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+/* Hash Tables Implementation.
+ *
+ * This file implements in memory hash tables with insert/del/replace/find/
+ * get-random-element operations. Hash tables will auto resize if needed
+ * tables of power of two in size are used, collisions are handled by
+ * chaining. See the source code for more information... :)
+ *
+ * Copyright (c) 2006-2012, Salvatore Sanfilippo <antirez at gmail dot com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * * Neither the name of Redis nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "fmacros.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdarg.h>
+#include <limits.h>
+#include <sys/time.h>
+
+#include "dict.h"
+#include "zmalloc.h"
+#include "redisassert.h"
+
+/* Using dictEnableResize() / dictDisableResize() we make possible to disable
+ * resizing and rehashing 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.
+ *
+ * Note that even when dict_can_resize is set to DICT_RESIZE_AVOID, not all
+ * resizes are prevented: a hash table is still allowed to grow if the ratio
+ * between the number of elements and the buckets > dict_force_resize_ratio. */
+static dictResizeEnable dict_can_resize = DICT_RESIZE_ENABLE;
+static unsigned int dict_force_resize_ratio = 5;
+
+/* -------------------------- types ----------------------------------------- */
+
+struct dictEntry {
+ void *key;
+ union {
+ void *val;
+ uint64_t u64;
+ int64_t s64;
+ double d;
+ } v;
+ struct dictEntry *next; /* Next entry in the same hash bucket. */
+ void *metadata[]; /* An arbitrary number of bytes (starting at a
+ * pointer-aligned address) of size as returned
+ * by dictType's dictEntryMetadataBytes(). */
+};
+
+typedef struct {
+ void *key;
+ dictEntry *next;
+} dictEntryNoValue;
+
+/* -------------------------- private prototypes ---------------------------- */
+
+static int _dictExpandIfNeeded(dict *d);
+static signed char _dictNextExp(unsigned long size);
+static int _dictInit(dict *d, dictType *type);
+static dictEntry *dictGetNext(const dictEntry *de);
+static dictEntry **dictGetNextRef(dictEntry *de);
+static void dictSetNext(dictEntry *de, dictEntry *next);
+
+/* -------------------------- hash functions -------------------------------- */
+
+static uint8_t dict_hash_function_seed[16];
+
+void dictSetHashFunctionSeed(uint8_t *seed) {
+ memcpy(dict_hash_function_seed,seed,sizeof(dict_hash_function_seed));
+}
+
+uint8_t *dictGetHashFunctionSeed(void) {
+ return dict_hash_function_seed;
+}
+
+/* The default hashing function uses SipHash implementation
+ * in siphash.c. */
+
+uint64_t siphash(const uint8_t *in, const size_t inlen, const uint8_t *k);
+uint64_t siphash_nocase(const uint8_t *in, const size_t inlen, const uint8_t *k);
+
+uint64_t dictGenHashFunction(const void *key, size_t len) {
+ return siphash(key,len,dict_hash_function_seed);
+}
+
+uint64_t dictGenCaseHashFunction(const unsigned char *buf, size_t len) {
+ return siphash_nocase(buf,len,dict_hash_function_seed);
+}
+
+/* --------------------- dictEntry pointer bit tricks ---------------------- */
+
+/* The 3 least significant bits in a pointer to a dictEntry determines what the
+ * pointer actually points to. If the least bit is set, it's a key. Otherwise,
+ * the bit pattern of the least 3 significant bits mark the kind of entry. */
+
+#define ENTRY_PTR_MASK 7 /* 111 */
+#define ENTRY_PTR_NORMAL 0 /* 000 */
+#define ENTRY_PTR_NO_VALUE 2 /* 010 */
+
+/* Returns 1 if the entry pointer is a pointer to a key, rather than to an
+ * allocated entry. Returns 0 otherwise. */
+static inline int entryIsKey(const dictEntry *de) {
+ return (uintptr_t)(void *)de & 1;
+}
+
+/* Returns 1 if the pointer is actually a pointer to a dictEntry struct. Returns
+ * 0 otherwise. */
+static inline int entryIsNormal(const dictEntry *de) {
+ return ((uintptr_t)(void *)de & ENTRY_PTR_MASK) == ENTRY_PTR_NORMAL;
+}
+
+/* Returns 1 if the entry is a special entry with key and next, but without
+ * value. Returns 0 otherwise. */
+static inline int entryIsNoValue(const dictEntry *de) {
+ return ((uintptr_t)(void *)de & ENTRY_PTR_MASK) == ENTRY_PTR_NO_VALUE;
+}
+
+/* Creates an entry without a value field. */
+static inline dictEntry *createEntryNoValue(void *key, dictEntry *next) {
+ dictEntryNoValue *entry = zmalloc(sizeof(*entry));
+ entry->key = key;
+ entry->next = next;
+ return (dictEntry *)(void *)((uintptr_t)(void *)entry | ENTRY_PTR_NO_VALUE);
+}
+
+static inline dictEntry *encodeMaskedPtr(const void *ptr, unsigned int bits) {
+ assert(((uintptr_t)ptr & ENTRY_PTR_MASK) == 0);
+ return (dictEntry *)(void *)((uintptr_t)ptr | bits);
+}
+
+static inline void *decodeMaskedPtr(const dictEntry *de) {
+ assert(!entryIsKey(de));
+ return (void *)((uintptr_t)(void *)de & ~ENTRY_PTR_MASK);
+}
+
+/* Decodes the pointer to an entry without value, when you know it is an entry
+ * without value. Hint: Use entryIsNoValue to check. */
+static inline dictEntryNoValue *decodeEntryNoValue(const dictEntry *de) {
+ return decodeMaskedPtr(de);
+}
+
+/* Returns 1 if the entry has a value field and 0 otherwise. */
+static inline int entryHasValue(const dictEntry *de) {
+ return entryIsNormal(de);
+}
+
+/* ----------------------------- API implementation ------------------------- */
+
+/* Reset hash table parameters already initialized with _dictInit()*/
+static void _dictReset(dict *d, int htidx)
+{
+ d->ht_table[htidx] = NULL;
+ d->ht_size_exp[htidx] = -1;
+ d->ht_used[htidx] = 0;
+}
+
+/* Create a new hash table */
+dict *dictCreate(dictType *type)
+{
+ size_t metasize = type->dictMetadataBytes ? type->dictMetadataBytes() : 0;
+ dict *d = zmalloc(sizeof(*d) + metasize);
+ if (metasize) {
+ memset(dictMetadata(d), 0, metasize);
+ }
+
+ _dictInit(d,type);
+ return d;
+}
+
+/* Initialize the hash table */
+int _dictInit(dict *d, dictType *type)
+{
+ _dictReset(d, 0);
+ _dictReset(d, 1);
+ d->type = type;
+ d->rehashidx = -1;
+ d->pauserehash = 0;
+ return DICT_OK;
+}
+
+/* Resize the table to the minimal size that contains all the elements,
+ * but with the invariant of a USED/BUCKETS ratio near to <= 1 */
+int dictResize(dict *d)
+{
+ unsigned long minimal;
+
+ if (dict_can_resize != DICT_RESIZE_ENABLE || dictIsRehashing(d)) return DICT_ERR;
+ minimal = d->ht_used[0];
+ if (minimal < DICT_HT_INITIAL_SIZE)
+ minimal = DICT_HT_INITIAL_SIZE;
+ return dictExpand(d, minimal);
+}
+
+/* Expand or create the hash table,
+ * when malloc_failed is non-NULL, it'll avoid panic if malloc fails (in which case it'll be set to 1).
+ * Returns DICT_OK if expand was performed, and DICT_ERR if skipped. */
+int _dictExpand(dict *d, unsigned long size, int* malloc_failed)
+{
+ if (malloc_failed) *malloc_failed = 0;
+
+ /* the size is invalid if it is smaller than the number of
+ * elements already inside the hash table */
+ if (dictIsRehashing(d) || d->ht_used[0] > size)
+ return DICT_ERR;
+
+ /* the new hash table */
+ dictEntry **new_ht_table;
+ unsigned long new_ht_used;
+ signed char new_ht_size_exp = _dictNextExp(size);
+
+ /* Detect overflows */
+ size_t newsize = 1ul<<new_ht_size_exp;
+ if (newsize < size || newsize * sizeof(dictEntry*) < newsize)
+ return DICT_ERR;
+
+ /* Rehashing to the same table size is not useful. */
+ if (new_ht_size_exp == d->ht_size_exp[0]) return DICT_ERR;
+
+ /* Allocate the new hash table and initialize all pointers to NULL */
+ if (malloc_failed) {
+ new_ht_table = ztrycalloc(newsize*sizeof(dictEntry*));
+ *malloc_failed = new_ht_table == NULL;
+ if (*malloc_failed)
+ return DICT_ERR;
+ } else
+ new_ht_table = zcalloc(newsize*sizeof(dictEntry*));
+
+ new_ht_used = 0;
+
+ /* 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_table[0] == NULL) {
+ d->ht_size_exp[0] = new_ht_size_exp;
+ d->ht_used[0] = new_ht_used;
+ d->ht_table[0] = new_ht_table;
+ return DICT_OK;
+ }
+
+ /* Prepare a second hash table for incremental rehashing */
+ d->ht_size_exp[1] = new_ht_size_exp;
+ d->ht_used[1] = new_ht_used;
+ d->ht_table[1] = new_ht_table;
+ d->rehashidx = 0;
+ return DICT_OK;
+}
+
+/* return DICT_ERR if expand was not performed */
+int dictExpand(dict *d, unsigned long size) {
+ return _dictExpand(d, size, NULL);
+}
+
+/* return DICT_ERR if expand failed due to memory allocation failure */
+int dictTryExpand(dict *d, unsigned long size) {
+ int malloc_failed;
+ _dictExpand(d, size, &malloc_failed);
+ return malloc_failed? DICT_ERR : DICT_OK;
+}
+
+/* Performs N steps of incremental rehashing. Returns 1 if there are still
+ * keys to move from the old to the new hash table, otherwise 0 is returned.
+ *
+ * Note that a rehashing step consists in moving a bucket (that may have more
+ * than one key as we use chaining) from the old to the new hash table, however
+ * since part of the hash table may be composed of empty spaces, it is not
+ * guaranteed that this function will rehash even a single bucket, since it
+ * will visit at max N*10 empty buckets in total, otherwise the amount of
+ * work it does would be unbound and the function may block for a long time. */
+int dictRehash(dict *d, int n) {
+ int empty_visits = n*10; /* Max number of empty buckets to visit. */
+ unsigned long s0 = DICTHT_SIZE(d->ht_size_exp[0]);
+ unsigned long s1 = DICTHT_SIZE(d->ht_size_exp[1]);
+ if (dict_can_resize == DICT_RESIZE_FORBID || !dictIsRehashing(d)) return 0;
+ if (dict_can_resize == DICT_RESIZE_AVOID &&
+ ((s1 > s0 && s1 / s0 < dict_force_resize_ratio) ||
+ (s1 < s0 && s0 / s1 < dict_force_resize_ratio)))
+ {
+ return 0;
+ }
+
+ while(n-- && d->ht_used[0] != 0) {
+ dictEntry *de, *nextde;
+
+ /* Note that rehashidx can't overflow as we are sure there are more
+ * elements because ht[0].used != 0 */
+ assert(DICTHT_SIZE(d->ht_size_exp[0]) > (unsigned long)d->rehashidx);
+ while(d->ht_table[0][d->rehashidx] == NULL) {
+ d->rehashidx++;
+ if (--empty_visits == 0) return 1;
+ }
+ de = d->ht_table[0][d->rehashidx];
+ /* Move all the keys in this bucket from the old to the new hash HT */
+ while(de) {
+ uint64_t h;
+
+ nextde = dictGetNext(de);
+ void *key = dictGetKey(de);
+ /* Get the index in the new hash table */
+ if (d->ht_size_exp[1] > d->ht_size_exp[0]) {
+ h = dictHashKey(d, key) & DICTHT_SIZE_MASK(d->ht_size_exp[1]);
+ } else {
+ /* We're shrinking the table. The tables sizes are powers of
+ * two, so we simply mask the bucket index in the larger table
+ * to get the bucket index in the smaller table. */
+ h = d->rehashidx & DICTHT_SIZE_MASK(d->ht_size_exp[1]);
+ }
+ if (d->type->no_value) {
+ if (d->type->keys_are_odd && !d->ht_table[1][h]) {
+ /* Destination bucket is empty and we can store the key
+ * directly without an allocated entry. Free the old entry
+ * if it's an allocated entry.
+ *
+ * TODO: Add a flag 'keys_are_even' and if set, we can use
+ * this optimization for these dicts too. We can set the LSB
+ * bit when stored as a dict entry and clear it again when
+ * we need the key back. */
+ assert(entryIsKey(key));
+ if (!entryIsKey(de)) zfree(decodeMaskedPtr(de));
+ de = key;
+ } else if (entryIsKey(de)) {
+ /* We don't have an allocated entry but we need one. */
+ de = createEntryNoValue(key, d->ht_table[1][h]);
+ } else {
+ /* Just move the existing entry to the destination table and
+ * update the 'next' field. */
+ assert(entryIsNoValue(de));
+ dictSetNext(de, d->ht_table[1][h]);
+ }
+ } else {
+ dictSetNext(de, d->ht_table[1][h]);
+ }
+ d->ht_table[1][h] = de;
+ d->ht_used[0]--;
+ d->ht_used[1]++;
+ de = nextde;
+ }
+ d->ht_table[0][d->rehashidx] = NULL;
+ d->rehashidx++;
+ }
+
+ /* Check if we already rehashed the whole table... */
+ if (d->ht_used[0] == 0) {
+ zfree(d->ht_table[0]);
+ /* Copy the new ht onto the old one */
+ d->ht_table[0] = d->ht_table[1];
+ d->ht_used[0] = d->ht_used[1];
+ d->ht_size_exp[0] = d->ht_size_exp[1];
+ _dictReset(d, 1);
+ d->rehashidx = -1;
+ return 0;
+ }
+
+ /* More to rehash... */
+ return 1;
+}
+
+long long timeInMilliseconds(void) {
+ struct timeval tv;
+
+ gettimeofday(&tv,NULL);
+ return (((long long)tv.tv_sec)*1000)+(tv.tv_usec/1000);
+}
+
+/* Rehash in ms+"delta" milliseconds. The value of "delta" is larger
+ * than 0, and is smaller than 1 in most cases. The exact upper bound
+ * depends on the running time of dictRehash(d,100).*/
+int dictRehashMilliseconds(dict *d, int ms) {
+ if (d->pauserehash > 0) return 0;
+
+ long long start = timeInMilliseconds();
+ int rehashes = 0;
+
+ while(dictRehash(d,100)) {
+ rehashes += 100;
+ if (timeInMilliseconds()-start > ms) break;
+ }
+ return rehashes;
+}
+
+/* This function performs just a step of rehashing, and only if hashing has
+ * not been paused for our hash table. When we have iterators in the
+ * middle of a rehashing we can't mess with the two hash tables otherwise
+ * some elements 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
+ * while it is actively used. */
+static void _dictRehashStep(dict *d) {
+ if (d->pauserehash == 0) dictRehash(d,1);
+}
+
+/* Return a pointer to the metadata section within the dict. */
+void *dictMetadata(dict *d) {
+ return &d->metadata;
+}
+
+/* Add an element to the target hash table */
+int dictAdd(dict *d, void *key, void *val)
+{
+ dictEntry *entry = dictAddRaw(d,key,NULL);
+
+ if (!entry) return DICT_ERR;
+ if (!d->type->no_value) dictSetVal(d, entry, val);
+ return DICT_OK;
+}
+
+/* Low level add or find:
+ * 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 they wish.
+ *
+ * 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,NULL);
+ * if (entry != NULL) dictSetSignedIntegerVal(entry,1000);
+ *
+ * Return values:
+ *
+ * If key already exists NULL is returned, and "*existing" is populated
+ * with the existing entry if existing is not NULL.
+ *
+ * If key was added, the hash entry is returned to be manipulated by the caller.
+ */
+dictEntry *dictAddRaw(dict *d, void *key, dictEntry **existing)
+{
+ /* Get the position for the new key or NULL if the key already exists. */
+ void *position = dictFindPositionForInsert(d, key, existing);
+ if (!position) return NULL;
+
+ /* Dup the key if necessary. */
+ if (d->type->keyDup) key = d->type->keyDup(d, key);
+
+ return dictInsertAtPosition(d, key, position);
+}
+
+/* Adds a key in the dict's hashtable at the position returned by a preceding
+ * call to dictFindPositionForInsert. This is a low level function which allows
+ * splitting dictAddRaw in two parts. Normally, dictAddRaw or dictAdd should be
+ * used instead. */
+dictEntry *dictInsertAtPosition(dict *d, void *key, void *position) {
+ dictEntry **bucket = position; /* It's a bucket, but the API hides that. */
+ dictEntry *entry;
+ /* If rehashing is ongoing, we insert in table 1, otherwise in table 0.
+ * Assert that the provided bucket is the right table. */
+ int htidx = dictIsRehashing(d) ? 1 : 0;
+ assert(bucket >= &d->ht_table[htidx][0] &&
+ bucket <= &d->ht_table[htidx][DICTHT_SIZE_MASK(d->ht_size_exp[htidx])]);
+ size_t metasize = dictEntryMetadataSize(d);
+ if (d->type->no_value) {
+ assert(!metasize); /* Entry metadata + no value not supported. */
+ if (d->type->keys_are_odd && !*bucket) {
+ /* We can store the key directly in the destination bucket without the
+ * allocated entry.
+ *
+ * TODO: Add a flag 'keys_are_even' and if set, we can use this
+ * optimization for these dicts too. We can set the LSB bit when
+ * stored as a dict entry and clear it again when we need the key
+ * back. */
+ entry = key;
+ assert(entryIsKey(entry));
+ } else {
+ /* Allocate an entry without value. */
+ entry = createEntryNoValue(key, *bucket);
+ }
+ } else {
+ /* Allocate the memory and store the new entry.
+ * Insert the element in top, with the assumption that in a database
+ * system it is more likely that recently added entries are accessed
+ * more frequently. */
+ entry = zmalloc(sizeof(*entry) + metasize);
+ assert(entryIsNormal(entry)); /* Check alignment of allocation */
+ if (metasize > 0) {
+ memset(dictEntryMetadata(entry), 0, metasize);
+ }
+ entry->key = key;
+ entry->next = *bucket;
+ }
+ *bucket = entry;
+ d->ht_used[htidx]++;
+
+ return entry;
+}
+
+/* Add or Overwrite:
+ * Add an element, discarding the old value if the key already exists.
+ * Return 1 if the key was added from scratch, 0 if there was already an
+ * element with such key and dictReplace() just performed a value update
+ * operation. */
+int dictReplace(dict *d, void *key, void *val)
+{
+ dictEntry *entry, *existing;
+
+ /* Try to add the element. If the key
+ * does not exists dictAdd will succeed. */
+ entry = dictAddRaw(d,key,&existing);
+ if (entry) {
+ dictSetVal(d, entry, val);
+ return 1;
+ }
+
+ /* 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. */
+ void *oldval = dictGetVal(existing);
+ dictSetVal(d, existing, val);
+ if (d->type->valDestructor)
+ d->type->valDestructor(d, oldval);
+ return 0;
+}
+
+/* Add or Find:
+ * dictAddOrFind() 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 *dictAddOrFind(dict *d, void *key) {
+ dictEntry *entry, *existing;
+ entry = dictAddRaw(d,key,&existing);
+ return entry ? entry : existing;
+}
+
+/* Search and remove an element. This is a helper function for
+ * dictDelete() and dictUnlink(), please check the top comment
+ * of those functions. */
+static dictEntry *dictGenericDelete(dict *d, const void *key, int nofree) {
+ uint64_t h, idx;
+ dictEntry *he, *prevHe;
+ int table;
+
+ /* dict is empty */
+ if (dictSize(d) == 0) return NULL;
+
+ if (dictIsRehashing(d)) _dictRehashStep(d);
+ h = dictHashKey(d, key);
+
+ for (table = 0; table <= 1; table++) {
+ idx = h & DICTHT_SIZE_MASK(d->ht_size_exp[table]);
+ he = d->ht_table[table][idx];
+ prevHe = NULL;
+ while(he) {
+ void *he_key = dictGetKey(he);
+ if (key == he_key || dictCompareKeys(d, key, he_key)) {
+ /* Unlink the element from the list */
+ if (prevHe)
+ dictSetNext(prevHe, dictGetNext(he));
+ else
+ d->ht_table[table][idx] = dictGetNext(he);
+ if (!nofree) {
+ dictFreeUnlinkedEntry(d, he);
+ }
+ d->ht_used[table]--;
+ return he;
+ }
+ prevHe = he;
+ he = dictGetNext(he);
+ }
+ if (!dictIsRehashing(d)) break;
+ }
+ return NULL; /* not found */
+}
+
+/* Remove an element, returning DICT_OK on success or DICT_ERR if the
+ * element was not found. */
+int dictDelete(dict *ht, const void *key) {
+ return dictGenericDelete(ht,key,0) ? DICT_OK : DICT_ERR;
+}
+
+/* Remove an element from the table, but without actually releasing
+ * the key, value and dictionary entry. The dictionary entry is returned
+ * if the element was found (and unlinked from the table), and the user
+ * should later call `dictFreeUnlinkedEntry()` with it in order to release it.
+ * Otherwise if the key is not found, NULL is returned.
+ *
+ * This function is useful when we want to remove something from the hash
+ * table but want to use its value before actually deleting the entry.
+ * Without this function the pattern would require two lookups:
+ *
+ * entry = dictFind(...);
+ * // Do something with entry
+ * dictDelete(dictionary,entry);
+ *
+ * Thanks to this function it is possible to avoid this, and use
+ * instead:
+ *
+ * entry = dictUnlink(dictionary,entry);
+ * // Do something with entry
+ * dictFreeUnlinkedEntry(entry); // <- This does not need to lookup again.
+ */
+dictEntry *dictUnlink(dict *d, const void *key) {
+ return dictGenericDelete(d,key,1);
+}
+
+/* You need to call this function to really free the entry after a call
+ * to dictUnlink(). It's safe to call this function with 'he' = NULL. */
+void dictFreeUnlinkedEntry(dict *d, dictEntry *he) {
+ if (he == NULL) return;
+ dictFreeKey(d, he);
+ dictFreeVal(d, he);
+ if (!entryIsKey(he)) zfree(decodeMaskedPtr(he));
+}
+
+/* Destroy an entire dictionary */
+int _dictClear(dict *d, int htidx, void(callback)(dict*)) {
+ unsigned long i;
+
+ /* Free all the elements */
+ for (i = 0; i < DICTHT_SIZE(d->ht_size_exp[htidx]) && d->ht_used[htidx] > 0; i++) {
+ dictEntry *he, *nextHe;
+
+ if (callback && (i & 65535) == 0) callback(d);
+
+ if ((he = d->ht_table[htidx][i]) == NULL) continue;
+ while(he) {
+ nextHe = dictGetNext(he);
+ dictFreeKey(d, he);
+ dictFreeVal(d, he);
+ if (!entryIsKey(he)) zfree(decodeMaskedPtr(he));
+ d->ht_used[htidx]--;
+ he = nextHe;
+ }
+ }
+ /* Free the table and the allocated cache structure */
+ zfree(d->ht_table[htidx]);
+ /* Re-initialize the table */
+ _dictReset(d, htidx);
+ return DICT_OK; /* never fails */
+}
+
+/* Clear & Release the hash table */
+void dictRelease(dict *d)
+{
+ _dictClear(d,0,NULL);
+ _dictClear(d,1,NULL);
+ zfree(d);
+}
+
+dictEntry *dictFind(dict *d, const void *key)
+{
+ dictEntry *he;
+ uint64_t h, idx, table;
+
+ if (dictSize(d) == 0) return NULL; /* dict is empty */
+ if (dictIsRehashing(d)) _dictRehashStep(d);
+ h = dictHashKey(d, key);
+ for (table = 0; table <= 1; table++) {
+ idx = h & DICTHT_SIZE_MASK(d->ht_size_exp[table]);
+ he = d->ht_table[table][idx];
+ while(he) {
+ void *he_key = dictGetKey(he);
+ if (key == he_key || dictCompareKeys(d, key, he_key))
+ return he;
+ he = dictGetNext(he);
+ }
+ if (!dictIsRehashing(d)) return NULL;
+ }
+ return NULL;
+}
+
+void *dictFetchValue(dict *d, const void *key) {
+ dictEntry *he;
+
+ he = dictFind(d,key);
+ return he ? dictGetVal(he) : NULL;
+}
+
+/* Find an element from the table, also get the plink of the entry. The entry
+ * is returned if the element is found, and the user should later call
+ * `dictTwoPhaseUnlinkFree` with it in order to unlink and release it. Otherwise if
+ * the key is not found, NULL is returned. These two functions should be used in pair.
+ * `dictTwoPhaseUnlinkFind` pauses rehash and `dictTwoPhaseUnlinkFree` resumes rehash.
+ *
+ * We can use like this:
+ *
+ * dictEntry *de = dictTwoPhaseUnlinkFind(db->dict,key->ptr,&plink, &table);
+ * // Do something, but we can't modify the dict
+ * dictTwoPhaseUnlinkFree(db->dict,de,plink,table); // We don't need to lookup again
+ *
+ * If we want to find an entry before delete this entry, this an optimization to avoid
+ * dictFind followed by dictDelete. i.e. the first API is a find, and it gives some info
+ * to the second one to avoid repeating the lookup
+ */
+dictEntry *dictTwoPhaseUnlinkFind(dict *d, const void *key, dictEntry ***plink, int *table_index) {
+ uint64_t h, idx, table;
+
+ if (dictSize(d) == 0) return NULL; /* dict is empty */
+ if (dictIsRehashing(d)) _dictRehashStep(d);
+ h = dictHashKey(d, key);
+
+ for (table = 0; table <= 1; table++) {
+ idx = h & DICTHT_SIZE_MASK(d->ht_size_exp[table]);
+ dictEntry **ref = &d->ht_table[table][idx];
+ while (ref && *ref) {
+ void *de_key = dictGetKey(*ref);
+ if (key == de_key || dictCompareKeys(d, key, de_key)) {
+ *table_index = table;
+ *plink = ref;
+ dictPauseRehashing(d);
+ return *ref;
+ }
+ ref = dictGetNextRef(*ref);
+ }
+ if (!dictIsRehashing(d)) return NULL;
+ }
+ return NULL;
+}
+
+void dictTwoPhaseUnlinkFree(dict *d, dictEntry *he, dictEntry **plink, int table_index) {
+ if (he == NULL) return;
+ d->ht_used[table_index]--;
+ *plink = dictGetNext(he);
+ dictFreeKey(d, he);
+ dictFreeVal(d, he);
+ if (!entryIsKey(he)) zfree(decodeMaskedPtr(he));
+ dictResumeRehashing(d);
+}
+
+void dictSetKey(dict *d, dictEntry* de, void *key) {
+ assert(!d->type->no_value);
+ if (d->type->keyDup)
+ de->key = d->type->keyDup(d, key);
+ else
+ de->key = key;
+}
+
+void dictSetVal(dict *d, dictEntry *de, void *val) {
+ assert(entryHasValue(de));
+ de->v.val = d->type->valDup ? d->type->valDup(d, val) : val;
+}
+
+void dictSetSignedIntegerVal(dictEntry *de, int64_t val) {
+ assert(entryHasValue(de));
+ de->v.s64 = val;
+}
+
+void dictSetUnsignedIntegerVal(dictEntry *de, uint64_t val) {
+ assert(entryHasValue(de));
+ de->v.u64 = val;
+}
+
+void dictSetDoubleVal(dictEntry *de, double val) {
+ assert(entryHasValue(de));
+ de->v.d = val;
+}
+
+int64_t dictIncrSignedIntegerVal(dictEntry *de, int64_t val) {
+ assert(entryHasValue(de));
+ return de->v.s64 += val;
+}
+
+uint64_t dictIncrUnsignedIntegerVal(dictEntry *de, uint64_t val) {
+ assert(entryHasValue(de));
+ return de->v.u64 += val;
+}
+
+double dictIncrDoubleVal(dictEntry *de, double val) {
+ assert(entryHasValue(de));
+ return de->v.d += val;
+}
+
+/* A pointer to the metadata section within the dict entry. */
+void *dictEntryMetadata(dictEntry *de) {
+ assert(entryHasValue(de));
+ return &de->metadata;
+}
+
+void *dictGetKey(const dictEntry *de) {
+ if (entryIsKey(de)) return (void*)de;
+ if (entryIsNoValue(de)) return decodeEntryNoValue(de)->key;
+ return de->key;
+}
+
+void *dictGetVal(const dictEntry *de) {
+ assert(entryHasValue(de));
+ return de->v.val;
+}
+
+int64_t dictGetSignedIntegerVal(const dictEntry *de) {
+ assert(entryHasValue(de));
+ return de->v.s64;
+}
+
+uint64_t dictGetUnsignedIntegerVal(const dictEntry *de) {
+ assert(entryHasValue(de));
+ return de->v.u64;
+}
+
+double dictGetDoubleVal(const dictEntry *de) {
+ assert(entryHasValue(de));
+ return de->v.d;
+}
+
+/* Returns a mutable reference to the value as a double within the entry. */
+double *dictGetDoubleValPtr(dictEntry *de) {
+ assert(entryHasValue(de));
+ return &de->v.d;
+}
+
+/* Returns the 'next' field of the entry or NULL if the entry doesn't have a
+ * 'next' field. */
+static dictEntry *dictGetNext(const dictEntry *de) {
+ if (entryIsKey(de)) return NULL; /* there's no next */
+ if (entryIsNoValue(de)) return decodeEntryNoValue(de)->next;
+ return de->next;
+}
+
+/* Returns a pointer to the 'next' field in the entry or NULL if the entry
+ * doesn't have a next field. */
+static dictEntry **dictGetNextRef(dictEntry *de) {
+ if (entryIsKey(de)) return NULL;
+ if (entryIsNoValue(de)) return &decodeEntryNoValue(de)->next;
+ return &de->next;
+}
+
+static void dictSetNext(dictEntry *de, dictEntry *next) {
+ assert(!entryIsKey(de));
+ if (entryIsNoValue(de)) {
+ dictEntryNoValue *entry = decodeEntryNoValue(de);
+ entry->next = next;
+ } else {
+ de->next = next;
+ }
+}
+
+/* Returns the memory usage in bytes of the dict, excluding the size of the keys
+ * and values. */
+size_t dictMemUsage(const dict *d) {
+ return dictSize(d) * sizeof(dictEntry) +
+ dictSlots(d) * sizeof(dictEntry*);
+}
+
+size_t dictEntryMemUsage(void) {
+ return sizeof(dictEntry);
+}
+
+/* A fingerprint is a 64 bit number that represents the state of the dictionary
+ * at a given time, it's just a few dict properties xored together.
+ * When an unsafe iterator is initialized, we get the dict fingerprint, and check
+ * the fingerprint again when the iterator is released.
+ * If the two fingerprints are different it means that the user of the iterator
+ * performed forbidden operations against the dictionary while iterating. */
+unsigned long long dictFingerprint(dict *d) {
+ unsigned long long integers[6], hash = 0;
+ int j;
+
+ integers[0] = (long) d->ht_table[0];
+ integers[1] = d->ht_size_exp[0];
+ integers[2] = d->ht_used[0];
+ integers[3] = (long) d->ht_table[1];
+ integers[4] = d->ht_size_exp[1];
+ integers[5] = d->ht_used[1];
+
+ /* We hash N integers by summing every successive integer with the integer
+ * hashing of the previous sum. Basically:
+ *
+ * Result = hash(hash(hash(int1)+int2)+int3) ...
+ *
+ * This way the same set of integers in a different order will (likely) hash
+ * to a different number. */
+ for (j = 0; j < 6; j++) {
+ hash += integers[j];
+ /* For the hashing step we use Tomas Wang's 64 bit integer hash. */
+ hash = (~hash) + (hash << 21); // hash = (hash << 21) - hash - 1;
+ hash = hash ^ (hash >> 24);
+ hash = (hash + (hash << 3)) + (hash << 8); // hash * 265
+ hash = hash ^ (hash >> 14);
+ hash = (hash + (hash << 2)) + (hash << 4); // hash * 21
+ hash = hash ^ (hash >> 28);
+ hash = hash + (hash << 31);
+ }
+ return hash;
+}
+
+void dictInitIterator(dictIterator *iter, dict *d)
+{
+ iter->d = d;
+ iter->table = 0;
+ iter->index = -1;
+ iter->safe = 0;
+ iter->entry = NULL;
+ iter->nextEntry = NULL;
+}
+
+void dictInitSafeIterator(dictIterator *iter, dict *d)
+{
+ dictInitIterator(iter, d);
+ iter->safe = 1;
+}
+
+void dictResetIterator(dictIterator *iter)
+{
+ if (!(iter->index == -1 && iter->table == 0)) {
+ if (iter->safe)
+ dictResumeRehashing(iter->d);
+ else
+ assert(iter->fingerprint == dictFingerprint(iter->d));
+ }
+}
+
+dictIterator *dictGetIterator(dict *d)
+{
+ dictIterator *iter = zmalloc(sizeof(*iter));
+ dictInitIterator(iter, d);
+ 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) {
+ if (iter->index == -1 && iter->table == 0) {
+ if (iter->safe)
+ dictPauseRehashing(iter->d);
+ else
+ iter->fingerprint = dictFingerprint(iter->d);
+ }
+ iter->index++;
+ if (iter->index >= (long) DICTHT_SIZE(iter->d->ht_size_exp[iter->table])) {
+ if (dictIsRehashing(iter->d) && iter->table == 0) {
+ iter->table++;
+ iter->index = 0;
+ } else {
+ break;
+ }
+ }
+ iter->entry = iter->d->ht_table[iter->table][iter->index];
+ } else {
+ iter->entry = iter->nextEntry;
+ }
+ if (iter->entry) {
+ /* We need to save the 'next' here, the iterator user
+ * may delete the entry we are returning. */
+ iter->nextEntry = dictGetNext(iter->entry);
+ return iter->entry;
+ }
+ }
+ return NULL;
+}
+
+void dictReleaseIterator(dictIterator *iter)
+{
+ dictResetIterator(iter);
+ zfree(iter);
+}
+
+/* Return a random entry from the hash table. Useful to
+ * implement randomized algorithms */
+dictEntry *dictGetRandomKey(dict *d)
+{
+ dictEntry *he, *orighe;
+ unsigned long h;
+ int listlen, listele;
+
+ if (dictSize(d) == 0) return NULL;
+ if (dictIsRehashing(d)) _dictRehashStep(d);
+ if (dictIsRehashing(d)) {
+ unsigned long s0 = DICTHT_SIZE(d->ht_size_exp[0]);
+ do {
+ /* We are sure there are no elements in indexes from 0
+ * to rehashidx-1 */
+ h = d->rehashidx + (randomULong() % (dictSlots(d) - d->rehashidx));
+ he = (h >= s0) ? d->ht_table[1][h - s0] : d->ht_table[0][h];
+ } while(he == NULL);
+ } else {
+ unsigned long m = DICTHT_SIZE_MASK(d->ht_size_exp[0]);
+ do {
+ h = randomULong() & m;
+ he = d->ht_table[0][h];
+ } while(he == NULL);
+ }
+
+ /* Now we found a non empty bucket, but it is a linked
+ * list and we need to get a random element from the list.
+ * The only sane way to do so is counting the elements and
+ * select a random index. */
+ listlen = 0;
+ orighe = he;
+ while(he) {
+ he = dictGetNext(he);
+ listlen++;
+ }
+ listele = random() % listlen;
+ he = orighe;
+ while(listele--) he = dictGetNext(he);
+ return he;
+}
+
+/* This function samples the dictionary to return a few keys from random
+ * locations.
+ *
+ * It does not guarantee to return all the keys specified in 'count', nor
+ * it does guarantee to return non-duplicated elements, however it will make
+ * some effort to do both things.
+ *
+ * Returned pointers to hash table entries are stored into 'des' that
+ * points to an array of dictEntry pointers. The array must have room for
+ * at least 'count' elements, that is the argument we pass to the function
+ * to tell how many random elements we need.
+ *
+ * The function returns the number of items stored into 'des', that may
+ * be less than 'count' if the hash table has less than 'count' elements
+ * inside, or if not enough elements were found in a reasonable amount of
+ * steps.
+ *
+ * Note that this function is not suitable when you need a good distribution
+ * of the returned items, but only when you need to "sample" a given number
+ * of continuous elements to run some kind of algorithm or to produce
+ * statistics. However the function is much faster than dictGetRandomKey()
+ * at producing N elements. */
+unsigned int dictGetSomeKeys(dict *d, dictEntry **des, unsigned int count) {
+ unsigned long j; /* internal hash table id, 0 or 1. */
+ unsigned long tables; /* 1 or 2 tables? */
+ unsigned long stored = 0, maxsizemask;
+ unsigned long maxsteps;
+
+ if (dictSize(d) < count) count = dictSize(d);
+ maxsteps = count*10;
+
+ /* Try to do a rehashing work proportional to 'count'. */
+ for (j = 0; j < count; j++) {
+ if (dictIsRehashing(d))
+ _dictRehashStep(d);
+ else
+ break;
+ }
+
+ tables = dictIsRehashing(d) ? 2 : 1;
+ maxsizemask = DICTHT_SIZE_MASK(d->ht_size_exp[0]);
+ if (tables > 1 && maxsizemask < DICTHT_SIZE_MASK(d->ht_size_exp[1]))
+ maxsizemask = DICTHT_SIZE_MASK(d->ht_size_exp[1]);
+
+ /* Pick a random point inside the larger table. */
+ unsigned long i = randomULong() & maxsizemask;
+ unsigned long emptylen = 0; /* Continuous empty entries so far. */
+ while(stored < count && maxsteps--) {
+ for (j = 0; j < tables; j++) {
+ /* Invariant of the dict.c rehashing: up to the indexes already
+ * visited in ht[0] during the rehashing, there are no populated
+ * buckets, so we can skip ht[0] for indexes between 0 and idx-1. */
+ if (tables == 2 && j == 0 && i < (unsigned long) d->rehashidx) {
+ /* Moreover, if we are currently out of range in the second
+ * table, there will be no elements in both tables up to
+ * the current rehashing index, so we jump if possible.
+ * (this happens when going from big to small table). */
+ if (i >= DICTHT_SIZE(d->ht_size_exp[1]))
+ i = d->rehashidx;
+ else
+ continue;
+ }
+ if (i >= DICTHT_SIZE(d->ht_size_exp[j])) continue; /* Out of range for this table. */
+ dictEntry *he = d->ht_table[j][i];
+
+ /* Count contiguous empty buckets, and jump to other
+ * locations if they reach 'count' (with a minimum of 5). */
+ if (he == NULL) {
+ emptylen++;
+ if (emptylen >= 5 && emptylen > count) {
+ i = randomULong() & maxsizemask;
+ emptylen = 0;
+ }
+ } else {
+ emptylen = 0;
+ while (he) {
+ /* Collect all the elements of the buckets found non empty while iterating.
+ * To avoid the issue of being unable to sample the end of a long chain,
+ * we utilize the Reservoir Sampling algorithm to optimize the sampling process.
+ * This means that even when the maximum number of samples has been reached,
+ * we continue sampling until we reach the end of the chain.
+ * See https://en.wikipedia.org/wiki/Reservoir_sampling. */
+ if (stored < count) {
+ des[stored] = he;
+ } else {
+ unsigned long r = randomULong() % (stored + 1);
+ if (r < count) des[r] = he;
+ }
+
+ he = dictGetNext(he);
+ stored++;
+ }
+ if (stored >= count) goto end;
+ }
+ }
+ i = (i+1) & maxsizemask;
+ }
+
+end:
+ return stored > count ? count : stored;
+}
+
+
+/* Reallocate the dictEntry, key and value allocations in a bucket using the
+ * provided allocation functions in order to defrag them. */
+static void dictDefragBucket(dict *d, dictEntry **bucketref, dictDefragFunctions *defragfns) {
+ dictDefragAllocFunction *defragalloc = defragfns->defragAlloc;
+ dictDefragAllocFunction *defragkey = defragfns->defragKey;
+ dictDefragAllocFunction *defragval = defragfns->defragVal;
+ while (bucketref && *bucketref) {
+ dictEntry *de = *bucketref, *newde = NULL;
+ void *newkey = defragkey ? defragkey(dictGetKey(de)) : NULL;
+ void *newval = defragval ? defragval(dictGetVal(de)) : NULL;
+ if (entryIsKey(de)) {
+ if (newkey) *bucketref = newkey;
+ assert(entryIsKey(*bucketref));
+ } else if (entryIsNoValue(de)) {
+ dictEntryNoValue *entry = decodeEntryNoValue(de), *newentry;
+ if ((newentry = defragalloc(entry))) {
+ newde = encodeMaskedPtr(newentry, ENTRY_PTR_NO_VALUE);
+ entry = newentry;
+ }
+ if (newkey) entry->key = newkey;
+ } else {
+ assert(entryIsNormal(de));
+ newde = defragalloc(de);
+ if (newde) de = newde;
+ if (newkey) de->key = newkey;
+ if (newval) de->v.val = newval;
+ }
+ if (newde) {
+ *bucketref = newde;
+ if (d->type->afterReplaceEntry)
+ d->type->afterReplaceEntry(d, newde);
+ }
+ bucketref = dictGetNextRef(*bucketref);
+ }
+}
+
+/* This is like dictGetRandomKey() from the POV of the API, but will do more
+ * work to ensure a better distribution of the returned element.
+ *
+ * This function improves the distribution because the dictGetRandomKey()
+ * problem is that it selects a random bucket, then it selects a random
+ * element from the chain in the bucket. However elements being in different
+ * chain lengths will have different probabilities of being reported. With
+ * this function instead what we do is to consider a "linear" range of the table
+ * that may be constituted of N buckets with chains of different lengths
+ * appearing one after the other. Then we report a random element in the range.
+ * In this way we smooth away the problem of different chain lengths. */
+#define GETFAIR_NUM_ENTRIES 15
+dictEntry *dictGetFairRandomKey(dict *d) {
+ dictEntry *entries[GETFAIR_NUM_ENTRIES];
+ unsigned int count = dictGetSomeKeys(d,entries,GETFAIR_NUM_ENTRIES);
+ /* Note that dictGetSomeKeys() may return zero elements in an unlucky
+ * run() even if there are actually elements inside the hash table. So
+ * when we get zero, we call the true dictGetRandomKey() that will always
+ * yield the element if the hash table has at least one. */
+ if (count == 0) return dictGetRandomKey(d);
+ unsigned int idx = rand() % count;
+ return entries[idx];
+}
+
+/* Function to reverse bits. Algorithm from:
+ * http://graphics.stanford.edu/~seander/bithacks.html#ReverseParallel */
+static unsigned long rev(unsigned long v) {
+ unsigned long s = CHAR_BIT * sizeof(v); // bit size; must be power of 2
+ unsigned long mask = ~0UL;
+ while ((s >>= 1) > 0) {
+ mask ^= (mask << s);
+ v = ((v >> s) & mask) | ((v << s) & ~mask);
+ }
+ return v;
+}
+
+/* dictScan() is used to iterate over the elements of a dictionary.
+ *
+ * Iterating works the following way:
+ *
+ * 1) Initially you call the function using a cursor (v) value of 0.
+ * 2) The function performs one step of the iteration, and returns the
+ * new cursor value you must use in the next call.
+ * 3) When the returned cursor is 0, the iteration is complete.
+ *
+ * The function guarantees all elements present in the
+ * dictionary get returned between the start and end of the iteration.
+ * However it is possible some elements get returned multiple times.
+ *
+ * For every element returned, the callback argument 'fn' is
+ * called with 'privdata' as first argument and the dictionary entry
+ * 'de' as second argument.
+ *
+ * HOW IT WORKS.
+ *
+ * The iteration algorithm was designed by Pieter Noordhuis.
+ * The main idea is to increment a cursor starting from the higher order
+ * bits. That is, instead of incrementing the cursor normally, the bits
+ * of the cursor are reversed, then the cursor is incremented, and finally
+ * the bits are reversed again.
+ *
+ * This strategy is needed because the hash table may be resized between
+ * iteration calls.
+ *
+ * dict.c hash tables are always power of two in size, and they
+ * use chaining, so the position of an element in a given table is given
+ * by computing the bitwise AND between Hash(key) and SIZE-1
+ * (where SIZE-1 is always the mask that is equivalent to taking the rest
+ * of the division between the Hash of the key and SIZE).
+ *
+ * For example if the current hash table size is 16, the mask is
+ * (in binary) 1111. The position of a key in the hash table will always be
+ * the last four bits of the hash output, and so forth.
+ *
+ * WHAT HAPPENS IF THE TABLE CHANGES IN SIZE?
+ *
+ * If the hash table grows, elements can go anywhere in one multiple of
+ * the old bucket: for example let's say we already iterated with
+ * a 4 bit cursor 1100 (the mask is 1111 because hash table size = 16).
+ *
+ * If the hash table will be resized to 64 elements, then the new mask will
+ * be 111111. The new buckets you obtain by substituting in ??1100
+ * with either 0 or 1 can be targeted only by keys we already visited
+ * when scanning the bucket 1100 in the smaller hash table.
+ *
+ * By iterating the higher bits first, because of the inverted counter, the
+ * cursor does not need to restart if the table size gets bigger. It will
+ * continue iterating using cursors without '1100' at the end, and also
+ * without any other combination of the final 4 bits already explored.
+ *
+ * Similarly when the table size shrinks over time, for example going from
+ * 16 to 8, if a combination of the lower three bits (the mask for size 8
+ * is 111) were already completely explored, it would not be visited again
+ * because we are sure we tried, for example, both 0111 and 1111 (all the
+ * variations of the higher bit) so we don't need to test it again.
+ *
+ * WAIT... YOU HAVE *TWO* TABLES DURING REHASHING!
+ *
+ * Yes, this is true, but we always iterate the smaller table first, then
+ * we test all the expansions of the current cursor into the larger
+ * table. For example if the current cursor is 101 and we also have a
+ * larger table of size 16, we also test (0)101 and (1)101 inside the larger
+ * table. This reduces the problem back to having only one table, where
+ * the larger one, if it exists, is just an expansion of the smaller one.
+ *
+ * LIMITATIONS
+ *
+ * This iterator is completely stateless, and this is a huge advantage,
+ * including no additional memory used.
+ *
+ * The disadvantages resulting from this design are:
+ *
+ * 1) It is possible we return elements more than once. However this is usually
+ * easy to deal with in the application level.
+ * 2) The iterator must return multiple elements per call, as it needs to always
+ * return all the keys chained in a given bucket, and all the expansions, so
+ * we are sure we don't miss keys moving during rehashing.
+ * 3) The reverse cursor is somewhat hard to understand at first, but this
+ * comment is supposed to help.
+ */
+unsigned long dictScan(dict *d,
+ unsigned long v,
+ dictScanFunction *fn,
+ void *privdata)
+{
+ return dictScanDefrag(d, v, fn, NULL, privdata);
+}
+
+/* Like dictScan, but additionally reallocates the memory used by the dict
+ * entries using the provided allocation function. This feature was added for
+ * the active defrag feature.
+ *
+ * The 'defragfns' callbacks are called with a pointer to memory that callback
+ * can reallocate. The callbacks should return a new memory address or NULL,
+ * where NULL means that no reallocation happened and the old memory is still
+ * valid. */
+unsigned long dictScanDefrag(dict *d,
+ unsigned long v,
+ dictScanFunction *fn,
+ dictDefragFunctions *defragfns,
+ void *privdata)
+{
+ int htidx0, htidx1;
+ const dictEntry *de, *next;
+ unsigned long m0, m1;
+
+ if (dictSize(d) == 0) return 0;
+
+ /* This is needed in case the scan callback tries to do dictFind or alike. */
+ dictPauseRehashing(d);
+
+ if (!dictIsRehashing(d)) {
+ htidx0 = 0;
+ m0 = DICTHT_SIZE_MASK(d->ht_size_exp[htidx0]);
+
+ /* Emit entries at cursor */
+ if (defragfns) {
+ dictDefragBucket(d, &d->ht_table[htidx0][v & m0], defragfns);
+ }
+ de = d->ht_table[htidx0][v & m0];
+ while (de) {
+ next = dictGetNext(de);
+ fn(privdata, de);
+ de = next;
+ }
+
+ /* Set unmasked bits so incrementing the reversed cursor
+ * operates on the masked bits */
+ v |= ~m0;
+
+ /* Increment the reverse cursor */
+ v = rev(v);
+ v++;
+ v = rev(v);
+
+ } else {
+ htidx0 = 0;
+ htidx1 = 1;
+
+ /* Make sure t0 is the smaller and t1 is the bigger table */
+ if (DICTHT_SIZE(d->ht_size_exp[htidx0]) > DICTHT_SIZE(d->ht_size_exp[htidx1])) {
+ htidx0 = 1;
+ htidx1 = 0;
+ }
+
+ m0 = DICTHT_SIZE_MASK(d->ht_size_exp[htidx0]);
+ m1 = DICTHT_SIZE_MASK(d->ht_size_exp[htidx1]);
+
+ /* Emit entries at cursor */
+ if (defragfns) {
+ dictDefragBucket(d, &d->ht_table[htidx0][v & m0], defragfns);
+ }
+ de = d->ht_table[htidx0][v & m0];
+ while (de) {
+ next = dictGetNext(de);
+ fn(privdata, de);
+ de = next;
+ }
+
+ /* Iterate over indices in larger table that are the expansion
+ * of the index pointed to by the cursor in the smaller table */
+ do {
+ /* Emit entries at cursor */
+ if (defragfns) {
+ dictDefragBucket(d, &d->ht_table[htidx1][v & m1], defragfns);
+ }
+ de = d->ht_table[htidx1][v & m1];
+ while (de) {
+ next = dictGetNext(de);
+ fn(privdata, de);
+ de = next;
+ }
+
+ /* Increment the reverse cursor not covered by the smaller mask.*/
+ v |= ~m1;
+ v = rev(v);
+ v++;
+ v = rev(v);
+
+ /* Continue while bits covered by mask difference is non-zero */
+ } while (v & (m0 ^ m1));
+ }
+
+ dictResumeRehashing(d);
+
+ return v;
+}
+
+/* ------------------------- private functions ------------------------------ */
+
+/* Because we may need to allocate huge memory chunk at once when dict
+ * expands, we will check this allocation is allowed or not if the dict
+ * type has expandAllowed member function. */
+static int dictTypeExpandAllowed(dict *d) {
+ if (d->type->expandAllowed == NULL) return 1;
+ return d->type->expandAllowed(
+ DICTHT_SIZE(_dictNextExp(d->ht_used[0] + 1)) * sizeof(dictEntry*),
+ (double)d->ht_used[0] / DICTHT_SIZE(d->ht_size_exp[0]));
+}
+
+/* Expand the hash table if needed */
+static int _dictExpandIfNeeded(dict *d)
+{
+ /* Incremental rehashing already in progress. Return. */
+ if (dictIsRehashing(d)) return DICT_OK;
+
+ /* If the hash table is empty expand it to the initial size. */
+ if (DICTHT_SIZE(d->ht_size_exp[0]) == 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 ((dict_can_resize == DICT_RESIZE_ENABLE &&
+ d->ht_used[0] >= DICTHT_SIZE(d->ht_size_exp[0])) ||
+ (dict_can_resize != DICT_RESIZE_FORBID &&
+ d->ht_used[0] / DICTHT_SIZE(d->ht_size_exp[0]) > dict_force_resize_ratio))
+ {
+ if (!dictTypeExpandAllowed(d))
+ return DICT_OK;
+ return dictExpand(d, d->ht_used[0] + 1);
+ }
+ return DICT_OK;
+}
+
+/* Our hash table capability is a power of two */
+static signed char _dictNextExp(unsigned long size)
+{
+ if (size <= DICT_HT_INITIAL_SIZE) return DICT_HT_INITIAL_EXP;
+ if (size >= LONG_MAX) return (8*sizeof(long)-1);
+
+ return 8*sizeof(long) - __builtin_clzl(size-1);
+}
+
+/* Finds and returns the position within the dict where the provided key should
+ * be inserted using dictInsertAtPosition if the key does not already exist in
+ * the dict. If the key exists in the dict, NULL is returned and the optional
+ * 'existing' entry pointer is populated, if provided. */
+void *dictFindPositionForInsert(dict *d, const void *key, dictEntry **existing) {
+ unsigned long idx, table;
+ dictEntry *he;
+ uint64_t hash = dictHashKey(d, key);
+ if (existing) *existing = NULL;
+ if (dictIsRehashing(d)) _dictRehashStep(d);
+
+ /* Expand the hash table if needed */
+ if (_dictExpandIfNeeded(d) == DICT_ERR)
+ return NULL;
+ for (table = 0; table <= 1; table++) {
+ idx = hash & DICTHT_SIZE_MASK(d->ht_size_exp[table]);
+ /* Search if this slot does not already contain the given key */
+ he = d->ht_table[table][idx];
+ while(he) {
+ void *he_key = dictGetKey(he);
+ if (key == he_key || dictCompareKeys(d, key, he_key)) {
+ if (existing) *existing = he;
+ return NULL;
+ }
+ he = dictGetNext(he);
+ }
+ if (!dictIsRehashing(d)) break;
+ }
+
+ /* If we are in the process of rehashing the hash table, the bucket is
+ * always returned in the context of the second (new) hash table. */
+ dictEntry **bucket = &d->ht_table[dictIsRehashing(d) ? 1 : 0][idx];
+ return bucket;
+}
+
+void dictEmpty(dict *d, void(callback)(dict*)) {
+ _dictClear(d,0,callback);
+ _dictClear(d,1,callback);
+ d->rehashidx = -1;
+ d->pauserehash = 0;
+}
+
+void dictSetResizeEnabled(dictResizeEnable enable) {
+ dict_can_resize = enable;
+}
+
+uint64_t dictGetHash(dict *d, const void *key) {
+ return dictHashKey(d, key);
+}
+
+/* Finds the dictEntry using pointer and pre-calculated hash.
+ * oldkey is a dead pointer and should not be accessed.
+ * the hash value should be provided using dictGetHash.
+ * no string / key comparison is performed.
+ * return value is a pointer to the dictEntry if found, or NULL if not found. */
+dictEntry *dictFindEntryByPtrAndHash(dict *d, const void *oldptr, uint64_t hash) {
+ dictEntry *he;
+ unsigned long idx, table;
+
+ if (dictSize(d) == 0) return NULL; /* dict is empty */
+ for (table = 0; table <= 1; table++) {
+ idx = hash & DICTHT_SIZE_MASK(d->ht_size_exp[table]);
+ he = d->ht_table[table][idx];
+ while(he) {
+ if (oldptr == dictGetKey(he))
+ return he;
+ he = dictGetNext(he);
+ }
+ if (!dictIsRehashing(d)) return NULL;
+ }
+ return NULL;
+}
+
+/* ------------------------------- Debugging ---------------------------------*/
+
+#define DICT_STATS_VECTLEN 50
+size_t _dictGetStatsHt(char *buf, size_t bufsize, dict *d, int htidx, int full) {
+ unsigned long i, slots = 0, chainlen, maxchainlen = 0;
+ unsigned long totchainlen = 0;
+ unsigned long clvector[DICT_STATS_VECTLEN];
+ size_t l = 0;
+
+ if (d->ht_used[htidx] == 0) {
+ return snprintf(buf,bufsize,
+ "Hash table %d stats (%s):\n"
+ "No stats available for empty dictionaries\n",
+ htidx, (htidx == 0) ? "main hash table" : "rehashing target");
+ }
+
+ if (!full) {
+ l += snprintf(buf+l,bufsize-l,
+ "Hash table %d stats (%s):\n"
+ " table size: %lu\n"
+ " number of elements: %lu\n",
+ htidx, (htidx == 0) ? "main hash table" : "rehashing target",
+ DICTHT_SIZE(d->ht_size_exp[htidx]), d->ht_used[htidx]);
+
+ /* Make sure there is a NULL term at the end. */
+ buf[bufsize-1] = '\0';
+ /* Unlike snprintf(), return the number of characters actually written. */
+ return strlen(buf);
+ }
+
+ /* Compute stats. */
+ for (i = 0; i < DICT_STATS_VECTLEN; i++) clvector[i] = 0;
+ for (i = 0; i < DICTHT_SIZE(d->ht_size_exp[htidx]); i++) {
+ dictEntry *he;
+
+ if (d->ht_table[htidx][i] == NULL) {
+ clvector[0]++;
+ continue;
+ }
+ slots++;
+ /* For each hash entry on this slot... */
+ chainlen = 0;
+ he = d->ht_table[htidx][i];
+ while(he) {
+ chainlen++;
+ he = dictGetNext(he);
+ }
+ clvector[(chainlen < DICT_STATS_VECTLEN) ? chainlen : (DICT_STATS_VECTLEN-1)]++;
+ if (chainlen > maxchainlen) maxchainlen = chainlen;
+ totchainlen += chainlen;
+ }
+
+ /* Generate human readable stats. */
+ l += snprintf(buf+l,bufsize-l,
+ "Hash table %d stats (%s):\n"
+ " table size: %lu\n"
+ " number of elements: %lu\n"
+ " different slots: %lu\n"
+ " max chain length: %lu\n"
+ " avg chain length (counted): %.02f\n"
+ " avg chain length (computed): %.02f\n"
+ " Chain length distribution:\n",
+ htidx, (htidx == 0) ? "main hash table" : "rehashing target",
+ DICTHT_SIZE(d->ht_size_exp[htidx]), d->ht_used[htidx], slots, maxchainlen,
+ (float)totchainlen/slots, (float)d->ht_used[htidx]/slots);
+
+ for (i = 0; i < DICT_STATS_VECTLEN-1; i++) {
+ if (clvector[i] == 0) continue;
+ if (l >= bufsize) break;
+ l += snprintf(buf+l,bufsize-l,
+ " %ld: %ld (%.02f%%)\n",
+ i, clvector[i], ((float)clvector[i]/DICTHT_SIZE(d->ht_size_exp[htidx]))*100);
+ }
+
+ /* Make sure there is a NULL term at the end. */
+ buf[bufsize-1] = '\0';
+ /* Unlike snprintf(), return the number of characters actually written. */
+ return strlen(buf);
+}
+
+void dictGetStats(char *buf, size_t bufsize, dict *d, int full) {
+ size_t l;
+ char *orig_buf = buf;
+ size_t orig_bufsize = bufsize;
+
+ l = _dictGetStatsHt(buf,bufsize,d,0,full);
+ if (dictIsRehashing(d) && bufsize > l) {
+ buf += l;
+ bufsize -= l;
+ _dictGetStatsHt(buf,bufsize,d,1,full);
+ }
+ /* Make sure there is a NULL term at the end. */
+ orig_buf[orig_bufsize-1] = '\0';
+}
+
+/* ------------------------------- Benchmark ---------------------------------*/
+
+#ifdef REDIS_TEST
+#include "testhelp.h"
+
+#define UNUSED(V) ((void) V)
+
+uint64_t hashCallback(const void *key) {
+ return dictGenHashFunction((unsigned char*)key, strlen((char*)key));
+}
+
+int compareCallback(dict *d, const void *key1, const void *key2) {
+ int l1,l2;
+ UNUSED(d);
+
+ l1 = strlen((char*)key1);
+ l2 = strlen((char*)key2);
+ if (l1 != l2) return 0;
+ return memcmp(key1, key2, l1) == 0;
+}
+
+void freeCallback(dict *d, void *val) {
+ UNUSED(d);
+
+ zfree(val);
+}
+
+char *stringFromLongLong(long long value) {
+ char buf[32];
+ int len;
+ char *s;
+
+ len = snprintf(buf,sizeof(buf),"%lld",value);
+ s = zmalloc(len+1);
+ memcpy(s, buf, len);
+ s[len] = '\0';
+ return s;
+}
+
+dictType BenchmarkDictType = {
+ hashCallback,
+ NULL,
+ NULL,
+ compareCallback,
+ freeCallback,
+ NULL,
+ NULL
+};
+
+#define start_benchmark() start = timeInMilliseconds()
+#define end_benchmark(msg) do { \
+ elapsed = timeInMilliseconds()-start; \
+ printf(msg ": %ld items in %lld ms\n", count, elapsed); \
+} while(0)
+
+/* ./redis-server test dict [<count> | --accurate] */
+int dictTest(int argc, char **argv, int flags) {
+ long j;
+ long long start, elapsed;
+ dict *dict = dictCreate(&BenchmarkDictType);
+ long count = 0;
+ int accurate = (flags & REDIS_TEST_ACCURATE);
+
+ if (argc == 4) {
+ if (accurate) {
+ count = 5000000;
+ } else {
+ count = strtol(argv[3],NULL,10);
+ }
+ } else {
+ count = 5000;
+ }
+
+ start_benchmark();
+ for (j = 0; j < count; j++) {
+ int retval = dictAdd(dict,stringFromLongLong(j),(void*)j);
+ assert(retval == DICT_OK);
+ }
+ end_benchmark("Inserting");
+ assert((long)dictSize(dict) == count);
+
+ /* Wait for rehashing. */
+ while (dictIsRehashing(dict)) {
+ dictRehashMilliseconds(dict,100);
+ }
+
+ start_benchmark();
+ for (j = 0; j < count; j++) {
+ char *key = stringFromLongLong(j);
+ dictEntry *de = dictFind(dict,key);
+ assert(de != NULL);
+ zfree(key);
+ }
+ end_benchmark("Linear access of existing elements");
+
+ start_benchmark();
+ for (j = 0; j < count; j++) {
+ char *key = stringFromLongLong(j);
+ dictEntry *de = dictFind(dict,key);
+ assert(de != NULL);
+ zfree(key);
+ }
+ end_benchmark("Linear access of existing elements (2nd round)");
+
+ start_benchmark();
+ for (j = 0; j < count; j++) {
+ char *key = stringFromLongLong(rand() % count);
+ dictEntry *de = dictFind(dict,key);
+ assert(de != NULL);
+ zfree(key);
+ }
+ end_benchmark("Random access of existing elements");
+
+ start_benchmark();
+ for (j = 0; j < count; j++) {
+ dictEntry *de = dictGetRandomKey(dict);
+ assert(de != NULL);
+ }
+ end_benchmark("Accessing random keys");
+
+ start_benchmark();
+ for (j = 0; j < count; j++) {
+ char *key = stringFromLongLong(rand() % count);
+ key[0] = 'X';
+ dictEntry *de = dictFind(dict,key);
+ assert(de == NULL);
+ zfree(key);
+ }
+ end_benchmark("Accessing missing");
+
+ start_benchmark();
+ for (j = 0; j < count; j++) {
+ char *key = stringFromLongLong(j);
+ int retval = dictDelete(dict,key);
+ assert(retval == DICT_OK);
+ key[0] += 17; /* Change first number to letter. */
+ retval = dictAdd(dict,key,(void*)j);
+ assert(retval == DICT_OK);
+ }
+ end_benchmark("Removing and adding");
+ dictRelease(dict);
+ return 0;
+}
+#endif