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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.flink.runtime.state;

import org.apache.flink.core.fs.FSDataInputStream;

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

/**
 * Wrapper around a FSDataInputStream to limit the maximum read offset.
 *
 * Based on the implementation from org.apache.commons.io.input.BoundedInputStream
 */
public class BoundedInputStream extends InputStream {
    private final FSDataInputStream delegate;
    private long endOffsetExclusive;
    private long position;
    private long mark;

    public BoundedInputStream(FSDataInputStream delegate, long endOffsetExclusive)
            throws IOException {
        this.position = delegate.getPos();
        this.mark = -1L;
        this.endOffsetExclusive = endOffsetExclusive;
        this.delegate = delegate;
    }

    public int read() throws IOException {
        if (endOffsetExclusive >= 0L && position >= endOffsetExclusive) {
            return -1;
        } else {
            int result = delegate.read();
            ++position;
            return result;
        }
    }

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

    public int read(byte[] b, int off, int len) throws IOException {
        if (endOffsetExclusive >= 0L && position >= endOffsetExclusive) {
            return -1;
        } else {
            long maxRead =
                    endOffsetExclusive >= 0L
                            ? Math.min((long) len, endOffsetExclusive - position)
                            : (long) len;
            int bytesRead = delegate.read(b, off, (int) maxRead);
            if (bytesRead == -1) {
                return -1;
            } else {
                position += (long) bytesRead;
                return bytesRead;
            }
        }
    }

    public long skip(long n) throws IOException {
        long toSkip = endOffsetExclusive >= 0L ? Math.min(n, endOffsetExclusive - position) : n;
        long skippedBytes = delegate.skip(toSkip);
        position += skippedBytes;
        return skippedBytes;
    }

    public int available() throws IOException {
        return endOffsetExclusive >= 0L && position >= endOffsetExclusive
                ? 0
                : delegate.available();
    }

    public String toString() {
        return delegate.toString();
    }

    public void close() throws IOException {
        delegate.close();
    }

    public synchronized void reset() throws IOException {
        delegate.reset();
        position = mark;
    }

    public synchronized void mark(int readlimit) {
        delegate.mark(readlimit);
        mark = position;
    }

    public long getEndOffsetExclusive() {
        return endOffsetExclusive;
    }

    public void setEndOffsetExclusive(long endOffsetExclusive) {
        this.endOffsetExclusive = endOffsetExclusive;
    }

    public boolean markSupported() {
        return delegate.markSupported();
    }
}