hadoop LayoutFlags 源码
haddop LayoutFlags 代码
文件路径：/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LayoutFlags.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.hdfs.protocol;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import org.apache.hadoop.classification.InterfaceAudience;
/**
* LayoutFlags represent features which the FSImage and edit logs can either
* support or not, independently of layout version.
*
* Note: all flags starting with 'test' are reserved for unit test purposes.
*/
@InterfaceAudience.Private
public class LayoutFlags {
/**
* Read next int from given input stream. If the value is not 0 (unsupported
* feature flags), throw appropriate IOException.
*
* @param in The stream to read from.
* @throws IOException If next byte read from given stream is not 0.
*/
public static void read(DataInputStream in) throws IOException {
int length = in.readInt();
if (length < 0) {
throw new IOException("The length of the feature flag section " +
"was negative at " + length + " bytes.");
} else if (length > 0) {
throw new IOException("Found feature flags which we can't handle. " +
"Please upgrade your software.");
}
}
private LayoutFlags() {
}
public static void write(DataOutputStream out) throws IOException {
out.writeInt(0);
}
}
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