parquet.column.values.deltastrings.DeltaByteArrayReader 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.deltastrings;
import java.io.IOException;
import parquet.column.values.ValuesReader;
import parquet.column.values.delta.DeltaBinaryPackingValuesReader;
import parquet.column.values.deltalengthbytearray.DeltaLengthByteArrayValuesReader;
import parquet.io.api.Binary;
/**
* Reads binary data written by {@link DeltaByteArrayWriter}
*
* @author Aniket Mokashi
*
*/
public class DeltaByteArrayReader extends ValuesReader {
private ValuesReader prefixLengthReader;
private ValuesReader suffixReader;
private Binary previous;
public DeltaByteArrayReader() {
this.prefixLengthReader = new DeltaBinaryPackingValuesReader();
this.suffixReader = new DeltaLengthByteArrayValuesReader();
this.previous = Binary.fromByteArray(new byte[0]);
}
@Override
public void initFromPage(int valueCount, byte[] page, int offset)
throws IOException {
prefixLengthReader.initFromPage(valueCount, page, offset);
int next = prefixLengthReader.getNextOffset();
suffixReader.initFromPage(valueCount, page, next);
}
@Override
public void skip() {
prefixLengthReader.skip();
suffixReader.skip();
}
@Override
public Binary readBytes() {
int prefixLength = prefixLengthReader.readInteger();
// This does not copy bytes
Binary suffix = suffixReader.readBytes();
int length = prefixLength + suffix.length();
// We have to do this to materialize the output
if(prefixLength != 0) {
byte[] out = new byte[length];
System.arraycopy(previous.getBytes(), 0, out, 0, prefixLength);
System.arraycopy(suffix.getBytes(), 0, out, prefixLength, suffix.length());
previous = Binary.fromByteArray(out);
} else {
previous = suffix;
}
return previous;
}
}