1 files changed, 113 insertions, 0 deletions
diff --git a/git/db/py/mem.py b/git/db/py/mem.py
new file mode 100644
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+++ b/git/db/py/mem.py
@@ -0,0 +1,113 @@
+# Copyright (C) 2010, 2011 Sebastian Thiel (byronimo@gmail.com) and contributors
+#
+# This module is part of GitDB and is released under
+# the New BSD License: http://www.opensource.org/licenses/bsd-license.php
+"""Contains the MemoryDatabase implementation"""
+from loose import PureLooseObjectODB
+from base import (
+						PureObjectDBR, 
+						PureObjectDBW
+					)
+
+from gitdb.base import (
+							OStream,
+							IStream,
+						)
+
+from gitdb.exc import (
+						BadObject,
+						UnsupportedOperation
+						)
+from gitdb.stream import (
+							ZippedStoreShaWriter,
+							DecompressMemMapReader,
+						)
+
+from cStringIO import StringIO
+
+__all__ = ("PureMemoryDB", )
+
+class PureMemoryDB(PureObjectDBR, PureObjectDBW):
+	"""A memory database stores everything to memory, providing fast IO and object
+	retrieval. It should be used to buffer results and obtain SHAs before writing
+	it to the actual physical storage, as it allows to query whether object already
+	exists in the target storage before introducing actual IO
+	
+	:note: memory is currently not threadsafe, hence the async methods cannot be used
+		for storing"""
+	
+	def __init__(self):
+		super(PureMemoryDB, self).__init__()
+		self._db = PureLooseObjectODB("path/doesnt/matter")
+		
+		# maps 20 byte shas to their OStream objects
+		self._cache = dict()
+		
+	def set_ostream(self, stream):
+		raise UnsupportedOperation("PureMemoryDB's always stream into memory")
+		
+	def store(self, istream):
+		zstream = ZippedStoreShaWriter()
+		self._db.set_ostream(zstream)
+		
+		istream = self._db.store(istream)
+		zstream.close()		# close to flush
+		zstream.seek(0)
+		
+		# don't provide a size, the stream is written in object format, hence the 
+		# header needs decompression
+		decomp_stream = DecompressMemMapReader(zstream.getvalue(), close_on_deletion=False) 
+		self._cache[istream.binsha] = OStream(istream.binsha, istream.type, istream.size, decomp_stream)
+		
+		return istream
+		
+	def store_async(self, reader):
+		raise UnsupportedOperation("PureMemoryDBs cannot currently be used for async write access")
+	
+	def has_object(self, sha):
+		return sha in self._cache
+
+	def info(self, sha):
+		# we always return streams, which are infos as well
+		return self.stream(sha)
+	
+	def stream(self, sha):
+		try:
+			ostream = self._cache[sha]
+			# rewind stream for the next one to read
+			ostream.stream.seek(0)
+			return ostream
+		except KeyError:
+			raise BadObject(sha)
+		# END exception handling
+	
+	def size(self):
+		return len(self._cache)
+		
+	def sha_iter(self):
+		return self._cache.iterkeys()
+		
+		
+	#{ Interface 
+	def stream_copy(self, sha_iter, odb):
+		"""Copy the streams as identified by sha's yielded by sha_iter into the given odb
+		The streams will be copied directly
+		:note: the object will only be written if it did not exist in the target db
+		:return: amount of streams actually copied into odb. If smaller than the amount
+			of input shas, one or more objects did already exist in odb"""
+		count = 0
+		for sha in sha_iter:
+			if odb.has_object(sha):
+				continue
+			# END check object existance
+			
+			ostream = self.stream(sha)
+			# compressed data including header
+			sio = StringIO(ostream.stream.data())
+			istream = IStream(ostream.type, ostream.size, sio, sha)
+			
+			odb.store(istream)
+			count += 1
+		# END for each sha
+		return count
+	#} END interface