Re: Looking for database library.

[Robert Moynihan]

Peter Hamilton-Scott wrote:
I'm trying to get the database functions to work, and after a lot of 
playing around I'm not finding this very intuitive, what with the 
sheer number of Dm... routines there are and that you have to do A 
before B before C and woe betide you if call E before B - you probably 
know the feeling! :-)

In short, does anyone know if there is a freeware library that 
simplifies database access? My app needs (or at least I think it 
needs) an app info block as I'd like to keep some database state 
external to the records it refers to. From what I find and see, app 
info blocks and control records are not well described though the 
database records is a little more easier to use.

To that end, I'm looking at using the first record as my control 
record and then having to union the data records. This is 
counter-productive. If there is a reliable library you know of I'd 
appreciate that, or failing that, a link to a good onlite site that 
does a walk-through of Palm database I/O?

Thanks.
Peter, it's certainly not all that hard to use the Dm functions to get 
to your goal.  I think you are reading too much into it.  Even if you 
could find a library to do it, getting that to work would be just as 
complicated.  Below are some samples that creates a database if it 
doesn't already exist, then add a record.  I edited them a little to 
protect the innocent, so I hope I didn't add any bugs.  Bob.

Boolean CreateDatabase(Char *dbName, UInt16 dbType, UInt16 dbAppId){
 LocalID       dbID;
 UInt16        attr;
 DmOpenRef     db = DmOpenDatabaseByTypeCreator(dbType, , dmModeReadWrite);
 //if it wasn't able to open then create it
 if (!db) {
   //if it can't create then bail out
   if (DmCreateDatabase(0, dbName, dbAppID, dbType, false)) return 1;
   //get the default attributes and add the db backup bit
   dbID=DmFindDatabase(0,dbName);
   DmDatabaseInfo(0,dbID,NULL, &attr, NULL, NULL, NULL, NULL, NULL, 
NULL, NULL, NULL, NULL);
   attr=attr | dmHdrAttrBackup;
   DmSetDatabaseInfo(0,dbID,NULL, &attr, NULL, NULL, NULL, NULL, NULL, 
NULL, NULL, NULL, NULL);
 }
 else DmCloseDatabase(db);
 return 0;
}

And this sample will open your db and write a string into it as a new 
record...

UInt16 WriteString(Char *st, UInt16 dbType, UInt16 dbAppId){
   MemHandle  recH=NULL;
   UInt8      *recP=NULL;
   UInt16     record=-1; //-1 puts new record at end
   DmOpenRef  db;
   db=DmOpenDatabaseByTypeCreator(dbType, dbAppId, dmModeReadWrite);
   if (db){
       recH=DmNewRecord(db,&record,StrLen(header)+3); //+3 is some 
padding at end
       recP=MemHandleLock(recH);
       DmSet(recP,0,MemHandleSize(recH),0);
       DmWrite(recP,0,header,StrLen(header));
       DmSet(recP,StrLen(header),1,10);
       MemHandleUnlock(recH);
       DmCloseDatabase(db);
   }
}


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