* tables of power of two in size are used, collisions are handled by
* chaining. See the source code for more information... :)
*
- * Copyright (c) 2006-201
0, Salvatore Sanfilippo <antirez at gmail dot com>
+ * Copyright (c) 2006-201
2, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
return key;
}
-/* 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;
+static uint32_t dict_hash_function_seed = 5381;
- while (len--)
- hash = ((hash << 5) + hash) + (*buf++); /* hash * 33 + c */
- return hash;
+void dictSetHashFunctionSeed(uint32_t seed) {
+ dict_hash_function_seed = seed;
+}
+
+uint32_t dictGetHashFunctionSeed(void) {
+ return dict_hash_function_seed;
+}
+
+/* MurmurHash2, by Austin Appleby
+ * Note - This code makes a few assumptions about how your machine behaves -
+ * 1. We can read a 4-byte value from any address without crashing
+ * 2. sizeof(int) == 4
+ *
+ * And it has a few limitations -
+ *
+ * 1. It will not work incrementally.
+ * 2. It will not produce the same results on little-endian and big-endian
+ * machines.
+ */
+unsigned int dictGenHashFunction(const void *key, int len) {
+ /* 'm' and 'r' are mixing constants generated offline.
+ They're not really 'magic', they just happen to work well. */
+ uint32_t seed = dict_hash_function_seed;
+ const uint32_t m = 0x5bd1e995;
+ const int r = 24;
+
+ /* Initialize the hash to a 'random' value */
+ uint32_t h = seed ^ len;
+
+ /* Mix 4 bytes at a time into the hash */
+ const unsigned char *data = (const unsigned char *)key;
+
+ while(len >= 4) {
+ uint32_t k = *(uint32_t*)data;
+
+ k *= m;
+ k ^= k >> r;
+ k *= m;
+
+ h *= m;
+ h ^= k;
+
+ data += 4;
+ len -= 4;
+ }
+
+ /* Handle the last few bytes of the input array */
+ switch(len) {
+ case 3: h ^= data[2] << 16;
+ case 2: h ^= data[1] << 8;
+ case 1: h ^= data[0]; h *= m;
+ };
+
+ /* Do a few final mixes of the hash to ensure the last few
+ * bytes are well-incorporated. */
+ h ^= h >> 13;
+ h *= m;
+ h ^= h >> 15;
+
+ return (unsigned int)h;
}
-/* And a case insensitive version */
+/* And a case insensitive hash function (based on djb hash) */
unsigned int dictGenCaseHashFunction(const unsigned char *buf, int len) {
- unsigned int hash = 5381;
+ unsigned int hash = (unsigned int)dict_hash_function_seed;
while (len--)
hash = ((hash << 5) + hash) + (tolower(*buf++)); /* hash * 33 + c */
/* ----------------------------- API implementation ------------------------- */
-/* Reset an hashtable already initialized with ht_init().
- * NOTE: This function should only called by ht_destroy(). */
+/* Reset a hash table already initialized with ht_init().
+ * NOTE: This function should only be called by ht_destroy(). */
static void _dictReset(dictht *ht)
{
ht->table = NULL;
}
/* Resize the table to the minimal size that contains all the elements,
- * but with the invariant of a USER/BUCKETS ratio near to <= 1 */
+ * but with the invariant of a USED/BUCKETS ratio near to <= 1 */
int dictResize(dict *d)
{
int minimal;
return dictExpand(d, minimal);
}
-/* Expand or create the hashtable */
+/* Expand or create the hash table */
int dictExpand(dict *d, unsigned long size)
{
- dictht n; /* the new hashtable */
+ dictht n; /* the new hash table */
unsigned long realsize = _dictNextPower(size);
/* the size is invalid if it is smaller than the number of
- * elements already inside the hashtable */
+ * elements already inside the hash table */
if (dictIsRehashing(d) || d->ht[0].used > size)
return DICT_ERR;
- /* Allocate the new hashtable and initialize all pointers to NULL */
+ /* Allocate the new hash table and initialize all pointers to NULL */
n.size = realsize;
n.sizemask = realsize-1;
n.table = zcalloc(realsize*sizeof(dictEntry*));
/* 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 exposed to the 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;
/* Allocate the memory and store the new entry */
ht = dictIsRehashing(d) ? &d->ht[1] : &d->ht[0];
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.
* 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)
unsigned int h, idx, table;
dictEntry *he;
- /* Expand the hashtable if needed */
+ /* Expand the hash table if needed */
if (_dictExpandIfNeeded(d) == DICT_ERR)
return -1;
/* Compute the key hash value */
/* 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;
}
d->iterators = 0;
}
+void dictEnableResize(void) {
+ dict_can_resize = 1;
+}
+
+void dictDisableResize(void) {
+ dict_can_resize = 0;
+}
+
+#if 0
+
+/* The following is code that we don't use for Redis currently, but that is part
+of the library. */
+
+/* ----------------------- Debugging ------------------------*/
+
#define DICT_STATS_VECTLEN 50
static void _dictPrintStatsHt(dictht *ht) {
unsigned long i, slots = 0, chainlen, maxchainlen = 0;
}
}
-void dictEnableResize(void) {
- dict_can_resize = 1;
-}
-
-void dictDisableResize(void) {
- 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)
projects / redis.git / blobdiff