com.cloudera.sqoop.io.FixedLengthInputStream.java Source code

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Here is the source code for com.cloudera.sqoop.io.FixedLengthInputStream.java

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/**
 * Licensed to Cloudera, Inc. under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  Cloudera, Inc. 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 com.cloudera.sqoop.io;

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

import org.apache.commons.io.input.CloseShieldInputStream;
import org.apache.commons.io.input.CountingInputStream;
import org.apache.commons.io.input.ProxyInputStream;

/**
 * Provides an InputStream that can consume a fixed maximum number of bytes
 * from an underlying stream. Closing the FixedLengthInputStream does not
 * close the underlying stream. After reading the maximum number of available
 * bytes this acts as though EOF has been reached.
 */
public class FixedLengthInputStream extends ProxyInputStream {

    private CountingInputStream countingIn;
    private long maxBytes;

    public FixedLengthInputStream(InputStream stream, long maxLen) {
        super(new CountingInputStream(new CloseShieldInputStream(stream)));

        // Save a correctly-typed reference to the underlying stream.
        this.countingIn = (CountingInputStream) this.in;
        this.maxBytes = maxLen;
    }

    /** @return the number of bytes already consumed by the client. */
    private long consumed() {
        return countingIn.getByteCount();
    }

    /**
     * @return number of bytes remaining to be read before the limit
     * is reached.
     */
    private long toLimit() {
        return maxBytes - consumed();
    }

    @Override
    public int available() throws IOException {
        return (int) Math.min(toLimit(), countingIn.available());
    }

    @Override
    public int read() throws IOException {
        if (toLimit() > 0) {
            return super.read();
        } else {
            return -1; // EOF.
        }
    }

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

    @Override
    public int read(byte[] buf, int start, int count) throws IOException {
        long limit = toLimit();
        if (limit == 0) {
            return -1; // EOF.
        } else {
            return super.read(buf, start, (int) Math.min(count, limit));
        }
    }
}