A record object is a retrieval record on the client side - created from result sets.
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);
const char *ZOOM_record_get (ZOOM_record rec, const char *type,
size_t *len);
ZOOM_record ZOOM_record_clone (ZOOM_record rec);
void ZOOM_record_destroy (ZOOM_record rec);
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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 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 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] holds record objects for the records. The array of records 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, ZOOM_record_get is provided. The function returns a pointer to certain record information. The 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.
Database of record is returned as a C null-terminated string. Return type const char *.
The transfer syntax (OID) of the record is returned as a C null-terminated string. Return type is const char *.
The record is returned in a display friendly format. Upon completion buffer is returned (type const char *) and length is stored in *len.
The record is returned in the internal YAZ specific format. For GRS-1, Explain, and others, the raw data is returned as type Z_External * which is just the type for the member retrievalRecord in type NamePlusRecord. For SUTRS and octet aligned record (including all MARCs) the octet buffer is returned and the length of the buffer.
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.