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This nifi-utils module should be a general purpose place to store widely and generally useful functions that any component might want to leverage. NO DEPENDENCIES should be added. This module is likely to be leveraged by every extension and should not bring along any other dependencies. The only dependency intended is the nifi-api and even this is expected to be already provided in any case where it would be used. The typical place this util would be found is within a nar and all nars already have nifi-api as a parent dependency. The nifi-api can be thought of as a NiFi Application Container level dependency.

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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.nifi.stream.io;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Objects;

public class RepeatingInputStream extends InputStream {
    private final byte[] toRepeat;
    private final int maxIterations;

    private InputStream bais;
    private int repeatCount;


    public RepeatingInputStream(final byte[] toRepeat, final int iterations) {
        if (iterations < 1) {
            throw new IllegalArgumentException();
        }
        if (Objects.requireNonNull(toRepeat).length == 0) {
            throw new IllegalArgumentException();
        }

        this.toRepeat = toRepeat;
        this.maxIterations = iterations;

        repeat();
        bais = new ByteArrayInputStream(toRepeat);
        repeatCount = 1;
    }

    @Override
    public int read() throws IOException {
        final int value = bais.read();
        if (value > -1) {
            return value;
        }

        final boolean repeated = repeat();
        if (repeated) {
            return bais.read();
        }

        return -1;
    }

    @Override
    public int read(final byte[] b, final int off, final int len) throws IOException {
        final int value = bais.read(b, off, len);
        if (value > -1) {
            return value;
        }

        final boolean repeated = repeat();
        if (repeated) {
            return bais.read(b, off, len);
        }

        return -1;
    }

    @Override
    public int read(final byte[] b) throws IOException {
        final int value = bais.read(b);
        if (value > -1) {
            return value;
        }

        final boolean repeated = repeat();
        if (repeated) {
            return bais.read(b);
        }

        return -1;
    }

    private boolean repeat() {
        if (repeatCount >= maxIterations) {
            return false;
        }

        repeatCount++;
        bais = new ByteArrayInputStream(toRepeat);

        return true;
    }
}