#include <assert.h>
#include <limits.h>
#include <sys/time.h>
+#include <ctype.h>
#include "dict.h"
#include "zmalloc.h"
/* Using dictEnableResize() / dictDisableResize() we make possible to
* enable/disable resizing of the hash table as needed. This is very important
* for Redis, as we use copy-on-write and don't want to move too much memory
- * around when there is a child performing saving operations. */
+ * around when there is a child performing saving operations.
+ *
+ * Note that even when dict_can_resize is set to 0, not all resizes are
+ * prevented: an hash table is still allowed to grow if the ratio between
+ * the number of elements and the buckets > dict_force_resize_ratio. */
static int dict_can_resize = 1;
+static unsigned int dict_force_resize_ratio = 5;
/* -------------------------- private prototypes ---------------------------- */
return key;
}
+static int dict_hash_function_seed = 5381;
+
+void dictSetHashFunctionSeed(unsigned int seed) {
+ dict_hash_function_seed = seed;
+}
+
+unsigned int dictGetHashFunctionSeed(void) {
+ return dict_hash_function_seed;
+}
+
/* Generic hash function (a popular one from Bernstein).
* I tested a few and this was the best. */
unsigned int dictGenHashFunction(const unsigned char *buf, int len) {
- unsigned int hash = 5381;
+ unsigned int hash = dict_hash_function_seed;
while (len--)
hash = ((hash << 5) + hash) + (*buf++); /* hash * 33 + c */
return hash;
}
+/* And a case insensitive version */
+unsigned int dictGenCaseHashFunction(const unsigned char *buf, int len) {
+ unsigned int hash = dict_hash_function_seed;
+
+ while (len--)
+ hash = ((hash << 5) + hash) + (tolower(*buf++)); /* hash * 33 + c */
+ return hash;
+}
+
/* ----------------------------- API implementation ------------------------- */
/* Reset an hashtable already initialized with ht_init().
}
/* Resize the table to the minimal size that contains all the elements,
- * but with the invariant of a USER/BUCKETS ration near to <= 1 */
+ * but with the invariant of a USER/BUCKETS ratio near to <= 1 */
int dictResize(dict *d)
{
int minimal;
if (dictIsRehashing(d) || d->ht[0].used > size)
return DICT_ERR;
+ /* Allocate the new hashtable and initialize all pointers to NULL */
n.size = realsize;
n.sizemask = realsize-1;
- n.table = zmalloc(realsize*sizeof(dictEntry*));
+ n.table = zcalloc(realsize*sizeof(dictEntry*));
n.used = 0;
- /* Initialize all the pointers to NULL */
- memset(n.table, 0, realsize*sizeof(dictEntry*));
-
/* Is this the first initialization? If so it's not really a rehashing
* we just set the first hash table so that it can accept keys. */
if (d->ht[0].table == NULL) {
/* Note that rehashidx can't overflow as we are sure there are more
* elements because ht[0].used != 0 */
+ assert(d->ht[0].size > (unsigned)d->rehashidx);
while(d->ht[0].table[d->rehashidx] == NULL) d->rehashidx++;
de = d->ht[0].table[d->rehashidx];
/* Move all the keys in this bucket from the old to the new hash HT */
}
/* This function performs just a step of rehashing, and only if there are
- * not iterators bound to our hash table. When we have iterators in the middle
- * of a rehashing we can't mess with the two hash tables otherwise some element
- * can be missed or duplicated.
+ * no safe iterators bound to our hash table. When we have iterators in the
+ * middle of a rehashing we can't mess with the two hash tables otherwise
+ * some element can be missed or duplicated.
*
* This function is called by common lookup or update operations in the
* dictionary so that the hash table automatically migrates from H1 to H2
/* Add an element to the target hash table */
int dictAdd(dict *d, void *key, void *val)
+{
+ dictEntry *entry = dictAddRaw(d,key);
+
+ if (!entry) return DICT_ERR;
+ dictSetVal(d, entry, val);
+ return DICT_OK;
+}
+
+/* Low level add. This function adds the entry but instead of setting
+ * a value returns the dictEntry structure to the user, that will make
+ * sure to fill the value field as he wishes.
+ *
+ * This function is also directly expoed to user API to be called
+ * mainly in order to store non-pointers inside the hash value, example:
+ *
+ * entry = dictAddRaw(dict,mykey);
+ * if (entry != NULL) dictSetSignedIntegerVal(entry,1000);
+ *
+ * Return values:
+ *
+ * If key already exists NULL is returned.
+ * If key was added, the hash entry is returned to be manipulated by the caller.
+ */
+dictEntry *dictAddRaw(dict *d, void *key)
{
int index;
dictEntry *entry;
/* Get the index of the new element, or -1 if
* the element already exists. */
if ((index = _dictKeyIndex(d, key)) == -1)
- return DICT_ERR;
+ return NULL;
- /* Allocates the memory and stores key */
+ /* Allocate the memory and store the new entry */
ht = dictIsRehashing(d) ? &d->ht[1] : &d->ht[0];
entry = zmalloc(sizeof(*entry));
entry->next = ht->table[index];
ht->used++;
/* Set the hash entry fields. */
- dictSetHashKey(d, entry, key);
- dictSetHashVal(d, entry, val);
- return DICT_OK;
+ dictSetKey(d, entry, key);
+ return entry;
}
/* Add an element, discarding the old if the key already exists.
return 1;
/* It already exists, get the entry */
entry = dictFind(d, key);
- /* Free the old value and set the new one */
/* Set the new value and free the old one. Note that it is important
* to do that in this order, as the value may just be exactly the same
* as the previous one. In this context, think to reference counting,
* you want to increment (set), and then decrement (free), and not the
* reverse. */
auxentry = *entry;
- dictSetHashVal(d, entry, val);
- dictFreeEntryVal(d, &auxentry);
+ dictSetVal(d, entry, val);
+ dictFreeVal(d, &auxentry);
return 0;
}
+/* dictReplaceRaw() is simply a version of dictAddRaw() that always
+ * returns the hash entry of the specified key, even if the key already
+ * exists and can't be added (in that case the entry of the already
+ * existing key is returned.)
+ *
+ * See dictAddRaw() for more information. */
+dictEntry *dictReplaceRaw(dict *d, void *key) {
+ dictEntry *entry = dictFind(d,key);
+
+ return entry ? entry : dictAddRaw(d,key);
+}
+
/* Search and remove an element */
static int dictGenericDelete(dict *d, const void *key, int nofree)
{
he = d->ht[table].table[idx];
prevHe = NULL;
while(he) {
- if (dictCompareHashKeys(d, key, he->key)) {
+ if (dictCompareKeys(d, key, he->key)) {
/* Unlink the element from the list */
if (prevHe)
prevHe->next = he->next;
else
d->ht[table].table[idx] = he->next;
if (!nofree) {
- dictFreeEntryKey(d, he);
- dictFreeEntryVal(d, he);
+ dictFreeKey(d, he);
+ dictFreeVal(d, he);
}
zfree(he);
d->ht[table].used--;
if ((he = ht->table[i]) == NULL) continue;
while(he) {
nextHe = he->next;
- dictFreeEntryKey(d, he);
- dictFreeEntryVal(d, he);
+ dictFreeKey(d, he);
+ dictFreeVal(d, he);
zfree(he);
ht->used--;
he = nextHe;
idx = h & d->ht[table].sizemask;
he = d->ht[table].table[idx];
while(he) {
- if (dictCompareHashKeys(d, key, he->key))
+ if (dictCompareKeys(d, key, he->key))
return he;
he = he->next;
}
dictEntry *he;
he = dictFind(d,key);
- return he ? dictGetEntryVal(he) : NULL;
+ return he ? dictGetVal(he) : NULL;
}
dictIterator *dictGetIterator(dict *d)
iter->d = d;
iter->table = 0;
iter->index = -1;
+ iter->safe = 0;
iter->entry = NULL;
iter->nextEntry = NULL;
return iter;
}
+dictIterator *dictGetSafeIterator(dict *d) {
+ dictIterator *i = dictGetIterator(d);
+
+ i->safe = 1;
+ return i;
+}
+
dictEntry *dictNext(dictIterator *iter)
{
while (1) {
if (iter->entry == NULL) {
dictht *ht = &iter->d->ht[iter->table];
- if (iter->index == -1 && iter->table == 0) iter->d->iterators++;
+ if (iter->safe && iter->index == -1 && iter->table == 0)
+ iter->d->iterators++;
iter->index++;
if (iter->index >= (signed) ht->size) {
if (dictIsRehashing(iter->d) && iter->table == 0) {
void dictReleaseIterator(dictIterator *iter)
{
- if (!(iter->index == -1 && iter->table == 0)) iter->d->iterators--;
+ if (iter->safe && !(iter->index == -1 && iter->table == 0))
+ iter->d->iterators--;
zfree(iter);
}
/* Expand the hash table if needed */
static int _dictExpandIfNeeded(dict *d)
{
- /* If the hash table is empty expand it to the intial size,
- * if the table is "full" dobule its size. */
+ /* Incremental rehashing already in progress. Return. */
if (dictIsRehashing(d)) return DICT_OK;
- if (d->ht[0].size == 0)
- return dictExpand(d, DICT_HT_INITIAL_SIZE);
- if (d->ht[0].used >= d->ht[0].size && dict_can_resize)
+
+ /* If the hash table is empty expand it to the intial size. */
+ if (d->ht[0].size == 0) return dictExpand(d, DICT_HT_INITIAL_SIZE);
+
+ /* If we reached the 1:1 ratio, and we are allowed to resize the hash
+ * table (global setting) or we should avoid it but the ratio between
+ * elements/buckets is over the "safe" threshold, we resize doubling
+ * the number of buckets. */
+ if (d->ht[0].used >= d->ht[0].size &&
+ (dict_can_resize ||
+ d->ht[0].used/d->ht[0].size > dict_force_resize_ratio))
+ {
return dictExpand(d, ((d->ht[0].size > d->ht[0].used) ?
d->ht[0].size : d->ht[0].used)*2);
+ }
return DICT_OK;
}
/* Search if this slot does not already contain the given key */
he = d->ht[table].table[idx];
while(he) {
- if (dictCompareHashKeys(d, key, he->key))
+ if (dictCompareKeys(d, key, he->key))
return -1;
he = he->next;
}
dict_can_resize = 0;
}
+#if 0
+
+/* The following are just example hash table types implementations.
+ * Not useful for Redis so they are commented out.
+ */
+
/* ----------------------- StringCopy Hash Table Type ------------------------*/
static unsigned int _dictStringCopyHTHashFunction(const void *key)
_dictStringDestructor, /* key destructor */
_dictStringDestructor, /* val destructor */
};
+#endif
projects / redis.git / blobdiff