/*
* 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.rcfile.binary;
import com.facebook.presto.spi.block.Block;
import com.facebook.presto.spi.block.BlockBuilder;
import com.facebook.presto.spi.type.Type;
import io.airlift.slice.Slice;
import io.airlift.slice.SliceOutput;
import static com.facebook.presto.rcfile.RcFileDecoderUtils.decodeVIntSize;
import static com.facebook.presto.rcfile.RcFileDecoderUtils.readVInt;
import static com.facebook.presto.rcfile.RcFileDecoderUtils.writeVInt;
import static java.lang.Math.toIntExact;
public class ListEncoding
extends BlockEncoding
{
private final BinaryColumnEncoding elementEncoding;
public ListEncoding(Type type, BinaryColumnEncoding elementEncoding)
{
super(type);
this.elementEncoding = elementEncoding;
}
@Override
public void encodeValue(Block block, int position, SliceOutput output)
{
Block list = block.getObject(position, Block.class);
writeVInt(output, list.getPositionCount());
// write null bits
int nullByte = 0;
for (int elementIndex = 0; elementIndex < list.getPositionCount(); elementIndex++) {
if (elementIndex != 0 && elementIndex % 8 == 0) {
output.writeByte(nullByte);
nullByte = 0;
}
if (!list.isNull(elementIndex)) {
nullByte |= (1 << (elementIndex % 8));
}
}
output.writeByte(nullByte);
// write values
for (int elementIndex = 0; elementIndex < list.getPositionCount(); elementIndex++) {
if (!list.isNull(elementIndex)) {
elementEncoding.encodeValueInto(list, elementIndex, output);
}
}
}
@Override
public void decodeValueInto(BlockBuilder builder, Slice slice, int offset, int length)
{
// entries in list
int entries = toIntExact(readVInt(slice, offset));
offset += decodeVIntSize(slice.getByte(offset));
// null bytes
int nullByteCur = offset;
int nullByteEnd = offset + (entries + 7) / 8;
// read elements starting after null bytes
int elementOffset = nullByteEnd;
BlockBuilder arrayBuilder = builder.beginBlockEntry();
for (int i = 0; i < entries; i++) {
if ((slice.getByte(nullByteCur) & (1 << (i % 8))) != 0) {
int valueOffset = elementEncoding.getValueOffset(slice, elementOffset);
int valueLength = elementEncoding.getValueLength(slice, elementOffset);
elementEncoding.decodeValueInto(arrayBuilder, slice, elementOffset + valueOffset, valueLength);
elementOffset = elementOffset + valueOffset + valueLength;
}
else {
arrayBuilder.appendNull();
}
// move onto the next null byte
if (7 == (i % 8)) {
nullByteCur++;
}
}
builder.closeEntry();
}
}