build system: Initial cmake support, work in progress

tools/cmake/utilities.cmake

@@ -0,0 +1,60 @@
+# set_default
+#
+# Define a variable to a default value if otherwise unset.
+#
+# Priority for new value is:
+# - Existing cmake value (ie set with cmake -D, or already set in CMakeLists)
+# - Value of any non-empty environment variable of the same name
+# - Default value as provided to function
+#
+function(set_default variable default_value)
+  if(NOT ${variable})
+    if($ENV{${variable}})
+      set(${variable} $ENV{${variable}} PARENT_SCOPE)
+    else()
+      set(${variable} ${default_value} PARENT_SCOPE)
+    endif()
+  endif()
+endfunction()
+
+# spaces2list
+#
+# Take a variable whose value was space-delimited values, convert to a cmake
+# list (semicolon-delimited)
+#
+# Note: if using this for directories, keeps the issue in place that
+# directories can't contain spaces...
+function(spaces2list variable_name)
+  string(REPLACE " " ";" tmp "${${variable_name}}")
+  set("${variable_name}" "${tmp}" PARENT_SCOPE)
+endfunction()
+
+# move_if_different
+#
+# If 'source' has different md5sum to 'destination' (or destination
+# does not exist, move it across.
+#
+# If 'source' has the same md5sum as 'destination', delete 'source'.
+#
+# Avoids timestamp updates for re-generated files where content hasn't
+# changed.
+function(move_if_different source destination)
+  set(do_copy 1)
+  file(GLOB dest_exists ${destination})
+  if(dest_exists)
+    file(MD5 ${source} source_md5)
+    file(MD5 ${destination} dest_md5)
+    if(source_md5 STREQUAL dest_md5)
+      set(do_copy "")
+    endif()
+  endif()
+
+  if(do_copy)
+    message("Moving ${source} -> ${destination}")
+    file(RENAME ${source} ${destination})
+  else()
+    message("Not moving ${source} -> ${destination}")
+    file(REMOVE ${source})
+  endif()
+
+endfunction()