/**
* 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.tools.offlineEditsViewer;
import java.io.IOException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.ByteToken;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.ShortToken;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.IntToken;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.VIntToken;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.LongToken;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.VLongToken;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.StringUTF8Token;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.StringTextToken;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.BlobToken;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.BytesWritableToken;
import static org.apache.hadoop.hdfs.tools.offlineEditsViewer.Tokenizer.EmptyToken;
/**
* An implementation of EditsVisitor can traverse the structure of an
* Hadoop edits log and respond to each of the structures within the file.
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
abstract public class EditsVisitor {
private Tokenizer tokenizer;
public EditsVisitor(Tokenizer tokenizer) {
this.tokenizer = tokenizer;
}
/**
* Begin visiting the edits log structure. Opportunity to perform
* any initialization necessary for the implementing visitor.
*/
abstract void start() throws IOException;
/**
* Finish visiting the edits log structure. Opportunity to perform any
* clean up necessary for the implementing visitor.
*/
abstract void finish() throws IOException;
/**
* Finish visiting the edits log structure after an error has occurred
* during the processing. Opportunity to perform any clean up necessary
* for the implementing visitor.
*/
abstract void finishAbnormally() throws IOException;
/**
* Visit non enclosing element of edits log with specified value.
*
* @param value a token to visit
*/
abstract Tokenizer.Token visit(Tokenizer.Token value) throws IOException;
/**
* Convenience shortcut method to parse a specific token type
*/
public ByteToken visitByte(EditsElement e) throws IOException {
return (ByteToken)visit(tokenizer.read(new ByteToken(e)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public ShortToken visitShort(EditsElement e) throws IOException {
return (ShortToken)visit(tokenizer.read(new ShortToken(e)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public IntToken visitInt(EditsElement e) throws IOException {
return (IntToken)visit(tokenizer.read(new IntToken(e)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public VIntToken visitVInt(EditsElement e) throws IOException {
return (VIntToken)visit(tokenizer.read(new VIntToken(e)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public LongToken visitLong(EditsElement e) throws IOException {
return (LongToken)visit(tokenizer.read(new LongToken(e)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public VLongToken visitVLong(EditsElement e) throws IOException {
return (VLongToken)visit(tokenizer.read(new VLongToken(e)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public StringUTF8Token visitStringUTF8(EditsElement e) throws IOException {
return (StringUTF8Token)visit(tokenizer.read(new StringUTF8Token(e)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public StringTextToken visitStringText(EditsElement e) throws IOException {
return (StringTextToken)visit(tokenizer.read(new StringTextToken(e)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public BlobToken visitBlob(EditsElement e, int length) throws IOException {
return (BlobToken)visit(tokenizer.read(new BlobToken(e, length)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public BytesWritableToken visitBytesWritable(EditsElement e) throws IOException {
return (BytesWritableToken)visit(tokenizer.read(new BytesWritableToken(e)));
}
/**
* Convenience shortcut method to parse a specific token type
*/
public EmptyToken visitEmpty(EditsElement e) throws IOException {
return (EmptyToken)visit(tokenizer.read(new EmptyToken(e)));
}
/**
* Begin visiting an element that encloses another element, such as
* the beginning of the list of blocks that comprise a file.
*
* @param value Token being visited
*/
abstract void visitEnclosingElement(Tokenizer.Token value)
throws IOException;
/**
* Convenience shortcut method (it virutally always uses EmptyToken)
*/
void visitEnclosingElement(EditsElement e) throws IOException {
visitEnclosingElement(tokenizer.read(new EmptyToken(e)));
}
/**
* Leave current enclosing element. Called, for instance, at the end of
* processing the blocks that compromise a file.
*/
abstract void leaveEnclosingElement() throws IOException;
}