misc.py: Add atomic_store()

Signed-off-by: Jan Lindemann <jan@janware.com>

tools/python/jwutils/misc.py

@@ -1,4 +1,12 @@
 import os, errno
+import atexit
+import tempfile
+
+_tmpfiles = set()
+
+def _cleanup():
+    for f in _tmpfiles:
+        os.unlink(f)
 
 def silentremove(filename): #export
     try:
@@ -15,3 +23,18 @@ def pad(token, total_size, right_align = False):
     if right_align:
         return space + token
     return token + space
+
+def atomic_store(contents, path): # export
+    if path[0:3] == '/dev':
+        with open(path, 'w') as outfile:
+            outfile.write(contents)
+        return
+    outfile = tempfile.NamedTemporaryFile(prefix=os.path.basename(path), delete=False, dir=os.path.dirname(path))
+    name = outfile.name
+    _tmpfiles.add(name)
+    outfile.write(contents)
+    outfile.close()
+    os.rename(name, path)
+    _tmpfiles.remove(name)
+
+atexit.register(_cleanup)