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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.EOFException;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * An InputStream that will throw EOFException if the underlying InputStream runs out of data before reaching the configured minimum amount of data
 */
public class MinimumLengthInputStream extends FilterInputStream {

    private final long minLength;
    private long consumedCount = 0L;

    public MinimumLengthInputStream(final InputStream in, final long minLength) {
        super(in);
        this.minLength = minLength;
    }

    @Override
    public int read() throws IOException {
        final int b = super.read();
        if (b < 0 && consumedCount < minLength) {
            throw new EOFException();
        }

        if (b >= 0) {
            consumedCount++;
        }

        return b;
    }

    @Override
    public int read(byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    public int read(byte[] b, int off, int len) throws IOException {
        final int num = super.read(b, off, len);

        if (num < 0 && consumedCount < minLength) {
            throw new EOFException();
        }

        if (num >= 0) {
            consumedCount += num;
        }

        return num;
    }

    @Override
    public long skip(final long n) throws IOException {
        long skipped = super.skip(n);
        if (skipped < 1) {
            final int b = super.read();
            if (b >= 0) {
                skipped = 1;
            }
        }

        if (skipped < 0 && consumedCount < minLength) {
            throw new EOFException();
        }

        if (skipped >= 0) {
            consumedCount += skipped;
        }

        return skipped;
    }

}