res/res_rtp_asterisk.c: Fixing possible divide by zero

Currently, when the Asterisk calculates rtp statistics, it uses
sample_count as a unsigned integer parameter. This would be fine
for most of cases, but in case of large enough number of sample_count,
this might be causing the divide by zero error.

ASTERISK-28321

Change-Id: If7e0629abaceddd2166eb012456c53033ea26249

diff --git a/res/res_rtp_asterisk.c b/res/res_rtp_asterisk.c
index c5d557ec1e6c966ef353485ae6dbf4729ba6e7b6..909d82a81644847dd95ffa606ca960630847bad9 100644 (file)
--- a/res/res_rtp_asterisk.c
+++ b/res/res_rtp_asterisk.c
@@ -2755,6 +2755,14 @@ static double normdev_compute(double normdev, double sample, unsigned int sample
        normdev = normdev * sample_count + sample;
        sample_count++;
 
+       /*
+        It's possible the sample_count hits the maximum value and back to 0.
+        Set to 1 to prevent the divide by zero crash if the sample_count is 0.
+        */
+       if (sample_count == 0) {
+               sample_count = 1;
+       }
+
        return normdev / sample_count;
 }
 
@@ -2771,6 +2779,14 @@ static double stddev_compute(double stddev, double sample, double normdev, doubl
        stddev = sample_count * stddev;
        sample_count++;
 
+       /*
+        It's possible the sample_count hits the maximum value and back to 0.
+        Set to 1 to prevent the divide by zero crash if the sample_count is 0.
+        */
+       if (sample_count == 0) {
+               sample_count = 1;
+       }
+
        return stddev +
                ( sample_count * SQUARE( (sample - normdev) / sample_count ) ) +
                ( SQUARE(sample - normdev_curent) / sample_count );