My problem with writing to database is now solved.
However another problem came up -- now I can't read from the DB.
I am getting "Bus error". The code I am using to read is:
static void drawProc(void *tableP, Int16 row, Int16 column, RectangleType *bounds)
{
Int16 y = bounds->topLeft.y + (bounds->extent.y - FntCharHeight()) / 2;
RectangleType r;
MemHandle h;
Airline *air1;
h = DmQueryRecord(gDB, (UInt16) row);
if (h)
{
air1 = (Airline *) MemHandleLock(h);
WinDrawTruncChars(air1->airlineName, StrLen(air1->airlineName),
bounds->topLeft.x + 2, y, bounds->extent.x);
r = *bounds;
RctInsetRectangle(&r, 1);
WinDrawRectangleFrame(rectangleFrame, &r);
MemHandleUnlock(h);
}
}
Thanks for your help.
Thomas,
Tuesday, August 5, 2003, 7:23:52 AM, you wrote:
TD> Hello Boris,
TD> this is more fundamental:
TD> 1) It seems, you dont understand the meaning of sizeof(). This function is
TD> processed at compile-time and just inserts the length of a specific
TD> data-type. That means:
TD> sizeof(UInt8) == 1
TD> sizeof(UInt16) == 2
TD> sizeof(Char) == 1
TD> sizeof(Char*) == 4 (its a pointer and all pointers are 32 bit)
TD> what about your struct? : struct Airline
TD> sizeof(Airline) == 6 since its a UInt16 and a Char*
TD> the sizeof-function only works for datatypes not for memory-chunks.
TD> 2) when you assign a new chunk of memory to airlineName, it resides
TD> somewhere in memory but not at the address of air.airlineName.
TD> Thats why you have to create the new record like this:
TD> ulLen=sizeof(air.airlineID)+StrLen(air.airlineName)+1;
TD> h = DmNewRecord(gDB, &index, ulLen);
TD> and write it to the record like this
TD> // The ID; here sizeof() works
TD> err = DmWrite(p, 0, &(air.airlineID), sizeof(air.airlineID));
TD> // The Name; here it does not.
TD> err = DmWrite(p, sizeof(air.airlineID), air.airlineName,
TD> StrLen(air.airlineName)+1);
TD> Hope this helps,
TD> Thomas
TD> "Boris Epshteyn" <[EMAIL PROTECTED]> schrieb im Newsbeitrag
TD> news:[EMAIL PROTECTED]
>>
>> Unfortunately this does not work. :(
>> I've tried to write the record with one DmWrite, without any success:
>> err = DmWrite(p, 0, &air, sizeof(air));
>>
>> Boris
>>
>>
>>
>> TD> Hello Boris,
>>
>> TD> I think your problem is there:
>>
>> >>err = DmWrite(p, sizeof(air.airlineID), &(air.airlineName),
>> TD> sizeof(air.airlineName));
>>
>> TD> it should be like this:
>> TD> err = DmWrite(p, sizeof(air.airlineID), air.airlineName,
>> TD> StrLen(air.airlineName));
>>
>> TD> 1) air.airlineName is already a pointer since you aquired it by
TD> MemPtrNew
>> TD> 2) sizeof(air.airlineName) is wrong since this is only a sizeof(Char*)
TD> which
>> TD> is 4 byte, not the length of your string.
>>
>> TD> Thomas
>>
>> TD> "Boris Epshteyn" <[EMAIL PROTECTED]> schrieb im Newsbeitrag
>> TD> news:[EMAIL PROTECTED]
>> >>
>> >> Hi,
>> >>
>> >> I am trying to create a DB from the static data. In my AppStart, if DB
>> >> does not exists, I create it with four records. The records is defined
>> >> as following:
>> >> typedef struct Airline
>> >> {
>> >> UInt16 airlineID;
>> >> char *airlineName;
>> >> } Airline;
>> >>
>> >> Since my airlineName is variable length, I am allocating memory for
>> >> it, then using StrCopy populating it. Using DmWrite I am writing itto
>> >> the database. But when my temporary object gets released, data from the
>> >> DB also disappears. I would appreciate any advice. Or, may you can
>> >> suggest an application/utility to create DB for initial load from
>> >> static data. I have tried pdbc, but when POSE gives an error when
>> >> trying to load db into POSE. The code for my appStart is:
>> >>
>> >> static char * airlines[AIRLINE_COUNT] = {"Delta", "AA Airline",
>> TD> "Lufthansa", "United"};
>> >>
>> >> static Err AppStart(void)
>> >> {
>> >> MemHandle han;
>> >> Err err = 0;
>> >>
>> >> gDB = DmOpenDatabaseByTypeCreator('DATA', kCreator,
TD> dmModeReadWrite);
>> >> if (!gDB) {
>> >> err = DmGetLastErr();
>> >> if (err == dmErrCantFind) {
>> >> err = DmCreateDatabase(0, "AirlineTable-ABCD", kCreator,
TD> 'DATA',
>> TD> false);
>> >> FrmCustomAlert(alrtNODB, "Created?", NULL, NULL);
>> >> if (err == 0) {
>> >> FrmCustomAlert(alrtNODB, NULL, NULL, NULL);
>> >> gDB = DmOpenDatabaseByTypeCreator('DATA', kCreator,
>> TD> dmModeReadWrite);
>> >> if (gDB) {
>> >> UInt16 i;
>> >> // create initial records
>> >> for (i = 0;i < AIRLINE_COUNT && err == 0; i++) {
>> >> Airline air;
>> >> UInt16 index = dmMaxRecordIndex;
>> >> MemHandle h;
>> >> air.airlineID = i + 110;
>> >> air.airlineName = MemPtrNew(StrLen(airlines[i]) +
TD> 1);
>> >> if (air.airlineName != NULL)
>> >> {
>> >> StrCopy(air.airlineName, airlines[i]);
>> >> }
>> >> h = DmNewRecord(gDB, &index, sizeof(air));
>> >> if (!h)
>> >> err = DmGetLastErr();
>> >> else {
>> >> MemPtr p = MemHandleLock(h);
>> >> MemPtr tr;
>> >> err = DmWrite(p, 0, &(air.airlineID),
>> TD> sizeof(air.airlineID));
>> >> err = DmWrite(p, sizeof(air.airlineID),
>> TD> &(air.airlineName), sizeof(air.airlineName));
>> >> MemHandleUnlock(h);
>> >> DmReleaseRecord(gDB, index, true);
>> >> }
>> >> MemPtrFree(air.airlineName);
>> >> }
>> >> }
>> >> }
>> >> }
>> >> }
>> >> FrmCustomAlert(alrtNODB, "Exiting Init", NULL, NULL);
>> >> return err;
>> >> }
>> >>
>> >> --
>> >> Best regards,
>> >> Boris mailto:[EMAIL PROTECTED]
>> >>
>> >>
>> >>
>>
>>
>>
>>
>> mailto:[EMAIL PROTECTED]
>>
>>
>>
mailto:[EMAIL PROTECTED]
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