parquet.column.values.boundedint.BitReader 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.boundedint;
import java.io.IOException;
import parquet.io.ParquetDecodingException;
class BitReader {
private int currentByte = 0;
private int currentPosition = 8;
private byte[] buf;
private int currentBufferPosition = 0;
private static final int[] byteGetValueMask = new int[8];
private static final int[] readMask = new int[32];
private int endBufferPosistion;
static {
int currentMask = 1;
for (int i = 0; i < byteGetValueMask.length; i++) {
byteGetValueMask[i] = currentMask;
currentMask <<= 1;
}
currentMask = 0;
for (int i = 0; i < readMask.length; i++) {
readMask[i] = currentMask;
currentMask <<= 1;
currentMask += 1;
}
}
/**
* Prepare to deserialize bit-packed integers from the given array.
* The array is not copied, so must not be mutated during the course of
* reading.
*/
public void prepare(byte[] buf, int offset, int length) {
this.buf = buf;
this.endBufferPosistion = offset + length;
currentByte = 0;
currentPosition = 8;
currentBufferPosition = offset;
}
/**
* Extract the given bit index from the given value.
*/
private static boolean extractBit(int val, int bit) {
return (val & byteGetValueMask[bit]) != 0;
}
/**
* Read an integer from the stream which is represented by a specified
* number of bits.
* @param bitsPerValue the number of bits used to represent the integer
*/
public int readNBitInteger(int bitsPerValue) {
int bits = bitsPerValue + currentPosition;
int currentValue = currentByte >>> currentPosition;
int toShift = 8 - currentPosition;
while (bits >= 8) {
currentByte = getNextByte();
currentValue |= currentByte << toShift;
toShift += 8;
bits -= 8;
}
currentValue &= readMask[bitsPerValue];
currentPosition = (bitsPerValue + currentPosition) % 8;
return currentValue;
}
private int getNextByte() {
if (currentBufferPosition < endBufferPosistion) {
return buf[currentBufferPosition++] & 0xFF;
}
return 0;
}
public boolean readBit() throws IOException {
if (currentPosition == 8) {
currentByte = getNextByte();
currentPosition = 0;
}
return extractBit(currentByte, currentPosition++);
}
public int readByte() {
currentByte |= (getNextByte() << 8);
int value = (currentByte >>> currentPosition) & 0xFF;
currentByte >>>= 8;
return value;
}
public int readUnsignedVarint() throws IOException {
int value = 0;
int i = 0;
int b;
while (((b = readByte()) & 0x80) != 0) {
value |= (b & 0x7F) << i;
i += 7;
if (i > 35) {
throw new ParquetDecodingException("Variable length quantity is too long");
}
}
return value | (b << i);
}
}