org.apache.hadoop.fs.ByteBufferUtil Maven / Gradle / Ivy
/**
* 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.fs;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.ByteBufferPool;
import org.apache.hadoop.thirdparty.com.google.common.base.Preconditions;
@InterfaceAudience.Private
@InterfaceStability.Evolving
public final class ByteBufferUtil {
/**
* Determine if a stream can do a byte buffer read via read(ByteBuffer buf)
*/
private static boolean streamHasByteBufferRead(InputStream stream) {
if (!(stream instanceof ByteBufferReadable)) {
return false;
}
if (!(stream instanceof FSDataInputStream)) {
return true;
}
return ((FSDataInputStream)stream).getWrappedStream()
instanceof ByteBufferReadable;
}
/**
* Perform a fallback read.
*/
public static ByteBuffer fallbackRead(
InputStream stream, ByteBufferPool bufferPool, int maxLength)
throws IOException {
if (bufferPool == null) {
throw new UnsupportedOperationException("zero-copy reads " +
"were not available, and you did not provide a fallback " +
"ByteBufferPool.");
}
boolean useDirect = streamHasByteBufferRead(stream);
ByteBuffer buffer = bufferPool.getBuffer(useDirect, maxLength);
if (buffer == null) {
throw new UnsupportedOperationException("zero-copy reads " +
"were not available, and the ByteBufferPool did not provide " +
"us with " + (useDirect ? "a direct" : "an indirect") +
"buffer.");
}
Preconditions.checkState(buffer.capacity() > 0);
Preconditions.checkState(buffer.isDirect() == useDirect);
maxLength = Math.min(maxLength, buffer.capacity());
boolean success = false;
try {
if (useDirect) {
buffer.clear();
buffer.limit(maxLength);
ByteBufferReadable readable = (ByteBufferReadable)stream;
int totalRead = 0;
while (true) {
if (totalRead >= maxLength) {
success = true;
break;
}
int nRead = readable.read(buffer);
if (nRead < 0) {
if (totalRead > 0) {
success = true;
}
break;
}
totalRead += nRead;
}
buffer.flip();
} else {
buffer.clear();
int nRead = stream.read(buffer.array(),
buffer.arrayOffset(), maxLength);
if (nRead >= 0) {
buffer.limit(nRead);
success = true;
}
}
} finally {
if (!success) {
// If we got an error while reading, or if we are at EOF, we
// don't need the buffer any more. We can give it back to the
// bufferPool.
bufferPool.putBuffer(buffer);
buffer = null;
}
}
return buffer;
}
}