replacement cache subsystem that's gestated in 2.1 and 3.0.

it rocks your world, baby.

svn path=/main/branches/2.0/; revision=2257

1 files changed, 103 insertions, 0 deletions

diff --git a/pym/cache/mappings.py b/pym/cache/mappings.py
new file mode 100644
index 000000000..2251c4449
--- /dev/null
+++ b/pym/cache/mappings.py
@@ -0,0 +1,103 @@
+# Copyright: 2005 Gentoo Foundation
+# Author(s): Brian Harring (ferringb@gentoo.org)
+# License: GPL2
+# $Id: mappings.py 2015 2005-09-20 23:14:26Z ferringb $
+
+import UserDict
+
+class ProtectedDict(UserDict.DictMixin):
+	"""
+	given an initial dict, this wraps that dict storing changes in a secondary dict, protecting
+	the underlying dict from changes
+	"""
+	__slots__=("orig","new","blacklist")
+
+	def __init__(self, orig):
+		self.orig = orig
+		self.new = {}
+		self.blacklist = {}
+
+
+	def __setitem__(self, key, val):
+		self.new[key] = val
+		if key in self.blacklist:
+			del self.blacklist[key]
+
+
+	def __getitem__(self, key):
+		if key in self.new:
+			return self.new[key]
+		if key in self.blacklist:
+			raise KeyError(key)
+		return self.orig[key]
+
+
+	def __delitem__(self, key):
+		if key in self.new:
+			del self.new[key]
+		elif key in self.orig:
+			if key not in self.blacklist:
+				self.blacklist[key] = True
+				return
+		raise KeyError(key)
+			
+
+	def __iter__(self):
+		for k in self.new.iterkeys():
+			yield k
+		for k in self.orig.iterkeys():
+			if k not in self.blacklist and k not in self.new:
+				yield k
+
+
+	def keys(self):
+		return list(self.__iter__())
+
+
+	def has_key(self, key):
+		return key in self.new or (key not in self.blacklist and key in self.orig)
+
+
+class LazyLoad(UserDict.DictMixin):
+	"""
+	Lazy loading of values for a dict
+	"""
+	__slots__=("pull", "d")
+
+	def __init__(self, pull_items_func, initial_items=[]):
+		self.d = {}
+		for k, v in initial_items:
+			self.d[k] = v
+		self.pull = pull_items_func
+
+	def __getitem__(self, key):
+		if key in self.d:
+			return self.d[key]
+		elif self.pull != None:
+			self.d.update(self.pull())
+			self.pull = None
+		return self.d[key]
+
+
+	def __iter__(self):
+		return iter(self.keys())
+
+	def keys(self):
+		if self.pull != None:
+			self.d.update(self.pull())
+			self.pull = None
+		return self.d.keys()
+
+
+	def has_key(self, key):
+		return key in self
+
+
+	def __contains__(self, key):
+		if key in self.d:
+			return True
+		elif self.pull != None:
+			self.d.update(self.pull())
+			self.pull = None
+		return key in self.d
+