function(_FarmhashSource_import)
  if(NOT DOWNLOAD_FARMHASH)
    set(FarmhashSource_FOUND FALSE PARENT_SCOPE)
    return()
  endif(NOT DOWNLOAD_FARMHASH)

  nnas_include(ExternalSourceTools)
  nnas_include(OptionTools)

  # NOTE TensorFlow 1.12 downloads farmhash from the following URL
  #      TensorFlow 1.13.1 downloads farmhash from the following URL
  #      TensorFlow 2.3.0 downloads farmhash from the following URL
  envoption(FARMHASH_1_12_URL https://github.com/google/farmhash/archive/816a4ae622e964763ca0862d9dbd19324a1eaf45.tar.gz)

  ExternalSource_Download(FARMHASH ${FARMHASH_1_12_URL})

  set(FarmhashSource_DIR ${FARMHASH_SOURCE_DIR} PARENT_SCOPE)
  set(FarmhashSource_FOUND TRUE PARENT_SCOPE)
endfunction(_FarmhashSource_import)

_FarmhashSource_import()