| /* |
| * 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.jackrabbit.oak.segment.azure; |
| |
| import com.microsoft.azure.storage.OperationContext; |
| import com.microsoft.azure.storage.StorageException; |
| import com.microsoft.azure.storage.blob.CloudBlob; |
| |
| import java.io.IOException; |
| import java.nio.charset.Charset; |
| import java.util.ArrayList; |
| import java.util.Collections; |
| import java.util.HashMap; |
| import java.util.List; |
| |
| import static java.lang.Math.min; |
| |
| public class ReverseFileReader { |
| |
| private static final int BUFFER_SIZE = 16 * 1024; |
| |
| private int bufferSize; |
| |
| private final CloudBlob blob; |
| |
| private byte[] buffer; |
| |
| private int bufferOffset; |
| |
| private int fileOffset; |
| |
| public ReverseFileReader(CloudBlob blob) throws StorageException { |
| this(blob, BUFFER_SIZE); |
| } |
| |
| public ReverseFileReader(CloudBlob blob, int bufferSize) throws StorageException { |
| this.blob = blob; |
| if (blob.exists()) { |
| this.fileOffset = (int) blob.getProperties().getLength(); |
| } else { |
| this.fileOffset = 0; |
| } |
| this.bufferSize = bufferSize; |
| } |
| |
| private void readBlock() throws IOException { |
| if (buffer == null) { |
| buffer = new byte[min(fileOffset, bufferSize)]; |
| } else if (fileOffset < buffer.length) { |
| buffer = new byte[fileOffset]; |
| } |
| |
| if (buffer.length > 0) { |
| fileOffset -= buffer.length; |
| try { |
| OperationContext opContext = new OperationContext(); |
| HashMap<String, String> userHeaders = new HashMap<>(); |
| userHeaders.put("If-Match", "*"); |
| opContext.setUserHeaders(userHeaders); |
| blob.downloadRangeToByteArray(fileOffset, Long.valueOf(buffer.length), buffer, 0, null, null, opContext); |
| } catch (StorageException e) { |
| throw new IOException(e); |
| } |
| } |
| bufferOffset = buffer.length; |
| } |
| |
| private String readUntilNewLine() { |
| if (bufferOffset == -1) { |
| return ""; |
| } |
| int stop = bufferOffset; |
| while (--bufferOffset >= 0) { |
| if (buffer[bufferOffset] == '\n') { |
| break; |
| } |
| } |
| // bufferOffset points either the previous '\n' character or -1 |
| return new String(buffer, bufferOffset + 1, stop - bufferOffset - 1, Charset.defaultCharset()); |
| } |
| |
| public String readLine() throws IOException { |
| if (bufferOffset == -1 && fileOffset == 0) { |
| return null; |
| } |
| |
| if (buffer == null) { |
| readBlock(); |
| } |
| |
| List<String> result = new ArrayList<>(1); |
| while (true) { |
| result.add(readUntilNewLine()); |
| if (bufferOffset > -1) { // stopped on the '\n' |
| break; |
| } |
| if (fileOffset == 0) { // reached the beginning of the file |
| break; |
| } |
| readBlock(); |
| } |
| Collections.reverse(result); |
| return String.join("", result); |
| } |
| } |