1 files changed, 38 insertions, 0 deletions
diff --git a/morphlib/artifactcachereference.py b/morphlib/artifactcachereference.py
new file mode 100644
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+++ b/morphlib/artifactcachereference.py
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+# Copyright (C) 2012  Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# 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.
+
+
+class ArtifactCacheReference(object):
+    '''Represent the information needed to retrieve an artifact
+
+    The artifact cache doesn't need to know the dependencies or the
+    morphology of an artifact, it just needs to know the basename
+
+    The basename could be generated, from the name, cache_key and kind,
+    but if the algorithm changes then morph wouldn't be able to find
+    old artifacts with a saved ArtifactCacheReference.
+
+    Conversely if it generated the basename then old strata wouldn't be
+    able to refer to new chunks, but strata change more often than the chunks.
+    '''
+
+    def __init__(self, basename):
+        self._basename = basename
+
+    def basename(self):
+        return self._basename
+
+    def metadata_basename(self, metadata_name):
+        return '%s.%s' % (self._basename, metadata_name)