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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
package org.apache.iotdb.rpc;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Arrays;
/**
* Helper class that wraps a byte[] so that it can expand and be reused. Users should call
* resizeIfNecessary to make sure the buffer has suitable capacity, and then use the array as
* needed.
*
* Resizing policies: Expanding: If the required size > current capacity * 1.5, expand to the
* required size, otherwise expand to current capacity * 1.5. Shrinking: If initial size < the
* required size < current capacity * 0.6, and such small requests last for more than 5 times,
* shrink to the middle of the required size and current capacity.
*/
class AutoResizingBuffer {
private byte[] array;
private int bufTooLargeCounter = RpcUtils.MAX_BUFFER_OVERSIZE_TIME;
private final int initialCapacity;
private long lastShrinkTime;
private static final Logger logger = LoggerFactory.getLogger(AutoResizingBuffer.class);
public AutoResizingBuffer(int initialCapacity) {
this.array = new byte[initialCapacity];
this.initialCapacity = initialCapacity;
}
public void resizeIfNecessary(int size) {
final int currentCapacity = this.array.length;
final double loadFactor = 0.6;
if (currentCapacity < size) {
// Increase by a factor of 1.5x
int growCapacity = currentCapacity + (currentCapacity >> 1);
int newCapacity = Math.max(growCapacity, size);
this.array = Arrays.copyOf(array, newCapacity);
bufTooLargeCounter = RpcUtils.MAX_BUFFER_OVERSIZE_TIME;
logger.debug(
"{} expand from {} to {}, request: {}", this, currentCapacity, newCapacity, size);
} else if (size > initialCapacity
&& currentCapacity * loadFactor > size
&& bufTooLargeCounter-- <= 0
&& System.currentTimeMillis() - lastShrinkTime > RpcUtils.MIN_SHRINK_INTERVAL) {
// do not resize if it is reading the request size and do not shrink too often
array = Arrays.copyOf(array, size + (currentCapacity - size) / 2);
bufTooLargeCounter = RpcUtils.MAX_BUFFER_OVERSIZE_TIME;
lastShrinkTime = System.currentTimeMillis();
logger.debug("{} shrink from {} to {}", this, currentCapacity, size);
}
}
public byte[] array() {
return this.array;
}
}