geode/cmake/CPM.cmake

set(CPM_DOWNLOAD_VERSION 0.38.1)

if(CPM_SOURCE_CACHE)
  set(CPM_DOWNLOAD_LOCATION "${CPM_SOURCE_CACHE}/cpm/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
elseif(DEFINED ENV{CPM_SOURCE_CACHE})
  set(CPM_DOWNLOAD_LOCATION "$ENV{CPM_SOURCE_CACHE}/cpm/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
else()
  set(CPM_DOWNLOAD_LOCATION "${CMAKE_BINARY_DIR}/cmake/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
endif()

# Expand relative path. This is important if the provided path contains a tilde (~)
get_filename_component(CPM_DOWNLOAD_LOCATION ${CPM_DOWNLOAD_LOCATION} ABSOLUTE)

function(download_cpm)
  message(STATUS "Downloading CPM.cmake to ${CPM_DOWNLOAD_LOCATION}")
  file(DOWNLOAD
       https://github.com/cpm-cmake/CPM.cmake/releases/download/v${CPM_DOWNLOAD_VERSION}/CPM.cmake
       ${CPM_DOWNLOAD_LOCATION}
  )
endfunction()

if(NOT (EXISTS ${CPM_DOWNLOAD_LOCATION}))
  download_cpm()
else()
  # resume download if it previously failed
  file(READ ${CPM_DOWNLOAD_LOCATION} check)
  if("${check}" STREQUAL "")
    download_cpm()
  endif()
  unset(check)
endif()

include(${CPM_DOWNLOAD_LOCATION})