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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.utils;

import java.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.RandomAccess;
import java.util.Set;
import java.util.function.IntFunction;

import com.google.common.collect.Maps;
import com.google.common.collect.Sets;

import org.apache.cassandra.db.TypeSizes;
import org.apache.cassandra.io.IVersionedSerializer;
import org.apache.cassandra.io.util.DataInputPlus;
import org.apache.cassandra.io.util.DataOutputPlus;

public class CollectionSerializer
{

    public static  void serializeCollection(IVersionedSerializer valueSerializer, Collection values, DataOutputPlus out, int version) throws IOException
    {
        out.writeUnsignedVInt(values.size());
        for (V value : values)
            valueSerializer.serialize(value, out, version);
    }

    public static  & RandomAccess> void serializeList(IVersionedSerializer valueSerializer, L values, DataOutputPlus out, int version) throws IOException
    {
        int size = values.size();
        out.writeUnsignedVInt(size);
        for (int i = 0 ; i < size ; ++i)
            valueSerializer.serialize(values.get(i), out, version);
    }

    public static  void serializeMap(IVersionedSerializer keySerializer, IVersionedSerializer valueSerializer, Map map, DataOutputPlus out, int version) throws IOException
    {
        out.writeUnsignedVInt(map.size());
        for (Map.Entry e : map.entrySet())
        {
            keySerializer.serialize(e.getKey(), out, version);
            valueSerializer.serialize(e.getValue(), out, version);
        }
    }

    public static > C deserializeCollection(IVersionedSerializer serializer, IntFunction factory, DataInputPlus in, int version) throws IOException
    {
        int size = (int) in.readUnsignedVInt();
        C result = factory.apply(size);
        while (size-- > 0)
            result.add(serializer.deserialize(in, version));
        return result;
    }

    public static > M deserializeMap(IVersionedSerializer keySerializer, IVersionedSerializer valueSerializer, IntFunction factory, DataInputPlus in, int version) throws IOException
    {
        int size = (int) in.readUnsignedVInt();
        M result = factory.apply(size);
        while (size-- > 0)
        {
            K key = keySerializer.deserialize(in, version);
            V value = valueSerializer.deserialize(in, version);
            result.put(key, value);
        }
        return result;
    }

    public static  long serializedSizeCollection(IVersionedSerializer valueSerializer, Collection values, int version)
    {
        long size = TypeSizes.sizeofUnsignedVInt(values.size());
        for (V value : values)
            size += valueSerializer.serializedSize(value, version);
        return size;
    }

    public static  & RandomAccess> long serializedSizeList(IVersionedSerializer valueSerializer, L values, int version) throws IOException
    {
        int items = values.size();
        long size = TypeSizes.sizeofUnsignedVInt(items);
        for (int i = 0 ; i < items ; ++i)
            size += valueSerializer.serializedSize(values.get(i), version);
        return size;
    }


    public static  long serializedSizeMap(IVersionedSerializer keySerializer, IVersionedSerializer valueSerializer, Map map, int version)
    {
        long size = TypeSizes.sizeofUnsignedVInt(map.size());
        for (Map.Entry e : map.entrySet())
            size += keySerializer.serializedSize(e.getKey(), version)
                  + valueSerializer.serializedSize(e.getValue(), version);
        return size;
    }

    public static  IntFunction> newHashSet()
    {
        return i -> i == 0 ? Collections.emptySet() : Sets.newHashSetWithExpectedSize(i);
    }

    public static  IntFunction> newHashMap()
    {
        return i -> i == 0 ? Collections.emptyMap() : Maps.newHashMapWithExpectedSize(i);
    }

}