private static DescriptorDigest getDiffIdByDecompressingFile(Path compressedFile)
      throws IOException {
    try (InputStream in =
        new CompressorStreamFactory(true)
            .createCompressorInputStream(
                new BufferedInputStream(Files.newInputStream(compressedFile)))) {
      return Digests.computeDigest(in).getDigest();
    } catch (CompressorException e) {
      throw new IOException(e);
    }
  }
Decompresses the file to obtain the diff ID.

@param compressedFile the file containing the compressed contents
@return the digest of the decompressed file
@throws IOException if an I/O exception occurs
jib-core/src/main/java/com/google/cloud/tools/jib/cache/CacheStorageWriter.java