130 lines
3.8 KiB
Java
130 lines
3.8 KiB
Java
/*
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* Copyright 2021 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* https://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, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.buffer.api.pool;
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/**
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* Internal primitive map implementation that is specifically optimised for the runs availability map use case in
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* {@link PoolChunk}.
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*/
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final class LongLongHashMap {
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private static final int MASK_TEMPLATE = ~1;
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private int mask;
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private long[] array;
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private int maxProbe;
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private long zeroVal;
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private final long emptyVal;
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LongLongHashMap(long emptyVal) {
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this.emptyVal = emptyVal;
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zeroVal = emptyVal;
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int initialSize = 32;
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array = new long[initialSize];
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mask = initialSize - 1;
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computeMaskAndProbe();
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}
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public long put(long key, long value) {
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if (key == 0) {
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long prev = zeroVal;
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zeroVal = value;
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return prev;
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}
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for (;;) {
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int index = index(key);
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for (int i = 0; i < maxProbe; i++) {
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long existing = array[index];
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if (existing == key || existing == 0) {
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long prev = existing == 0? emptyVal : array[index + 1];
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array[index] = key;
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array[index + 1] = value;
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for (; i < maxProbe; i++) { // Nerf any existing misplaced entries.
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index = index + 2 & mask;
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if (array[index] == key) {
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array[index] = 0;
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prev = array[index + 1];
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break;
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}
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}
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return prev;
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}
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index = index + 2 & mask;
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}
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expand(); // Grow array and re-hash.
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}
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}
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public void remove(long key) {
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if (key == 0) {
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zeroVal = emptyVal;
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return;
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}
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int index = index(key);
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for (int i = 0; i < maxProbe; i++) {
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long existing = array[index];
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if (existing == key) {
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array[index] = 0;
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break;
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}
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index = index + 2 & mask;
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}
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}
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public long get(long key) {
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if (key == 0) {
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return zeroVal;
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}
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int index = index(key);
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for (int i = 0; i < maxProbe; i++) {
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long existing = array[index];
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if (existing == key) {
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return array[index + 1];
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}
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index = index + 2 & mask;
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}
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return emptyVal;
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}
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private int index(long key) {
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// Hash with murmur64, and mask.
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key ^= key >>> 33;
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key *= 0xff51afd7ed558ccdL;
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key ^= key >>> 33;
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key *= 0xc4ceb9fe1a85ec53L;
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key ^= key >>> 33;
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return (int) key & mask;
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}
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private void expand() {
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long[] prev = array;
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array = new long[prev.length * 2];
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computeMaskAndProbe();
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for (int i = 0; i < prev.length; i += 2) {
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long key = prev[i];
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if (key != 0) {
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long val = prev[i + 1];
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put(key, val);
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}
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}
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}
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private void computeMaskAndProbe() {
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int length = array.length;
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mask = length - 1 & MASK_TEMPLATE;
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maxProbe = (int) Math.log(length);
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}
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}
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