/**
* 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.bitpacking;
import static parquet.bytes.BytesUtils.getWidthFromMaxInt;
import static parquet.column.values.bitpacking.BitPacking.createBitPackingReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import parquet.Log;
import parquet.bytes.BytesUtils;
import parquet.column.values.ValuesReader;
import parquet.column.values.bitpacking.BitPacking.BitPackingReader;
import parquet.io.ParquetDecodingException;
/**
* a column reader that packs the ints in the number of bits required based on the maximum size.
*
* @author Julien Le Dem
*
*/
public class BitPackingValuesReader extends ValuesReader {
private static final Log LOG = Log.getLog(BitPackingValuesReader.class);
private ByteArrayInputStream in;
private BitPackingReader bitPackingReader;
private final int bitsPerValue;
private int nextOffset;
/**
* @param bound the maximum value stored by this column
*/
public BitPackingValuesReader(int bound) {
this.bitsPerValue = getWidthFromMaxInt(bound);
}
/**
* {@inheritDoc}
* @see parquet.column.values.ValuesReader#readInteger()
*/
@Override
public int readInteger() {
try {
return bitPackingReader.read();
} catch (IOException e) {
throw new ParquetDecodingException(e);
}
}
/**
* {@inheritDoc}
* @see parquet.column.values.ValuesReader#initFromPage(long, byte[], int)
*/
@Override
public void initFromPage(int valueCount, byte[] in, int offset) throws IOException {
int effectiveBitLength = valueCount * bitsPerValue;
int length = BytesUtils.paddedByteCountFromBits(effectiveBitLength);
if (Log.DEBUG) LOG.debug("reading " + length + " bytes for " + valueCount + " values of size " + bitsPerValue + " bits." );
this.in = new ByteArrayInputStream(in, offset, length);
this.bitPackingReader = createBitPackingReader(bitsPerValue, this.in, valueCount);
this.nextOffset = offset + length;
}
@Override
public int getNextOffset() {
return nextOffset;
}
@Override
public void skip() {
readInteger();
}
}