just do (char *)your_void_ptr++
Rik
> -----Original Message-----
> From: Jacob Vitas Vogelstein [SMTP:[EMAIL PROTECTED]]
> Sent: 25 September 2000 15:26
> To: Palm Developer Forum
> Subject: Re: Which pointer type to use when accessing a record?
>
> I guess what I'm basically asking is, "is there any way to defeat the
> compiler's 'smart' pointer math and just add byte values to a pointer?"
>
> Thanks again
>
> "Jacob Vitas Vogelstein" <[EMAIL PROTECTED]> wrote in message
> news:25268@palm-dev-forum...
> >
> > This question stems from my general inexperience with the C programming
> > language... I'll state the question first, then my example code. After I
> get
> > a record handle with DmQueryRecord, I lock it down and get a VoidPtr
> from
> > MemHandleLock. This pointer points to the start of my record in the
> > database, and I want to access the second field of the database, in my
> case,
> > at an offset of sizeof(WChar). But when I try to access that field by
> > saying: *(myPtr + myOffset), the compiler complains that it can't add
> > anything to a VoidPtr type. So I have to cast it as something. Depending
> on
> > how I cast it, I get different values returned to me for both the
> *(myPtr)
> > variable and the (*myPtr + myOffset) variable. Since I may have many
> > different types of data in my database, what's the right way to cast the
> > pointer to correctly access the variables? Thanks for your help. Code
> > follows.
> >
> >
> > I defined the properties of a record in my database like this:
> >
> > #define DB_PEN_DOWN_START 0
> > #define DB_PEN_DOWN_SIZE sizeof(WChar)
> > #define DB_PEN_UP_START (DB_PEN_DOWN_START + DB_PEN_DOWN_SIZE)
> > #define DB_PEN_UP_SIZE sizeof(WChar)
> > #define DB_PENSTROKE_RECORD_SIZE (DB_PEN_DOWN_SIZE + DB_PEN_UP_SIZE)
> >
> >
> > And now I want to access the information. So I call:
> >
> > VoidHand hrecord;
> > VoidPtr precord;
> > cursor = 0;
> > hrecord = DmQueryRecord( prevAppHackDB, cursor );
> > precord = MemHandleLock( hrecord );
> >
> >
> > And finally, I want to write the value of the record into two fields on
> my
> > form, using a home-made function called 'StrToField' that takes the name
> of
> > the field, the size of the data to write, and the data itself as
> parameters.
> >
> > WChar temp;
> > char tempstr[10];
> > temp = *((WCharPtr)precord + DB_PEN_DOWN_START); // DB_PEN_DOWN_START =
> 0
> > StrIToH(tempstr, temp);
> > StrToField(ControlPanelFormStartBtnField, sizeof(tempstr), tempstr); //
> > RETURNS THE RIGHT THING
> > temp = *((WCharPtr)precord + DB_PEN_UP_START); // DB_PEN_UP_START =
> > sizeof(WChar)
> > StrIToH(tempstr, temp);
> > StrToField(ControlPanelFormEndBtnField, sizeof(tempstr), tempstr); //
> > RETURNS THE WRONG THING
> >
> > MemHandleUnlock(hrecord);
> >
> >
> >
> >
>
>
>
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