1 files changed, 33 insertions, 0 deletions
diff --git a/hacking/build_library/build_ansible/change_detection.py b/hacking/build_library/build_ansible/change_detection.py
new file mode 100644
index 0000000..22e21d3
--- /dev/null
+++ b/hacking/build_library/build_ansible/change_detection.py
@@ -0,0 +1,33 @@
+# Copyright: (c) 2018, Ansible Project
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+
+def update_file_if_different(filename, b_data):
+    """
+    Replace file content only if content is different.
+
+    This preserves timestamps in case the file content has not changed.  It performs multiple
+    operations on the file so it is not atomic and may be slower than simply writing to the file.
+
+    :arg filename: The filename to write to
+    :b_data: Byte string containing the data to write to the file
+    """
+    try:
+        with open(filename, 'rb') as f:
+            b_data_old = f.read()
+    except IOError as e:
+        if e.errno != 2:
+            raise
+        # File did not exist, set b_data_old to a sentinel value so that
+        # b_data gets written to the filename
+        b_data_old = None
+
+    if b_data_old != b_data:
+        with open(filename, 'wb') as f:
+            f.write(b_data)
+        return True
+
+    return False