This is a source of the problem ...
newSize += StrLen((Char *) neu_titelText) + 1; // you are adding
actual buffer length
when in fact what you mean is ...
newSize += sizeof(char *) // this is correct since the struct contains
a pointer, not the
actual buffer
Another way to think of it is, that the size of the
Veranstaltung structure is actually a constant.
On Sunday, March 17, 2002, at 03:52 AM, Dyk Corman wrote:
> Hi!
>
> Could anybody please help me with this code?
> I've been trying to fix the problem for 2 days, but didn't succeed..
>
> I have a structure defined as follows:
>
> typedef struct {
> UInt32 id;
> Boolean selected;
> VeranstaltungDateTimeType date;
> const char *titel;
> const char *location;
> }Veranstaltung;
>
>
> I would like to change the titel which is a text field, but I'm always
> getting error messages: "Error with DmWriteCheck"
>
> That's the code (based on the ToDo-example)
>
> the new titel is saved in new_titelText.
>
> recordH = DmQueryRecord(db, recordNum);
> recordP = (Veranstaltung*) MemHandleLock(recordH)
>
> // Calculate the size of the changed record. First,
> // find the size of the data used from the old record.
> newSize = sizeof (UInt32) + 1 + sizeof(Boolean) + 1 +
> sizeof(VeranstaltungDateTimeType) + 1;
> newSize += StrLen((Char *) neu_titelText) + 1;
> newSize += StrLen(recordP->location) + 1;
>
> // If the new description is longer, expand the record.
> curSize = MemPtrSize (recordP);
>
> // The interesting part is that even when I'm just adding one
> character to the title,
> // the newSize is about 94, when the curSize is about 24...
>
> if (newSize > curSize)
> {
> MemPtrUnlock (recordP);
> err = MemHandleResize (recordH, newSize);
> recordP = (Veranstaltung*) MemHandleLock (recordH);
> }
>
> // Move the location field.
> offset = sizeof(UInt32) + sizeof(Boolean) +
> sizeof(VeranstaltungDateTimeType)
> + 1 + StrLen (neu_titelText) + 1;
> c = recordP->titel;
> c += StrLen(c) + 1;
> DmWrite (recordP, offset, c, StrLen(c) + 1);
>
>
> // Write the new titel field.
> offset = sizeof(UInt32) + sizeof(Boolean) +
> sizeof(VeranstaltungDateTimeType) + 1;
> DmStrCopy (recordP, offset, neu_titelText);
>
> // If the new description is shorter, shrink the record.
> if (newSize < curSize)
> MemHandleResize (recordH, newSize);
>
>
> Does anybody have any idea why this code doesn't work and
> why the newSize is much more than the curSize even if I'm just
> changing some characters???
>
> Many many thanks,
>
> Dyk
>
>
>
>
>
>
>
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