Re: [Qemu-block] [Qemu-devel] [PATCH v2 01/49] opts: produce valid command line in qemu_opts_print

[Eric Blake]

On 08/21/2015 09:36 AM, Kővágó, Zoltán wrote:
> This will let us print options in a format that the user would actually
> write it on the command line (foo=bar,baz=asd,etc=def), without
> prepending a spurious comma at the beginning of the list, or quoting
> values unnecessarily.  This patch provides the following changes:
> * write id=, if the option has an id
> * do not print separator before the first element
> * do not quote string arguments
> * properly escape commas (,) for QEMU
> 
> Reviewed-by: Markus Armbruster <address@hidden>
> Reviewed-by: Stefan Hajnoczi <address@hidden>
> Reviewed-by: Marc-André Lureau <address@hidden>
> Signed-off-by: Kővágó, Zoltán <address@hidden>
> ---

> +++ b/util/qemu-option.c
> @@ -730,14 +730,35 @@ void qemu_opts_del(QemuOpts *opts)
>      g_free(opts);
>  }
>  
> -void qemu_opts_print(QemuOpts *opts, const char *sep)
> +/* print value, escaping any commas in value */
> +static void escaped_print(const char *value)
> +{
> +    const char *ptr;
> +
> +    for (ptr = value; *ptr; ++ptr) {
> +        if (*ptr == ',') {
> +            putchar(',');
> +        }
> +        putchar(*ptr);
> +    }

I guess this not in a hot path.  (If it were, I might suggest using
strchr() to skip to the next command, and fwrite() to output blocks of
data between commas, rather than putchar() at a time; but unless it
shows up in a benchmark that might be premature optimization)

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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