391 lines
11 KiB
C
391 lines
11 KiB
C
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/*
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* Copyright 2006 The Android Open Source Project
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*
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* Hash table. The dominant calls are add and lookup, with removals
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* happening very infrequently. We use probing, and don't worry much
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* about tombstone removal.
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*/
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#include <stdlib.h>
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#include <assert.h>
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#define LOG_TAG "minzip"
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#include "Log.h"
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#include "Hash.h"
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/* table load factor, i.e. how full can it get before we resize */
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//#define LOAD_NUMER 3 // 75%
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//#define LOAD_DENOM 4
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#define LOAD_NUMER 5 // 62.5%
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#define LOAD_DENOM 8
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//#define LOAD_NUMER 1 // 50%
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//#define LOAD_DENOM 2
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/*
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* Compute the capacity needed for a table to hold "size" elements.
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*/
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size_t mzHashSize(size_t size) {
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return (size * LOAD_DENOM) / LOAD_NUMER +1;
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}
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/*
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* Round up to the next highest power of 2.
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*
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* Found on http://graphics.stanford.edu/~seander/bithacks.html.
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*/
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unsigned int roundUpPower2(unsigned int val)
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{
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val--;
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val |= val >> 1;
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val |= val >> 2;
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val |= val >> 4;
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val |= val >> 8;
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val |= val >> 16;
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val++;
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return val;
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}
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/*
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* Create and initialize a hash table.
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*/
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HashTable* mzHashTableCreate(size_t initialSize, HashFreeFunc freeFunc)
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{
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HashTable* pHashTable;
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assert(initialSize > 0);
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pHashTable = (HashTable*) malloc(sizeof(*pHashTable));
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if (pHashTable == NULL)
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return NULL;
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pHashTable->tableSize = roundUpPower2(initialSize);
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pHashTable->numEntries = pHashTable->numDeadEntries = 0;
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pHashTable->freeFunc = freeFunc;
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pHashTable->pEntries =
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(HashEntry*) calloc((size_t)pHashTable->tableSize, sizeof(HashTable));
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if (pHashTable->pEntries == NULL) {
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free(pHashTable);
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return NULL;
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}
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return pHashTable;
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}
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/*
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* Clear out all entries.
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*/
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void mzHashTableClear(HashTable* pHashTable)
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{
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HashEntry* pEnt;
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int i;
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pEnt = pHashTable->pEntries;
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for (i = 0; i < pHashTable->tableSize; i++, pEnt++) {
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if (pEnt->data == HASH_TOMBSTONE) {
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// nuke entry
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pEnt->data = NULL;
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} else if (pEnt->data != NULL) {
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// call free func then nuke entry
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if (pHashTable->freeFunc != NULL)
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(*pHashTable->freeFunc)(pEnt->data);
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pEnt->data = NULL;
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}
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}
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pHashTable->numEntries = 0;
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pHashTable->numDeadEntries = 0;
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}
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/*
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* Free the table.
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*/
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void mzHashTableFree(HashTable* pHashTable)
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{
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if (pHashTable == NULL)
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return;
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mzHashTableClear(pHashTable);
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free(pHashTable->pEntries);
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free(pHashTable);
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}
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#ifndef NDEBUG
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/*
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* Count up the number of tombstone entries in the hash table.
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*/
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static int countTombStones(HashTable* pHashTable)
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{
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int i, count;
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for (count = i = 0; i < pHashTable->tableSize; i++) {
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if (pHashTable->pEntries[i].data == HASH_TOMBSTONE)
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count++;
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}
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return count;
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}
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#endif
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/*
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* Resize a hash table. We do this when adding an entry increased the
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* size of the table beyond its comfy limit.
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*
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* This essentially requires re-inserting all elements into the new storage.
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*
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* If multiple threads can access the hash table, the table's lock should
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* have been grabbed before issuing the "lookup+add" call that led to the
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* resize, so we don't have a synchronization problem here.
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*/
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static bool resizeHash(HashTable* pHashTable, int newSize)
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{
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HashEntry* pNewEntries;
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int i;
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assert(countTombStones(pHashTable) == pHashTable->numDeadEntries);
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//LOGI("before: dead=%d\n", pHashTable->numDeadEntries);
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pNewEntries = (HashEntry*) calloc(newSize, sizeof(HashTable));
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if (pNewEntries == NULL)
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return false;
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for (i = 0; i < pHashTable->tableSize; i++) {
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void* data = pHashTable->pEntries[i].data;
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if (data != NULL && data != HASH_TOMBSTONE) {
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int hashValue = pHashTable->pEntries[i].hashValue;
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int newIdx;
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/* probe for new spot, wrapping around */
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newIdx = hashValue & (newSize-1);
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while (pNewEntries[newIdx].data != NULL)
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newIdx = (newIdx + 1) & (newSize-1);
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pNewEntries[newIdx].hashValue = hashValue;
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pNewEntries[newIdx].data = data;
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}
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}
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free(pHashTable->pEntries);
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pHashTable->pEntries = pNewEntries;
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pHashTable->tableSize = newSize;
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pHashTable->numDeadEntries = 0;
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assert(countTombStones(pHashTable) == 0);
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return true;
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}
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/*
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* Look up an entry.
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*
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* We probe on collisions, wrapping around the table.
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*/
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void* mzHashTableLookup(HashTable* pHashTable, unsigned int itemHash, void* item,
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HashCompareFunc cmpFunc, bool doAdd)
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{
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HashEntry* pEntry;
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HashEntry* pEnd;
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void* result = NULL;
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assert(pHashTable->tableSize > 0);
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assert(item != HASH_TOMBSTONE);
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assert(item != NULL);
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/* jump to the first entry and probe for a match */
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pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)];
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pEnd = &pHashTable->pEntries[pHashTable->tableSize];
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while (pEntry->data != NULL) {
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if (pEntry->data != HASH_TOMBSTONE &&
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pEntry->hashValue == itemHash &&
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(*cmpFunc)(pEntry->data, item) == 0)
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{
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/* match */
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//LOGD("+++ match on entry %d\n", pEntry - pHashTable->pEntries);
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break;
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}
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pEntry++;
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if (pEntry == pEnd) { /* wrap around to start */
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if (pHashTable->tableSize == 1)
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break; /* edge case - single-entry table */
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pEntry = pHashTable->pEntries;
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}
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//LOGI("+++ look probing %d...\n", pEntry - pHashTable->pEntries);
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}
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if (pEntry->data == NULL) {
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if (doAdd) {
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pEntry->hashValue = itemHash;
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pEntry->data = item;
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pHashTable->numEntries++;
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/*
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* We've added an entry. See if this brings us too close to full.
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*/
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if ((pHashTable->numEntries+pHashTable->numDeadEntries) * LOAD_DENOM
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> pHashTable->tableSize * LOAD_NUMER)
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{
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if (!resizeHash(pHashTable, pHashTable->tableSize * 2)) {
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/* don't really have a way to indicate failure */
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LOGE("Dalvik hash resize failure\n");
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abort();
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}
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/* note "pEntry" is now invalid */
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} else {
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//LOGW("okay %d/%d/%d\n",
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// pHashTable->numEntries, pHashTable->tableSize,
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// (pHashTable->tableSize * LOAD_NUMER) / LOAD_DENOM);
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}
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/* full table is bad -- search for nonexistent never halts */
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assert(pHashTable->numEntries < pHashTable->tableSize);
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result = item;
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} else {
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assert(result == NULL);
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}
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} else {
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result = pEntry->data;
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}
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return result;
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}
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/*
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* Remove an entry from the table.
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*
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* Does NOT invoke the "free" function on the item.
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*/
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bool mzHashTableRemove(HashTable* pHashTable, unsigned int itemHash, void* item)
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{
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HashEntry* pEntry;
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HashEntry* pEnd;
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assert(pHashTable->tableSize > 0);
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/* jump to the first entry and probe for a match */
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pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)];
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pEnd = &pHashTable->pEntries[pHashTable->tableSize];
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while (pEntry->data != NULL) {
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if (pEntry->data == item) {
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//LOGI("+++ stepping on entry %d\n", pEntry - pHashTable->pEntries);
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pEntry->data = HASH_TOMBSTONE;
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pHashTable->numEntries--;
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pHashTable->numDeadEntries++;
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return true;
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}
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pEntry++;
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if (pEntry == pEnd) { /* wrap around to start */
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if (pHashTable->tableSize == 1)
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break; /* edge case - single-entry table */
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pEntry = pHashTable->pEntries;
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}
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//LOGI("+++ del probing %d...\n", pEntry - pHashTable->pEntries);
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}
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return false;
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}
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/*
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* Execute a function on every entry in the hash table.
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*
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* If "func" returns a nonzero value, terminate early and return the value.
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*/
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int mzHashForeach(HashTable* pHashTable, HashForeachFunc func, void* arg)
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{
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int i, val;
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for (i = 0; i < pHashTable->tableSize; i++) {
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HashEntry* pEnt = &pHashTable->pEntries[i];
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if (pEnt->data != NULL && pEnt->data != HASH_TOMBSTONE) {
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val = (*func)(pEnt->data, arg);
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if (val != 0)
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return val;
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}
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}
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return 0;
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}
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/*
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* Look up an entry, counting the number of times we have to probe.
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*
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* Returns -1 if the entry wasn't found.
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*/
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int countProbes(HashTable* pHashTable, unsigned int itemHash, const void* item,
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HashCompareFunc cmpFunc)
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{
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HashEntry* pEntry;
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HashEntry* pEnd;
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int count = 0;
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assert(pHashTable->tableSize > 0);
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assert(item != HASH_TOMBSTONE);
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assert(item != NULL);
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/* jump to the first entry and probe for a match */
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pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)];
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pEnd = &pHashTable->pEntries[pHashTable->tableSize];
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while (pEntry->data != NULL) {
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if (pEntry->data != HASH_TOMBSTONE &&
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pEntry->hashValue == itemHash &&
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(*cmpFunc)(pEntry->data, item) == 0)
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{
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/* match */
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break;
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}
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pEntry++;
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if (pEntry == pEnd) { /* wrap around to start */
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if (pHashTable->tableSize == 1)
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break; /* edge case - single-entry table */
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pEntry = pHashTable->pEntries;
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}
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count++;
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}
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if (pEntry->data == NULL)
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return -1;
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return count;
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}
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/*
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* Evaluate the amount of probing required for the specified hash table.
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*
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* We do this by running through all entries in the hash table, computing
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* the hash value and then doing a lookup.
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*
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* The caller should lock the table before calling here.
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*/
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void mzHashTableProbeCount(HashTable* pHashTable, HashCalcFunc calcFunc,
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HashCompareFunc cmpFunc)
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{
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int numEntries, minProbe, maxProbe, totalProbe;
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HashIter iter;
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numEntries = maxProbe = totalProbe = 0;
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minProbe = 65536*32767;
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for (mzHashIterBegin(pHashTable, &iter); !mzHashIterDone(&iter);
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mzHashIterNext(&iter))
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{
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const void* data = (const void*)mzHashIterData(&iter);
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int count;
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count = countProbes(pHashTable, (*calcFunc)(data), data, cmpFunc);
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numEntries++;
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if (count < minProbe)
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minProbe = count;
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if (count > maxProbe)
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maxProbe = count;
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totalProbe += count;
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}
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LOGI("Probe: min=%d max=%d, total=%d in %d (%d), avg=%.3f\n",
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minProbe, maxProbe, totalProbe, numEntries, pHashTable->tableSize,
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(float) totalProbe / (float) numEntries);
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}
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