@Override
    protected void decodeNext() {
      current.keyLength = currentBuffer.getInt();
      current.valueLength = currentBuffer.getInt();
      current.ensureSpaceForKey();
      currentBuffer.get(current.keyBuffer, 0, current.keyLength);
      current.valueOffset = currentBuffer.position();
      currentBuffer.skip(current.valueLength);
      if (includesTags()) {
        // Read short as unsigned, high byte first
        current.tagsLength = ((currentBuffer.get() & 0xff) << 8) ^ (currentBuffer.get() & 0xff);
        currentBuffer.skip(current.tagsLength);
      }
      if (includesMvcc()) {
        current.memstoreTS = ByteBufferUtils.readVLong(currentBuffer);
      } else {
        current.memstoreTS = 0;
      }
      current.nextKvOffset = currentBuffer.position();
    }
Just copy data, do not do any kind of compression. Use for comparison and benchmarking.
hbase-common/src/main/java/org/apache/hadoop/hbase/io/encoding/CopyKeyDataBlockEncoder.java