X-Git-Url: http://git.indexdata.com/?a=blobdiff_plain;f=doc%2Fzoom.xml;h=315e78e1a1e56914d6750bdbfd90477f541c882b;hb=02da040a0671d09dfe19790a53ff6408740e7cde;hp=c350599cec85b2cc64af79ccad15587b1446a926;hpb=67e7a7a13ff1e787b9e5cfe84494dfd446c1bcb9;p=yaz-moved-to-github.git diff --git a/doc/zoom.xml b/doc/zoom.xml index c350599..315e78e 100644 --- a/doc/zoom.xml +++ b/doc/zoom.xml @@ -1,4 +1,4 @@ - + Building clients with ZOOM @@ -10,16 +10,16 @@ The lack of a simple Z39.50 client API for &yaz; has become more - and more apparent over time. So when the first ZOOM specification + and more apparent over time. So when the first &zoom; specification became available, an implementation for &yaz; was quickly developed. For the first time, it is now as easy (or easier!) to develop clients than servers with &yaz;. This - chapter describes the ZOOM C binding. Before going futher, please + chapter describes the &zoom; C binding. Before going futher, please reconsider whether C is the right programming language for the job. There are other language bindings available for &yaz;, and still more - are in active development. See the ZOOM website at - zoom.z3950.org for + are in active development. See the + ZOOM website for more information. @@ -40,6 +40,11 @@ that because of typedefs. All destroy methods should gracefully ignore a NULL pointer. + + In each of the sections below you'll find a sub section called + protocol behavior, that descries how the API maps to the Z39.50 + protocol. + Connections The Connection object is a session with a target. @@ -75,21 +80,21 @@ Z3950_connection_destroy. - const char *Z3950_connection_option (Z3950_connection c, - const char *key, - const char *val); + void Z3950_connection_option_set (Z3950_connection c, + const char *key, + const char *val); + + const char *Z3950_connection_option_get (Z3950_connection c, + const char *key); + const char *Z3950_connection_host (Z3950_connection c); - The Z3950_connection_option allows you to - inspect or set an option given by key - for the connection. - If val is non-NULL that - holds the new value for option. - Otherwise, if val is - NULL, - the option is unchanged. - The function returns the previous value of the option. + The Z3950_connection_option_set allows you to + set an option given by key to the value + value for the connection. + Function Z3950_connection_option_get returns + the value for an option given by key. ZOOM Connection Options @@ -122,7 +127,8 @@ asyncIf true (1) the connection operates in asynchronous operation which means that all calls are non-blocking - except Z3950_event. + except + Z3950_event. 0 maximumRecordSize Maximum size of single record. @@ -153,6 +159,44 @@ holds messages for the error and additional-info if passed as non-NULL. + Protocol behavior + + The calls Z3950_connection_new and + Z3950_connection_connect establises a TCP/IP + connection and sends an Initialize Request to the target if + possible. In addition, the calls waits for an Initialize Response + from the target and the result is inspected (OK or rejected). + + + If proxy is set then the client will establish + a TCP/IP connection with the peer as specified by the + proxy host and the hostname as part of the + connect calls will be set as part of the Initialize Request. + The proxy server will then "forward" the PDU's transparently + to the target behind the proxy. + + + For the authentication parameters, if option user + is set and both options group and + pass are unset, then Open style + authentication is used (Version 2/3) in which case the username + is usually followed by a slash, then by a password. + If either group + or pass is set then idPass authentication + (Version 3 only) is used. If none of the options are set, no + authentication parameters are set as part of the Initialize Request + (obviously). + + + When option async is 1, it really means that + all network operations are postponed (and queued) until the + function Z3950_event is invoked. When doing so + it doesn't make sense to check for errors after + Z3950_connection_new is called since that + operation "connecting - and init" is still incomplete and the + API cannot tell the outcome (yet). + + Queries @@ -180,6 +224,13 @@ sort criteria using the same string notation for sort as offered by the YAZ client. + Protocol behavior + + The query object is just an interface for the member Query + in the SearchRequest. The sortby-function is an interface to the + sortSequence member of the SortRequest. + + Result sets @@ -205,31 +256,25 @@ creating query objects is not necessary. - const char *Z3950_resultset_option (Z3950_resultset r, - const char *key, - const char *val); + void Z3950_resultset_option_set (Z3950_resultset r, + const char *key, + const char *val); - int Z3950_resultset_size (Z3950_resultset r); + const char *Z3950_resultset_option_get (Z3950_resultset r, + const char *key); - void *Z3950_resultset_get (Z3950_resultset s, size_t pos, - const char *type, size_t *len); + size_t Z3950_resultset_size (Z3950_resultset r); - Function Z3950_resultset_options sets or - modifies an option for a result set similar to - Z3950_connection_option. + Functions Z3950_resultset_options_set and + Z3950_resultset_get sets and gets an option + for a result set similar to Z3950_connection_option_get + and Z3950_connection_option_set. The number of hits also called result-count is returned by function Z3950_resultset_size. - - Function Z3950_resultset_get is similar to - - Z3950_record_get but - instead of operating on a record object, it operates on a record on - a given offset within a result set. -
ZOOM Result set Options @@ -269,8 +314,8 @@ value, then target will return all records using small element set name 0 - largeSetLowerBoundIf hits is greator than this value, the target - will return no records. + largeSetLowerBoundIf hits is greator than this + value, the target will return no records. 1 mediumSetPresentNumberThis value represents @@ -293,6 +338,57 @@
+ + Protocol behavior + + The creation of a result set involves at least a SearchRequest + - SearchResponse protocol handshake. Following that, if a sort + critieria was specified as part of the query, a sortRequest - + SortResponse handshake takes place. Note that it is necessary to + perform sorting before any retrieval takes place, so no records will + be returned from the target as part of the SearchResponse because these + would be unsorted. Hence, piggyback is disabled when sort critieria + is set. Following Search - and a Possible sort, Retrieval takes + place - as one or more Present Requests - Present Response being + transferred. + + + The API allows for two different modes for retrieval. A high level + mode which is somewhat more powerful and a low level one. + The low level is "enabled" when the settings + smallSetUpperBound, + mediumSetPresentNumber and + largeSetLowerBound are set. The low level mode + thus allows you to precisely set how records are returned as part + of a search response as offered by the Z39.50 protocol. + Since the client may be retrieving records as part of the + search response, this mode doesn't work well if sorting is used. + + + The high-level mode allows you to fetch a range of records from + the result set with a given start offset. When you use this mode + the client will automatically use piggyback if that is possible + with the target and perform one or more present requests as needed. + Even if the target returns fewer records as part of a present response + because of a record size limit, etc. the client will repeat sending + present requests. As an example, if option start + is 0 (default) and count is 4, and + piggyback is 1 (default) and no sorting critieria + is specified, then the client will attempt to retrieve the 4 + records as part the search response (using piggyback). On the other + hand, if either start is positive or if + a sorting criteria is set, or if piggyback + is 0, then the client will not perform piggyback but send Present + Requests instead. + + + If either of the options mediumSetElementSetName and + smallSetElementSetName are unset, the value + of option elementSetName is used for piggyback + searches. This means that for the high-level mode you only have + to specify one elementSetName option rather than three. + + Records @@ -308,16 +404,24 @@ void *Z3950_record_get (Z3950_record rec, const char *type, size_t *len); + Z3950_record Z3950_record_dup (Z3950_record rec); + void Z3950_record_destroy (Z3950_record rec); - Records are created by functions + References to temporary records are returned by functions Z3950_resultset_records or - Z3950_resultset_record - and destroyed by Z3950_record_destroy. + Z3950_resultset_record. + + + If a persistent pointer to a record is desired + Z3950_record_dup should be used. + It returns a record reference that at any + later stage should be destroyed by + Z3950_record_destroy. - A single record is created and returned by function + A single record is returned by function Z3950_resultset_record that takes a position as argument. First record has position zero. If no record could be obtained NULL is returned. @@ -326,7 +430,8 @@ Function Z3950_resultset_records retrieves a number of records from a result set. Parameter start and count specifies the range of records to - be returned. Upon completion array recs[0], ..recs[count-1] + be returned. Upon completion array + recs[0], ..recs[count-1] holds record objects for the records. The array of records recs should be allocate prior to calling Z3950_resultset_records. Note that for those @@ -340,14 +445,47 @@ nature (type) of the pointer depends on the type given. In addition for certain types, the length len passed will be set to the size in bytes of - the returned information. The types database, - syntax and render are - supported. More will be added later. + the returned information. + + database + Database of record is returned + as a C null-terminated string. Return type char *. + + + syntax + The transfer syntax (OID) of the record is returned + as a C null-terminated string. Return type char *. + + + render + The record is returned in a display friendly + format. Upon completion buffer is returned + (type char *) and length is stored in + *len. + + + raw + The record is returned in the internal + YAZ specific format. The raw data is returned as type + Z_External * which is just the type for + the member retrievalRecord in + type NamePlusRecord. + + + + Protocol behavior + + The functions Z3950_resultset_record and + Z3950_resultset_records inspects the client-side + record cache. If the records(s) were not found, i.e. not yet retrieved + from, they are fetched using Present Requests. + + Options - Most &zoom; objects provide a way to specify options to default behaviour. + Most &zoom; objects provide a way to specify options to default behavior. From an implementation point of view a set of options is just like an associate array / hash array, etc. @@ -394,7 +532,7 @@ occurred for connection cs[n-1]. When no events are pending for the connections, a value of zero is returned. - To make sure all outstanding requests are performed call this function + To ensure that all outstanding requests are performed call this function repeatedly until zero is returned.