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A module that is everything required to understands Druid Segments
/*
* 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.druid.utils;
import com.google.common.base.Preconditions;
/**
* A circular buffer that supports random bidirectional access.
*
* @param Type of object to be stored in the buffer
*/
public class CircularBuffer
{
@SuppressWarnings("unused")
public E[] getBuffer()
{
return buffer;
}
private final E[] buffer;
private int start = 0;
private int size = 0;
public CircularBuffer(int capacity)
{
Preconditions.checkArgument(capacity > 0, "Capacity must be greater than 0.");
buffer = (E[]) new Object[capacity];
}
public void add(E item)
{
buffer[start++] = item;
if (start >= buffer.length) {
start = 0;
}
if (size < buffer.length) {
size++;
}
}
/**
* Access object at a given index, starting from the latest entry added and moving backwards.
*/
public E getLatest(int index)
{
Preconditions.checkArgument(index >= 0 && index < size, "invalid index");
int bufferIndex = start - index - 1;
if (bufferIndex < 0) {
bufferIndex = buffer.length + bufferIndex;
}
return buffer[bufferIndex];
}
/**
* Access object at a given index, starting from the earliest entry added and moving forward.
*/
public E get(int index)
{
Preconditions.checkArgument(index >= 0 && index < size, "invalid index");
int bufferIndex = (start - size + index) % buffer.length;
if (bufferIndex < 0) {
bufferIndex += buffer.length;
}
return buffer[bufferIndex];
}
public int size()
{
return size;
}
}