[kupfer: 8/31] puid: A first experiment with Persitent Global Identifiers

[Ulrik Sverdrup <usverdrup src gnome org>]

commit 1780411e20b30cc9ba3a7c01c18f18aeb05ae386
Author: Ulrik Sverdrup <ulrik sverdrup gmail com>
Date:   Wed Dec 30 18:20:38 2009 +0100

    puid: A first experiment with Persitent Global Identifiers
    
    puid assigns an identification token, currently implemented in three
    different ways, ordered by precedence:
    
    1. A QFULR/qpfer: URL
    2. A serialized representation if the object is marked accordingly
    3. Its repr

 kupfer/puid.py |   70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 70 insertions(+), 0 deletions(-)
---
diff --git a/kupfer/puid.py b/kupfer/puid.py
new file mode 100644
index 0000000..9636fa6
--- /dev/null
+++ b/kupfer/puid.py
@@ -0,0 +1,70 @@
+"""
+Persistent Globally Unique Indentifiers for KupferObjects.
+"""
+
+try:
+	import cPickle as pickle
+except ImportError:
+	import pickle
+
+from kupfer import data
+from kupfer import pretty
+from kupfer import qfurl
+
+SERIALIZABLE_ATTRIBUTE = "serilizable"
+
+class SerializedObject (object):
+	def __init__(self, obj):
+		self.data = pickle.dumps(obj, pickle.HIGHEST_PROTOCOL)
+	def __eq__(self, other):
+		return isinstance(other, type(self)) and self.data == other.data
+	def reconstruct(self):
+		return pickle.loads(self.data)
+
+def get_unique_id(obj):
+	if obj is None:
+		return None
+	if hasattr(obj, "qf_id"):
+		return str(qfurl.qfurl(obj))
+	if hasattr(obj, SERIALIZABLE_ATTRIBUTE):
+		return SerializedObject(obj)
+	return repr(obj)
+
+def is_reference(puid):
+	"Return True if @puid is a reference-type ID"
+	return not isinstance(puid, SerializedObject)
+
+def _find_obj_in_catalog(puid, catalog, excluding=None):
+	if puid.startswith(qfurl.QFURL_SCHEME):
+		qfu = qfurl.qfurl(url=puid)
+		return qfu.resolve_in_catalog(catalog)
+	for src in catalog:
+		if excluding is not None and src == excluding:
+			continue
+		for obj in src.get_leaves():
+			if repr(obj) == puid:
+				return obj
+	return None
+
+def resolve_unique_id(puid, excluding=None):
+	"""
+	Resolve unique id @puid inside @catalog
+	"""
+	if puid is None:
+		return None
+	if isinstance(puid, SerializedObject):
+		try:
+			return puid.reconstruct()
+		except Exception, exc:
+			pretty.print_debug(__name__, type(exc).__name__, exc)
+			return None
+	sc = data.GetSourceController()
+	obj = _find_obj_in_catalog(puid, sc._pre_root, excluding=excluding)
+	if obj is not None:
+		pretty.print_debug(__name__, "Resolving %s to %s" % (puid, obj))
+		return obj
+	other_sources = set(sc.sources) - set(sc._pre_root)
+	obj = _find_obj_in_catalog(puid, other_sources, excluding=excluding)
+	pretty.print_debug(__name__, "Resolving %s to %s" % (puid, obj))
+	return obj
+