Heikki, * Heikki Linnakangas (heikki.linnakan...@iki.fi) wrote: > This patch alleviates that in two ways. First, instead of storing pointers > in the hash table, store 16-bit indexes into the hist_entries array. That > slashes the size of the hash table to 1/2 or 1/4 of the original, depending > on the pointer width. Secondly, adjust the size of the hash table based on > input size. For very small inputs, you don't need a large hash table to > avoid collisions.
The coverity scanner has a bit of an issue with this patch which, at
least on first blush, looks like a valid concern.
While the change in pg_lzcompress.c:pglz_find_match() to loop on:
while (hent != INVALID_ENTRY_PTR)
{
const char *ip = input;
const char *hp = hent->pos;
looks good, and INVALID_ENTRY_PTR is the address of the first entry in
the array (and can't be NULL), towards the end of the loop we do:
hent = hent->next;
if (hent)
...
Should we really be checking for 'hent != INVALID_ENTRY_PTR' here? If
not, and hent really can end up as NULL, then we're going to segfault
on the next loop due to the unchecked 'hent->pos' early in the loop.
If hent can never be NULL, then we probably don't need this check at
all.
Thanks,
Stephen
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