/**
* 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.db;
import java.util.Arrays;
import java.util.Collection;
import java.security.MessageDigest;
import java.io.IOException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.commons.lang.ArrayUtils;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.db.IClock.ClockRelationship;
import org.apache.cassandra.io.util.DataOutputBuffer;
import org.apache.cassandra.utils.FBUtilities;
/**
* Column is immutable, which prevents all kinds of confusion in a multithreaded environment.
* (TODO: look at making SuperColumn immutable too. This is trickier but is probably doable
* with something like PCollections -- http://code.google.com
*/
public class Column implements IColumn
{
private static Logger logger = LoggerFactory.getLogger(Column.class);
public static ColumnSerializer serializer(ClockType clockType)
{
return new ColumnSerializer(clockType);
}
protected final byte[] name;
protected final byte[] value;
protected final IClock clock;
Column(byte[] name)
{
this(name, ArrayUtils.EMPTY_BYTE_ARRAY);
}
public Column(byte[] name, byte[] value)
{
// safe to set to null, only used for filter comparisons
this(name, value, null);
}
public Column(byte[] name, byte[] value, IClock clock)
{
assert name != null;
assert value != null;
assert name.length <= IColumn.MAX_NAME_LENGTH;
this.name = name;
this.value = value;
this.clock = clock;
}
public byte[] name()
{
return name;
}
public Column getSubColumn(byte[] columnName)
{
throw new UnsupportedOperationException("This operation is unsupported on simple columns.");
}
public byte[] value()
{
return value;
}
public Collection<IColumn> getSubColumns()
{
throw new UnsupportedOperationException("This operation is unsupported on simple columns.");
}
public IClock clock()
{
return clock;
}
public boolean isMarkedForDelete()
{
return false;
}
public IClock getMarkedForDeleteAt()
{
throw new IllegalStateException("column is not marked for delete");
}
public IClock mostRecentLiveChangeAt()
{
return clock;
}
public int size()
{
/*
* Size of a column is =
* size of a name (short + length of the string)
* + 1 byte to indicate if the column has been deleted
* + x bytes depending on IClock size
* + 4 bytes which basically indicates the size of the byte array
* + entire byte array.
*/
return DBConstants.shortSize_ + name.length + DBConstants.boolSize_ + clock.size() + DBConstants.intSize_ + value.length;
}
/*
* This returns the size of the column when serialized.
* @see com.facebook.infrastructure.db.IColumn#serializedSize()
*/
public int serializedSize()
{
return size();
}
public void addColumn(IColumn column)
{
throw new UnsupportedOperationException("This operation is not supported for simple columns.");
}
public IColumn diff(IColumn column)
{
if (ClockRelationship.GREATER_THAN == column.clock().compare(clock))
{
return column;
}
return null;
}
public void updateDigest(MessageDigest digest)
{
digest.update(name);
digest.update(value);
DataOutputBuffer buffer = new DataOutputBuffer();
try
{
clock.serialize(buffer);
buffer.writeByte((isMarkedForDelete()) ? ColumnSerializer.DELETION_MASK : 0);
}
catch (IOException e)
{
throw new RuntimeException(e);
}
digest.update(buffer.getData(), 0, buffer.getLength());
}
public int getLocalDeletionTime()
{
throw new IllegalStateException("column is not marked for delete");
}
// note that we do not call this simply compareTo since it also makes sense to compare Columns by name
public ClockRelationship comparePriority(Column o)
{
ClockRelationship rel = clock.compare(o.clock());
// tombstone always wins ties.
if (isMarkedForDelete())
{
switch (rel)
{
case EQUAL:
return ClockRelationship.GREATER_THAN;
default:
return rel;
}
}
if (o.isMarkedForDelete())
{
switch (rel)
{
case EQUAL:
return ClockRelationship.LESS_THAN;
default:
return rel;
}
}
// compare value as tie-breaker for equal clocks
if (ClockRelationship.EQUAL == rel)
{
int valRel = FBUtilities.compareByteArrays(value, o.value);
if (1 == valRel)
return ClockRelationship.GREATER_THAN;
if (0 == valRel)
return ClockRelationship.EQUAL;
// -1 == valRel
return ClockRelationship.LESS_THAN;
}
// neither is tombstoned and clocks are different
return rel;
}
@Override
public boolean equals(Object o)
{
if (this == o)
return true;
if (o == null || getClass() != o.getClass())
return false;
Column column = (Column)o;
if (clock != null ? !clock.equals(column.clock) : column.clock != null)
return false;
if (!Arrays.equals(name, column.name))
return false;
return Arrays.equals(value, column.value);
}
@Override
public int hashCode()
{
int result = name != null ? Arrays.hashCode(name) : 0;
result = 31 * result + (value != null ? Arrays.hashCode(value) : 0);
result = 31 * result + (clock != null ? clock.hashCode() : 0);
return result;
}
public String getString(AbstractType comparator)
{
StringBuilder sb = new StringBuilder();
sb.append(comparator.getString(name));
sb.append(":");
sb.append(isMarkedForDelete());
sb.append(":");
sb.append(value.length);
sb.append("@");
sb.append(clock.toString());
return sb.toString();
}
}