ru.yandex.clickhouse.response.ClickHouseLZ4Stream Maven / Gradle / Ivy

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JDBC driver for ClickHouse
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package ru.yandex.clickhouse.response;

import net.jpountz.lz4.LZ4Factory;
import net.jpountz.lz4.LZ4FastDecompressor;
import ru.yandex.clickhouse.util.ClickHouseBlockChecksum;
import ru.yandex.clickhouse.util.Utils;

import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Reader from clickhouse in lz4
 */

public class ClickHouseLZ4Stream extends InputStream {

    private static final LZ4Factory factory = LZ4Factory.fastestInstance();

    public static final int MAGIC = 0x82;

    private final InputStream stream;
    private final DataInputStream dataWrapper;

    private byte[] currentBlock;
    private int pointer;

    public ClickHouseLZ4Stream(InputStream stream) {
        this.stream = stream;
        dataWrapper = new DataInputStream(stream);
    }

    @Override
    public int read() throws IOException {
        if (!checkNext()) return -1;
        byte b = currentBlock[pointer];
        pointer += 1;
        return b & 0xFF;
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        if (b == null) {
            throw new NullPointerException();
        } else if (off < 0 || len < 0 || len > b.length - off) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return 0;
        }

        if (!checkNext()) return -1;

        int copied = 0;
        int targetPointer = off;
        while(copied != len) {
            int toCopy = Math.min(currentBlock.length - pointer, len - copied);
            System.arraycopy(currentBlock, pointer, b, targetPointer, toCopy);
            targetPointer += toCopy;
            pointer += toCopy;
            copied += toCopy;
            if (!checkNext()) { //finished
                return copied;
            }
        }
        return copied;
    }

    @Override
    public void close() throws IOException {
        stream.close();
    }

    private boolean checkNext() throws IOException {
        if (currentBlock == null || pointer == currentBlock.length) {
            currentBlock = readNextBlock();
            pointer = 0;
        }
        return currentBlock != null;
    }

    // every block is:
    private byte[] readNextBlock() throws IOException {
        int read = stream.read();
        if (read < 0) return null;

        byte[] checksum = new byte[16];
        checksum[0] = (byte)read;
        // checksum - 16 bytes.
        Utils.readFully(dataWrapper, checksum, 1, 15);
        ClickHouseBlockChecksum expected = ClickHouseBlockChecksum.fromBytes(checksum);
        // header:
        // 1 byte - 0x82 (shows this is LZ4)
        int magic = dataWrapper.readUnsignedByte();
        if (magic != MAGIC) throw new IOException("Magic is not correct: " + magic);
        // 4 bytes - size of the compressed data including 9 bytes of the header
        int compressedSizeWithHeader = Utils.readInt(dataWrapper);
        // 4 bytes - size of uncompressed data
        int uncompressedSize = Utils.readInt(dataWrapper);
        int compressedSize = compressedSizeWithHeader - 9; //header
        byte[] block = new byte[compressedSize];
        // compressed data: compressed_size - 9 байт.
        Utils.readFully(dataWrapper, block);

        ClickHouseBlockChecksum real = ClickHouseBlockChecksum.calculateForBlock((byte)magic, compressedSizeWithHeader, uncompressedSize, block, compressedSize);
        if (!real.equals(expected)) {
            throw new IllegalArgumentException("Checksum doesn't match: corrupted data.");
        }

        byte[] decompressed = new byte[uncompressedSize];
        LZ4FastDecompressor decompressor = factory.fastDecompressor();
        decompressor.decompress(block, 0, decompressed, 0, uncompressedSize);
        return decompressed;
    }


}