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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
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/*
 * 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.cassandra.io.sstable.metadata;

import java.io.*;
import java.util.*;

import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.io.sstable.Component;
import org.apache.cassandra.io.sstable.Descriptor;
import org.apache.cassandra.io.util.DataOutputPlus;
import org.apache.cassandra.io.util.DataOutputStreamAndChannel;
import org.apache.cassandra.io.util.FileDataInput;
import org.apache.cassandra.io.util.FileUtils;
import org.apache.cassandra.io.util.RandomAccessReader;
import org.apache.cassandra.utils.FBUtilities;

/**
 * Metadata serializer for SSTables version >= 'k'.
 *
 *  * File format := | number of components (4 bytes) | toc | component1 | component2 | ... |
 * toc         := | component type (4 bytes) | position of component |
 * 
 *
 * IMetadataComponent.Type's ordinal() defines the order of serialization.
 */
public class MetadataSerializer implements IMetadataSerializer
{
    private static final Logger logger = LoggerFactory.getLogger(MetadataSerializer.class);

    public void serialize(Map components, DataOutputPlus out) throws IOException
    {
        // sort components by type
        List sortedComponents = Lists.newArrayList(components.values());
        Collections.sort(sortedComponents);

        // write number of component
        out.writeInt(components.size());
        // build and write toc
        int lastPosition = 4 + (8 * sortedComponents.size());
        for (MetadataComponent component : sortedComponents)
        {
            MetadataType type = component.getType();
            // serialize type
            out.writeInt(type.ordinal());
            // serialize position
            out.writeInt(lastPosition);
            lastPosition += type.serializer.serializedSize(component);
        }
        // serialize components
        for (MetadataComponent component : sortedComponents)
        {
            component.getType().serializer.serialize(component, out);
        }
    }

    public Map deserialize(Descriptor descriptor, EnumSet types) throws IOException
    {
        Map components;
        logger.debug("Load metadata for {}", descriptor);
        File statsFile = new File(descriptor.filenameFor(Component.STATS));
        if (!statsFile.exists())
        {
            logger.debug("No sstable stats for {}", descriptor);
            components = Maps.newHashMap();
            components.put(MetadataType.STATS, MetadataCollector.defaultStatsMetadata());
        }
        else
        {
            try (RandomAccessReader r = RandomAccessReader.open(statsFile))
            {
                components = deserialize(descriptor, r, types);
            }
        }
        return components;
    }

    public MetadataComponent deserialize(Descriptor descriptor, MetadataType type) throws IOException
    {
        return deserialize(descriptor, EnumSet.of(type)).get(type);
    }

    public Map deserialize(Descriptor descriptor, FileDataInput in, EnumSet types) throws IOException
    {
        Map components = Maps.newHashMap();
        // read number of components
        int numComponents = in.readInt();
        // read toc
        Map toc = new HashMap<>(numComponents);
        for (int i = 0; i < numComponents; i++)
        {
            toc.put(MetadataType.values()[in.readInt()], in.readInt());
        }
        for (MetadataType type : types)
        {
            MetadataComponent component = null;
            if (toc.containsKey(type))
            {
                in.seek(toc.get(type));
                component = type.serializer.deserialize(descriptor.version, in);
            }
            components.put(type, component);
        }
        return components;
    }

    public void mutateLevel(Descriptor descriptor, int newLevel) throws IOException
    {
        logger.debug("Mutating {} to level {}", descriptor.filenameFor(Component.STATS), newLevel);
        Map currentComponents = deserialize(descriptor, EnumSet.allOf(MetadataType.class));
        StatsMetadata stats = (StatsMetadata) currentComponents.remove(MetadataType.STATS);
        // mutate level
        currentComponents.put(MetadataType.STATS, stats.mutateLevel(newLevel));
        rewriteSSTableMetadata(descriptor, currentComponents);
    }

    public void mutateRepairedAt(Descriptor descriptor, long newRepairedAt) throws IOException
    {
        logger.debug("Mutating {} to repairedAt time {}", descriptor.filenameFor(Component.STATS), newRepairedAt);
        Map currentComponents = deserialize(descriptor, EnumSet.allOf(MetadataType.class));
        StatsMetadata stats = (StatsMetadata) currentComponents.remove(MetadataType.STATS);
        // mutate level
        currentComponents.put(MetadataType.STATS, stats.mutateRepairedAt(newRepairedAt));
        rewriteSSTableMetadata(descriptor, currentComponents);
    }

    private void rewriteSSTableMetadata(Descriptor descriptor, Map currentComponents) throws IOException
    {
        Descriptor tmpDescriptor = descriptor.asType(Descriptor.Type.TEMP);

        try (DataOutputStreamAndChannel out = new DataOutputStreamAndChannel(new FileOutputStream(tmpDescriptor.filenameFor(Component.STATS))))
        {
            serialize(currentComponents, out);
            out.flush();
        }
        // we cant move a file on top of another file in windows:
        if (FBUtilities.isWindows())
            FileUtils.delete(descriptor.filenameFor(Component.STATS));
        FileUtils.renameWithConfirm(tmpDescriptor.filenameFor(Component.STATS), descriptor.filenameFor(Component.STATS));

    }
}