From 736a8a8ac7abfeab5edb8dfd73ecf0b2c0282e61 Mon Sep 17 00:00:00 2001
From: Paul Sokolovsky
Date: Sun, 12 Mar 2017 22:28:45 +0300
Subject: zephyr: Make sure that generated prj.conf is updated only on content
 changes.

This is a typical problem with make: we want to trigger rebuilds only
if file actually changed, not if its timestamp changed. In this case,
it's aggravated by the fact that prj.conf depends on the value of
BOARD variable, so we need to do some tricks anyway. We still don't
try to detect if just BOARD changed, just try to generate new
prj.conf.tmp every time (quick), but do actual replacement of prj.conf
only if its content changed.
---
 zephyr/makeprj.py | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 zephyr/makeprj.py

(limited to 'zephyr/makeprj.py')

diff --git a/zephyr/makeprj.py b/zephyr/makeprj.py
new file mode 100644
index 000000000..239c877cd
--- /dev/null
+++ b/zephyr/makeprj.py
@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+import sys
+import os
+import hashlib
+
+
+def hash_file(fname):
+    if not os.path.exists(fname):
+        return b""
+    hasher = hashlib.md5()
+    with open(fname, "rb") as f:
+        hasher.update(f.read())
+    return hasher.digest()
+
+
+old_digest = hash_file(sys.argv[3])
+
+with open(sys.argv[3] + ".tmp", "wb") as f:
+    f.write(open(sys.argv[1], "rb").read())
+    if os.path.exists(sys.argv[2]):
+        f.write(open(sys.argv[2], "rb").read())
+
+new_digest = hash_file(sys.argv[3] + ".tmp")
+
+if new_digest != old_digest:
+    print("Replacing")
+    os.rename(sys.argv[3] + ".tmp", sys.argv[3])
+else:
+    os.remove(sys.argv[3] + ".tmp")
-- 
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