SRW version 1.0 does not
696 ZOOM_scanset ZOOM_connection_scan (ZOOM_connection c,
697 const char *startterm);
699 size_t ZOOM_scanset_size(ZOOM_scanset scan);
701 const char * ZOOM_scanset_term(ZOOM_scanset scan, size_t pos,
702 int *occ, size_t *len);
704 const char * ZOOM_scanset_display_term(ZOOM_scanset scan, size_t pos,
705 int *occ, size_t *len);
707 void ZOOM_scanset_destroy (ZOOM_scanset scan);
709 const char *ZOOM_scanset_option_get (ZOOM_scanset scan,
712 void ZOOM_scanset_option_set (ZOOM_scanset scan, const char *key,
716 The scan set is created by function
717 <function>ZOOM_connection_scan</function> which performs a scan
718 operation on the connection using the specified startterm.
719 If the operation was successful, the size of the scan set can be
720 retrieved by a call to <function>ZOOM_scanset_size</function>.
721 Like result sets, the items are numbered 0,..size-1.
722 To obtain information about a particular scan term, call function
723 <function>ZOOM_scanset_term</function>. This function takes
724 a scan set offset <literal>pos</literal> and returns a pointer
725 to a <emphasis>raw term</emphasis> or <literal>NULL</literal> if
727 If present, the <literal>occ</literal> and <literal>len</literal>
728 are set to the number of occurrences and the length
729 of the actual term respectively.
730 <function>ZOOM_scanset_display_term</function> is similar to
731 <function>ZOOM_scanset_term</function> except that it returns
732 the <emphasis>display term</emphasis> rather than the raw term.
733 In a few cases, the term is different from display term. Always
734 use the display term for display and the raw term for subsequent
735 scan operations (to get more terms, next scan result, etc).
738 A scan set may be freed by a call to function
739 <function>ZOOM_scanset_destroy</function>.
740 Functions <function>ZOOM_scanset_option_get</function> and
741 <function>ZOOM_scanset_option_set</function> retrieves and sets
742 an option respectively.
745 <table frame="top"><title>ZOOM Scan Set Options</title>
747 <colspec colwidth="4*" colname="name"></colspec>
748 <colspec colwidth="7*" colname="description"></colspec>
749 <colspec colwidth="2*" colname="default"></colspec>
752 <entry>Option</entry>
753 <entry>Description</entry>
754 <entry>Default</entry>
759 number</entry><entry>Number of Scan Terms requested in next scan.
760 After scan it holds the actual number of terms returned.
761 </entry><entry>10</entry></row>
763 position</entry><entry>Preferred Position of term in response
764 in next scan; actual position after completion of scan.
765 </entry><entry>1</entry></row>
767 stepSize</entry><entry>Step Size
768 </entry><entry>0</entry></row>
770 scanStatus</entry><entry>An integer indicating the Scan Status
772 </entry><entry>0</entry></row>
778 <sect1 id="zoom.options"><title>Options</title>
780 Most &zoom; objects provide a way to specify options to change behavior.
781 From an implementation point of view a set of options is just like
782 an associative array / hash array, etc.
785 ZOOM_options ZOOM_options_create (void);
787 ZOOM_options ZOOM_options_create_with_parent (ZOOM_options parent);
789 void ZOOM_options_destroy (ZOOM_options opt);
792 const char *ZOOM_options_get (ZOOM_options opt, const char *name);
794 void ZOOM_options_set (ZOOM_options opt, const char *name,
798 typedef const char *(*ZOOM_options_callback)
799 (void *handle, const char *name);
801 ZOOM_options_callback
802 ZOOM_options_set_callback (ZOOM_options opt,
803 ZOOM_options_callback c,
807 <sect1 id="zoom.events"><title>Events</title>
809 If you're developing non-blocking applications, you have to deal
813 int ZOOM_event (int no, ZOOM_connection *cs);
816 The <function>ZOOM_event</function> executes pending events for
817 a number of connections. Supply the number of connections in
818 <literal>no</literal> and an array of connections in
819 <literal>cs</literal> (<literal>cs[0] ... cs[no-1]</literal>).
820 A pending event could be a sending a search, receiving a response,
822 When an event has occurred for one of the connections, this function
823 returns a positive integer <literal>n</literal> denoting that an event
824 occurred for connection <literal>cs[n-1]</literal>.
825 When no events are pending for the connections, a value of zero is
827 To ensure that all outstanding requests are performed call this function
828 repeatedly until zero is returned.
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