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/*
 * Hibernate Search, full-text search for your domain model
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later
 * See the lgpl.txt file in the root directory or .
 */
package org.hibernate.search.elasticsearch.util.impl;

import java.util.ArrayList;
import java.util.List;

/**
 * A fixed-size, random-access collection that removes the first element when it becomes full.
 *
 * 

The indices accepted by this container are within a bounded range. This range may start at any * positive integer value, i.e. the container may not allow access to element at index {@code 0}, but * only indices {@code 102-134} for instance. The range will advance automatically as the window gets full * and more elements are added. * * @author Yoann Rodiere */ public class Window { /** * The external index of the first element in this window, i.e. the index that will give * access to the first element when given to {@link #get(int)}. *

If the window is empty, this will be the index of the next added element. */ private int externalStartIndex; /** * The number of elements that can be added before the first element gets automatically erased. */ private int capacity; /** * The initial value of {@link #externalStartIndex}, for use in {@link #clear()}. */ private final int initialExternalStartIndex; /** * The actual data. */ private final List elementData; /** * The position where the first element in this window is stored within {{@link #elementData}. *

If the window is empty, this will be the index of the next added element. */ private int internalStartIndex; /** * The number of elements in this window. */ private int size; /** * @param initialIndex The index of the first added element. * @param capacity The number of elements that can be added before the first element gets automatically erased. */ public Window(int initialIndex, int capacity) { if ( capacity <= 0 ) { throw new IllegalArgumentException( "capacity must be at least 1" ); } this.initialExternalStartIndex = initialIndex; this.capacity = capacity; externalStartIndex = initialIndex; elementData = new ArrayList<>(); // Take advantage of ArrayList's "smart" growth and O(1) random access internalStartIndex = 0; size = 0; } public int start() { return externalStartIndex; } /** * @return The number of elements in this element container. */ public int size() { return size; } public boolean isEmpty() { return size == 0; } /** * @return The maximum number of element that can fit this window. */ public int capacity() { return capacity; } public E get(int externalIndex) { rangeCheck( externalIndex ); int internalIndex = ( externalIndex - externalStartIndex + internalStartIndex ) % capacity; return elementData.get( internalIndex ); } private void rangeCheck(int externalIndex) { int start = start(); if ( externalIndex < start || start + size() <= externalIndex ) { throw new IndexOutOfBoundsException(); } } /** * Add an element, removing the first element if it's necessary in order to respect the size limit. * * @param element The element to add. * @return {@code true} to indicate the element has been added. */ public boolean add(E element) { int newElementIndex = ( internalStartIndex + size ) % capacity; if ( size == capacity ) { // Overflow: drop the first element internalStartIndex = ( internalStartIndex + 1 ) % capacity; ++externalStartIndex; } else { ++size; } if ( newElementIndex == elementData.size() ) { elementData.add( element ); } else { elementData.set( newElementIndex, element ); } return true; } public void clear() { this.externalStartIndex = initialExternalStartIndex; // Clear references for the GC for ( int i = 0; i < size; i++ ) { elementData.set( (internalStartIndex + i ) % capacity, null ); } this.internalStartIndex = 0; this.size = 0; } }





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