tally: don't add extra bucket unless buckets == 0
authorRusty Russell <rusty@rustcorp.com.au>
Sat, 25 Sep 2010 02:15:12 +0000 (11:45 +0930)
committerRusty Russell <rusty@rustcorp.com.au>
Sat, 25 Sep 2010 02:15:12 +0000 (11:45 +0930)
That way we match our comment about optimal tally_new() arg matching histogram height.

ccan/tally/tally.c
ccan/tally/test/run-renormalize.c

index 9f2a4591f8c3ce5ddd05b8f29702ff2761784dad..b3ac863ba68119aedc59973b72c1d3716bb35867 100644 (file)
@@ -16,25 +16,28 @@ struct tally {
        size_t total[2];
        /* This allows limited frequency analysis. */
        unsigned buckets, step_bits;
-       size_t counts[1 /* [buckets] */ ];
+       size_t counts[1 /* Actually: [buckets] */ ];
 };
 
 struct tally *tally_new(unsigned buckets)
 {
        struct tally *tally;
 
+       /* There is always 1 bucket. */
+       if (buckets == 0)
+               buckets = 1;
+
        /* Check for overflow. */
        if (buckets && SIZE_MAX / buckets < sizeof(tally->counts[0]))
                return NULL;
-       tally = malloc(sizeof(*tally) + sizeof(tally->counts[0])*buckets);
+       tally = malloc(sizeof(*tally) + sizeof(tally->counts[0])*(buckets-1));
        if (tally) {
                tally->max = ((size_t)1 << (SIZET_BITS - 1));
                tally->min = ~tally->max;
                tally->total[0] = tally->total[1] = 0;
-               /* There is always 1 bucket. */
-               tally->buckets = buckets+1;
+               tally->buckets = buckets;
                tally->step_bits = 0;
-               memset(tally->counts, 0, sizeof(tally->counts[0])*(buckets+1));
+               memset(tally->counts, 0, sizeof(tally->counts[0])*buckets);
        }
        return tally;
 }
@@ -422,7 +425,7 @@ char *tally_histogram(const struct tally *tally,
        } else {
                /* We create a temporary then renormalize so < height. */
                /* FIXME: Antialias properly! */
-               tmp = tally_new(tally->buckets-1);
+               tmp = tally_new(tally->buckets);
                if (!tmp)
                        return NULL;
                tmp->min = tally->min;
index 5ec8b6780d41fa988e910a8001edaf1346306e07..7c141528d236b82335edf4923fd7117f252059f3 100644 (file)
@@ -3,7 +3,7 @@
 
 int main(void)
 {
-       struct tally *tally = tally_new(1);
+       struct tally *tally = tally_new(2);
 
        plan_tests(4);
        tally->min = 0;