diff --git a/bitbake/lib/bb/checksum.py b/bitbake/lib/bb/checksum.py
new file mode 100644
index 0000000..514ff0b
--- /dev/null
+++ b/bitbake/lib/bb/checksum.py
@@ -0,0 +1,90 @@
+# Local file checksum cache implementation
+#
+# Copyright (C) 2012 Intel Corporation
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+import os
+import stat
+import bb.utils
+import logging
+from bb.cache import MultiProcessCache
+
+logger = logging.getLogger("BitBake.Cache")
+
+try:
+    import cPickle as pickle
+except ImportError:
+    import pickle
+    logger.info("Importing cPickle failed. "
+                "Falling back to a very slow implementation.")
+
+
+# mtime cache (non-persistent)
+# based upon the assumption that files do not change during bitbake run
+class FileMtimeCache(object):
+    cache = {}
+
+    def cached_mtime(self, f):
+        if f not in self.cache:
+            self.cache[f] = os.stat(f)[stat.ST_MTIME]
+        return self.cache[f]
+
+    def cached_mtime_noerror(self, f):
+        if f not in self.cache:
+            try:
+                self.cache[f] = os.stat(f)[stat.ST_MTIME]
+            except OSError:
+                return 0
+        return self.cache[f]
+
+    def update_mtime(self, f):
+        self.cache[f] = os.stat(f)[stat.ST_MTIME]
+        return self.cache[f]
+
+    def clear(self):
+        self.cache.clear()
+
+# Checksum + mtime cache (persistent)
+class FileChecksumCache(MultiProcessCache):
+    cache_file_name = "local_file_checksum_cache.dat"
+    CACHE_VERSION = 1
+
+    def __init__(self):
+        self.mtime_cache = FileMtimeCache()
+        MultiProcessCache.__init__(self)
+
+    def get_checksum(self, f):
+        entry = self.cachedata[0].get(f)
+        cmtime = self.mtime_cache.cached_mtime(f)
+        if entry:
+            (mtime, hashval) = entry
+            if cmtime == mtime:
+                return hashval
+            else:
+                bb.debug(2, "file %s changed mtime, recompute checksum" % f)
+
+        hashval = bb.utils.md5_file(f)
+        self.cachedata_extras[0][f] = (cmtime, hashval)
+        return hashval
+
+    def merge_data(self, source, dest):
+        for h in source[0]:
+            if h in dest:
+                (smtime, _) = source[0][h]
+                (dmtime, _) = dest[0][h]
+                if smtime > dmtime:
+                    dest[0][h] = source[0][h]
+            else:
+                dest[0][h] = source[0][h]