| /* |
| * 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.util; |
| |
| import java.nio.ByteBuffer; |
| |
| /** |
| * Rebufferer for reading data by a RandomAccessReader. |
| */ |
| public interface Rebufferer extends ReaderFileProxy |
| { |
| /** |
| * Rebuffer (move on or seek to) a given position, and return a buffer that can be used there. |
| * The only guarantee about the size of the returned data is that unless rebuffering at the end of the file, |
| * the buffer will not be empty and will contain the requested position, i.e. |
| * {@code offset <= position < offset + bh.buffer().limit()}, but the buffer will not be positioned there. |
| */ |
| BufferHolder rebuffer(long position); |
| |
| /** |
| * Called when a reader is closed. Should clean up reader-specific data. |
| */ |
| void closeReader(); |
| |
| interface BufferHolder |
| { |
| /** |
| * Returns a useable buffer (i.e. one whose position and limit can be freely modified). Its limit will be set |
| * to the size of the available data in the buffer. |
| * The buffer must be treated as read-only. |
| */ |
| ByteBuffer buffer(); |
| |
| /** |
| * Position in the file of the start of the buffer. |
| */ |
| long offset(); |
| |
| /** |
| * To be called when this buffer is no longer in use. Must be called for all BufferHolders, or ChunkCache |
| * will not be able to free blocks. |
| */ |
| void release(); |
| } |
| |
| BufferHolder EMPTY = new BufferHolder() |
| { |
| final ByteBuffer EMPTY_BUFFER = ByteBuffer.allocate(0); |
| |
| @Override |
| public ByteBuffer buffer() |
| { |
| return EMPTY_BUFFER; |
| } |
| |
| @Override |
| public long offset() |
| { |
| return 0; |
| } |
| |
| @Override |
| public void release() |
| { |
| // nothing to do |
| } |
| }; |
| } |