[PATCH] lib: fwts_klog: optimize regex scanning

[Keng-Yu Lin]

On Tue, Jul 24, 2012 at 3:55 AM, Colin King <colin.king at canonical.com> wrote:
> From: Colin Ian King <colin.king at canonical.com>
>
> pcre allows one to optimize regex matching and without it i386
> systems seem to randomly break (which isn't expected) on some
> regex pattern matches.  So, use the pcre study and also add some
> safe-guarding in the code to ensure we only compare regexes if
> the compiled form is not NULL.
>
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> ---
>  src/lib/include/fwts_klog.h |    1 +
>  src/lib/src/fwts_klog.c     |   26 ++++++++++++++++++++++----
>  2 files changed, 23 insertions(+), 4 deletions(-)
>
> diff --git a/src/lib/include/fwts_klog.h b/src/lib/include/fwts_klog.h
> index 3bbed5f..a47cf7a 100644
> --- a/src/lib/include/fwts_klog.h
> +++ b/src/lib/include/fwts_klog.h
> @@ -44,6 +44,7 @@ typedef struct {
>          const char *pattern;
>         const char *advice;
>         pcre *re;
> +       pcre_extra *extra;
>  } fwts_klog_pattern;
>
>  typedef void (*fwts_klog_progress_func)(fwts_framework *fw, int percent);
> diff --git a/src/lib/src/fwts_klog.c b/src/lib/src/fwts_klog.c
> index 93dbb06..ea713e8 100644
> --- a/src/lib/src/fwts_klog.c
> +++ b/src/lib/src/fwts_klog.c
> @@ -230,7 +230,8 @@ void fwts_klog_scan_patterns(fwts_framework *fw,
>                 int matched = 0;
>                 switch (pattern->compare_mode) {
>                 case FWTS_COMPARE_REGEX:
> -                       matched = (pcre_exec(pattern->re, NULL, line, strlen(line), 0, 0, vector, 1) == 0);
> +                       if (pattern->re)
> +                               matched = (pcre_exec(pattern->re, pattern->extra, line, strlen(line), 0, 0, vector, 1) == 0);
>                         break;
>                 case FWTS_COMPARE_STRING:
>                 default:
> @@ -354,8 +355,16 @@ static int fwts_klog_check(fwts_framework *fw,
>                 if ((patterns[i].advice = fwts_json_str(fw, table, i, obj, "advice")) == NULL)
>                         goto fail;
>
> -               if ((patterns[i].re = pcre_compile(patterns[i].pattern, 0, &error, &erroffset, NULL)) == NULL)
> +               if ((patterns[i].re = pcre_compile(patterns[i].pattern, 0, &error, &erroffset, NULL)) == NULL) {
>                         fwts_log_error(fw, "Regex %s failed to compile: %s.", patterns[i].pattern, error);
> +                       patterns[i].re = NULL;
> +               } else {
> +                       patterns[i].extra = pcre_study(patterns[i].re, 0, &error);
> +                       if (error != NULL) {
> +                               fwts_log_error(fw, "Regex %s failed to optimize: %s.", patterns[i].pattern, error);
> +                               patterns[i].re = NULL;
> +                       }
> +               }
>         }
>         /* We've now collected up the scan patterns, lets scan the log for errors */
>         ret = fwts_klog_scan(fw, klog, fwts_klog_scan_patterns, progress, patterns, errors);
> @@ -364,6 +373,8 @@ fail:
>         for (i=0; i<n; i++)
>                 if (patterns[i].re)
>                         pcre_free(patterns[i].re);
> +               if (patterns[i].extra)
> +                       pcre_free(patterns[i].extra);
>         free(patterns);
>  fail_put:
>         json_object_put(klog_objs);
> @@ -398,15 +409,22 @@ static void fwts_klog_regex_find_callback(fwts_framework *fw, char *line, int re
>         const char *error;
>         int erroffset;
>         pcre *re;
> +       pcre_extra *extra;
>         int rc;
>         int vector[1];
>
>         re = pcre_compile(pattern, 0, &error, &erroffset, NULL);
>         if (re != NULL) {
> -               rc = pcre_exec(re, NULL, line, strlen(line), 0, 0, vector, 1);
> +               extra = pcre_study(re, 0, &error);
> +               if (error)
> +                       return;
> +
> +               rc = pcre_exec(re, extra, line, strlen(line), 0, 0, vector, 1);
> +               if (extra)
> +                       free(extra);
> +               pcre_free(re);
>                 if (rc == 0)
>                         (*match)++;
> -               pcre_free(re);
>         }
>  }
>
> --
> 1.7.10.4
>
Acked-by: Keng-Yu Lin <kengyu at canonical.com>
(LP: #1028031)