morphlib: add cachekeycomputer class

1 files changed, 79 insertions, 0 deletions

diff --git a/morphlib/cachekeycomputer.py b/morphlib/cachekeycomputer.py
new file mode 100644
index 00000000..ade74b79
--- /dev/null
+++ b/morphlib/cachekeycomputer.py
@@ -0,0 +1,79 @@
+# 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.
+
+
+import hashlib
+
+import morphlib
+
+class CacheKeyComputer():
+
+    def __init__(self, env):
+        self._arch = morphlib.util.arch()
+        self._env = self._filterenv(env)
+        self._calculated = {}
+
+    def _filterenv(self, env):
+        return dict([(k, env[k]) for k in ("USER", "USERNAME", "LOGNAME",
+                                           "TOOLCHAIN_TARGET", "PREFIX",
+                                           "BOOTSTRAP", "CFLAGS")])
+
+    def get_cache_key(self, source):
+        return self._hash_id(self.get_cache_id(source))
+
+    def _hash_id(self, cache_id):
+        sha = hashlib.sha256()
+        self._hash_dict(sha, cache_id)
+        return sha.hexdigest()
+
+    def _hash_thing(self, sha, thing):
+        if type(thing) == dict:
+            self._hash_dict(sha, thing)
+        elif type(thing) == list:
+            self._hash_list(sha, thing)
+        elif type(thing) == tuple:
+            self._hash_tuple(sha, thing)
+        else:
+            sha.update(str(thing))
+
+    def _hash_dict(self, sha, d):
+        for tup in sorted(d.iteritems()):
+            self._hash_thing(sha, tup)
+
+    def _hash_list(self, sha, l):
+        for item in l:
+            self._hash_thing(sha, item)
+
+    def _hash_tuple(self, sha, tup):
+        for item in tup:
+            self._hash_thing(sha, item)
+
+    def get_cache_id(self, source):
+        try:
+            return self._calculated[source]
+        except KeyError:
+            cacheid = self._calculate(source)
+            self._calculated[source] = cacheid
+            return cacheid
+
+    def _calculate(self, source):
+        return {
+            'arch': self._arch,
+            'env': self._env,
+            'ref': source.sha1,
+            'filename': source.filename,
+            'kids': [self.get_cache_id(dependency)
+                     for dependency in source.dependencies],
+        }