| /* |
| * Copyright (C) 2008 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| /* |
| * Hash table. The dominant calls are add and lookup, with removals |
| * happening very infrequently. We use probing, and don't worry much |
| * about tombstone removal. |
| */ |
| #include "Dalvik.h" |
| |
| #include <stdlib.h> |
| |
| /* table load factor, i.e. how full can it get before we resize */ |
| //#define LOAD_NUMER 3 // 75% |
| //#define LOAD_DENOM 4 |
| #define LOAD_NUMER 5 // 62.5% |
| #define LOAD_DENOM 8 |
| //#define LOAD_NUMER 1 // 50% |
| //#define LOAD_DENOM 2 |
| |
| /* |
| * Compute the capacity needed for a table to hold "size" elements. |
| */ |
| size_t dvmHashSize(size_t size) { |
| return (size * LOAD_DENOM) / LOAD_NUMER +1; |
| } |
| |
| |
| /* |
| * Create and initialize a hash table. |
| */ |
| HashTable* dvmHashTableCreate(size_t initialSize, HashFreeFunc freeFunc) |
| { |
| HashTable* pHashTable; |
| |
| assert(initialSize > 0); |
| |
| pHashTable = (HashTable*) malloc(sizeof(*pHashTable)); |
| if (pHashTable == NULL) |
| return NULL; |
| |
| dvmInitMutex(&pHashTable->lock); |
| |
| pHashTable->tableSize = dexRoundUpPower2(initialSize); |
| pHashTable->numEntries = pHashTable->numDeadEntries = 0; |
| pHashTable->freeFunc = freeFunc; |
| pHashTable->pEntries = |
| (HashEntry*) malloc(pHashTable->tableSize * sizeof(HashEntry)); |
| if (pHashTable->pEntries == NULL) { |
| free(pHashTable); |
| return NULL; |
| } |
| |
| memset(pHashTable->pEntries, 0, pHashTable->tableSize * sizeof(HashEntry)); |
| return pHashTable; |
| } |
| |
| /* |
| * Clear out all entries. |
| */ |
| void dvmHashTableClear(HashTable* pHashTable) |
| { |
| HashEntry* pEnt; |
| int i; |
| |
| pEnt = pHashTable->pEntries; |
| for (i = 0; i < pHashTable->tableSize; i++, pEnt++) { |
| if (pEnt->data == HASH_TOMBSTONE) { |
| // nuke entry |
| pEnt->data = NULL; |
| } else if (pEnt->data != NULL) { |
| // call free func then nuke entry |
| if (pHashTable->freeFunc != NULL) |
| (*pHashTable->freeFunc)(pEnt->data); |
| pEnt->data = NULL; |
| } |
| } |
| |
| pHashTable->numEntries = 0; |
| pHashTable->numDeadEntries = 0; |
| } |
| |
| /* |
| * Free the table. |
| */ |
| void dvmHashTableFree(HashTable* pHashTable) |
| { |
| if (pHashTable == NULL) |
| return; |
| dvmHashTableClear(pHashTable); |
| free(pHashTable->pEntries); |
| free(pHashTable); |
| } |
| |
| #ifndef NDEBUG |
| /* |
| * Count up the number of tombstone entries in the hash table. |
| */ |
| static int countTombStones(HashTable* pHashTable) |
| { |
| int i, count; |
| |
| for (count = i = 0; i < pHashTable->tableSize; i++) { |
| if (pHashTable->pEntries[i].data == HASH_TOMBSTONE) |
| count++; |
| } |
| return count; |
| } |
| #endif |
| |
| /* |
| * Resize a hash table. We do this when adding an entry increased the |
| * size of the table beyond its comfy limit. |
| * |
| * This essentially requires re-inserting all elements into the new storage. |
| * |
| * If multiple threads can access the hash table, the table's lock should |
| * have been grabbed before issuing the "lookup+add" call that led to the |
| * resize, so we don't have a synchronization problem here. |
| */ |
| static bool resizeHash(HashTable* pHashTable, int newSize) |
| { |
| HashEntry* pNewEntries; |
| int i; |
| |
| assert(countTombStones(pHashTable) == pHashTable->numDeadEntries); |
| //LOGI("before: dead=%d\n", pHashTable->numDeadEntries); |
| |
| pNewEntries = (HashEntry*) calloc(newSize, sizeof(HashEntry)); |
| if (pNewEntries == NULL) |
| return false; |
| |
| for (i = 0; i < pHashTable->tableSize; i++) { |
| void* data = pHashTable->pEntries[i].data; |
| if (data != NULL && data != HASH_TOMBSTONE) { |
| int hashValue = pHashTable->pEntries[i].hashValue; |
| int newIdx; |
| |
| /* probe for new spot, wrapping around */ |
| newIdx = hashValue & (newSize-1); |
| while (pNewEntries[newIdx].data != NULL) |
| newIdx = (newIdx + 1) & (newSize-1); |
| |
| pNewEntries[newIdx].hashValue = hashValue; |
| pNewEntries[newIdx].data = data; |
| } |
| } |
| |
| free(pHashTable->pEntries); |
| pHashTable->pEntries = pNewEntries; |
| pHashTable->tableSize = newSize; |
| pHashTable->numDeadEntries = 0; |
| |
| assert(countTombStones(pHashTable) == 0); |
| return true; |
| } |
| |
| /* |
| * Look up an entry. |
| * |
| * We probe on collisions, wrapping around the table. |
| */ |
| void* dvmHashTableLookup(HashTable* pHashTable, u4 itemHash, void* item, |
| HashCompareFunc cmpFunc, bool doAdd) |
| { |
| HashEntry* pEntry; |
| HashEntry* pEnd; |
| void* result = NULL; |
| |
| assert(pHashTable->tableSize > 0); |
| assert(item != HASH_TOMBSTONE); |
| assert(item != NULL); |
| |
| /* jump to the first entry and probe for a match */ |
| pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)]; |
| pEnd = &pHashTable->pEntries[pHashTable->tableSize]; |
| while (pEntry->data != NULL) { |
| if (pEntry->data != HASH_TOMBSTONE && |
| pEntry->hashValue == itemHash && |
| (*cmpFunc)(pEntry->data, item) == 0) |
| { |
| /* match */ |
| //LOGD("+++ match on entry %d\n", pEntry - pHashTable->pEntries); |
| break; |
| } |
| |
| pEntry++; |
| if (pEntry == pEnd) { /* wrap around to start */ |
| if (pHashTable->tableSize == 1) |
| break; /* edge case - single-entry table */ |
| pEntry = pHashTable->pEntries; |
| } |
| |
| //LOGI("+++ look probing %d...\n", pEntry - pHashTable->pEntries); |
| } |
| |
| if (pEntry->data == NULL) { |
| if (doAdd) { |
| pEntry->hashValue = itemHash; |
| pEntry->data = item; |
| pHashTable->numEntries++; |
| |
| /* |
| * We've added an entry. See if this brings us too close to full. |
| */ |
| if ((pHashTable->numEntries+pHashTable->numDeadEntries) * LOAD_DENOM |
| > pHashTable->tableSize * LOAD_NUMER) |
| { |
| if (!resizeHash(pHashTable, pHashTable->tableSize * 2)) { |
| /* don't really have a way to indicate failure */ |
| LOGE("Dalvik hash resize failure\n"); |
| dvmAbort(); |
| } |
| /* note "pEntry" is now invalid */ |
| } else { |
| //LOGW("okay %d/%d/%d\n", |
| // pHashTable->numEntries, pHashTable->tableSize, |
| // (pHashTable->tableSize * LOAD_NUMER) / LOAD_DENOM); |
| } |
| |
| /* full table is bad -- search for nonexistent never halts */ |
| assert(pHashTable->numEntries < pHashTable->tableSize); |
| result = item; |
| } else { |
| assert(result == NULL); |
| } |
| } else { |
| result = pEntry->data; |
| } |
| |
| return result; |
| } |
| |
| /* |
| * Remove an entry from the table. |
| * |
| * Does NOT invoke the "free" function on the item. |
| */ |
| bool dvmHashTableRemove(HashTable* pHashTable, u4 itemHash, void* item) |
| { |
| HashEntry* pEntry; |
| HashEntry* pEnd; |
| |
| assert(pHashTable->tableSize > 0); |
| |
| /* jump to the first entry and probe for a match */ |
| pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)]; |
| pEnd = &pHashTable->pEntries[pHashTable->tableSize]; |
| while (pEntry->data != NULL) { |
| if (pEntry->data == item) { |
| //LOGI("+++ stepping on entry %d\n", pEntry - pHashTable->pEntries); |
| pEntry->data = HASH_TOMBSTONE; |
| pHashTable->numEntries--; |
| pHashTable->numDeadEntries++; |
| return true; |
| } |
| |
| pEntry++; |
| if (pEntry == pEnd) { /* wrap around to start */ |
| if (pHashTable->tableSize == 1) |
| break; /* edge case - single-entry table */ |
| pEntry = pHashTable->pEntries; |
| } |
| |
| //LOGI("+++ del probing %d...\n", pEntry - pHashTable->pEntries); |
| } |
| |
| return false; |
| } |
| |
| /* |
| * Scan every entry in the hash table and evaluate it with the specified |
| * indirect function call. If the function returns 1, remove the entry from |
| * the table. |
| * |
| * Does NOT invoke the "free" function on the item. |
| * |
| * Returning values other than 0 or 1 will abort the routine. |
| */ |
| int dvmHashForeachRemove(HashTable* pHashTable, HashForeachRemoveFunc func) |
| { |
| int i, val; |
| |
| for (i = 0; i < pHashTable->tableSize; i++) { |
| HashEntry* pEnt = &pHashTable->pEntries[i]; |
| |
| if (pEnt->data != NULL && pEnt->data != HASH_TOMBSTONE) { |
| val = (*func)(pEnt->data); |
| if (val == 1) { |
| pEnt->data = HASH_TOMBSTONE; |
| pHashTable->numEntries--; |
| pHashTable->numDeadEntries++; |
| } |
| else if (val != 0) { |
| return val; |
| } |
| } |
| } |
| return 0; |
| } |
| |
| |
| /* |
| * Execute a function on every entry in the hash table. |
| * |
| * If "func" returns a nonzero value, terminate early and return the value. |
| */ |
| int dvmHashForeach(HashTable* pHashTable, HashForeachFunc func, void* arg) |
| { |
| int i, val; |
| |
| for (i = 0; i < pHashTable->tableSize; i++) { |
| HashEntry* pEnt = &pHashTable->pEntries[i]; |
| |
| if (pEnt->data != NULL && pEnt->data != HASH_TOMBSTONE) { |
| val = (*func)(pEnt->data, arg); |
| if (val != 0) |
| return val; |
| } |
| } |
| |
| return 0; |
| } |
| |
| |
| /* |
| * Look up an entry, counting the number of times we have to probe. |
| * |
| * Returns -1 if the entry wasn't found. |
| */ |
| static int countProbes(HashTable* pHashTable, u4 itemHash, const void* item, |
| HashCompareFunc cmpFunc) |
| { |
| HashEntry* pEntry; |
| HashEntry* pEnd; |
| int count = 0; |
| |
| assert(pHashTable->tableSize > 0); |
| assert(item != HASH_TOMBSTONE); |
| assert(item != NULL); |
| |
| /* jump to the first entry and probe for a match */ |
| pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)]; |
| pEnd = &pHashTable->pEntries[pHashTable->tableSize]; |
| while (pEntry->data != NULL) { |
| if (pEntry->data != HASH_TOMBSTONE && |
| pEntry->hashValue == itemHash && |
| (*cmpFunc)(pEntry->data, item) == 0) |
| { |
| /* match */ |
| break; |
| } |
| |
| pEntry++; |
| if (pEntry == pEnd) { /* wrap around to start */ |
| if (pHashTable->tableSize == 1) |
| break; /* edge case - single-entry table */ |
| pEntry = pHashTable->pEntries; |
| } |
| |
| count++; |
| } |
| if (pEntry->data == NULL) |
| return -1; |
| |
| return count; |
| } |
| |
| /* |
| * Evaluate the amount of probing required for the specified hash table. |
| * |
| * We do this by running through all entries in the hash table, computing |
| * the hash value and then doing a lookup. |
| * |
| * The caller should lock the table before calling here. |
| */ |
| void dvmHashTableProbeCount(HashTable* pHashTable, HashCalcFunc calcFunc, |
| HashCompareFunc cmpFunc) |
| { |
| int numEntries, minProbe, maxProbe, totalProbe; |
| HashIter iter; |
| |
| numEntries = maxProbe = totalProbe = 0; |
| minProbe = 65536*32767; |
| |
| for (dvmHashIterBegin(pHashTable, &iter); !dvmHashIterDone(&iter); |
| dvmHashIterNext(&iter)) |
| { |
| const void* data = (const void*)dvmHashIterData(&iter); |
| int count; |
| |
| count = countProbes(pHashTable, (*calcFunc)(data), data, cmpFunc); |
| |
| numEntries++; |
| |
| if (count < minProbe) |
| minProbe = count; |
| if (count > maxProbe) |
| maxProbe = count; |
| totalProbe += count; |
| } |
| |
| LOGI("Probe: min=%d max=%d, total=%d in %d (%d), avg=%.3f\n", |
| minProbe, maxProbe, totalProbe, numEntries, pHashTable->tableSize, |
| (float) totalProbe / (float) numEntries); |
| } |