| /** |
| * 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; |
| |
| import java.io.IOException; |
| import java.nio.ByteBuffer; |
| |
| /** |
| * Wraps different possible read implementations so that callers can be |
| * strategy-agnostic. |
| */ |
| interface ReaderStrategy { |
| /** |
| * Read from a block using the blockReader. |
| * @param blockReader |
| * @return number of bytes read |
| * @throws IOException |
| */ |
| int readFromBlock(BlockReader blockReader) throws IOException; |
| |
| /** |
| * Read from a block using the blockReader with desired length to read. |
| * @param blockReader |
| * @param length number of bytes desired to read, not ensured |
| * @return number of bytes read |
| * @throws IOException |
| */ |
| int readFromBlock(BlockReader blockReader, int length) throws IOException; |
| |
| /** |
| * Read or copy from a src buffer. |
| * @param src |
| * @return number of bytes copied |
| * Note: the position of the src buffer is not changed after the call |
| */ |
| int readFromBuffer(ByteBuffer src); |
| |
| /** |
| * Read or copy length of data bytes from a src buffer with desired length. |
| * @param src |
| * @return number of bytes copied |
| * Note: the position of the src buffer is not changed after the call |
| */ |
| int readFromBuffer(ByteBuffer src, int length); |
| |
| /** |
| * @return the target read buffer that reads data into. |
| */ |
| ByteBuffer getReadBuffer(); |
| |
| /** |
| * @return the target length to read. |
| */ |
| int getTargetLength(); |
| } |
| |
| /** |
| * Used to read bytes into a byte array buffer. Note it's not thread-safe |
| * and the behavior is not defined if concurrently operated. |
| */ |
| class ByteArrayStrategy implements ReaderStrategy { |
| private final DFSClient dfsClient; |
| private final ReadStatistics readStatistics; |
| private final byte[] readBuf; |
| private int offset; |
| private final int targetLength; |
| |
| /** |
| * The constructor. |
| * @param readBuf target buffer to read into |
| * @param offset offset into the buffer |
| * @param targetLength target length of data |
| * @param readStatistics statistics counter |
| */ |
| public ByteArrayStrategy(byte[] readBuf, int offset, int targetLength, |
| ReadStatistics readStatistics, |
| DFSClient dfsClient) { |
| this.readBuf = readBuf; |
| this.offset = offset; |
| this.targetLength = targetLength; |
| this.readStatistics = readStatistics; |
| this.dfsClient = dfsClient; |
| } |
| |
| @Override |
| public ByteBuffer getReadBuffer() { |
| return ByteBuffer.wrap(readBuf, offset, targetLength); |
| } |
| |
| @Override |
| public int getTargetLength() { |
| return targetLength; |
| } |
| |
| @Override |
| public int readFromBlock(BlockReader blockReader) throws IOException { |
| return readFromBlock(blockReader, targetLength); |
| } |
| |
| @Override |
| public int readFromBlock(BlockReader blockReader, |
| int length) throws IOException { |
| int nRead = blockReader.read(readBuf, offset, length); |
| if (nRead > 0) { |
| offset += nRead; |
| } |
| return nRead; |
| } |
| |
| @Override |
| public int readFromBuffer(ByteBuffer src) { |
| return readFromBuffer(src, src.remaining()); |
| } |
| |
| @Override |
| public int readFromBuffer(ByteBuffer src, int length) { |
| ByteBuffer dup = src.duplicate(); |
| dup.get(readBuf, offset, length); |
| offset += length; |
| return length; |
| } |
| } |
| |
| /** |
| * Used to read bytes into a user-supplied ByteBuffer. Note it's not thread-safe |
| * and the behavior is not defined if concurrently operated. When read operation |
| * is performed, the position of the underlying byte buffer will move forward as |
| * stated in ByteBufferReadable#read(ByteBuffer buf) method. |
| */ |
| class ByteBufferStrategy implements ReaderStrategy { |
| private final DFSClient dfsClient; |
| private final ReadStatistics readStatistics; |
| private final ByteBuffer readBuf; |
| private final int targetLength; |
| |
| /** |
| * The constructor. |
| * @param readBuf target buffer to read into |
| * @param readStatistics statistics counter |
| */ |
| ByteBufferStrategy(ByteBuffer readBuf, |
| ReadStatistics readStatistics, |
| DFSClient dfsClient) { |
| this.readBuf = readBuf; |
| this.targetLength = readBuf.remaining(); |
| this.readStatistics = readStatistics; |
| this.dfsClient = dfsClient; |
| } |
| |
| @Override |
| public ByteBuffer getReadBuffer() { |
| return readBuf; |
| } |
| |
| @Override |
| public int readFromBlock(BlockReader blockReader) throws IOException { |
| return readFromBlock(blockReader, readBuf.remaining()); |
| } |
| |
| @Override |
| public int readFromBlock(BlockReader blockReader, |
| int length) throws IOException { |
| ByteBuffer tmpBuf = readBuf.duplicate(); |
| tmpBuf.limit(tmpBuf.position() + length); |
| int nRead = blockReader.read(tmpBuf); |
| // Only when data are read, update the position |
| if (nRead > 0) { |
| readBuf.position(readBuf.position() + nRead); |
| } |
| |
| return nRead; |
| } |
| |
| @Override |
| public int getTargetLength() { |
| return targetLength; |
| } |
| |
| @Override |
| public int readFromBuffer(ByteBuffer src) { |
| return readFromBuffer(src, src.remaining()); |
| } |
| |
| @Override |
| public int readFromBuffer(ByteBuffer src, int length) { |
| ByteBuffer dup = src.duplicate(); |
| int newLen = Math.min(readBuf.remaining(), dup.remaining()); |
| newLen = Math.min(newLen, length); |
| dup.limit(dup.position() + newLen); |
| readBuf.put(dup); |
| return newLen; |
| } |
| } |