uorb topic header generator: only create new files if the file content really changed

Makefile

@@ -227,12 +227,15 @@ updatesubmodules:
 MSG_DIR = $(PX4_BASE)msg/px4_msgs
 MSG_TEMPLATE_DIR = $(PX4_BASE)msg/templates
 TOPICS_DIR = $(PX4_BASE)src/modules/uORB/topics
+TOPICS_TEMPORARY_DIR = $(BUILD_DIR)topics_temporary
 
 .PHONY: generateuorbtopicheaders
 generateuorbtopicheaders:
 	@$(ECHO) "Generating uORB topic headers"
 	$(Q) ($(PX4_BASE)/Tools/px_generate_uorb_topic_headers.py -d $(MSG_DIR) \
-		-o $(TOPICS_DIR) -e $(MSG_TEMPLATE_DIR))
+		-o $(TOPICS_DIR) -e $(MSG_TEMPLATE_DIR) -t $(TOPICS_TEMPORARY_DIR))
+# clean up temporary files
+	$(Q) (rm -r $(TOPICS_TEMPORARY_DIR))
 
 #
 # Testing targets

Tools/px_generate_uorb_topic_headers.py

@@ -39,6 +39,8 @@ message files
 """
 from __future__ import print_function
 import os
+import shutil
+import filecmp
 import argparse
 import genmsg.template_tools
 
@@ -76,7 +78,46 @@ def convert_dir(inputdir, outputdir, templatedir):
         for f in os.listdir(inputdir):
                 fn = os.path.join(inputdir, f)
                 if os.path.isfile(fn):
-            convert_file(fn, outputdir, templatedir, includepath)
+                        convert_file(
+                            fn,
+                            outputdir,
+                            templatedir,
+                            includepath)
+
+
+def copy_changed(inputdir, outputdir):
+        """
+        Copies files from inputdir to outputdir if they don't exist in
+        ouputdir or if their content changed
+        """
+        for f in os.listdir(inputdir):
+                fni = os.path.join(inputdir, f)
+                if os.path.isfile(fni):
+                        # Check if f exists in outpoutdir, copy the file if not
+                        fno = os.path.join(outputdir, f)
+                        if not os.path.isfile(fno):
+                                shutil.copy(fni, fno)
+                                print("{0}: new header file".format(f))
+                                continue
+                        # The file exists in inputdir and outputdir
+                        # only copy if contents do not match
+                        if not filecmp.cmp(fni, fno):
+                                shutil.copy(fni, fno)
+                                print("{0}: updated".format(f))
+                                continue
+
+                        print("{0}: unchanged".format(f))
+
+def convert_dir_save(inputdir, outputdir, templatedir, temporarydir):
+        """
+        Converts all .msg files in inputdir to uORB header files
+        Unchanged existing files are not overwritten.
+        """
+        # Create new headers in temporary output directory
+        convert_dir(inputdir, temporarydir, templatedir)
+
+        # Copy changed headers from temporary dir to output dir
+        copy_changed(temporarydir, outputdir)
 
 if __name__ == "__main__":
         parser = argparse.ArgumentParser(
@@ -89,10 +130,20 @@ if __name__ == "__main__":
                             help='directory with template files',)
         parser.add_argument('-o', dest='outputdir',
                             help='output directory for header files')
+        parser.add_argument('-t', dest='temporarydir',
+                            help='temporary directory')
         args = parser.parse_args()
 
         if args.file is not None:
                 for f in args.file:
-            convert_file(f, args.outputdir, args.templatedir, incl_default)
+                        convert_file(
+                            f,
+                            args.outputdir,
+                            args.templatedir,
+                            incl_default)
         elif args.dir is not None:
-            convert_dir(args.dir, args.outputdir, args.templatedir)
+                convert_dir_save(
+                    args.dir,
+                    args.outputdir,
+                    args.templatedir,
+                    args.temporarydir)