/*
* Licensed 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 com.facebook.presto.serde;
import com.facebook.presto.spi.block.Block;
import com.facebook.presto.spi.block.BlockCursor;
import com.facebook.presto.spi.block.BlockEncoding;
import com.facebook.presto.spi.block.RandomAccessBlock;
import com.facebook.presto.block.rle.RunLengthBlockEncoding;
import com.facebook.presto.block.rle.RunLengthEncodedBlock;
import io.airlift.slice.SliceOutput;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
public class RunLengthEncoder
implements Encoder
{
private final SliceOutput sliceOutput;
private boolean finished;
private int positionCount;
private RandomAccessBlock lastValue;
private RunLengthBlockEncoding encoding;
public RunLengthEncoder(SliceOutput sliceOutput)
{
this.sliceOutput = checkNotNull(sliceOutput, "sliceOutput is null");
}
@Override
public Encoder append(Block block)
{
checkNotNull(block, "block is null");
checkState(!finished, "already finished");
if (encoding == null) {
encoding = new RunLengthBlockEncoding(block.getEncoding());
}
BlockCursor cursor = block.cursor();
while (cursor.advanceNextPosition()) {
if (lastValue == null) {
lastValue = cursor.getSingleValueBlock();
}
else if (!lastValue.equalTo(0, cursor)) {
writeBlock();
lastValue = cursor.getSingleValueBlock();
}
positionCount++;
}
return this;
}
private void writeBlock()
{
RunLengthEncodedBlock block = new RunLengthEncodedBlock(lastValue, positionCount);
encoding.writeBlock(sliceOutput, block);
lastValue = null;
positionCount = 0;
}
@Override
public BlockEncoding finish()
{
checkState(encoding != null, "nothing appended");
checkState(!finished, "already finished");
finished = true;
// Flush out final block if there exists one (null if they were all empty blocks)
if (positionCount > 0) {
writeBlock();
}
return encoding;
}
}