On Wed, 11 Jul 2007, Brian Downing wrote:
> + while (window_memory_limit &&
> + window_memory_usage > window_memory_limit &&
> + count > 1) {
> + uint32_t tail = idx - count;
> + if (tail > idx) {
> + tail += window + 1;
> + tail %= window;
> + }
> + free_unpacked(array + tail);
> + count--;
> + }
This is bogus. Suppose window = 10 and only array entries 8, 9, 0, 1
and 2 are populated. In that case idx = 2 and count should be 4 (not
counting the current entry yet). You want to evict entry 8.
-- tail = 2 - 4 = -2 (or a big uint32_t value)
-- tail > idx is true
-- tail += window + 1 -> -2 + 10 + 1 = 9
-- tail %= window is useless
-- you free entry 9 instead of entry 8.
Instead, you should do:
tail = idx - count;
if (tail > idx)
tail += window;
or even:
tail = (idx + window - count) % window;
> next:
> idx++;
> + if (count < window)
> + count++;
And of course you want:
if (count + 1 < window)
count++;
So not to count the new entry when the window gets full.
Nicolas
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