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Code Block

language	java
title	Interface

public interface CacheObjectTransformer {
    /** Additional space required to store the transformed data. */
    public int OVERHEAD = 2;

    /**
     * Transforms the data.
     *
     * @param original Original data.
     * @return Transformed data or {@code null} when transformation is not possible/suitable.
     */
    public ByteBuffer transform(ByteBuffer original);

    /**
     * Restores the data.
     *
     * @param transformed Transformed data.
     * @return Restored data.
     */
    public ByteBuffer restore(ByteBuffer transformed);

    /**
     * Returns {@code true} when direct byte buffers are required.
     *
     * @return Direct flag.
     */
    public boolean direct();
}

This API is known for the overhead used to store transformed data and allows users to use direct and wrapped byte buffers.

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Code Block

language	java
title	Compression

class CompressionTransformer extends CacheObjectTransformerAdapter {
	protected ByteBuffer transform(ByteBuffer original) throws IgniteCheckedException {                     
		int locOverhead = 4; // Original length.
        int totalOverhead = CacheObjectTransformerCacheObjectTransformerUtils.OVERHEAD + locOverhead;

        int origSize = original.remaining();
        int lim = origSize - totalOverhead;          

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

        ByteBuffer compressed = byteBuffer(lim);

		compressed.position(locOverhead);

		Zstd.compress(compressed, original, 1);

        compressed.flip(); 

		compressed.putInt(origSize);

		compressed.rewind();          

        return compressed;
    }

    protected ByteBuffer restore(ByteBuffer transformed) {
        ByteBuffer restored = byteBuffer(transformed.getInt());

        Zstd.decompress(restored, transformed);

        restored.flip();
              
        return restored;
    }
}

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