hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LimitInputStream.java

/*
 *
 * 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.hadoop.util;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

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

import org.apache.hadoop.classification.InterfaceStability.Unstable;

/**
 * Copied from guava source code v15 (LimitedInputStream)
 * Guava deprecated LimitInputStream in v14 and removed it in v15. Copying this class here
 * allows to be compatible with guava 11 to 15+.
 * 
 * Originally: org.apache.hadoop.hbase.io.LimitInputStream
 */
@Unstable
public final class LimitInputStream extends FilterInputStream {
  private long left;
  private long mark = -1;

  public LimitInputStream(InputStream in, long limit) {
    super(in);
    checkNotNull(in);
    checkArgument(limit >= 0, "limit must be non-negative");
    left = limit;
  }

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

  // it's okay to mark even if mark isn't supported, as reset won't work
  @Override
  public synchronized void mark(int readLimit) {
    in.mark(readLimit);
    mark = left;
  }

  @Override
  public int read() throws IOException {
    if (left == 0) {
      return -1;
    }

    int result = in.read();
    if (result != -1) {
      --left;
    }
    return result;
  }

  @Override
  public int read(byte[] b, int off, int len) throws IOException {
    if (len == 0) {
      return 0;
    }
    if (left == 0) {
      return -1;
    }

    len = (int) Math.min(len, left);
    int result = in.read(b, off, len);
    if (result != -1) {
      left -= result;
    }
    return result;
  }

  @Override
  public synchronized void reset() throws IOException {
    if (!in.markSupported()) {
      throw new IOException("Mark not supported");
    }
    if (mark == -1) {
      throw new IOException("Mark not set");
    }

    in.reset();
    left = mark;
  }

  @Override
  public long skip(long n) throws IOException {
    n = Math.min(n, left);
    long skipped = in.skip(n);
    left -= skipped;
    return skipped;
  }
}