org.apache.lucene.store.BufferedChecksum.java Source code

Introduction

Here is the source code for org.apache.lucene.store.BufferedChecksum.java

Source

/*
 * 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.lucene.store;

import java.util.zip.Checksum;

/** 
 * Wraps another {@link Checksum} with an internal buffer
 * to speed up checksum calculations.
 */
public class BufferedChecksum implements Checksum {
    private final Checksum in;
    private final byte buffer[];
    private int upto;
    /** Default buffer size: 256 */
    public static final int DEFAULT_BUFFERSIZE = 256;

    /** Create a new BufferedChecksum with {@link #DEFAULT_BUFFERSIZE} */
    public BufferedChecksum(Checksum in) {
        this(in, DEFAULT_BUFFERSIZE);
    }

    /** Create a new BufferedChecksum with the specified bufferSize */
    public BufferedChecksum(Checksum in, int bufferSize) {
        this.in = in;
        this.buffer = new byte[bufferSize];
    }

    @Override
    public void update(int b) {
        if (upto == buffer.length) {
            flush();
        }
        buffer[upto++] = (byte) b;
    }

    @Override
    public void update(byte[] b, int off, int len) {
        if (len >= buffer.length) {
            flush();
            in.update(b, off, len);
        } else {
            if (upto + len > buffer.length) {
                flush();
            }
            System.arraycopy(b, off, buffer, upto, len);
            upto += len;
        }
    }

    @Override
    public long getValue() {
        flush();
        return in.getValue();
    }

    @Override
    public void reset() {
        upto = 0;
        in.reset();
    }

    private void flush() {
        if (upto > 0) {
            in.update(buffer, 0, upto);
        }
        upto = 0;
    }
}