Re: [igt-dev] [PATCH i-g-t v2 1/2] runner: Ensure generated json is properly UTF8-encoded

[Petri Latvala <petri.latvala@intel.com>]

On Wed, Jan 15, 2020 at 12:29:57PM +0200, Arkadiusz Hiler wrote:
> On Fri, Jan 10, 2020 at 02:06:41PM +0200, Petri Latvala wrote:
> > Sometimes tests output garbage (e.g. due to extreme occurrences of
> > https://gitlab.freedesktop.org/drm/igt-gpu-tools/issues/55) but we
> > need to present the garbage as results.
> > 
> > We already ignore any test output after the first \0, and for the rest
> > of the bytes that are not directly UTF-8 as-is, we can quite easily
> > represent them with two-byte UTF-8 encoding.
> > 
> > libjson-c already expects the string you feed it through
> > json_object_new_string* functions to be UTF-8.
> > 
> > v2: Rebase, adjust for dynamic subtest parsing
> > 
> > Signed-off-by: Petri Latvala <petri.latvala@intel.com>
> > Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
> > Reviewed-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com> #v1
> > ---
> >  runner/resultgen.c | 45 +++++++++++++++++++++++++++++++++++----------
> >  1 file changed, 35 insertions(+), 10 deletions(-)
> > 
> > diff --git a/runner/resultgen.c b/runner/resultgen.c
> > index 2c8a55da..105ec887 100644
> > --- a/runner/resultgen.c
> > +++ b/runner/resultgen.c
> > @@ -405,15 +405,40 @@ static void free_matches(struct matches *matches)
> >  	free(matches->items);
> >  }
> >  
> > +static struct json_object *new_escaped_json_string(const char *buf, size_t len)
> > +{
> > +	struct json_object *obj;
> > +	char *str = NULL;
> > +	size_t strsize = 0;
> > +	size_t i;
> > +
> > +	for (i = 0; i < len; i++) {
> > +		if (buf[i] > 0 && buf[i] < 128) {
> > +			str = realloc(str, strsize + 1);
> > +			str[strsize] = buf[i];
> > +			++strsize;
> > +		} else {
> > +			/* Encode > 128 character to UTF-8. */
> > +			str = realloc(str, strsize + 2);
> > +			str[strsize] = ((unsigned char)buf[i] >> 6) | 0xC0;
> > +			str[strsize + 1] = ((unsigned char)buf[i] & 0x3F) | 0x80;
> > +			strsize += 2;
> > +		}
> > +	}
> > +
> > +	obj = json_object_new_string_len(str, strsize);
> > +	free(str);
> > +
> > +	return obj;
> > +}
> 
> Looking at this for the 3rd time I wonder whether this realloc() every
> character is not too costly, especially that we do that for every field.

Do you mean as opposed to allocating a larger chunk at a time? realloc
already does this.

With a quick whipup test, realloc()ing same pointer repeatedly for
sizes 1 to 0xffffff (randomly chosen end point) with increments of 1,
the returned pointer was different a total of 29 times. For funzies, a
total of 9 times when stdout was a pipe instead of tty.

> Have you tried comparing times igt_results for some intermediates with
> large dmesgs?

I can do that but I won't be expecting much difference.


-- 
Petri Latvala
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