The Tor Browser: js/jsd/jshash.cpp@6474c204b198 (annotated)

js/jsd/jshash.cpp@6474c204b198 (annotated)

js/jsd/jshash.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  * vim: set ts=8 sts=4 et sw=4 tw=99:
  * 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/. */
 /*
  * PR hash table package.
  */
 #include "jshash.h"
 #include "mozilla/MathAlgorithms.h"
 #include <stdlib.h>
 #include <string.h>
 #include "jstypes.h"
 #include "js/Utility.h"
 using namespace js;
 using mozilla::CeilingLog2Size;
 using mozilla::RotateLeft;
 /* Compute the number of buckets in ht */
 #define NBUCKETS(ht)    JS_BIT(JS_HASH_BITS - (ht)->shift)
 /* The smallest table has 16 buckets */
 #define MINBUCKETSLOG2  4
 #define MINBUCKETS      JS_BIT(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 *
 DefaultAllocTable(void *pool, size_t size)
 {
     return js_malloc(size);
 }
 static void
 DefaultFreeTable(void *pool, void *item, size_t size)
 {
     js_free(item);
 }
 static JSHashEntry *
 DefaultAllocEntry(void *pool, const void *key)
 {
     return (JSHashEntry*) js_malloc(sizeof(JSHashEntry));
 }
 static void
 DefaultFreeEntry(void *pool, JSHashEntry *he, unsigned flag)
 {
     if (flag == HT_FREE_ENTRY)
         js_free(he);
 }
 static const JSHashAllocOps defaultHashAllocOps = {
     DefaultAllocTable, DefaultFreeTable,
     DefaultAllocEntry, DefaultFreeEntry
 };
 JSHashTable *
 JS_NewHashTable(uint32_t n, JSHashFunction keyHash,
                 JSHashComparator keyCompare, JSHashComparator valueCompare,
                 const JSHashAllocOps *allocOps, void *allocPriv)
 {
     JSHashTable *ht;
     size_t nb;
     if (n <= MINBUCKETS) {
         n = MINBUCKETSLOG2;
     } else {
         n = CeilingLog2Size(n);
         if (int32_t(n) < 0)
             return nullptr;
     }
     if (!allocOps) allocOps = &defaultHashAllocOps;
     ht = (JSHashTable*) allocOps->allocTable(allocPriv, sizeof *ht);
     if (!ht)
         return nullptr;
     memset(ht, 0, sizeof *ht);
     ht->shift = JS_HASH_BITS - n;
     n = JS_BIT(n);
     nb = n * sizeof(JSHashEntry *);
     ht->buckets = (JSHashEntry**) allocOps->allocTable(allocPriv, nb);
     if (!ht->buckets) {
         allocOps->freeTable(allocPriv, ht, nb);
         return nullptr;
     }
     memset(ht->buckets, 0, nb);
     ht->keyHash = keyHash;
     ht->keyCompare = keyCompare;
     ht->valueCompare = valueCompare;
     ht->allocOps = allocOps;
     ht->allocPriv = allocPriv;
     return ht;
 }
 void
 JS_HashTableDestroy(JSHashTable *ht)
 {
     uint32_t i, n;
     JSHashEntry *he, **hep;
     const JSHashAllocOps *allocOps = ht->allocOps;
     void *allocPriv = ht->allocPriv;
     n = NBUCKETS(ht);
     for (i = 0; i < n; i++) {
         hep = &ht->buckets[i];
         while ((he = *hep) != nullptr) {
             *hep = 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, n * sizeof ht->buckets[0]);
 #ifdef DEBUG
     memset(ht, 0xDB, sizeof *ht);
 #endif
     allocOps->freeTable(allocPriv, ht, sizeof *ht);
 }
 /*
  * Multiplicative hash, from Knuth 6.4.
  */
 #define BUCKET_HEAD(ht, keyHash)                                              \
     (&(ht)->buckets[((keyHash) * JS_GOLDEN_RATIO) >> (ht)->shift])
 JSHashEntry **
 JS_HashTableRawLookup(JSHashTable *ht, JSHashNumber keyHash, const void *key)
 {
     JSHashEntry *he, **hep, **hep0;
 #ifdef JS_HASHMETER
     ht->nlookups++;
 #endif
     hep = hep0 = BUCKET_HEAD(ht, keyHash);
     while ((he = *hep) != nullptr) {
         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 JS_HASHMETER
         ht->nsteps++;
 #endif
     }
     return hep;
 }
 static bool
 Resize(JSHashTable *ht, uint32_t newshift)
 {
     size_t nb, nentries, i;
     JSHashEntry **oldbuckets, *he, *next, **hep;
     size_t nold = NBUCKETS(ht);
     MOZ_ASSERT(newshift < JS_HASH_BITS);
     nb = (size_t)1 << (JS_HASH_BITS - newshift);
     /* Integer overflow protection. */
     if (nb > (size_t)-1 / sizeof(JSHashEntry*))
         return false;
     nb *= sizeof(JSHashEntry*);
     oldbuckets = ht->buckets;
     ht->buckets = (JSHashEntry**)ht->allocOps->allocTable(ht->allocPriv, nb);
     if (!ht->buckets) {
         ht->buckets = oldbuckets;
         return false;
     }
     memset(ht->buckets, 0, nb);
     ht->shift = newshift;
     nentries = ht->nentries;
     for (i = 0; nentries != 0; i++) {
         for (he = oldbuckets[i]; he; he = next) {
             MOZ_ASSERT(nentries != 0);
             --nentries;
             next = he->next;
             hep = BUCKET_HEAD(ht, he->keyHash);
             /*
              * We do not require unique entries, instead appending he to the
              * chain starting at hep.
              */
             while (*hep)
                 hep = &(*hep)->next;
             he->next = nullptr;
             *hep = he;
         }
     }
 #ifdef DEBUG
     memset(oldbuckets, 0xDB, nold * sizeof oldbuckets[0]);
 #endif
     ht->allocOps->freeTable(ht->allocPriv, oldbuckets,
                             nold * sizeof oldbuckets[0]);
     return true;
 }
 JSHashEntry *
 JS_HashTableRawAdd(JSHashTable *ht, JSHashEntry **&hep,
                    JSHashNumber keyHash, const void *key, void *value)
 {
     uint32_t n;
     JSHashEntry *he;
     /* Grow the table if it is overloaded */
     n = NBUCKETS(ht);
     if (ht->nentries >= OVERLOADED(n)) {
         if (!Resize(ht, ht->shift - 1))
             return nullptr;
 #ifdef JS_HASHMETER
         ht->ngrows++;
 #endif
         hep = JS_HashTableRawLookup(ht, keyHash, key);
     }
     /* Make a new key value entry */
     he = ht->allocOps->allocEntry(ht->allocPriv, key);
     if (!he)
         return nullptr;
     he->keyHash = keyHash;
     he->key = key;
     he->value = value;
     he->next = *hep;
     *hep = he;
     ht->nentries++;
     return he;
 }
 JSHashEntry *
 JS_HashTableAdd(JSHashTable *ht, const void *key, void *value)
 {
     JSHashNumber keyHash;
     JSHashEntry *he, **hep;
     keyHash = ht->keyHash(key);
     hep = JS_HashTableRawLookup(ht, keyHash, key);
     if ((he = *hep) != nullptr) {
         /* 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 JS_HashTableRawAdd(ht, hep, keyHash, key, value);
 }
 void
 JS_HashTableRawRemove(JSHashTable *ht, JSHashEntry **hep, JSHashEntry *he)
 {
     uint32_t n;
     *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)) {
         Resize(ht, ht->shift + 1);
 #ifdef JS_HASHMETER
         ht->nshrinks++;
 #endif
     }
 }
 bool
 JS_HashTableRemove(JSHashTable *ht, const void *key)
 {
     JSHashNumber keyHash;
     JSHashEntry *he, **hep;
     keyHash = ht->keyHash(key);
     hep = JS_HashTableRawLookup(ht, keyHash, key);
     if ((he = *hep) == nullptr)
         return false;
     /* Hit; remove element */
     JS_HashTableRawRemove(ht, hep, he);
     return true;
 }
 void *
 JS_HashTableLookup(JSHashTable *ht, const void *key)
 {
     JSHashNumber keyHash;
     JSHashEntry *he, **hep;
     keyHash = ht->keyHash(key);
     hep = JS_HashTableRawLookup(ht, keyHash, key);
     if ((he = *hep) != nullptr) {
         return he->value;
     }
     return nullptr;
 }
 /*
 ** Iterate over the entries in the hash table calling func for each
 ** entry found. Stop if "f" says to (return value & JS_ENUMERATE_STOP).
 ** Return a count of the number of elements scanned.
 */
 int
 JS_HashTableEnumerateEntries(JSHashTable *ht, JSHashEnumerator f, void *arg)
 {
     JSHashEntry *he, **hep, **bucket;
     uint32_t nlimit, n, nbuckets, newlog2;
     int rv;
     nlimit = ht->nentries;
     n = 0;
     for (bucket = ht->buckets; n != nlimit; ++bucket) {
         hep = bucket;
         while ((he = *hep) != nullptr) {
             MOZ_ASSERT(n < nlimit);
             rv = f(he, n, arg);
             n++;
             if (rv & HT_ENUMERATE_REMOVE) {
                 *hep = he->next;
                 ht->allocOps->freeEntry(ht->allocPriv, he, HT_FREE_ENTRY);
                 --ht->nentries;
             } else {
                 hep = &he->next;
             }
             if (rv & HT_ENUMERATE_STOP) {
                 goto out;
             }
         }
     }
 out:
     /* Shrink table if removal of entries made it underloaded */
     if (ht->nentries != nlimit) {
         MOZ_ASSERT(ht->nentries < nlimit);
         nbuckets = NBUCKETS(ht);
         if (MINBUCKETS < nbuckets && ht->nentries < UNDERLOADED(nbuckets)) {
             newlog2 = CeilingLog2Size(ht->nentries);
             if (newlog2 < MINBUCKETSLOG2)
                 newlog2 = MINBUCKETSLOG2;
             /*  Check that we really shrink the table. */
             MOZ_ASSERT(JS_HASH_BITS - ht->shift > newlog2);
             Resize(ht, JS_HASH_BITS - newlog2);
         }
     }
     return (int)n;
 }
 #ifdef JS_HASHMETER
 #include <stdio.h>
 void
 JS_HashTableDumpMeter(JSHashTable *ht, JSHashEnumerator dump, FILE *fp)
 {
     double sqsum, mean, sigma;
     uint32_t nchains, nbuckets;
     uint32_t i, n, maxChain, maxChainLen;
     JSHashEntry *he;
     sqsum = 0;
     nchains = 0;
     maxChain = 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++;
         sqsum += n * n;
         if (n > maxChainLen) {
             maxChainLen = n;
             maxChain = i;
         }
     }
     mean = JS_MeanAndStdDev(nchains, ht->nentries, sqsum, &sigma);
     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", sigma);
     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 /* JS_HASHMETER */
 int
 JS_HashTableDump(JSHashTable *ht, JSHashEnumerator dump, FILE *fp)
 {
     int count;
     count = JS_HashTableEnumerateEntries(ht, dump, fp);
 #ifdef JS_HASHMETER
     JS_HashTableDumpMeter(ht, dump, fp);
 #endif
     return count;
 }
 JSHashNumber
 JS_HashString(const void *key)
 {
     JSHashNumber h;
     const unsigned char *s;
     h = 0;
     for (s = (const unsigned char *)key; *s; s++)
         h = RotateLeft(h, 4) ^ *s;
     return h;
 }
 int
 JS_CompareValues(const void *v1, const void *v2)
 {
     return v1 == v2;
 }

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js/jsd/jshash.cpp@6474c204b198 (annotated)

js/jsd/jshash.cpp