The Tor Browser: nsprpub/lib/ds/plhash.c@7e26c7da4463 (annotated)

nsprpub/lib/ds/plhash.c@7e26c7da4463 (annotated)

nsprpub/lib/ds/plhash.c

Wed, 31 Dec 2014 06:55:50 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:55:50 +0100
changeset 2: 7e26c7da4463
permissions: -rw-r--r--

Added tag UPSTREAM_283F7C6 for changeset ca08bd8f51b2

 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 /*
  * PL hash table package.
  */
 #include "plhash.h"
 #include "prbit.h"
 #include "prlog.h"
 #include "prmem.h"
 #include "prtypes.h"
 #include <stdlib.h>
 #include <string.h>
 /* Compute the number of buckets in ht */
 #define NBUCKETS(ht)    (1 << (PL_HASH_BITS - (ht)->shift))
 /* The smallest table has 16 buckets */
 #define MINBUCKETSLOG2  4
 #define MINBUCKETS      (1 << MINBUCKETSLOG2)
 /* Compute the maximum entries given n buckets that we will tolerate, ~90% */
 #define OVERLOADED(n)   ((n) - ((n) >> 3))
 /* Compute the number of entries below which we shrink the table by half */
 #define UNDERLOADED(n)  (((n) > MINBUCKETS) ? ((n) >> 2) : 0)
 /*
 ** Stubs for default hash allocator ops.
 */
 static void * PR_CALLBACK
 DefaultAllocTable(void *pool, PRSize size)
 {
     return PR_MALLOC(size);
 }
 static void PR_CALLBACK
 DefaultFreeTable(void *pool, void *item)
 {
     PR_Free(item);
 }
 static PLHashEntry * PR_CALLBACK
 DefaultAllocEntry(void *pool, const void *key)
 {
     return PR_NEW(PLHashEntry);
 }
 static void PR_CALLBACK
 DefaultFreeEntry(void *pool, PLHashEntry *he, PRUintn flag)
 {
     if (flag == HT_FREE_ENTRY)
         PR_Free(he);
 }
 static PLHashAllocOps defaultHashAllocOps = {
     DefaultAllocTable, DefaultFreeTable,
     DefaultAllocEntry, DefaultFreeEntry
 };
 PR_IMPLEMENT(PLHashTable *)
 PL_NewHashTable(PRUint32 n, PLHashFunction keyHash,
                 PLHashComparator keyCompare, PLHashComparator valueCompare,
                 const PLHashAllocOps *allocOps, void *allocPriv)
 {
     PLHashTable *ht;
     PRSize nb;
     if (n <= MINBUCKETS) {
         n = MINBUCKETSLOG2;
     } else {
         n = PR_CeilingLog2(n);
         if ((PRInt32)n < 0)
             return 0;
     }
     if (!allocOps) allocOps = &defaultHashAllocOps;
     ht = (PLHashTable*)((*allocOps->allocTable)(allocPriv, sizeof *ht));
     if (!ht)
 	return 0;
     memset(ht, 0, sizeof *ht);
     ht->shift = PL_HASH_BITS - n;
     n = 1 << n;
     nb = n * sizeof(PLHashEntry *);
     ht->buckets = (PLHashEntry**)((*allocOps->allocTable)(allocPriv, nb));
     if (!ht->buckets) {
         (*allocOps->freeTable)(allocPriv, ht);
         return 0;
     }
     memset(ht->buckets, 0, nb);
     ht->keyHash = keyHash;
     ht->keyCompare = keyCompare;
     ht->valueCompare = valueCompare;
     ht->allocOps = allocOps;
     ht->allocPriv = allocPriv;
     return ht;
 }
 PR_IMPLEMENT(void)
 PL_HashTableDestroy(PLHashTable *ht)
 {
     PRUint32 i, n;
     PLHashEntry *he, *next;
     const PLHashAllocOps *allocOps = ht->allocOps;
     void *allocPriv = ht->allocPriv;
     n = NBUCKETS(ht);
     for (i = 0; i < n; i++) {
         for (he = ht->buckets[i]; he; he = next) {
             next = he->next;
             (*allocOps->freeEntry)(allocPriv, he, HT_FREE_ENTRY);
         }
     }
 #ifdef DEBUG
     memset(ht->buckets, 0xDB, n * sizeof ht->buckets[0]);
 #endif
     (*allocOps->freeTable)(allocPriv, ht->buckets);
 #ifdef DEBUG
     memset(ht, 0xDB, sizeof *ht);
 #endif
     (*allocOps->freeTable)(allocPriv, ht);
 }
 /*
 ** Multiplicative hash, from Knuth 6.4.
 */
 #define GOLDEN_RATIO    0x9E3779B9U  /* 2/(1+sqrt(5))*(2^32) */
 PR_IMPLEMENT(PLHashEntry **)
 PL_HashTableRawLookup(PLHashTable *ht, PLHashNumber keyHash, const void *key)
 {
     PLHashEntry *he, **hep, **hep0;
     PLHashNumber h;
 #ifdef HASHMETER
     ht->nlookups++;
 #endif
     h = keyHash * GOLDEN_RATIO;
     h >>= ht->shift;
     hep = hep0 = &ht->buckets[h];
     while ((he = *hep) != 0) {
         if (he->keyHash == keyHash && (*ht->keyCompare)(key, he->key)) {
             /* Move to front of chain if not already there */
             if (hep != hep0) {
                 *hep = he->next;
                 he->next = *hep0;
                 *hep0 = he;
             }
             return hep0;
         }
         hep = &he->next;
 #ifdef HASHMETER
         ht->nsteps++;
 #endif
     }
     return hep;
 }
 /*
 ** Same as PL_HashTableRawLookup but doesn't reorder the hash entries.
 */
 PR_IMPLEMENT(PLHashEntry **)
 PL_HashTableRawLookupConst(PLHashTable *ht, PLHashNumber keyHash,
                            const void *key)
 {
     PLHashEntry *he, **hep;
     PLHashNumber h;
 #ifdef HASHMETER
     ht->nlookups++;
 #endif
     h = keyHash * GOLDEN_RATIO;
     h >>= ht->shift;
     hep = &ht->buckets[h];
     while ((he = *hep) != 0) {
         if (he->keyHash == keyHash && (*ht->keyCompare)(key, he->key)) {
             break;
         }
         hep = &he->next;
 #ifdef HASHMETER
         ht->nsteps++;
 #endif
     }
     return hep;
 }
 PR_IMPLEMENT(PLHashEntry *)
 PL_HashTableRawAdd(PLHashTable *ht, PLHashEntry **hep,
                    PLHashNumber keyHash, const void *key, void *value)
 {
     PRUint32 i, n;
     PLHashEntry *he, *next, **oldbuckets;
     PRSize nb;
     /* Grow the table if it is overloaded */
     n = NBUCKETS(ht);
     if (ht->nentries >= OVERLOADED(n)) {
         oldbuckets = ht->buckets;
         nb = 2 * n * sizeof(PLHashEntry *);
         ht->buckets = (PLHashEntry**)
             ((*ht->allocOps->allocTable)(ht->allocPriv, nb));
         if (!ht->buckets) {
             ht->buckets = oldbuckets;
             return 0;
         }
         memset(ht->buckets, 0, nb);
 #ifdef HASHMETER
         ht->ngrows++;
 #endif
         ht->shift--;
         for (i = 0; i < n; i++) {
             for (he = oldbuckets[i]; he; he = next) {
                 next = he->next;
                 hep = PL_HashTableRawLookup(ht, he->keyHash, he->key);
                 PR_ASSERT(*hep == 0);
                 he->next = 0;
                 *hep = he;
             }
         }
 #ifdef DEBUG
         memset(oldbuckets, 0xDB, n * sizeof oldbuckets[0]);
 #endif
         (*ht->allocOps->freeTable)(ht->allocPriv, oldbuckets);
         hep = PL_HashTableRawLookup(ht, keyHash, key);
     }
     /* Make a new key value entry */
     he = (*ht->allocOps->allocEntry)(ht->allocPriv, key);
     if (!he)
 	return 0;
     he->keyHash = keyHash;
     he->key = key;
     he->value = value;
     he->next = *hep;
     *hep = he;
     ht->nentries++;
     return he;
 }
 PR_IMPLEMENT(PLHashEntry *)
 PL_HashTableAdd(PLHashTable *ht, const void *key, void *value)
 {
     PLHashNumber keyHash;
     PLHashEntry *he, **hep;
     keyHash = (*ht->keyHash)(key);
     hep = PL_HashTableRawLookup(ht, keyHash, key);
     if ((he = *hep) != 0) {
         /* Hit; see if values match */
         if ((*ht->valueCompare)(he->value, value)) {
             /* key,value pair is already present in table */
             return he;
         }
         if (he->value)
             (*ht->allocOps->freeEntry)(ht->allocPriv, he, HT_FREE_VALUE);
         he->value = value;
         return he;
     }
     return PL_HashTableRawAdd(ht, hep, keyHash, key, value);
 }
 PR_IMPLEMENT(void)
 PL_HashTableRawRemove(PLHashTable *ht, PLHashEntry **hep, PLHashEntry *he)
 {
     PRUint32 i, n;
     PLHashEntry *next, **oldbuckets;
     PRSize nb;
     *hep = he->next;
     (*ht->allocOps->freeEntry)(ht->allocPriv, he, HT_FREE_ENTRY);
     /* Shrink table if it's underloaded */
     n = NBUCKETS(ht);
     if (--ht->nentries < UNDERLOADED(n)) {
         oldbuckets = ht->buckets;
         nb = n * sizeof(PLHashEntry*) / 2;
         ht->buckets = (PLHashEntry**)(
             (*ht->allocOps->allocTable)(ht->allocPriv, nb));
         if (!ht->buckets) {
             ht->buckets = oldbuckets;
             return;
         }
         memset(ht->buckets, 0, nb);
 #ifdef HASHMETER
         ht->nshrinks++;
 #endif
         ht->shift++;
         for (i = 0; i < n; i++) {
             for (he = oldbuckets[i]; he; he = next) {
                 next = he->next;
                 hep = PL_HashTableRawLookup(ht, he->keyHash, he->key);
                 PR_ASSERT(*hep == 0);
                 he->next = 0;
                 *hep = he;
             }
         }
 #ifdef DEBUG
         memset(oldbuckets, 0xDB, n * sizeof oldbuckets[0]);
 #endif
         (*ht->allocOps->freeTable)(ht->allocPriv, oldbuckets);
     }
 }
 PR_IMPLEMENT(PRBool)
 PL_HashTableRemove(PLHashTable *ht, const void *key)
 {
     PLHashNumber keyHash;
     PLHashEntry *he, **hep;
     keyHash = (*ht->keyHash)(key);
     hep = PL_HashTableRawLookup(ht, keyHash, key);
     if ((he = *hep) == 0)
         return PR_FALSE;
     /* Hit; remove element */
     PL_HashTableRawRemove(ht, hep, he);
     return PR_TRUE;
 }
 PR_IMPLEMENT(void *)
 PL_HashTableLookup(PLHashTable *ht, const void *key)
 {
     PLHashNumber keyHash;
     PLHashEntry *he, **hep;
     keyHash = (*ht->keyHash)(key);
     hep = PL_HashTableRawLookup(ht, keyHash, key);
     if ((he = *hep) != 0) {
         return he->value;
     }
     return 0;
 }
 /*
 ** Same as PL_HashTableLookup but doesn't reorder the hash entries.
 */
 PR_IMPLEMENT(void *)
 PL_HashTableLookupConst(PLHashTable *ht, const void *key)
 {
     PLHashNumber keyHash;
     PLHashEntry *he, **hep;
     keyHash = (*ht->keyHash)(key);
     hep = PL_HashTableRawLookupConst(ht, keyHash, key);
     if ((he = *hep) != 0) {
         return he->value;
     }
     return 0;
 }
 /*
 ** Iterate over the entries in the hash table calling func for each
 ** entry found. Stop if "f" says to (return value & PR_ENUMERATE_STOP).
 ** Return a count of the number of elements scanned.
 */
 PR_IMPLEMENT(int)
 PL_HashTableEnumerateEntries(PLHashTable *ht, PLHashEnumerator f, void *arg)
 {
     PLHashEntry *he, **hep;
     PRUint32 i, nbuckets;
     int rv, n = 0;
     PLHashEntry *todo = 0;
     nbuckets = NBUCKETS(ht);
     for (i = 0; i < nbuckets; i++) {
         hep = &ht->buckets[i];
         while ((he = *hep) != 0) {
             rv = (*f)(he, n, arg);
             n++;
             if (rv & (HT_ENUMERATE_REMOVE | HT_ENUMERATE_UNHASH)) {
                 *hep = he->next;
                 if (rv & HT_ENUMERATE_REMOVE) {
                     he->next = todo;
                     todo = he;
                 }
             } else {
                 hep = &he->next;
             }
             if (rv & HT_ENUMERATE_STOP) {
                 goto out;
             }
         }
     }
 out:
     hep = &todo;
     while ((he = *hep) != 0) {
         PL_HashTableRawRemove(ht, hep, he);
     }
     return n;
 }
 #ifdef HASHMETER
 #include <math.h>
 #include <stdio.h>
 PR_IMPLEMENT(void)
 PL_HashTableDumpMeter(PLHashTable *ht, PLHashEnumerator dump, FILE *fp)
 {
     double mean, variance;
     PRUint32 nchains, nbuckets;
     PRUint32 i, n, maxChain, maxChainLen;
     PLHashEntry *he;
     variance = 0;
     nchains = 0;
     maxChainLen = 0;
     nbuckets = NBUCKETS(ht);
     for (i = 0; i < nbuckets; i++) {
         he = ht->buckets[i];
         if (!he)
             continue;
         nchains++;
         for (n = 0; he; he = he->next)
             n++;
         variance += n * n;
         if (n > maxChainLen) {
             maxChainLen = n;
             maxChain = i;
         }
     }
     mean = (double)ht->nentries / nchains;
     variance = fabs(variance / nchains - mean * mean);
     fprintf(fp, "\nHash table statistics:\n");
     fprintf(fp, "     number of lookups: %u\n", ht->nlookups);
     fprintf(fp, "     number of entries: %u\n", ht->nentries);
     fprintf(fp, "       number of grows: %u\n", ht->ngrows);
     fprintf(fp, "     number of shrinks: %u\n", ht->nshrinks);
     fprintf(fp, "   mean steps per hash: %g\n", (double)ht->nsteps
                                                 / ht->nlookups);
     fprintf(fp, "mean hash chain length: %g\n", mean);
     fprintf(fp, "    standard deviation: %g\n", sqrt(variance));
     fprintf(fp, " max hash chain length: %u\n", maxChainLen);
     fprintf(fp, "        max hash chain: [%u]\n", maxChain);
     for (he = ht->buckets[maxChain], i = 0; he; he = he->next, i++)
         if ((*dump)(he, i, fp) != HT_ENUMERATE_NEXT)
             break;
 }
 #endif /* HASHMETER */
 PR_IMPLEMENT(int)
 PL_HashTableDump(PLHashTable *ht, PLHashEnumerator dump, FILE *fp)
 {
     int count;
     count = PL_HashTableEnumerateEntries(ht, dump, fp);
 #ifdef HASHMETER
     PL_HashTableDumpMeter(ht, dump, fp);
 #endif
     return count;
 }
 PR_IMPLEMENT(PLHashNumber)
 PL_HashString(const void *key)
 {
     PLHashNumber h;
     const PRUint8 *s;
     h = 0;
     for (s = (const PRUint8*)key; *s; s++)
         h = PR_ROTATE_LEFT32(h, 4) ^ *s;
     return h;
 }
 PR_IMPLEMENT(int)
 PL_CompareStrings(const void *v1, const void *v2)
 {
     return strcmp((const char*)v1, (const char*)v2) == 0;
 }
 PR_IMPLEMENT(int)
 PL_CompareValues(const void *v1, const void *v2)
 {
     return v1 == v2;
 }

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nsprpub/lib/ds/plhash.c@7e26c7da4463 (annotated)

nsprpub/lib/ds/plhash.c