1 files changed, 38 insertions, 0 deletions
diff --git a/waflib/Tools/md5_tstamp.py b/waflib/Tools/md5_tstamp.py
new file mode 100644
index 00000000..2a587925
--- /dev/null
+++ b/waflib/Tools/md5_tstamp.py
@@ -0,0 +1,38 @@
+#! /usr/bin/env python
+# encoding: utf-8
+
+"""
+Re-calculate md5 hashes of files only when the file time have changed.
+
+The hashes can also reflect either the file contents (STRONGEST=True) or the
+file time and file size.
+
+The performance benefits of this module are usually insignificant.
+"""
+
+import os, stat
+from waflib import Utils, Build, Node
+
+STRONGEST = True
+
+Build.SAVED_ATTRS.append('hashes_md5_tstamp')
+def h_file(self):
+	filename = self.abspath()
+	st = os.stat(filename)
+
+	cache = self.ctx.hashes_md5_tstamp
+	if filename in cache and cache[filename][0] == st.st_mtime:
+		return cache[filename][1]
+
+	if STRONGEST:
+		ret = Utils.h_file(filename)
+	else:
+		if stat.S_ISDIR(st[stat.ST_MODE]):
+			raise IOError('Not a file')
+		ret = Utils.md5(str((st.st_mtime, st.st_size)).encode()).digest()
+
+	cache[filename] = (st.st_mtime, ret)
+	return ret
+h_file.__doc__ = Node.Node.h_file.__doc__
+Node.Node.h_file = h_file
+