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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.IOException;
import java.io.InputStream;

public class LimitingInputStream extends InputStream {

    private final InputStream in;
    private final long limit;
    private long bytesRead = 0;
    private volatile boolean limitReached = false;
    private long markOffset = -1L;

    /**
     * Constructs a limited input stream whereby if the limit is reached all
     * subsequent calls to read will return a -1 and hasLimitReached() will
     * indicate true. The limit is inclusive so if all 100 bytes of a 100 byte
     * stream are read it will be true, otherwise false.
     *
     * @param in the underlying input stream
     * @param limit maximum length of bytes to read from underlying input stream
     */
    public LimitingInputStream(final InputStream in, final long limit) {
        this.in = in;
        this.limit = limit;
    }

    public boolean hasReachedLimit() throws IOException {
        return limitReached;
    }

    private int markLimitReached() {
        limitReached = true;
        return -1;
    }

    @Override
    public int read() throws IOException {
        if (bytesRead >= limit) {
            return markLimitReached();
        }

        final int val = in.read();
        if (val > -1) {
            bytesRead++;
        }
        return val;
    }

    @Override
    public int read(final byte[] b) throws IOException {
        if (bytesRead >= limit) {
            return markLimitReached();
        }

        final int maxToRead = (int) Math.min(b.length, limit - bytesRead);

        final int val = in.read(b, 0, maxToRead);
        if (val > 0) {
            bytesRead += val;
        }
        return val;
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        if (bytesRead >= limit) {
            return markLimitReached();
        }

        final int maxToRead = (int) Math.min(len, limit - bytesRead);

        final int val = in.read(b, off, maxToRead);
        if (val > 0) {
            bytesRead += val;
        }
        return val;
    }

    @Override
    public long skip(final long n) throws IOException {
        final long toSkip = Math.min(n, limit - bytesRead);
        final long skipped = in.skip(toSkip);
        bytesRead += skipped;
        return skipped;
    }

    @Override
    public int available() throws IOException {
        return in.available();
    }

    @Override
    public void close() throws IOException {
        in.close();
    }

    @Override
    public void mark(int readlimit) {
        in.mark(readlimit);
        markOffset = bytesRead;
    }

    @Override
    public boolean markSupported() {
        return in.markSupported();
    }

    @Override
    public void reset() throws IOException {
        in.reset();

        if (markOffset >= 0) {
            bytesRead = markOffset;
        }
        markOffset = -1;
    }

    public long getLimit() {
        return limit;
    }
}