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Diffstat (limited to 'src/dict.c')
| -rw-r--r-- | src/dict.c | 1749 |
1 files changed, 1749 insertions, 0 deletions
diff --git a/src/dict.c b/src/dict.c new file mode 100644 index 0000000..e34fa02 --- /dev/null +++ b/src/dict.c @@ -0,0 +1,1749 @@ +/* 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 |