Re: reading stored memory

[Robert Moynihan]

Scott Erickson wrote:
Bob,
   Here is what I got at this point.  Is this pretty much what I need to do 
to read through all dbs on the device?
 

Here's a function that I use to build a list of databases in one of my 
apps.  I haven't really typed this out all that well, but it should give 
some ideas. 

First I initialize the 2 variables, then call BuildDBList() with the 
type of db that I am looking for.  Note that this ONLY looks for dbs 
created by my app, so the CreatorID is hardcoded as RPNAppID.  Using 
NULL here would search for all creators.  Once the list has been created 
in memory, it is really easy to refer to it; see the bit of code at the 
bottom.

//these are globals that I can access from any part of my app
MemHandle    dbListH=NULL;
UInt16        gLockCount=0;
//this defines the structure for dbList
typedef struct {
   UInt16    card;
   LocalID    currentDB;
   UInt16    other;
} myDbListType;
//this function builds the list.  I do this once, and only again when I 
detect that a change has been made.
void BuildDBList(UInt32 type)
//type could be NULL if you want to search for ALL types.
{
   DmSearchStateType state;
   Boolean        latestVer=false;  //this is usually false for apps
   UInt16        card;
   LocalID     currentDB=0;
   UInt16        attributesP;
   UInt16        count=0;
   UInt16        maxCount=10;
   Err        Error;
   Char        dbName[32];
   LocalID        appInfoIDP;
   Char        *ch=(void*)&type;
   myDbListType    *dbListP;

   //initialize memory for dblist
   if (dbListH){
       MemHandleFree(dbListH);
       dbListH=NULL;
   }
   dbListH=MemHandleNew(maxCount*sizeof(myDbListType));
   dbListP=myMemHandleLock(dbListH);
   Error = DmGetNextDatabaseByTypeCreator(true, &state, type, RPNAppID, 
latestVer, &card, &currentDB);
   //Build list of names
   while (!Error && currentDB && count<256) {
       Error = DmDatabaseInfo(card, currentDB, 
dbName,&attributesP,NULL,NULL,NULL,NULL,NULL,&appInfoIDP,NULL,NULL,NULL);
       if (StrNCompare(ch+1,dbName+4,3)==0){
           //grow the list if necessary
           if (count==maxCount){
               Err err;
               maxCount+=10;
               myMemPtrUnlock(dbListP);
               err=MemHandleResize(dbListH,maxCount*sizeof(myDbListType));
               dbListP=myMemHandleLock(dbListH);
               if (err){
                   maxCount-=10;
                   break;
               }
           }
           //add entry to dbList
           dbListP[count].card=card;
           dbListP[count].currentDB=currentDB;
           if (type=='BPgm'){
               DmOpenRef    db;
               UInt16        key;
               db=DmOpenDatabase(card,currentDB,dmModeReadOnly);
               GetProgHeader(db, NULL, &key, NULL);
               DmCloseDatabase(db);
               dbListP[count].other=key;
           }
           else
               dbListP[count].other=0;
       count++;
       }
       Error = DmGetNextDatabaseByTypeCreator(false, &state, type, 
RPNAppID, latestVer, &card, &currentDB);
   }
   dbListCount=count;
   SysQSort (dbListP, count, sizeof(myDbListType), myCompareDBNames, 0);
   myMemPtrUnlock(dbListP);
}

The list is a list of card numbers and localIDs for databases.  With 
this list in place it is easy to populate a popup list, for instance.  
If I wanted to find the name of the databases in my list I would do 
something like this...
{
       myDbListType    *dbListP;
       UInt16         dbIndex=index; //this is the index of the list 
member that I am interested in
         char         name[32];

       dbListP=myMemHandleLock(dbListH);
       DmDatabaseInfo(dbListP[dbIndex].card, 
dbListP[dbIndex].currentDB, 
name,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL);
       myMemPtrUnlock(dbListP);
}

When you are done with the list just do MemHandleFree(dbListH) and set 
dbListCount to 0.

Bob.
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