parquet.column.values.rle.RunLengthBitPackingHybridValuesReader Maven / Gradle / Ivy
/**
* Copyright 2012 Twitter, Inc.
*
* 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 parquet.column.values.rle;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import parquet.Ints;
import parquet.bytes.BytesUtils;
import parquet.column.values.ValuesReader;
import parquet.io.ParquetDecodingException;
/**
* This ValuesReader does all the reading in {@link #initFromPage}
* and stores the values in an in memory buffer, which is less than ideal.
*
* @author Alex Levenson
*/
public class RunLengthBitPackingHybridValuesReader extends ValuesReader {
private final int bitWidth;
private RunLengthBitPackingHybridDecoder decoder;
public RunLengthBitPackingHybridValuesReader(int bitWidth) {
this.bitWidth = bitWidth;
}
@Override
public int initFromPage(long valueCountL, byte[] page, int offset) throws IOException {
// TODO: we are assuming valueCount < Integer.MAX_VALUE
// we should address this here and elsewhere
int valueCount = Ints.checkedCast(valueCountL);
if (valueCount <= 0) {
// readInteger() will never be called,
// there is no data to read
return offset;
}
ByteArrayInputStream in = new ByteArrayInputStream(page, offset, page.length - offset);
int length = BytesUtils.readIntLittleEndian(in);
decoder = new RunLengthBitPackingHybridDecoder(bitWidth, in);
// 4 is for the length which is stored as 4 bytes little endian
return offset + length + 4;
}
@Override
public int readInteger() {
try {
return decoder.readInt();
} catch (IOException e) {
throw new ParquetDecodingException(e);
}
}
@Override
public void skip() {
readInteger();
}
}