IgfsTestInputStream.java

/*
 * 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.ignite.internal.processors.igfs;

import java.io.IOException;
import java.io.InputStream;

/**
 * Test input stream with predictable data output and zero memory usage.
 */
class IgfsTestInputStream extends InputStream {
    /** This stream length. */
    private long size;

    /** Salt for input data generation. */
    private long salt;

    /** Current stream position. */
    private long pos;

    /**
     * Constructs test input stream.
     *
     * @param size This stream length.
     * @param salt Salt for input data generation.
     */
    IgfsTestInputStream(long size, long salt) {
        this.size = size;
        this.salt = salt;
    }

    /** {@inheritDoc} */
    @Override public synchronized int read() throws IOException {
        if (pos >= size)
            return -1;

        long next = salt ^ (salt * pos++);

        next ^= next >>> 32;
        next ^= next >>> 16;
        next ^= next >>> 8;

        return (int)(0xFF & next);
    }

    /** {@inheritDoc} */
    @Override public synchronized long skip(long n) throws IOException {
        pos += Math.min(n, size - pos);

        return size - pos;
    }
}