761417898 commented on code in PR #560: URL: https://github.com/apache/tsfile/pull/560#discussion_r2261779244
########## java/tsfile/src/main/java/org/apache/tsfile/encoding/decoder/CamelDecoder.java: ########## @@ -0,0 +1,273 @@ +/* + * 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.tsfile.encoding.decoder; + +import org.apache.tsfile.common.bitStream.BitInputStream; +import org.apache.tsfile.common.bitStream.ByteBufferBackedInputStream; +import org.apache.tsfile.exception.encoding.TsFileDecodingException; +import org.apache.tsfile.file.metadata.enums.TSEncoding; +import org.apache.tsfile.utils.ReadWriteForEncodingUtils; + +import java.io.IOException; +import java.io.InputStream; +import java.nio.ByteBuffer; +import java.util.LinkedList; +import java.util.List; + +public class CamelDecoder extends Decoder { + // === Constants for decoding === + private static final int BITS_FOR_SIGN = 1; + private static final int BITS_FOR_TYPE = 1; + private static final int BITS_FOR_FIRST_VALUE = 64; + private static final int BITS_FOR_LEADING_ZEROS = 6; + private static final int BITS_FOR_SIGNIFICANT_BITS = 6; + private static final int BITS_FOR_DECIMAL_COUNT = 4; + private static final int DOUBLE_TOTAL_BITS = 64; + private static final int DOUBLE_MANTISSA_BITS = 52; + private static final int DECIMAL_MAX_COUNT = 15; + + // === Camel state === + private long previousValue = 0; + private boolean isFirst = true; + private long storedVal = 0; + + // === Precomputed tables === + public static final long[] powers = new long[DECIMAL_MAX_COUNT]; + public static final long[] threshold = new long[DECIMAL_MAX_COUNT]; + public static final int[] mValueBits = new int[DECIMAL_MAX_COUNT]; + + static { + for (int l = 1; l <= DECIMAL_MAX_COUNT; l++) { + int idx = l - 1; + powers[idx] = (long) Math.pow(10, l); + long divisor = 1L << l; + threshold[idx] = powers[idx] / divisor; + mValueBits[idx] = (int) Math.ceil(Math.log(threshold[idx]) / Math.log(2)); + } + } + + private BitInputStream in; + private final GorillaDecoder gorillaDecoder; + + public CamelDecoder(InputStream inputStream, long totalBits) { + super(TSEncoding.CAMEL); + // Initialize bit-level reader and nested Gorilla decoder + this.in = new BitInputStream(inputStream, totalBits); + this.gorillaDecoder = new GorillaDecoder(); + } + + public CamelDecoder() { + super(TSEncoding.CAMEL); + this.gorillaDecoder = new GorillaDecoder(); + } + + @Override + public boolean hasNext(ByteBuffer buffer) throws IOException { + if (cacheIndex < valueCache.size()) { + return true; + } + if (in != null && in.availableBits() > 0) { + return true; + } + return buffer.hasRemaining(); + } + + @Override + public void reset() { + this.in = null; + this.isFirst = true; + this.previousValue = 0L; + this.storedVal = 0L; + this.gorillaDecoder.leadingZeros = Integer.MAX_VALUE; + this.gorillaDecoder.trailingZeros = 0; + } + + // Cache for batch decoding + private List<Double> valueCache = new LinkedList<>(); + private int cacheIndex = 0; + + @Override + public double readDouble(ByteBuffer buffer) { + try { + // If the current block has been fully read, load the next block + if (cacheIndex >= valueCache.size()) { + // If no BitInputStream is available or all bits have been consumed + if (in == null || in.availableBits() == 0) { + if (!buffer.hasRemaining()) { + throw new TsFileDecodingException("No more data to decode"); + } + + ByteBuffer slice = buffer.slice(); // Keep this + ByteBufferBackedInputStream bais = new ByteBufferBackedInputStream(slice); + + // Read the number of bits in the current block + int blockBits = ReadWriteForEncodingUtils.readVarInt(bais); + this.in = new BitInputStream(bais, blockBits); + + // Reset decoder state for the new block + this.isFirst = true; + this.storedVal = 0L; + this.previousValue = 0L; + this.gorillaDecoder.leadingZeros = Integer.MAX_VALUE; + this.gorillaDecoder.trailingZeros = 0; + + // Decode the entire block into a temporary value cache + List<Double> newValues = getValues(); + if (newValues.isEmpty()) { + throw new TsFileDecodingException("Unexpected empty block"); + } + valueCache = newValues; + cacheIndex = 0; + + // Advance the buffer position by the number of bytes consumed + // int consumed = temp.length - bais.available(); + int consumed = bais.getConsumed(); + + buffer.position(buffer.position() + consumed); + } + } + + // Return the next decoded value from the cache + return valueCache.get(cacheIndex++); + } catch (IOException e) { + throw new TsFileDecodingException(e.getMessage()); + } + } + + /** Nested class to handle fallback encoding (Gorilla) for double values. */ + public class GorillaDecoder { + private int leadingZeros = Integer.MAX_VALUE; + private int trailingZeros = 0; + + /** Decode next value using Gorilla algorithm. */ + public double decode(BitInputStream in) throws IOException { + if (isFirst) { + previousValue = in.readLong(BITS_FOR_FIRST_VALUE); + isFirst = false; + return Double.longBitsToDouble(previousValue); + } + + boolean controlBit = in.readBit(); + if (!controlBit) { + return Double.longBitsToDouble(previousValue); + } + + boolean reuseBlock = !in.readBit(); + long xor; + if (reuseBlock) { + int sigBits = DOUBLE_TOTAL_BITS - leadingZeros - trailingZeros; + if (sigBits == 0) { + return Double.longBitsToDouble(previousValue); + } + xor = in.readLong(sigBits) << trailingZeros; + } else { + leadingZeros = in.readInt(BITS_FOR_LEADING_ZEROS); + int sigBits = in.readInt(BITS_FOR_SIGNIFICANT_BITS) + 1; + trailingZeros = DOUBLE_TOTAL_BITS - leadingZeros - sigBits; + xor = in.readLong(sigBits) << trailingZeros; + } + + previousValue ^= xor; + return Double.longBitsToDouble(previousValue); + } + } + + /** Retrieve nested GorillaDecoder. */ + public GorillaDecoder getGorillaDecoder() { + return gorillaDecoder; + } + + /** Read all values until stream is exhausted. */ + public List<Double> getValues() throws IOException { + List<Double> list = new LinkedList<>(); + Double val; + while ((val = next()) != null) { + list.add(val); + } + return list; + } + + /** Decode next available value, return null if no more bits. */ + private Double next() throws IOException { + if (in.availableBits() <= 0) { + return null; + } Review Comment: fixed -- This is an automated message from the Apache Git Service. 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