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/*
* Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH under
* one or more contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright ownership.
* Licensed under the Zeebe Community License 1.1. You may not use this file
* except in compliance with the Zeebe Community License 1.1.
*/
package io.camunda.zeebe.journal.file;
import io.camunda.zeebe.journal.CorruptedJournalException;
import io.camunda.zeebe.journal.util.ChecksumGenerator;
import java.nio.ByteBuffer;
import org.agrona.DirectBuffer;
import org.agrona.concurrent.UnsafeBuffer;
final class SegmentDescriptorReader {
private final DescriptorMetadataDecoder metadataDecoder = new DescriptorMetadataDecoder();
private final SegmentDescriptorDecoder segmentDescriptorDecoder = new SegmentDescriptorDecoder();
private final MessageHeaderDecoder headerDecoder = new MessageHeaderDecoder();
private final ChecksumGenerator checksumGen = new ChecksumGenerator();
private final DirectBuffer directBuffer = new UnsafeBuffer();
private int actingSchemaVersion = segmentDescriptorDecoder.sbeSchemaVersion();
private long id;
private long index;
private int maxSegmentSize;
// index of the last entry in this segment. Can be 0 if not set, even if an entry exists.
private long lastIndex;
// position of the last entry in this segment. Can be 0 if not set, even if an entry exists.
private int lastPosition;
private int encodedLength;
private long checksum;
SegmentDescriptor readFrom(final ByteBuffer buffer) {
directBuffer.wrap(buffer);
final byte version;
try {
version = directBuffer.getByte(0);
if (version >= SegmentDescriptor.META_VERSION && version <= SegmentDescriptor.CUR_VERSION) {
readV2Descriptor(directBuffer);
} else {
throw new UnknownVersionException(
String.format(
"Expected version to be one (%d %d] but read %d instead.",
SegmentDescriptor.META_VERSION, SegmentDescriptor.CUR_VERSION, version));
}
} catch (final IndexOutOfBoundsException error) {
// Previously SegmentLoader checks if the file has sufficient size for the descriptor. But
// it
// is not checked anymore because the encoded length is not known before reading.
throw new CorruptedJournalException("Failed to read segment descriptor", error);
}
return new SegmentDescriptor(
version,
actingSchemaVersion,
id,
index,
maxSegmentSize,
lastIndex,
lastPosition,
encodedLength);
}
/**
* Validates the headers' schema and template ids, as well as the metadata's checksum, before
* loading the descriptor's fields.
*/
private void readV2Descriptor(final DirectBuffer buffer) {
// validate metadata header
validateHeader(
buffer,
SegmentDescriptor.VERSION_LENGTH,
metadataDecoder.sbeSchemaId(),
metadataDecoder.sbeTemplateId());
final int descHeaderOffset = readChecksum(buffer, SegmentDescriptor.VERSION_LENGTH);
// validate descriptor header
validateHeader(
buffer,
descHeaderOffset,
segmentDescriptorDecoder.sbeSchemaId(),
segmentDescriptorDecoder.sbeTemplateId());
final int totalLength = readDescriptor(buffer, descHeaderOffset);
// length of the header + descriptor
final int descriptorLength = totalLength - descHeaderOffset;
validateChecksum(buffer, descHeaderOffset, descriptorLength);
}
private void validateChecksum(
final DirectBuffer buffer, final int descHeaderOffset, final int descriptorLength) {
final ByteBuffer slice = ByteBuffer.allocate(descriptorLength);
buffer.getBytes(descHeaderOffset, slice, descriptorLength);
final long computedChecksum = checksumGen.compute(slice, 0, descriptorLength);
if (computedChecksum != checksum) {
throw new CorruptedJournalException(
"Descriptor doesn't match checksum (possibly due to corruption).");
}
}
/**
* Loads the descriptor's fields.
*
* @param offset offset where the descriptor's header starts
* @return offset after reading the descriptor
*/
private int readDescriptor(final DirectBuffer buffer, final int offset) {
headerDecoder.wrap(buffer, offset);
actingSchemaVersion = headerDecoder.version();
segmentDescriptorDecoder.wrap(
directBuffer,
offset + headerDecoder.encodedLength(),
headerDecoder.blockLength(),
actingSchemaVersion);
id = segmentDescriptorDecoder.id();
index = segmentDescriptorDecoder.index();
maxSegmentSize = segmentDescriptorDecoder.maxSegmentSize();
lastIndex = Math.max(0, segmentDescriptorDecoder.lastIndex());
lastPosition = Math.max(0, (int) segmentDescriptorDecoder.lastPosition());
encodedLength =
offset + headerDecoder.encodedLength() + segmentDescriptorDecoder.encodedLength();
return encodedLength;
}
/**
* Loads the metadata's checksum field.
*
* @return offset after the metadata
*/
private int readChecksum(final DirectBuffer buffer, final int offset) {
headerDecoder.wrap(buffer, offset);
metadataDecoder.wrap(
buffer,
offset + headerDecoder.encodedLength(),
headerDecoder.blockLength(),
headerDecoder.version());
checksum = metadataDecoder.checksum();
return offset + headerDecoder.encodedLength() + metadataDecoder.encodedLength();
}
/** Validate that the header's schema and template ids match the expected ones. */
private void validateHeader(
final DirectBuffer buffer, final int offset, final int schemaId, final int templateId) {
headerDecoder.wrap(buffer, offset);
if (headerDecoder.schemaId() != schemaId || headerDecoder.templateId() != templateId) {
throw new CorruptedJournalException(
String.format(
"Cannot read header. Read schema and template ids ('%d' and '%d') don't match expected '%d' and %d'.",
headerDecoder.schemaId(), headerDecoder.templateId(), schemaId, templateId));
}
}
}
