reinterpret or static_cast?

[Frank A. Uepping]

Hi,
look at this function, which does some low-level IO.

void writen(int fd, const void* data, size_t size)
{
while (size) {
int n = write(fd, data, size);
if (n < 0)
throw logic_error...

static_cast<con st char*>(data) += n; // reinterpret_cas t?
size -= n;
}
}

Here it is necessary to do a cast in order to do some pointer arithmetic.
Is the static_cast or the reinterpret_cas t appropriate?

/FAU

[Ron Natalie]

Re: reinterpret or static_cast?


"Frank A. Uepping" <null.0.fau@spa mgourmet.com> wrote in message news:bpgme4$qpv $08$1@news.t-online.com...
[color=blue]
> Here it is necessary to do a cast in order to do some pointer arithmetic.
> Is the static_cast or the reinterpret_cas t appropriate?[/color]

I'd prefer static_cast (in it's undo defined conversions role), but I don't know that
it is more appropriate than reinterpret_cas t in this case.

[Andrey Tarasevich]

Re: reinterpret or static_cast?

Frank A. Uepping wrote:[color=blue]
> Hi,
> look at this function, which does some low-level IO.
>
> void writen(int fd, const void* data, size_t size)
> {
> while (size) {
> int n = write(fd, data, size);
> if (n < 0)
> throw logic_error...
>
> static_cast<con st char*>(data) += n; // reinterpret_cas t?[/color]

This will not even compile. The result of this cast in an rvalue.
Operator '+=' cannot be applied to an rvalue. Most likely is was
supposed to be

static_cast<con st char*&>(data) += n

But I don't think this is a valid technique, regardless of the cast
operator used. The more proper way to do this would be the following

data = static_cast<con st char*>(data) + n;

[color=blue]
> size -= n;
> }
> }
>
> Here it is necessary to do a cast in order to do some pointer arithmetic.
> Is the static_cast or the reinterpret_cas t appropriate?
> ...[/color]

--
Best regards,
Andrey Tarasevich