ringbuffers on os9

[vvvv]

this is part of a program i am writing to receive data at interrupt time and
put it into a ringbuffer. i am crashing! can somebody point out my mistake?
does it have to do with Handles?

here is my ringbuffer:
typedef struct RINGBUFFER_Tag{
Handle buff;
unsigned long buffSize;
unsigned long buffCount;
int wError;
MYTHING* buffStart;
MYTHING* buffEnd;
MYTHING* buffHead;
MYTHING* buffTail;
} RINGBUFFER;


on program start, i call MakeBuffer(500):

long MakeBuffer(int size){
inbuffer = new RINGBUFFER;
inbuffer->buff = NewHandle(size * sizeof(MYTHING));
HLock(inbuffer->buff);

inbuffer->buffCount = 0L;
inbuffer->buffSize = size;
inbuffer->buffStart = (MYTHING *)inbuffer->buff;
inbuffer->buffEnd = (MYTHING *)inbuffer->buff + inbuffer->buffSize;
inbuffer->buffTail =(MYTHING *)inbuffer->buff;
inbuffer->buffHead = (MYTHING *)inbuffer->buff;

// i was DebugStr-ing here to see if there was MemErr(), and wasn't
getting any errors
// is there a better way of testing here than that?
return 0;
}



at interrupt time, i receive: MYTHING* pkt in a callback.

i process pkt like this at interrupt time in my callback proc:

MYTHING incoming = (MYTHING)*pkt;
(MYTHING)*inbuffer->buffHead = incoming;// i tried casting about 10 diff
ways, no luck

++inbuffer->buffHead;
++inbuffer->buffCount;

if(inbuffer->buffHead >=inbuffer->buffEnd)
inbuffer->buffHead = inbuffer->buffStart;

I crash at this point. help!

vvvv

[Sean McBride]

In article <2vg3b.61699$Sq.10740812@twister.nyc.rr.com>,
"vvvv" <noone@nowhere.com> wrote:

> this is part of a program i am writing to receive data at interrupt time and
> put it into a ringbuffer. i am crashing! can somebody point out my mistake?
> does it have to do with Handles?

<http://developer.apple.com/documentation/mac/Memory/Memory-62.html>
says:

"Note that Memory Manager routines like HLock return their results via
MemError and therefore should not be called in interrupt code."

You have to be realy careful what you call at interrupt time.

[vvvv]

i redid my ringbuffer to have NewPtr instead of newhandle, and all the
problems went away.

which begs the question...why?

memory is NOT easy!

vvvv


"Manfred Lippert" <mani@mani.de> wrote in message
news:BB7504AD.192B4%mani@mani.de...

> > Handle buff;
> > [...]
> > MYTHING* buffStart;
> > [...]
> > inbuffer->buffStart = (MYTHING *)inbuffer->buff;

>
> A Mac Handle is a "pointer to a pointer", so I think you have to write the
> following here (and on some other places):
>
> inbuffer->buffStart = (MYTHING *)*(inbuffer->buff);
>
> Bye,
> Mani
>

[Dmitry Markman]

On 8/30/03 1:01, in article BB75A803.6CDE%dimamarkman@attbi.com, "Dmitry
Markman" <dimamarkman@attbi.com> wrote:

> typedef *Ptr Handle

sorry should be

typedef Ptr * Handle;

Dmitry Markman

[Frederick Cheung]

On Sat, 30 Aug 2003, vvvv wrote:

> i redid my ringbuffer to have NewPtr instead of newhandle, and all the
> problems went away.
>
> which begs the question...why?

Because a pointer is not the same thing as a handle.

Fred