/*
* 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.nifi.provenance.toc;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import org.apache.nifi.stream.io.StreamUtils;
/**
* Standard implementation of TocReader.
*
* Expects .toc file to be in the following format;
*
* byte 0: version
* byte 1: boolean: compressionFlag -> 0 = journal is NOT compressed, 1 = journal is compressed
* byte 2-9: long: offset of block 0
* byte 10-17: long: offset of block 1
* ...
* byte (N*8+2)-(N*8+9): long: offset of block N
*/
public class StandardTocReader implements TocReader {
private final boolean compressed;
private final long[] offsets;
private final long[] firstEventIds;
private final File file;
public StandardTocReader(final File file) throws IOException {
this.file = file;
final long fileLength = file.length();
if (fileLength < 2) {
throw new EOFException();
}
try (final FileInputStream fis = new FileInputStream(file)) {
final byte[] buffer = new byte[(int) fileLength];
StreamUtils.fillBuffer(fis, buffer);
final int version = buffer[0];
final int compressionFlag = buffer[1];
if ( compressionFlag == 0 ) {
compressed = false;
} else if ( compressionFlag == 1 ) {
compressed = true;
} else {
throw new IOException("Table of Contents file " + file + " appears to be corrupt: could not read 'compression flag' from header; "
+ "expected value of 0 or 1 but got " + compressionFlag);
}
final int blockInfoBytes;
switch (version) {
case 1:
blockInfoBytes = 8;
break;
case 2:
default:
blockInfoBytes = 16;
break;
}
final int numBlocks = (buffer.length - 2) / blockInfoBytes;
offsets = new long[numBlocks];
if ( version > 1 ) {
firstEventIds = new long[numBlocks];
} else {
firstEventIds = new long[0];
}
int index = 2;
for (int i=0; i < numBlocks; i++) {
offsets[i] = readLong(buffer, index);
index += 8;
if ( version > 1 ) {
firstEventIds[i] = readLong(buffer, index);
index += 8;
}
}
}
}
private long readLong(final byte[] buffer, final int offset) {
return ((long) buffer[offset] << 56) +
((long) (buffer[offset + 1] & 0xFF) << 48) +
((long) (buffer[offset + 2] & 0xFF) << 40) +
((long) (buffer[offset + 3] & 0xFF) << 32) +
((long) (buffer[offset + 4] & 0xFF) << 24) +
((long) (buffer[offset + 5] & 0xFF) << 16) +
((long) (buffer[offset + 6] & 0xFF) << 8) +
(buffer[offset + 7] & 0xFF);
}
@Override
public boolean isCompressed() {
return compressed;
}
@Override
public File getFile() {
return file;
}
@Override
public long getBlockOffset(final int blockIndex) {
if ( blockIndex >= offsets.length ) {
return -1L;
}
return offsets[blockIndex];
}
@Override
public long getFirstEventIdForBlock(final int blockIndex) {
if (blockIndex >= firstEventIds.length) {
return -1L;
}
return firstEventIds[blockIndex];
}
@Override
public long getLastBlockOffset() {
if ( offsets.length == 0 ) {
return 0L;
}
return offsets[offsets.length - 1];
}
@Override
public void close() {
}
@Override
public int getBlockIndex(final long blockOffset) {
for (int i=0; i < offsets.length; i++) {
if ( offsets[i] > blockOffset ) {
// if the offset is less than the offset of our first block,
// just return 0 to indicate the first block. Otherwise,
// return i-1 because i represents the first block whose offset is
// greater than 'blockOffset'.
return (i == 0) ? 0 : i-1;
}
}
// None of the blocks have an offset greater than the provided offset.
// Therefore, if the event is present, it must be in the last block.
return offsets.length - 1;
}
@Override
public Integer getBlockIndexForEventId(final long eventId) {
// if we don't have event ID's stored in the TOC (which happens for version 1 of the TOC),
// or if the event ID is less than the first Event ID in this TOC, then the Event ID
// is unknown -- return null.
if ( firstEventIds.length == 0 || eventId < firstEventIds[0] ) {
return null;
}
for (int i=1; i < firstEventIds.length; i++) {
if ( firstEventIds[i] > eventId ) {
return i-1;
}
}
// None of the blocks start with an Event ID greater than the provided ID.
// Therefore, if the event is present, it must be in the last block.
return firstEventIds.length - 1;
}
@Override
public String toString() {
return "StandardTocReader[file=" + file + ", compressed=" + compressed + "]";
}
}