mirrors/emacs
1
Fork 0
mirror of git://git.sv.gnu.org/emacs.git synced 2026-01-03 02:31:03 -08:00
Code Issues Projects Releases Wiki Activity

Make sure that probe sequence visits all buckets in the hash table by (a) ensuring that hash tables are a power of 2 in size; (b) ensuring that the probe step is odd.

Browse source 
Copied from Perforce
 Change: 180252
 ServerID: perforce.ravenbrook.com
This commit is contained in:
Gareth Rees 2012-11-02 11:16:10 +00:00
parent bf1480c169
commit e42bab4f76
1 changed files with 16 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

26
mps/example/scheme/scheme-malloc.c
View file

@ -414,12 +414,14 @@ static obj_t make_buckets(size_t length)
static obj_t make_table(size_t length)
{
size_t size = sizeof(table_s);
size_t l, size = sizeof(table_s);
obj_t obj = (obj_t)malloc(size);
if(obj == NULL) error("out of memory");
total += size;
obj->table.type = TYPE_TABLE;
obj->table.buckets = make_buckets(length);
/* round up to next power of 2 */
for(l = 1; l < length; l *= 2);
obj->table.buckets = make_buckets(l);
return obj;
}
@ -487,15 +489,17 @@ static unsigned long hash(const char *s) {
*/
static obj_t *find(char *string) {
unsigned long i, h;
unsigned long i, h, probe;
h = hash(string) & (symtab_size-1);
i = h;
h = hash(string);
probe = (h >> 8) | 1;
h &= (symtab_size-1);
i = h;
do {
if(symtab[i] == NULL ||
strcmp(string, symtab[i]->symbol.string) == 0)
return &symtab[i];
i = (i+h+1) & (symtab_size-1);
i = (i+probe) & (symtab_size-1);
} while(i != h);
return NULL;
@ -552,12 +556,14 @@ static obj_t intern(char *string) {
*/
static struct bucket_s *buckets_find(obj_t buckets, obj_t key)
{
union {char s[sizeof(obj_t) + 1]; void *addr;} u = {""};
unsigned long i, h;
union {char s[sizeof(obj_t) + 1]; obj_t addr;} u = {""};
unsigned long i, h, probe;
struct bucket_s *result = NULL;
assert(TYPE(buckets) == TYPE_BUCKETS);
u.addr = key;
h = hash(u.s) & (buckets->buckets.length-1);
h = hash(u.s);
probe = (h >> 8) | 1;
h &= (buckets->buckets.length-1);
i = h;
do {
struct bucket_s *b = &buckets->buckets.bucket[i];
@ -565,7 +571,7 @@ static struct bucket_s *buckets_find(obj_t buckets, obj_t key)
return b;
if(result == NULL && b->key == obj_deleted)
result = b;
i = (i+h+1) & (buckets->buckets.length-1);
i = (i+probe) & (buckets->buckets.length-1);
} while(i != h);
return result;
}