diff options
Diffstat (limited to 'lib/typesafe.h')
| -rw-r--r-- | lib/typesafe.h | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/lib/typesafe.h b/lib/typesafe.h index 3292b6ec8b..8eb59c33b7 100644 --- a/lib/typesafe.h +++ b/lib/typesafe.h @@ -783,6 +783,12 @@ struct thash_head { struct thash_item **entries; uint32_t count; + /* tabshift can be 0 if the hash table is empty and entries is NULL. + * otherwise it will always be 2 or larger because it contains + * the shift value *plus 1*. This is a trick to make HASH_SIZE return + * the correct value (with the >> 1) for tabshift == 0, without needing + * a conditional branch. + */ uint8_t tabshift; uint8_t minshift, maxshift; }; @@ -791,8 +797,11 @@ struct thash_head { ((1U << (tabshift)) >> 1) #define HASH_SIZE(head) \ _HASH_SIZE((head).tabshift) -#define _HASH_KEY(tabshift, val) \ - ((val) >> (33 - (tabshift))) +#define _HASH_KEY(tabshift, val) \ + ({ \ + assume((tabshift) >= 2 && (tabshift) <= 33); \ + (val) >> (33 - (tabshift)); \ + }) #define HASH_KEY(head, val) \ _HASH_KEY((head).tabshift, val) #define HASH_GROW_THRESHOLD(head) \ @@ -939,6 +948,8 @@ macro_pure size_t prefix ## _count(const struct prefix##_head *h) \ macro_pure bool prefix ## _member(const struct prefix##_head *h, \ const type *item) \ { \ + if (!h->hh.tabshift) \ + return NULL; \ uint32_t hval = item->field.hi.hashval, hbits = HASH_KEY(h->hh, hval); \ const struct thash_item *hitem = h->hh.entries[hbits]; \ while (hitem && hitem->hashval < hval) \ |