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Code Block

language	java
title	SPI

public interface CacheObjectTransformerSpi extends IgniteSpi {
    /** Additional space required to store the transformed data. */
    public int OVERHEAD = 6;

    /**
     * Transforms the data.
     *
     * @param bytes  Byte array contains the data.
     * @param offset Data offset.
     * @param length Data length.
     * @return Byte array contains the transformed data started with non-filled area with {@link #OVERHEAD} size.
     * @throws IgniteCheckedException when transformation is not possible/suitable.
     */
    public byte[] transform(byte[] bytes, int offset, int length) throws IgniteCheckedException;

      

	/**
     * Restores the data.
     *
     * @param bytes  Byte array ending with the transformed data.
     * @param offset Transformed data offset.
     * @param length Original data length.
     * @return Byte array contains the restored data.
     */
    public byte[] restore(byte[] bytes, int offset, int length); 
}

This API is known for the overhead used to store transformed data and is able to work with byte arrays with custom offsets, which is necessary to guarantee performance.

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Code Block

language	java
title	CacheObjectTransformerSpiAdapter

public abstract class CacheObjectTransformerSpiAdapter extends IgniteSpiAdapter implements CacheObjectTransformerSpi {
...
    /**
     * Transforms the data.
     *
     * @param original Original data.
     * @return Transformed data.
     * @throws IgniteCheckedException when transformation is not possible/suitable.
     */
    protected abstract ByteBuffer transform(ByteBuffer original) throws IgniteCheckedException;

      

	/**
     * Restores the data.
     *
     * @param transformed Transformed data.
     * @param length Original data length.
     * @return Restored data.
     */
    protected abstract ByteBuffer restore(ByteBuffer transformed, int length); 
}

Compression example

Code Block

language	java
title	CompressionSpi

class CompressionTransformerSpi extends CacheObjectTransformerSpiAdapter {
    private static final LZ4Factory lz4Factory = LZ4Factory.fastestInstance();

    protected ByteBuffer transform(ByteBuffer original) throws IgniteCheckedException {
        int lim = original.remaining() - CacheObjectTransformerSpi.OVERHEAD;

        if (lim <= 0)
            throw new IgniteCheckedException("Compression is not profitable.");

        ByteBuffer compressed = byteBuffer(lim);

        Zstd.compress(compressed, original, 1);

        compressed.flip();             

        return compressed;
    }

    protected ByteBuffer restore(ByteBuffer transformed, int length) {
        ByteBuffer restored = byteBuffer(length);

        Zstd.decompress(restored, transformed);

        restored.flip();
              
        return restored;
    }
}

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Compression example