X-Git-Url: http://git.indexdata.com/?a=blobdiff_plain;f=doc%2Fzoom.xml;h=2937474acbd5f6cd68b16bd5334c7100a234317f;hb=78942f568d83ea621661bfcd2d3f25eee3d316a1;hp=ff34527b52891c9b51cd17316bc4f01340658e85;hpb=33c05384cfbca55da4ff97e5b2047b16596c72f7;p=yaz-moved-to-github.git diff --git a/doc/zoom.xml b/doc/zoom.xml index ff34527..2937474 100644 --- a/doc/zoom.xml +++ b/doc/zoom.xml @@ -1,20 +1,23 @@ - - ZOOM + + Building clients with ZOOM - &zoom; is an acronym for Z39.50 Object Oriented Model and is - an initiative started by Mike Taylor. The goal of &zoom; is to + &zoom; is an acronym for 'Z39.50 Object-Orientation Model' and is + an initiative started by Mike Taylor (Mike is from the UK, which + explains the peculiar name of the model). The goal of &zoom; is to provide a common Z39.50 client API not bound to a particular programming language or toolkit. - The lack of a simple Z39.50 client API for &yaz; was more apparanet - than ever. So, when the first ZOOM specification was available - an implementation for &yaz; was developed. For the first time, it is - now easier to develop clients than servers with &yaz;. This - chapter describes the ZOOM C binding. Before going futher - reconsider whether C is still the programming language of your - choice. There are other language bindings available and others + 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 + 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 + 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 more information. @@ -29,7 +32,7 @@ The C language misses many features found in object oriented languages - such as C++, Java, etc. For example, you'll have to, manually, + such as C++, Java, etc. For example, you'll have to manually, destroy all objects you create, even though you may think of them as temporary. Most objects has a _create - and a _destroy variant. @@ -37,15 +40,20 @@ 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. #include <yaz/zoom.h> - + Z3950_connection Z3950_connection_new (const char *host, int portnum); - + Z3950_connection Z3950_connection_create (Z3950_options options); void Z3950_connection_connect(Z3950_connection c, const char *host, @@ -56,19 +64,19 @@ Connection objects are created with either function Z3950_connection_new or Z3950_connection_create. - The former both creates and attempts to establishes a network - connection with the target. The latter doesn't establishes - a connection immediately, thus allowing you to set specify options - before establishing network connection using function + The former creates and automatically attempts to establish a network + connection with the target. The latter doesn't establish + a connection immediately, thus allowing you to specify options + before establishing network connection using the function Z3950_connection_connect. If the portnumber, portnum, is zero, the host is consulted for a port specification. If no port is given, 210 is used. A colon denotes the beginning of a port number in the host string. If the host string includes a - slash that specifies a database for the connection. + slash, the following part specifies a database for the connection. - Connection objects should be destroyed using function + Connection objects should be destroyed using the function Z3950_connection_destroy. @@ -83,7 +91,8 @@ for the connection. If val is non-NULL that holds the new value for option. - Otherwise, if val is NULL + Otherwise, if val is + NULL, the option is unchanged. The function returns the previous value of the option. @@ -92,101 +101,145 @@ - - - Option - Description - Default - - - - - implementationNameName of Your client - none - - userAuthentication user name + + + Option + Description + Default + + + + + implementationNameName of Your client + none + + userAuthentication user name + none + + groupAuthentication group name + none + + passAuthentication password none - - groupAuthentication group name - none - - passAuthentication password - none - - proxyProxy host - none - - asyncIf true (1) the connection operates in - asynchronous operatio which means that all calls are non-blocking - except Z3950_event. - 0 - - maximumRecordSize Maximum size of single record. - 1 MB - - preferredMessageSize Maximum size of multiple records. - 1 MB - - + + proxyProxy host + none + + asyncIf true (1) the connection operates in + asynchronous operation which means that all calls are non-blocking + except + Z3950_event. + 0 + + maximumRecordSize Maximum size of single record. + 1 MB + + preferredMessageSize Maximum size of multiple records. + 1 MB + + - Function Z3950_connection_host returns + Function Z3950_connection_host returns the host for the connection as specified in a call to - Z3950_connection_new or - Z3950_connection_connect. - This function returns NULL if host isn't - set for the connection. + Z3950_connection_new or + Z3950_connection_connect. + This function returns NULL if host isn't + set for the connection. int Z3950_connection_error (Z3950_connection c, const char **cp, const char **addinfo); - Use Z3950_connection_error to check for - errors for the last operation(s) performed. The function returns - zero if no errors occurred; non-zero otherwise indicating the error. - Pointers cp and addinfo - holds messages for the error and additional-info if passed as - non-NULL. + Use Z3950_connection_error to check for + errors for the last operation(s) performed. The function returns + zero if no errors occurred; non-zero otherwise indicating the error. + Pointers cp and addinfo + 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). + + - Search objects + Queries - Search objects defines how result sets are obtained. They - act like queries. + Query objects represents queries. - Z3950_search Z3950_search_create(void); + Z3950_query Z3950_query_create(void); - void Z3950_search_destroy(Z3950_search s); + void Z3950_query_destroy(Z3950_query q); - int Z3950_search_prefix(Z3950_search s, const char *str); + int Z3950_query_prefix(Z3950_query q, const char *str); - int Z3950_search_sortby(Z3950_search s, const char *criteria); + int Z3950_query_sortby(Z3950_query q, const char *criteria); - Create search objects using Z3950_search_create - and destroy them by calling Z3950_search_destroy. - RPN-queries can be specified in PQF - notation by using the - function Z3950_search_prefix. More - query types will be added later, such as - CCL to RPN-mapping, native CCL query, - etc. In addition to a search, a sort critieria may be set. Function - Z3950_search_sortby specifies a - sort criteria using the same string notation for sort as offered by - the YAZ client. + Create query objects using Z3950_query_create + and destroy them by calling Z3950_query_destroy. + RPN-queries can be specified in PQF + notation by using the + function Z3950_query_prefix. More + query types will be added later, such as + CCL to RPN-mapping, native CCL query, + etc. In addition to a search, a sort criteria may be set. Function + Z3950_query_sortby specifies a + 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 - The result set object is a container for records returned from - a target. - search. + The result set object is a container for records returned from + a target. Z3950_resultset Z3950_connection_search(Z3950_connection, - Z3950_search q); + Z3950_query q); Z3950_resultset Z3950_connection_search_pqf(Z3950_connection c, const char *q); @@ -194,12 +247,13 @@ void Z3950_resultset_destroy(Z3950_resultset r); - Function Z3950_connection_search creates - a result set given a connection - and search object. - Destroy a result set by calling - Z3950_resultset_destroy. - Simple clients using PQF only may use function - Z3950_connection_search_pqf instead. + Function Z3950_connection_search creates + a result set given a connection and query. + Destroy a result set by calling + Z3950_resultset_destroy. + Simple clients may using PQF only may use function + Z3950_connection_search_pqf in which case + creating query objects is not necessary. const char *Z3950_resultset_option (Z3950_resultset r, @@ -208,124 +262,230 @@ int Z3950_resultset_size (Z3950_resultset r); - void *Z3950_resultset_get (Z3950_resultset s, int pos, - const char *type, int *len); + void *Z3950_resultset_get (Z3950_resultset s, size_t pos, + const char *type, size_t *len); - Function X3950_resultset_options sets or - modifies an option for a result set similar to + Function Z3950_resultset_options sets or + modifies an option for a result set similar to Z3950_connection_option. - The number of hits also called result-set is returned by - function 3950_resultset_size. + The number of hits also called result-count is returned by + function Z3950_resultset_size. - Function Z3950_resultset_get is similar to - + 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. + instead of operating on a record object, it operates on a record on + a given offset within a result set. ZOOM Result set Options - - - Option - Description - Default - - - - - piggybackTrue (1) if piggyback should be - used in searches; false (0) if not. - 1 - - startOffset of first record we wish to - retrieve from the target. Note first record has offset 0 - unlike the protocol specifications where first record has position - 1. - 0 - - countNumber of records to be retrieved. - 0 - - elementSetNameElement-Set name of records. - Most targets should honor element set name B - and F for brief and full respectively. - none - - preferredRecordSyntaxPreferred Syntax, like - USMARC, SUTRS, etc. - none - - databaseNameOne or more database names - separated by character plus (+). - Default - - + + + Option + Description + Default + + + + + piggybackTrue (1) if piggyback should be + used in searches; false (0) if not. + 1 + + startOffset of first record to be + retrieved from target. First record has offset 0 unlike the + protocol specifications where first record has position 1. + 0 + + countNumber of records to be retrieved. + 0 + + elementSetNameElement-Set name of records. + Most targets should honor element set name B + and F for brief and full respectively. + none + + preferredRecordSyntaxPreferred Syntax, such as + USMARC, SUTRS, etc. + none + + smallSetUpperBoundIf hits is less than or equal to this + 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. + 1 + + mediumSetPresentNumberThis value represents + the number of records to be returned as part of a search when when + hits is less than or equal to large set lower bound and if hits + is greator than small set upper bound. + 0 + + smallSetElementSetName + The element set name to be used for small result sets. + none + + mediumSetElementSetName + The element set name to be for medium-sized result sets. + none + + databaseNameOne or more database names + separated by character plus (+). + Default + +
+ + 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 - A record object is a retrival record on the client side - - created from result sets. + A record object is a retrival record on the client side - + created from result sets. void Z3950_resultset_records (Z3950_resultset r, Z3950_record *recs, - size_t *cnt); - Z3950_record Z3950_resultset_record (Z3950_resultset s, int pos); + size_t start, size_t count); + Z3950_record Z3950_resultset_record (Z3950_resultset s, size_t pos); void *Z3950_record_get (Z3950_record rec, const char *type, - int *len); + size_t *len); void Z3950_record_destroy (Z3950_record rec); - Records are created by functions - Z3950_resultset_records or - Z3950_resultset_record - and destroyed by Z3950_resultset_destroy. + Records are created by functions + Z3950_resultset_records or + Z3950_resultset_record + and destroyed by Z3950_record_destroy. - A single record is created and returned by function - Z3950_resultset_record that takes a - position as argument. First record has position zero. - If no record could be obtained NULL. + A single record is created and 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. - Function Z39_resultset_recordsretrieves - a number of records from a result set. Options start - and count specifies the range of records to - be returned. Upon completion recs[0], ..recs[*cnt] - holds record objects for the records. These array of records + 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] + holds record objects for the records. The array of records recs should be allocate prior to calling - Z3950_resultset_records. Note that for - records that couldn't be retrieved from the target - recs[ ..] is NULL. + Z3950_resultset_records. Note that for those + records that couldn't be retrieved from the target + recs[ ..] is set to NULL. - In order to extract information about a single record, - Z3950_record_get is provided. The - function returns a pointer to certain record information. The - 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. + In order to extract information about a single record, + Z3950_record_get is provided. The + function returns a pointer to certain record information. The + 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. + + database + The database that holds the record is returned + as a C string. Return type char *. + + + syntax + The transfer syntax (OID) of the record is returned + as a C 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 * 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 objects in &zoom; allows you to specify options to change - behaviour. From an implementation point of view a set of options - is just like an associate array / hash array, etc. + 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. Z3950_options Z3950_options_create (void); @@ -352,26 +512,26 @@ Events - If you're developing non-blocking applications you have to deal - with events. + If you're developing non-blocking applications, you have to deal + with events. - int Z3950_event (int no, Z3950_connection *cs); + int Z3950_event (int no, Z3950_connection *cs); - The Z3950_event executes pending events for - a number of connections. Supply the number of connections in - no and an array of connections in - cs (cs[0] ... cs[no-1]). - A pending event could be a sending a search, receiving a response, - etc. - When an event has a occured for one of the connections this function - returns a positive integer n denoting that an event - 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 is function - repeatedly until zero is returned. + The Z3950_event executes pending events for + a number of connections. Supply the number of connections in + no and an array of connections in + cs (cs[0] ... cs[no-1]). + A pending event could be a sending a search, receiving a response, + etc. + When an event has a occured for one of the connections, this function + returns a positive integer n denoting that an event + occurred for connection cs[n-1]. + When no events are pending for the connections, a value of zero is + returned. + To ensure that all outstanding requests are performed call this function + repeatedly until zero is returned. @@ -386,7 +546,7 @@ sgml-indent-step:1 sgml-indent-data:t sgml-parent-document: "yaz.xml" - sgml-local-catalogs: "../../docbook/docbook.cat" + sgml-local-catalogs: nil sgml-namecase-general:t End: -->