| /** |
| * 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.server.namenode; |
| |
| import java.io.Closeable; |
| import java.io.IOException; |
| |
| /** |
| * A generic abstract class to support reading edits log data from |
| * persistent storage. |
| * |
| * It should stream bytes from the storage exactly as they were written |
| * into the #{@link EditLogOutputStream}. |
| */ |
| abstract class EditLogInputStream implements JournalStream, Closeable { |
| /** |
| * @return the first transaction which will be found in this stream |
| */ |
| public abstract long getFirstTxId() throws IOException; |
| |
| /** |
| * @return the last transaction which will be found in this stream |
| */ |
| public abstract long getLastTxId() throws IOException; |
| |
| |
| /** |
| * Close the stream. |
| * @throws IOException if an error occurred while closing |
| */ |
| public abstract void close() throws IOException; |
| |
| /** |
| * Read an operation from the stream |
| * @return an operation from the stream or null if at end of stream |
| * @throws IOException if there is an error reading from the stream |
| */ |
| public abstract FSEditLogOp readOp() throws IOException; |
| |
| /** |
| * Get the layout version of the data in the stream. |
| * @return the layout version of the ops in the stream. |
| * @throws IOException if there is an error reading the version |
| */ |
| public abstract int getVersion() throws IOException; |
| |
| /** |
| * Get the "position" of in the stream. This is useful for |
| * debugging and operational purposes. |
| * |
| * Different stream types can have a different meaning for |
| * what the position is. For file streams it means the byte offset |
| * from the start of the file. |
| * |
| * @return the position in the stream |
| */ |
| public abstract long getPosition(); |
| |
| /** |
| * Return the size of the current edits log. |
| */ |
| abstract long length() throws IOException; |
| } |