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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.
/*
* 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.serializers;
import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.List;
import org.apache.cassandra.db.TypeSizes;
import org.apache.cassandra.db.marshal.ByteBufferAccessor;
import org.apache.cassandra.db.marshal.ValueAccessor;
import org.apache.cassandra.transport.ProtocolVersion;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.utils.ByteBufferUtil;
public abstract class CollectionSerializer extends TypeSerializer
{
protected abstract List serializeValues(T value);
protected abstract int getElementCount(T value);
public abstract T deserializeForNativeProtocol(V value, ValueAccessor accessor, ProtocolVersion version);
public T deserializeForNativeProtocol(ByteBuffer value, ProtocolVersion version)
{
return deserializeForNativeProtocol(value, ByteBufferAccessor.instance, version);
}
public abstract void validateForNativeProtocol(V value, ValueAccessor accessor, ProtocolVersion version);
public ByteBuffer serialize(T input)
{
List values = serializeValues(input);
// See deserialize() for why using the protocol v3 variant is the right thing to do.
return pack(values, ByteBufferAccessor.instance, getElementCount(input), ProtocolVersion.V3);
}
public T deserialize(V value, ValueAccessor accessor)
{
// The only cases we serialize/deserialize collections internally (i.e. not for the protocol sake),
// is:
// 1) when collections are frozen
// 2) for internal calls.
// In both case, using the protocol 3 version variant is the right thing to do.
return deserializeForNativeProtocol(value, accessor, ProtocolVersion.V3);
}
public void validate(T1 value, ValueAccessor accessor) throws MarshalException
{
// Same thing as above
validateForNativeProtocol(value, accessor, ProtocolVersion.V3);
}
public static ByteBuffer pack(Collection values, int elements, ProtocolVersion version)
{
return pack(values, ByteBufferAccessor.instance, elements, version);
}
public static V pack(Collection values, ValueAccessor accessor, int elements, ProtocolVersion version)
{
int size = 0;
for (V value : values)
size += sizeOfValue(value, accessor, version);
ByteBuffer result = ByteBuffer.allocate(sizeOfCollectionSize(elements, version) + size);
writeCollectionSize(result, elements, version);
for (V value : values)
{
writeValue(result, value, accessor, version);
}
return accessor.valueOf((ByteBuffer) result.flip());
}
protected static void writeCollectionSize(ByteBuffer output, int elements, ProtocolVersion version)
{
output.putInt(elements);
}
public static int readCollectionSize(ByteBuffer input, ProtocolVersion version)
{
return readCollectionSize(input, ByteBufferAccessor.instance, version);
}
public static int readCollectionSize(V value, ValueAccessor accessor, ProtocolVersion version)
{
return accessor.toInt(value);
}
public static int sizeOfCollectionSize(int elements, ProtocolVersion version)
{
return TypeSizes.INT_SIZE;
}
public static void writeValue(ByteBuffer output, V value, ValueAccessor accessor, ProtocolVersion version)
{
if (value == null)
{
output.putInt(-1);
return;
}
output.putInt(accessor.size(value));
accessor.write(value, output);
}
public static V readValue(V input, ValueAccessor accessor, int offset, ProtocolVersion version)
{
int size = accessor.getInt(input, offset);
if (size < 0)
return null;
return accessor.slice(input, offset + TypeSizes.INT_SIZE, size);
}
protected static void skipValue(ByteBuffer input, ProtocolVersion version)
{
int size = input.getInt();
input.position(input.position() + size);
}
public static int skipValue(V input, ValueAccessor accessor, int offset, ProtocolVersion version)
{
int size = accessor.getInt(input, offset);
return TypeSizes.sizeof(size) + size;
}
public static int sizeOfValue(V value, ValueAccessor accessor, ProtocolVersion version)
{
return value == null ? 4 : 4 + accessor.size(value);
}
/**
* Extract an element from a serialized collection.
*
* Note that this is only supported to sets and maps. For sets, this mostly ends up being
* a check for the presence of the provide key: it will return the key if it's present and
* {@code null} otherwise.
*
* @param collection the serialized collection. This cannot be {@code null}.
* @param key the key to extract (This cannot be {@code null} nor {@code ByteBufferUtil.UNSET_BYTE_BUFFER}).
* @param comparator the type to use to compare the {@code key} value to those
* in the collection.
* @return the value associated with {@code key} if one exists, {@code null} otherwise
*/
public abstract ByteBuffer getSerializedValue(ByteBuffer collection, ByteBuffer key, AbstractType comparator);
/**
* Returns the slice of a collection directly from its serialized value.
*
If the slice contains no elements an empty collection will be returned for frozen collections, and a
* {@code null} one for non-frozen collections.
*
* @param collection the serialized collection. This cannot be {@code null}.
* @param from the left bound of the slice to extract. This cannot be {@code null} but if this is
* {@code ByteBufferUtil.UNSET_BYTE_BUFFER}, then the returned slice starts at the beginning
* of {@code collection}.
* @param comparator the type to use to compare the {@code from} and {@code to} values to those
* in the collection.
* @param frozen {@code true} if the collection is a frozen one, {@code false} otherwise
* @return a serialized collection corresponding to slice {@code [from, to]} of {@code collection}.
*/
public abstract ByteBuffer getSliceFromSerialized(ByteBuffer collection,
ByteBuffer from,
ByteBuffer to,
AbstractType comparator,
boolean frozen);
/**
* Creates a new serialized map composed from the data from {@code input} between {@code startPos}
* (inclusive) and {@code endPos} (exclusive), assuming that data holds {@code count} elements.
*/
protected ByteBuffer copyAsNewCollection(ByteBuffer input, int count, int startPos, int endPos, ProtocolVersion version)
{
int sizeLen = sizeOfCollectionSize(count, version);
if (count == 0)
return ByteBuffer.allocate(sizeLen);
int bodyLen = endPos - startPos;
ByteBuffer output = ByteBuffer.allocate(sizeLen + bodyLen);
writeCollectionSize(output, count, version);
output.position(0);
ByteBufferUtil.copyBytes(input, startPos, output, sizeLen, bodyLen);
return output;
}
}