| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.iotdb.tsfile.encoding.encoder; |
| |
| import java.io.ByteArrayOutputStream; |
| |
| import static org.apache.iotdb.tsfile.common.conf.TSFileConfig.GORILLA_ENCODING_ENDING_INTEGER; |
| import static org.apache.iotdb.tsfile.common.conf.TSFileConfig.LEADING_ZERO_BITS_LENGTH_32BIT; |
| import static org.apache.iotdb.tsfile.common.conf.TSFileConfig.MEANINGFUL_XOR_BITS_LENGTH_32BIT; |
| import static org.apache.iotdb.tsfile.common.conf.TSFileConfig.VALUE_BITS_LENGTH_32BIT; |
| |
| /** |
| * This class includes code modified from Michael Burman's gorilla-tsc project. |
| * |
| * <p>Copyright: 2016-2018 Michael Burman and/or other contributors |
| * |
| * <p>Project page: https://github.com/burmanm/gorilla-tsc |
| * |
| * <p>License: http://www.apache.org/licenses/LICENSE-2.0 |
| */ |
| public class IntGorillaEncoder extends GorillaEncoderV2 { |
| |
| private static final int ONE_ITEM_MAX_SIZE = |
| (2 |
| + LEADING_ZERO_BITS_LENGTH_32BIT |
| + MEANINGFUL_XOR_BITS_LENGTH_32BIT |
| + VALUE_BITS_LENGTH_32BIT) |
| / Byte.SIZE |
| + 1; |
| |
| private int storedValue = 0; |
| |
| @Override |
| public final int getOneItemMaxSize() { |
| return ONE_ITEM_MAX_SIZE; |
| } |
| |
| @Override |
| public final void encode(int value, ByteArrayOutputStream out) { |
| if (firstValueWasWritten) { |
| compressValue(value, out); |
| } else { |
| writeFirst(value, out); |
| firstValueWasWritten = true; |
| } |
| } |
| |
| @Override |
| public void flush(ByteArrayOutputStream out) { |
| // ending stream |
| encode(GORILLA_ENCODING_ENDING_INTEGER, out); |
| |
| // flip the byte no matter it is empty or not |
| // the empty ending byte is necessary when decoding |
| bitsLeft = 0; |
| flipByte(out); |
| |
| // the encoder may be reused, so let us reset it |
| reset(); |
| } |
| |
| @Override |
| protected void reset() { |
| super.reset(); |
| storedValue = 0; |
| } |
| |
| private void writeFirst(int value, ByteArrayOutputStream out) { |
| storedValue = value; |
| writeBits(value, VALUE_BITS_LENGTH_32BIT, out); |
| } |
| |
| private void compressValue(int value, ByteArrayOutputStream out) { |
| int xor = storedValue ^ value; |
| storedValue = value; |
| |
| if (xor == 0) { |
| skipBit(out); |
| } else { |
| writeBit(out); |
| |
| int leadingZeros = Integer.numberOfLeadingZeros(xor); |
| int trailingZeros = Integer.numberOfTrailingZeros(xor); |
| if (leadingZeros >= storedLeadingZeros && trailingZeros >= storedTrailingZeros) { |
| writeExistingLeading(xor, out); |
| } else { |
| writeNewLeading(xor, leadingZeros, trailingZeros, out); |
| } |
| } |
| } |
| |
| /** |
| * If there at least as many leading zeros and as many trailing zeros as previous value, control |
| * bit = 0 (type a). |
| * |
| * <p>store the meaningful XORed value |
| * |
| * @param xor XOR between previous value and current |
| */ |
| private void writeExistingLeading(int xor, ByteArrayOutputStream out) { |
| skipBit(out); |
| |
| int significantBits = VALUE_BITS_LENGTH_32BIT - storedLeadingZeros - storedTrailingZeros; |
| writeBits(xor >>> storedTrailingZeros, significantBits, out); |
| } |
| |
| /** |
| * Stores the length of the number of leading zeros in the next 5 bits. |
| * |
| * <p>Stores the length of the meaningful XORed value in the next 5 bits |
| * |
| * <p>Stores the meaningful bits of the XORed value |
| * |
| * <p>(type b) |
| * |
| * @param xor XOR between previous value and current |
| * @param leadingZeros New leading zeros |
| * @param trailingZeros New trailing zeros |
| */ |
| private void writeNewLeading( |
| int xor, int leadingZeros, int trailingZeros, ByteArrayOutputStream out) { |
| writeBit(out); |
| |
| int significantBits = VALUE_BITS_LENGTH_32BIT - leadingZeros - trailingZeros; |
| |
| // Number of leading zeros in the next 5 bits |
| // Maximum number of leadingZeros is stored with 5 bits to allow up to 31 leading zeros, which |
| // are necessary when storing int values |
| // Note that in this method the number of leading zeros won't be 32 |
| writeBits(leadingZeros, LEADING_ZERO_BITS_LENGTH_32BIT, out); |
| // Length of meaningful bits in the next 5 bits |
| // Note that in this method the number of meaningful bits is always positive and could be 32, |
| // so we have to use (significantBits - 1) in storage |
| writeBits((long) significantBits - 1, MEANINGFUL_XOR_BITS_LENGTH_32BIT, out); |
| // Store the meaningful bits of XOR |
| writeBits(xor >>> trailingZeros, significantBits, out); |
| |
| storedLeadingZeros = leadingZeros; |
| storedTrailingZeros = trailingZeros; |
| } |
| } |