Slide 10.18: Line-by-line anatomy of DB.c (cont.)   Slide 10.20: Line-by-line anatomy of DB.c (cont.)   Home

Line-by-line Anatomy of DB.c (Cont.)

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if ( DmQueryRecord( db, seek ) == NULL ) seek++;
This function MemHandle DmQueryRecord( DmOpenRef dbP, UInt16 index ) returns a handle to a record for reading only (does not set the busy bit).

• dbP: DmOpenRef to open database
• index: Which record to retrieve

if ( DmSetRecordInfo( db, index, &attr, NULL ) )
This function Err DmSetRecordInfo( DmOpenRef dbP, UInt16 index, UInt16 *attrP, UInt32 *uniqueIDP ) sets record information stored in the database header.

• dbP: DmOpenRef to open database
• index: Index of record
• attrP: Pointer to new attribute variable, or NULL. See “Record Attribute Constants” for a list of possible values.
• uniqueIDP: Pointer to new unique ID variable, or NULL

DmDatabaseSize( dbCard, dbID, NULL, &totalBytes, &dataBytes );
This function Err DmDatabaseSize( UInt16 cardNo, LocalID dbID, UInt32 *numRecordsP, UInt32 *totalBytesP, UInt32 *dataBytesP ) retrieves size information on a database.

• cardNo: Card number the database resides on
• dbID: Database ID of the database

For the following parameters, pass NULL if you don't want to retrieve them.

• numRecordsP: The total number of records in the database
• totalBytesP: The total number of bytes used by the database including the overhead
• dataBytesP: The total number of bytes used to store just each record's data, not including overhead