if(NOT IONOBASE_IS_EXTERNAL_PROJECT)
  set(IONOBASE_PREFIX "" CACHE PATH "The path to the prefix of an libionobase installation")
  set(IONOBASE_INCLUDE_DIR "" CACHE PATH "The path to the headers of an libionobase installation")
  set(IONOBASE_LIBRARY_DIR "" CACHE PATH "The path to the library of an libionobase installation")

  set(_search_paths "")
  if(IONOBASE_INCLUDE_DIR AND EXISTS ${IONOBASE_INCLUDE_DIR})
    list(APPEND _search_paths ${IONOBASE_INCLUDE_DIR})
  endif()
  if(IONOBASE_PREFIX AND EXISTS ${IONOBASE_PREFIX})
    list(APPEND _search_paths "${IONOBASE_PREFIX}/include")
  endif()
  find_path(
    IONOBASE_INCLUDE_DIRS
    NAMES ionobase/interchfor.h
    PATHS ${_search_paths})

  set(_search_paths "")
  if(IONOBASE_LIBRARY_DIR AND EXISTS ${IONOBASE_LIBRARY_DIR})
    list(APPEND _search_paths ${IONOBASE_LIBRARY_DIR})
  endif()
  if(IONOBASE_PREFIX AND EXISTS ${IONOBASE_PREFIX})
    list(APPEND _search_paths "${IONOBASE_PREFIX}/lib")
  endif()
  find_library(
    IONOBASE_LIBRARIES
    NAMES ionobase
    PATHS ${_search_paths})
  unset(_search_paths)

  if(IONOBASE_INCLUDE_DIRS AND IONOBASE_LIBRARIES)
    set(IONOBASE_FOUND TRUE)
  endif()

  if(IONOBASE_FOUND)
    if(NOT IONOBASE_FIND_QUIETLY)
      message(STATUS "Found libionobase")
    endif()
    set(HAVE_IONOBASE 1)
  elseif(IONOBASE_FOUND)
    if(IONOBASE_FIND_REQUIRED)
      message(FATAL_ERROR "Could not find libionobase")
    endif()
  endif()
endif()