X-Git-Url: http://git.indexdata.com/?p=yaz-moved-to-github.git;a=blobdiff_plain;f=doc%2Fzoom.xml;h=b08d798c8ad69243e95ff1505cf1696ffe4b8dc6;hp=c350599cec85b2cc64af79ccad15587b1446a926;hb=3599bbc013ec757862d8a2d6e62aa6a432ba4514;hpb=67e7a7a13ff1e787b9e5cfe84494dfd446c1bcb9 diff --git a/doc/zoom.xml b/doc/zoom.xml index c350599..b08d798 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. @@ -31,7 +31,7 @@ - The C language misses many features found in object oriented languages + The C language misses features found in object oriented languages 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 @@ -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. @@ -47,23 +52,23 @@ #include <yaz/zoom.h> - Z3950_connection Z3950_connection_new (const char *host, int portnum); + ZOOM_connection ZOOM_connection_new (const char *host, int portnum); - Z3950_connection Z3950_connection_create (Z3950_options options); + ZOOM_connection ZOOM_connection_create (ZOOM_options options); - void Z3950_connection_connect(Z3950_connection c, const char *host, + void ZOOM_connection_connect(ZOOM_connection c, const char *host, int portnum); - void Z3950_connection_destroy (Z3950_connection c); + void ZOOM_connection_destroy (ZOOM_connection c); Connection objects are created with either function - Z3950_connection_new or - Z3950_connection_create. + ZOOM_connection_new or + ZOOM_connection_create. 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. + ZOOM_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 @@ -72,26 +77,24 @@ Connection objects should be destroyed using the function - Z3950_connection_destroy. + ZOOM_connection_destroy. - const char *Z3950_connection_option (Z3950_connection c, - const char *key, - const char *val); - const char *Z3950_connection_host (Z3950_connection c); + void ZOOM_connection_option_set (ZOOM_connection c, + const char *key, + const char *val); + + const char *ZOOM_connection_option_get (ZOOM_connection c, + const char *key); - 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 ZOOM_connection_option_set allows you to + set an option given by key to the value + value for the connection. + Function ZOOM_connection_option_get returns + the value for an option given by key. - ZOOM Connection Options +
ZOOM Connection Options @@ -117,12 +120,17 @@ passAuthentication password none + hostTarget host. This setting is "read-only". + It's automatically set internally when connecting to a target. + none + proxyProxy host none asyncIf true (1) the connection operates in asynchronous operation which means that all calls are non-blocking - except Z3950_event. + except + ZOOM_event. 0 maximumRecordSize Maximum size of single record. @@ -133,53 +141,90 @@
- - 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. - - int Z3950_connection_error (Z3950_connection c, const char **cp, + int ZOOM_connection_error (ZOOM_connection c, const char **cp, const char **addinfo); - Use Z3950_connection_error to check for + Use ZOOM_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 ZOOM_connection_new and + ZOOM_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 ZOOM_event is invoked. When doing so + it doesn't make sense to check for errors after + ZOOM_connection_new is called since that + operation "connecting - and init" is still incomplete and the + API cannot tell the outcome (yet). + + Queries Query objects represents queries. - Z3950_query Z3950_query_create(void); + ZOOM_query ZOOM_query_create(void); - void Z3950_query_destroy(Z3950_query q); + void ZOOM_query_destroy(ZOOM_query q); - int Z3950_query_prefix(Z3950_query q, const char *str); + int ZOOM_query_prefix(ZOOM_query q, const char *str); - int Z3950_query_sortby(Z3950_query q, const char *criteria); + int ZOOM_query_sortby(ZOOM_query q, const char *criteria); - Create query objects using Z3950_query_create - and destroy them by calling Z3950_query_destroy. + Create query objects using ZOOM_query_create + and destroy them by calling ZOOM_query_destroy. RPN-queries can be specified in PQF notation by using the - function Z3950_query_prefix. More + function ZOOM_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 + ZOOM_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 @@ -187,48 +232,42 @@ a target. - Z3950_resultset Z3950_connection_search(Z3950_connection, - Z3950_query q); + ZOOM_resultset ZOOM_connection_search(ZOOM_connection, + ZOOM_query q); - Z3950_resultset Z3950_connection_search_pqf(Z3950_connection c, - const char *q); + ZOOM_resultset ZOOM_connection_search_pqf(ZOOM_connection c, + const char *q); - void Z3950_resultset_destroy(Z3950_resultset r); + void ZOOM_resultset_destroy(ZOOM_resultset r); - Function Z3950_connection_search creates + Function ZOOM_connection_search creates a result set given a connection and query. Destroy a result set by calling - Z3950_resultset_destroy. + ZOOM_resultset_destroy. Simple clients may using PQF only may use function - Z3950_connection_search_pqf in which case + ZOOM_connection_search_pqf in which case creating query objects is not necessary. - const char *Z3950_resultset_option (Z3950_resultset r, - const char *key, - const char *val); + void ZOOM_resultset_option_set (ZOOM_resultset r, + const char *key, + const char *val); - int Z3950_resultset_size (Z3950_resultset r); + const char *ZOOM_resultset_option_get (ZOOM_resultset r, + const char *key); - void *Z3950_resultset_get (Z3950_resultset s, size_t pos, - const char *type, size_t *len); + size_t ZOOM_resultset_size (ZOOM_resultset r); - Function Z3950_resultset_options sets or - modifies an option for a result set similar to - Z3950_connection_option. + Functions ZOOM_resultset_options_set and + ZOOM_resultset_get sets and gets an option + for a result set similar to ZOOM_connection_option_get + and ZOOM_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. + function ZOOM_resultset_size. ZOOM Result set Options @@ -265,12 +304,16 @@ USMARC, SUTRS, etc. none + schemaSchema for retrieval, such as + Gils-schema, Geo-schema, 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. + largeSetLowerBoundIf hits is greator than this + value, the target will return no records. 1 mediumSetPresentNumberThis value represents @@ -290,9 +333,65 @@ databaseNameOne or more database names separated by character plus (+). Default + + setnameName of Result Set (Result Set ID). + If this option isn't set, the ZOOM module will automatically + allocate a result set name. + 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 @@ -300,101 +399,191 @@ created from result sets. - void Z3950_resultset_records (Z3950_resultset r, - Z3950_record *recs, - size_t start, size_t count); - Z3950_record Z3950_resultset_record (Z3950_resultset s, size_t pos); + void ZOOM_resultset_records (ZOOM_resultset r, + ZOOM_record *recs, + size_t start, size_t count); + ZOOM_record ZOOM_resultset_record (ZOOM_resultset s, size_t pos); + + void *ZOOM_record_get (ZOOM_record rec, const char *type, + size_t *len); - void *Z3950_record_get (Z3950_record rec, const char *type, - size_t *len); + ZOOM_record ZOOM_record_clone (ZOOM_record rec); - void Z3950_record_destroy (Z3950_record rec); + void ZOOM_record_destroy (ZOOM_record rec); - Records are created by functions - Z3950_resultset_records or - Z3950_resultset_record - and destroyed by Z3950_record_destroy. + References to temporary records are returned by functions + ZOOM_resultset_records or + ZOOM_resultset_record. + + + If a persistent reference to a record is desired + ZOOM_record_clone should be used. + It returns a record reference that should be destroyed + by a call to ZOOM_record_destroy. - A single record is created and returned by function - Z3950_resultset_record that takes a + A single record is returned by function + ZOOM_resultset_record that takes a position as argument. First record has position zero. If no record could be obtained NULL is returned. - Function Z3950_resultset_records retrieves + Function ZOOM_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 + recs should be allocated prior the call + ZOOM_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 + ZOOM_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 + nature (type) of the pointer depends on the parameter, + type. + 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 ZOOM_resultset_record and + ZOOM_resultset_records inspects the client-side + record cache. Records not found in cache are fetched using + Present. + The functions may block (and perform network I/O) - even though option + async is 1, because they return records objects. + (and there's no way to return records objects without retrieving them!). + + + There is a trick, however, in the usage of function + ZOOM_resultset_records that allows for + delayed retrieval (and makes it non-blocking). By passing + a null pointer for recs you're indicating + you're not interested in getting records objects + now. + + Options - Most &zoom; objects provide a way to specify options to default behaviour. + Most &zoom; objects provide a way to specify options to change behavior. From an implementation point of view a set of options is just like - an associate array / hash array, etc. + an associative array / hash array, etc. - Z3950_options Z3950_options_create (void); + ZOOM_options ZOOM_options_create (void); - Z3950_options Z3950_options_create_with_parent (Z3950_options parent); + ZOOM_options ZOOM_options_create_with_parent (ZOOM_options parent); - void Z3950_options_destroy (Z3950_options opt); + void ZOOM_options_destroy (ZOOM_options opt); - const char *Z3950_options_get (Z3950_options opt, const char *name); + const char *ZOOM_options_get (ZOOM_options opt, const char *name); - void Z3950_options_set (Z3950_options opt, const char *name, - const char *v); + void ZOOM_options_set (ZOOM_options opt, const char *name, + const char *v); - typedef const char *(*Z3950_options_callback) + typedef const char *(*ZOOM_options_callback) (void *handle, const char *name); - Z3950_options_callback - Z3950_options_set_callback (Z3950_options opt, - Z3950_options_callback c, - void *handle); + ZOOM_options_callback + ZOOM_options_set_callback (ZOOM_options opt, + ZOOM_options_callback c, + void *handle); + Scsn + + This section describes an interface for Scan. Scan is not an + official part of the ZOOM model yet. The result of a scan operation + is the ZOOM_scanset which is a set of terms + returned by a target. + + + ZOOM_scanset ZOOM_connection_scan (ZOOM_connection c, + const char *startterm); + + size_t ZOOM_scanset_size(ZOOM_scanset scan); + + const char * ZOOM_scanset_term(ZOOM_scanset scan, size_t pos, + int *occ, size_t *len); + + + void ZOOM_scanset_destroy (ZOOM_scanset scan); + + + The scan set is created by function + ZOOM_connection_scan which performs a scan + operation on the connection and start term given. + If the operation was successful, the size of the scan set can be + retrived by a call to ZOOM_scanset_size. + Like result sets, the items are numbered 0,..size-1. + To obtain information about a particular scan term, call function + ZOOM_scanset_term. This function takes + a scan set offset pos and returns a pointer + to an actual term or NULL if non-present. + If present, the occ and len + are set to the number of occurrences and the length + of the actual term respectively. + A scan set may be freed by a call to function + ZOOM_scanset_destroy. + + Events If you're developing non-blocking applications, you have to deal with events. - int Z3950_event (int no, Z3950_connection *cs); + int ZOOM_event (int no, ZOOM_connection *cs); - The Z3950_event executes pending events for + The ZOOM_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 + When an event has 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 this function + To ensure that all outstanding requests are performed call this function repeatedly until zero is returned.