io.questdb.std.IntLongAssociativeCache Maven / Gradle / Ivy
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*
* Copyright (c) 2014-2019 Appsicle
* Copyright (c) 2019-2020 QuestDB
*
* 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.
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package io.questdb.std;
public class IntLongAssociativeCache {
public static final long NO_VALUE = -1L;
public static final int UNUSED_KEY = 0;
private static final int MIN_BLOCKS = 2;
private static final int NOT_FOUND = -1;
private static final int MINROWS = 16;
private final int[] keys;
private final long[] values;
private final int rmask;
private final int bmask;
private final int blocks;
private final int bshift;
public IntLongAssociativeCache(int blocks, int rows) {
this.blocks = Math.max(MIN_BLOCKS, Numbers.ceilPow2(blocks));
rows = Math.max(MINROWS, Numbers.ceilPow2(rows));
int size = rows * this.blocks;
if (size < 0) {
throw new OutOfMemoryError();
}
this.keys = new int[size];
this.values = new long[size];
this.rmask = rows - 1;
this.bmask = this.blocks - 1;
this.bshift = Numbers.msb(this.blocks);
}
public long peek(int key) {
int index = getIndex(key);
if (index == NOT_FOUND) {
return NO_VALUE;
}
return values[index];
}
public long poll(int key) {
int index = getIndex(key);
if (index == NOT_FOUND) {
return NO_VALUE;
}
long value = values[index];
// Unsafe.arrayPut(values, index, 0);
keys[index] = UNUSED_KEY;
return value;
}
public int put(int key, long value) {
int lo = lo(key);
int ok = keys[lo + bmask];
System.arraycopy(keys, lo, keys, lo + 1, bmask);
System.arraycopy(values, lo, values, lo + 1, bmask);
keys[lo] = key;
values[lo] = value;
return ok;
}
private int getIndex(int key) {
int lo = lo(key);
for (int i = lo, hi = lo + blocks; i < hi; i++) {
int k = keys[i];
if (k == UNUSED_KEY) {
return NOT_FOUND;
}
if (k == key) {
return i;
}
}
return NOT_FOUND;
}
private int lo(int key) {
return (key & rmask) << bshift;
}
}