Re: [Qemu-devel] [PATCH 18/19] nbd/client: refactor TRACE of NBD_MAGIC

[Eric Blake]

On 05/30/2017 09:30 AM, Vladimir Sementsov-Ogievskiy wrote:
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
>  nbd/client.c | 26 +++++++++++++++++---------
>  1 file changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/nbd/client.c b/nbd/client.c
> index 3d15596120..52f7981c9c 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -426,6 +426,21 @@ static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
>      return QIO_CHANNEL(tioc);
>  }
>  
> +static const char *nbd_magic_to_string(char *out, const char *in,
> +                                       size_t count)
> +{
> +    size_t i;
> +
> +    for (i = 0; i < count; ++i) {
> +        if (in[i] == '\0') {
> +            out[i] = '\0';
> +            break;
> +        }
> +        out[i] = qemu_isprint(in[i]) ? in[i] : '.';
> +    }
> +
> +    return out;
> +}

Do we really need this?

> -    TRACE("Magic is %c%c%c%c%c%c%c%c",
> -          qemu_isprint(buf[0]) ? buf[0] : '.',
> -          qemu_isprint(buf[1]) ? buf[1] : '.',
> -          qemu_isprint(buf[2]) ? buf[2] : '.',
> -          qemu_isprint(buf[3]) ? buf[3] : '.',
> -          qemu_isprint(buf[4]) ? buf[4] : '.',
> -          qemu_isprint(buf[5]) ? buf[5] : '.',
> -          qemu_isprint(buf[6]) ? buf[6] : '.',
> -          qemu_isprint(buf[7]) ? buf[7] : '.');
> +    TRACE("Magic is %s", nbd_magic_to_string(print_buf, buf, 9));

Would it be any simpler to just print the received magic as a 64-bit
number in hex, instead of trying to string-ize it?  Either the client
sends the right magic (the usual case), so we don't need to waste time
string-izing it, or the client is bogus and sent us garbage (where
printing a hex value is just as efficient as string-izing things to see
what the garbage actually was).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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