public InputStream createDecompressionStream(InputStream downStream, Decompressor decompressor,
      int downStreamBufferSize) throws IOException {
      CompressionCodec codec = getCodec(conf);
      // Set the internal buffer size to read from down stream.
      if (downStreamBufferSize > 0) {
        ((Configurable) codec).getConf().setInt("io.file.buffer.size", downStreamBufferSize);
      }
      CompressionInputStream cis = codec.createInputStream(downStream, decompressor);
      BufferedInputStream bis2 = new BufferedInputStream(cis, DATA_IBUF_SIZE);
      return bis2;

    }
Reload configuration for the given algorithm.
<p>
NOTE: Experts only. This can only be done safely during process startup, before the
algorithm's codecs are in use. If the codec implementation is changed, the new implementation
may not be fully compatible with what was loaded at static initialization time, leading to
potential data corruption. Mostly used by unit tests.
@param conf configuration
hbase-common/src/main/java/org/apache/hadoop/hbase/io/compress/Compression.java