| /* |
| * 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.cassandra.io.sstable; |
| |
| import java.io.Closeable; |
| import java.io.IOException; |
| import java.nio.ByteBuffer; |
| |
| /** |
| * Reads keys from an SSTable. |
| * <p/> |
| * It is specific to SSTable format how the keys are read but in general the assumption is that it will read all the |
| * keys in the order as they are placed in data file. |
| * <p/> |
| * After creating it, it should be at the first key. Unless the SSTable is empty, {@link #key()}, |
| * {@link #keyPositionForSecondaryIndex()} and {@link #dataPosition()} should return approriate values. If there is |
| * no data, {@link #isExhausted()} returns {@code true}. In order to move to the next key, {@link #advance()} should be |
| * called. It returns {@code true} if the reader moved to the next key; otherwise, there is no more data to read and |
| * the reader is exhausted. When the reader is exhausted, return values of {@link #key()}, |
| * {@link #keyPositionForSecondaryIndex()} and {@link #dataPosition()} are undefined. |
| */ |
| public interface KeyReader extends Closeable |
| { |
| /** |
| * Current key |
| */ |
| ByteBuffer key(); |
| |
| /** |
| * Position in the component preferred for reading keys. This is specific to SSTable implementation |
| */ |
| long keyPositionForSecondaryIndex(); |
| |
| /** |
| * Position in the data file where the associated content resides |
| */ |
| long dataPosition(); |
| |
| /** |
| * Moves the iterator forward. Returns false if we reach EOF and there nothing more to read |
| */ |
| boolean advance() throws IOException; |
| |
| /** |
| * Returns true if we reach EOF |
| */ |
| boolean isExhausted(); |
| |
| /** |
| * Resets the iterator to the initial position |
| */ |
| void reset() throws IOException; |
| |
| /** |
| * Closes the iterator quietly |
| */ |
| @Override |
| void close(); |
| } |