| /** |
| * 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.raid; |
| |
| import java.io.InputStream; |
| import java.io.OutputStream; |
| import java.io.IOException; |
| import java.util.Arrays; |
| |
| import org.apache.hadoop.util.Progressable; |
| |
| /** |
| * Wraps over multiple input streams and provides an input stream that is |
| * an XOR of the streams. |
| */ |
| class ParityInputStream extends InputStream { |
| private static final int DEFAULT_BUFSIZE = 5*1024*1024; |
| private InputStream[] streams; |
| private byte[] xor; |
| private byte[] buf; |
| private int bufSize; |
| private long remaining; |
| private int available = 0; |
| private int readPos = 0; |
| |
| public ParityInputStream( |
| InputStream[] streams, long parityBlockSize, byte[] buf, byte[] xor) { |
| assert buf.length == xor.length; |
| bufSize = buf.length; |
| this.streams = streams; |
| remaining = parityBlockSize; |
| this.buf = buf; |
| this.xor = xor; |
| } |
| |
| @Override |
| public int read() throws IOException { |
| makeAvailable(); |
| if (available == 0) { |
| return -1; |
| } |
| int ret = xor[readPos]; |
| readPos++; |
| available--; |
| return ret; |
| } |
| |
| @Override |
| public int read(byte b[], int off, int len) throws IOException { |
| makeAvailable(); |
| if (available == 0) { |
| return -1; |
| } |
| int ret = Math.min(len, available); |
| for (int i = 0; i < ret; ++i) { |
| b[off+i] = xor[readPos+i]; |
| } |
| readPos += ret; |
| available -= ret; |
| return ret; |
| } |
| |
| public void close() throws IOException { |
| for (InputStream i: streams) { |
| i.close(); |
| } |
| } |
| |
| /** |
| * Send the contents of the stream to the sink. |
| * @param sink |
| * @param reporter |
| * @throws IOException |
| */ |
| public void drain(OutputStream sink, Progressable reporter) |
| throws IOException { |
| |
| while (true) { |
| makeAvailable(); |
| if (available == 0) { |
| break; |
| } |
| sink.write(xor, readPos, available); |
| available = 0; |
| if (reporter != null) { |
| reporter.progress(); |
| } |
| } |
| } |
| |
| /** |
| * Make some bytes available for reading in the internal buffer. |
| * @throws IOException |
| */ |
| private void makeAvailable() throws IOException { |
| if (available > 0 || remaining <= 0) { |
| return; |
| } |
| // Read some bytes from the first stream. |
| int xorlen = (int)Math.min(remaining, bufSize); |
| readExact(streams[0], xor, xorlen); |
| |
| // Read bytes from all the other streams and xor them. |
| for (int i = 1; i < streams.length; i++) { |
| readExact(streams[i], buf, xorlen); |
| |
| for (int j = 0; j < xorlen; j++) { |
| xor[j] ^= buf[j]; |
| } |
| } |
| |
| remaining -= xorlen; |
| available = xorlen; |
| readPos = 0; |
| readPos = 0; |
| } |
| |
| private static void readExact(InputStream in, byte[] bufs, int toRead) |
| throws IOException { |
| int tread = 0; |
| while (tread < toRead) { |
| int read = in.read(bufs, tread, toRead - tread); |
| if (read == -1) { |
| // If the stream ends, fill in zeros. |
| Arrays.fill(bufs, tread, toRead, (byte)0); |
| tread = toRead; |
| } else { |
| tread += read; |
| } |
| } |
| assert tread == toRead; |
| } |
| |
| } |
| |