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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.io.util;
import org.apache.cassandra.utils.Shared;
import org.apache.cassandra.utils.vint.VIntCoding;
import java.io.DataOutput;
import java.io.IOException;
import java.nio.ByteBuffer;
import com.google.common.primitives.Ints;
import static org.apache.cassandra.utils.Shared.Scope.SIMULATION;
/**
* Extension to DataOutput that provides for writing ByteBuffer and Memory, potentially with an efficient
* implementation that is zero copy or at least has reduced bounds checking overhead.
*/
@Shared(scope = SIMULATION)
public interface DataOutputPlus extends DataOutput
{
// write the buffer without modifying its position
void write(ByteBuffer buffer) throws IOException;
default void write(ReadableMemory memory, long offset, long length) throws IOException
{
for (ByteBuffer buffer : memory.asByteBuffers(offset, length))
write(buffer);
}
default void writeVInt(long i) throws IOException
{
VIntCoding.writeVInt(i, this);
}
/** @deprecated See CASSANDRA-18099 */
@Deprecated(since = "5.0")
default void writeVInt(int i)
{
throw new UnsupportedOperationException("Use writeVInt32/readVInt32");
}
default void writeVInt32(int i) throws IOException
{
VIntCoding.writeVInt32(i, this);
}
/**
* This is more efficient for storing unsigned values, both in storage and CPU burden.
*
* Note that it is still possible to store negative values, they just take up more space.
* So this method doesn't forbid e.g. negative sentinel values in future, if they need to be snuck in.
* A protocol version bump can then be introduced to improve efficiency.
*/
default void writeUnsignedVInt(long i) throws IOException
{
VIntCoding.writeUnsignedVInt(i, this);
}
/** @deprecated See CASSANDRA-18099 */
@Deprecated(since = "5.0")
default void writeUnsignedVInt(int i)
{
throw new UnsupportedOperationException("Use writeUnsignedVInt32/readUnsignedVInt32");
}
default void writeUnsignedVInt32(int i) throws IOException
{
VIntCoding.writeUnsignedVInt32(i, this);
}
/**
* An efficient way to write the type {@code bytes} of a long
*
* @param register - the long value to be written
* @param bytes - the number of bytes the register occupies. Valid values are between 1 and 8 inclusive.
* @throws IOException
*/
default void writeMostSignificantBytes(long register, int bytes) throws IOException
{
switch (bytes)
{
case 0:
break;
case 1:
writeByte((int)(register >>> 56));
break;
case 2:
writeShort((int)(register >> 48));
break;
case 3:
writeShort((int)(register >> 48));
writeByte((int)(register >> 40));
break;
case 4:
writeInt((int)(register >> 32));
break;
case 5:
writeInt((int)(register >> 32));
writeByte((int)(register >> 24));
break;
case 6:
writeInt((int)(register >> 32));
writeShort((int)(register >> 16));
break;
case 7:
writeInt((int)(register >> 32));
writeShort((int)(register >> 16));
writeByte((int)(register >> 8));
break;
case 8:
writeLong(register);
break;
default:
throw new IllegalArgumentException();
}
}
/**
* Returns the current position of the underlying target like a file-pointer
* or the position withing a buffer. Not every implementation may support this
* functionality. Whether or not this functionality is supported can be checked
* via the {@link #hasPosition()}.
*
* @throws UnsupportedOperationException if the implementation does not support
* position
*/
default long position()
{
throw new UnsupportedOperationException();
}
/**
* If the implementation supports providing a position, this method returns
* {@code true}, otherwise {@code false}.
*/
default boolean hasPosition()
{
return false;
}
// The methods below support page-aware layout for writing. These would only be implemented if position() is
// also supported.
/**
* Returns the number of bytes that a page can take at maximum.
*/
default int maxBytesInPage()
{
throw new UnsupportedOperationException();
}
/**
* Pad this with zeroes until the next page boundary. If the destination position
* is already at a page boundary, do not do anything.
*/
default void padToPageBoundary() throws IOException
{
long position = position();
long bytesLeft = PageAware.padded(position) - position;
write(PageAware.EmptyPage.EMPTY_PAGE, 0, Ints.checkedCast(bytesLeft));
}
/**
* Returns how many bytes are left in the page.
*/
default int bytesLeftInPage()
{
throw new UnsupportedOperationException();
}
/**
* Returns the next padded position. This is either the current position (if already padded), or the start of next
* page.
*/
default long paddedPosition()
{
throw new UnsupportedOperationException();
}
}