339 lines
10 KiB
C++
339 lines
10 KiB
C++
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/*
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* Copyright (C) 2011 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#define LOG_TAG "BasicHashtable"
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#include <math.h>
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#include <utils/Log.h>
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#include <utils/BasicHashtable.h>
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#include <utils/misc.h>
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namespace android {
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BasicHashtableImpl::BasicHashtableImpl(size_t entrySize, bool hasTrivialDestructor,
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size_t minimumInitialCapacity, float loadFactor) :
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mBucketSize(entrySize + sizeof(Bucket)), mHasTrivialDestructor(hasTrivialDestructor),
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mLoadFactor(loadFactor), mSize(0),
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mFilledBuckets(0), mBuckets(NULL) {
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determineCapacity(minimumInitialCapacity, mLoadFactor, &mBucketCount, &mCapacity);
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}
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BasicHashtableImpl::BasicHashtableImpl(const BasicHashtableImpl& other) :
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mBucketSize(other.mBucketSize), mHasTrivialDestructor(other.mHasTrivialDestructor),
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mCapacity(other.mCapacity), mLoadFactor(other.mLoadFactor),
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mSize(other.mSize), mFilledBuckets(other.mFilledBuckets),
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mBucketCount(other.mBucketCount), mBuckets(other.mBuckets) {
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if (mBuckets) {
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SharedBuffer::bufferFromData(mBuckets)->acquire();
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}
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}
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void BasicHashtableImpl::dispose() {
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if (mBuckets) {
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releaseBuckets(mBuckets, mBucketCount);
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}
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}
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void BasicHashtableImpl::clone() {
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if (mBuckets) {
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void* newBuckets = allocateBuckets(mBucketCount);
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copyBuckets(mBuckets, newBuckets, mBucketCount);
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releaseBuckets(mBuckets, mBucketCount);
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mBuckets = newBuckets;
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}
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}
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void BasicHashtableImpl::setTo(const BasicHashtableImpl& other) {
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if (mBuckets) {
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releaseBuckets(mBuckets, mBucketCount);
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}
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mCapacity = other.mCapacity;
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mLoadFactor = other.mLoadFactor;
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mSize = other.mSize;
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mFilledBuckets = other.mFilledBuckets;
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mBucketCount = other.mBucketCount;
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mBuckets = other.mBuckets;
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if (mBuckets) {
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SharedBuffer::bufferFromData(mBuckets)->acquire();
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}
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}
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void BasicHashtableImpl::clear() {
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if (mBuckets) {
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if (mFilledBuckets) {
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SharedBuffer* sb = SharedBuffer::bufferFromData(mBuckets);
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if (sb->onlyOwner()) {
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destroyBuckets(mBuckets, mBucketCount);
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for (size_t i = 0; i < mSize; i++) {
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Bucket& bucket = bucketAt(mBuckets, i);
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bucket.cookie = 0;
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}
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} else {
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releaseBuckets(mBuckets, mBucketCount);
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mBuckets = NULL;
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}
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mFilledBuckets = 0;
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}
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mSize = 0;
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}
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}
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ssize_t BasicHashtableImpl::next(ssize_t index) const {
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if (mSize) {
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while (size_t(++index) < mBucketCount) {
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const Bucket& bucket = bucketAt(mBuckets, index);
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if (bucket.cookie & Bucket::PRESENT) {
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return index;
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}
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}
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}
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return -1;
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}
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ssize_t BasicHashtableImpl::find(ssize_t index, hash_t hash,
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const void* __restrict__ key) const {
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if (!mSize) {
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return -1;
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}
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hash = trimHash(hash);
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if (index < 0) {
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index = chainStart(hash, mBucketCount);
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const Bucket& bucket = bucketAt(mBuckets, size_t(index));
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if (bucket.cookie & Bucket::PRESENT) {
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if (compareBucketKey(bucket, key)) {
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return index;
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}
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} else {
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if (!(bucket.cookie & Bucket::COLLISION)) {
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return -1;
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}
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}
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}
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size_t inc = chainIncrement(hash, mBucketCount);
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for (;;) {
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index = chainSeek(index, inc, mBucketCount);
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const Bucket& bucket = bucketAt(mBuckets, size_t(index));
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if (bucket.cookie & Bucket::PRESENT) {
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if ((bucket.cookie & Bucket::HASH_MASK) == hash
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&& compareBucketKey(bucket, key)) {
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return index;
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}
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}
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if (!(bucket.cookie & Bucket::COLLISION)) {
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return -1;
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}
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}
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}
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size_t BasicHashtableImpl::add(hash_t hash, const void* entry) {
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if (!mBuckets) {
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mBuckets = allocateBuckets(mBucketCount);
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} else {
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edit();
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}
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hash = trimHash(hash);
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for (;;) {
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size_t index = chainStart(hash, mBucketCount);
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Bucket* bucket = &bucketAt(mBuckets, size_t(index));
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if (bucket->cookie & Bucket::PRESENT) {
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size_t inc = chainIncrement(hash, mBucketCount);
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do {
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bucket->cookie |= Bucket::COLLISION;
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index = chainSeek(index, inc, mBucketCount);
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bucket = &bucketAt(mBuckets, size_t(index));
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} while (bucket->cookie & Bucket::PRESENT);
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}
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uint32_t collision = bucket->cookie & Bucket::COLLISION;
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if (!collision) {
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if (mFilledBuckets >= mCapacity) {
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rehash(mCapacity * 2, mLoadFactor);
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continue;
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}
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mFilledBuckets += 1;
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}
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bucket->cookie = collision | Bucket::PRESENT | hash;
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mSize += 1;
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initializeBucketEntry(*bucket, entry);
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return index;
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}
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}
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void BasicHashtableImpl::removeAt(size_t index) {
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edit();
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Bucket& bucket = bucketAt(mBuckets, index);
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bucket.cookie &= ~Bucket::PRESENT;
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if (!(bucket.cookie & Bucket::COLLISION)) {
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mFilledBuckets -= 1;
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}
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mSize -= 1;
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if (!mHasTrivialDestructor) {
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destroyBucketEntry(bucket);
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}
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}
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void BasicHashtableImpl::rehash(size_t minimumCapacity, float loadFactor) {
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if (minimumCapacity < mSize) {
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minimumCapacity = mSize;
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}
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size_t newBucketCount, newCapacity;
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determineCapacity(minimumCapacity, loadFactor, &newBucketCount, &newCapacity);
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if (newBucketCount != mBucketCount || newCapacity != mCapacity) {
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if (mBuckets) {
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void* newBuckets;
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if (mSize) {
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newBuckets = allocateBuckets(newBucketCount);
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for (size_t i = 0; i < mBucketCount; i++) {
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const Bucket& fromBucket = bucketAt(mBuckets, i);
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if (fromBucket.cookie & Bucket::PRESENT) {
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hash_t hash = fromBucket.cookie & Bucket::HASH_MASK;
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size_t index = chainStart(hash, newBucketCount);
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Bucket* toBucket = &bucketAt(newBuckets, size_t(index));
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if (toBucket->cookie & Bucket::PRESENT) {
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size_t inc = chainIncrement(hash, newBucketCount);
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do {
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toBucket->cookie |= Bucket::COLLISION;
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index = chainSeek(index, inc, newBucketCount);
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toBucket = &bucketAt(newBuckets, size_t(index));
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} while (toBucket->cookie & Bucket::PRESENT);
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}
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toBucket->cookie = Bucket::PRESENT | hash;
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initializeBucketEntry(*toBucket, fromBucket.entry);
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}
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}
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} else {
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newBuckets = NULL;
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}
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releaseBuckets(mBuckets, mBucketCount);
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mBuckets = newBuckets;
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mFilledBuckets = mSize;
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}
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mBucketCount = newBucketCount;
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mCapacity = newCapacity;
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}
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mLoadFactor = loadFactor;
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}
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void* BasicHashtableImpl::allocateBuckets(size_t count) const {
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size_t bytes = count * mBucketSize;
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SharedBuffer* sb = SharedBuffer::alloc(bytes);
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LOG_ALWAYS_FATAL_IF(!sb, "Could not allocate %u bytes for hashtable with %u buckets.",
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uint32_t(bytes), uint32_t(count));
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void* buckets = sb->data();
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for (size_t i = 0; i < count; i++) {
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Bucket& bucket = bucketAt(buckets, i);
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bucket.cookie = 0;
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}
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return buckets;
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}
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void BasicHashtableImpl::releaseBuckets(void* __restrict__ buckets, size_t count) const {
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SharedBuffer* sb = SharedBuffer::bufferFromData(buckets);
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if (sb->release(SharedBuffer::eKeepStorage) == 1) {
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destroyBuckets(buckets, count);
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SharedBuffer::dealloc(sb);
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}
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}
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void BasicHashtableImpl::destroyBuckets(void* __restrict__ buckets, size_t count) const {
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if (!mHasTrivialDestructor) {
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for (size_t i = 0; i < count; i++) {
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Bucket& bucket = bucketAt(buckets, i);
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if (bucket.cookie & Bucket::PRESENT) {
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destroyBucketEntry(bucket);
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}
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}
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}
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}
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void BasicHashtableImpl::copyBuckets(const void* __restrict__ fromBuckets,
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void* __restrict__ toBuckets, size_t count) const {
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for (size_t i = 0; i < count; i++) {
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const Bucket& fromBucket = bucketAt(fromBuckets, i);
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Bucket& toBucket = bucketAt(toBuckets, i);
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toBucket.cookie = fromBucket.cookie;
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if (fromBucket.cookie & Bucket::PRESENT) {
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initializeBucketEntry(toBucket, fromBucket.entry);
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}
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}
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}
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// Table of 31-bit primes where each prime is no less than twice as large
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// as the previous one. Generated by "primes.py".
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static size_t PRIMES[] = {
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5,
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11,
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23,
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47,
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97,
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197,
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397,
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797,
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1597,
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3203,
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6421,
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12853,
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25717,
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51437,
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102877,
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205759,
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411527,
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823117,
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1646237,
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3292489,
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6584983,
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13169977,
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26339969,
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52679969,
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105359939,
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210719881,
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421439783,
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842879579,
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1685759167,
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0,
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};
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void BasicHashtableImpl::determineCapacity(size_t minimumCapacity, float loadFactor,
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size_t* __restrict__ outBucketCount, size_t* __restrict__ outCapacity) {
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LOG_ALWAYS_FATAL_IF(loadFactor <= 0.0f || loadFactor > 1.0f,
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"Invalid load factor %0.3f. Must be in the range (0, 1].", loadFactor);
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size_t count = ceilf(minimumCapacity / loadFactor) + 1;
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size_t i = 0;
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while (count > PRIMES[i] && i < NELEM(PRIMES)) {
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i++;
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}
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count = PRIMES[i];
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LOG_ALWAYS_FATAL_IF(!count, "Could not determine required number of buckets for "
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"hashtable with minimum capacity %u and load factor %0.3f.",
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uint32_t(minimumCapacity), loadFactor);
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*outBucketCount = count;
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*outCapacity = ceilf((count - 1) * loadFactor);
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}
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}; // namespace android
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