null pointer question???

[nysfp@hotmail.com]

unsigned char *Buf;
Buf = new unsigned char[100];
unsigned long sz = 100 * sizeof(unsigned char);
Read(Buf,&sz);
Occassional app crash at Read(Buf,&sz) call.
maybe empty data, null Buf??.
what's best way?.

Lib:
Read ( unsigned char * Buf ,
unsigned long * BufSize );




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[Jakob Bieling]

Re: null pointer question???

"nysfp@hotmail. com" <u557861328@spa wnkill.ip-mobilphone.net> wrote in
message news:l.10650696 89.1681823730@[63.127.215.130]...[color=blue]
> unsigned char *Buf;
> Buf = new unsigned char[100];
> unsigned long sz = 100 * sizeof(unsigned char);
> Read(Buf,&sz);
> Occassional app crash at Read(Buf,&sz) call.
> maybe empty data, null Buf??.[/color]

Maybe, yes. Maybe the error lies elsewhere. The point is that the error
obviously occurs inside 'Read' and you have not shown anything about that
function. If it is function of a third-party library, you should try asking
the developers or a forum dedicated to this library. Otherwise, please show
the relevant code of that function.

hth
--
jb

(replace y with x if you want to reply by e-mail)

[Kevin Goodsell]

Re: null pointer question???

nysfp@hotmail.c om wrote:
[color=blue]
> unsigned char *Buf;
> Buf = new unsigned char[100];
> unsigned long sz = 100 * sizeof(unsigned char);[/color]

sizeof(unsigned char) is a fancy way of writing 1.
[color=blue]
> Read(Buf,&sz);
> Occassional app crash at Read(Buf,&sz) call.
> maybe empty data, null Buf??.
> what's best way?.
>
> Lib:
> Read ( unsigned char * Buf ,
> unsigned long * BufSize );[/color]

Why is this a pointer? Are you sure the library is not modifying your
size, causing it to be incorrect when you call this function later?

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

[Karl Heinz Buchegger]

Re: null pointer question???



"nysfp@hotmail. com" wrote:[color=blue]
>
> unsigned char *Buf;
> Buf = new unsigned char[100];
> unsigned long sz = 100 * sizeof(unsigned char);
> Read(Buf,&sz);
> Occassional app crash at Read(Buf,&sz) call.
> maybe empty data, null Buf??.
> what's best way?.
>
> Lib:
> Read ( unsigned char * Buf ,
> unsigned long * BufSize );
>[/color]

I think you are using your library the wrong way.
An interface like the above is usually feed like this:

unsigned char *Buf;
unsigned long BuffSize;

Buf = new unsigned char [ 100 ];
BuffSize = 100;

Read( Buf, &BuffSize );

and read will modify BuffSize to the number of unsigned chars
it put into Buf. But it wants to know in the beginning how large
that buffer actually is, in order to avoid what you have seen:
accessing the array out of bounds and thus end up in an access
violation.

Consult your documentation, if that's what Read does.

--
Karl Heinz Buchegger
kbuchegg@gascad .at

[Karl Heinz Buchegger]

Re: null pointer question???



Karl Heinz Buchegger wrote:[color=blue]
>
> "nysfp@hotmail. com" wrote:[color=green]
> >
> > unsigned char *Buf;
> > Buf = new unsigned char[100];
> > unsigned long sz = 100 * sizeof(unsigned char);
> > Read(Buf,&sz);
> > Occassional app crash at Read(Buf,&sz) call.
> > maybe empty data, null Buf??.
> > what's best way?.
> >
> > Lib:
> > Read ( unsigned char * Buf ,
> > unsigned long * BufSize );
> >[/color]
>
> I think you are using your library the wrong way.
> An interface like the above is usually feed like this:
>
> unsigned char *Buf;
> unsigned long BuffSize;
>
> Buf = new unsigned char [ 100 ];
> BuffSize = 100;
>
> Read( Buf, &BuffSize );
>[/color]

Ooops. Sorry. At reread I notices that thats exactly
what you are doing.

--
Karl Heinz Buchegger
kbuchegg@gascad .at