| /** |
| * 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.hdfs.util; |
| |
| import java.io.EOFException; |
| import java.io.FilterInputStream; |
| import java.io.IOException; |
| import java.io.InputStream; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| import com.google.common.base.Preconditions; |
| |
| /** |
| * An InputStream implementations which reads from some other InputStream |
| * but expects an exact number of bytes. Any attempts to read past the |
| * specified number of bytes will return as if the end of the stream |
| * was reached. If the end of the underlying stream is reached prior to |
| * the specified number of bytes, an EOFException is thrown. |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Evolving |
| public class ExactSizeInputStream extends FilterInputStream { |
| private int remaining; |
| |
| /** |
| * Construct an input stream that will read no more than |
| * 'numBytes' bytes. |
| * |
| * If an EOF occurs on the underlying stream before numBytes |
| * bytes have been read, an EOFException will be thrown. |
| * |
| * @param in the inputstream to wrap |
| * @param numBytes the number of bytes to read |
| */ |
| public ExactSizeInputStream(InputStream in, int numBytes) { |
| super(in); |
| Preconditions.checkArgument(numBytes >= 0, |
| "Negative expected bytes: ", numBytes); |
| this.remaining = numBytes; |
| } |
| |
| @Override |
| public int available() throws IOException { |
| return Math.min(super.available(), remaining); |
| } |
| |
| @Override |
| public int read() throws IOException { |
| // EOF if we reached our limit |
| if (remaining <= 0) { |
| return -1; |
| } |
| final int result = super.read(); |
| if (result >= 0) { |
| --remaining; |
| } else if (remaining > 0) { |
| // Underlying stream reached EOF but we haven't read the expected |
| // number of bytes. |
| throw new EOFException( |
| "Premature EOF. Expected " + remaining + "more bytes"); |
| } |
| return result; |
| } |
| |
| @Override |
| public int read(final byte[] b, final int off, int len) |
| throws IOException { |
| if (remaining <= 0) { |
| return -1; |
| } |
| len = Math.min(len, remaining); |
| final int result = super.read(b, off, len); |
| if (result >= 0) { |
| remaining -= result; |
| } else if (remaining > 0) { |
| // Underlying stream reached EOF but we haven't read the expected |
| // number of bytes. |
| throw new EOFException( |
| "Premature EOF. Expected " + remaining + "more bytes"); |
| } |
| return result; |
| } |
| |
| @Override |
| public long skip(final long n) throws IOException { |
| final long result = super.skip(Math.min(n, remaining)); |
| if (result > 0) { |
| remaining -= result; |
| } else if (remaining > 0) { |
| // Underlying stream reached EOF but we haven't read the expected |
| // number of bytes. |
| throw new EOFException( |
| "Premature EOF. Expected " + remaining + "more bytes"); |
| } |
| return result; |
| } |
| |
| @Override |
| public boolean markSupported() { |
| return false; |
| } |
| |
| @Override |
| public void mark(int readlimit) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| } |