# 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 gitdb.db.loose import LooseObjectDB
from gitdb.db.base import (
ObjectDBR,
ObjectDBW
)
from gitdb.base import (
OStream,
IStream,
)
from gitdb.exc import (
BadObject,
UnsupportedOperation
)
from gitdb.stream import (
ZippedStoreShaWriter,
DecompressMemMapReader,
)
from io import BytesIO
__all__ = ("MemoryDB", )
class MemoryDB(ObjectDBR, ObjectDBW):
"""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"""
def __init__(self):
super().__init__()
self._db = LooseObjectDB("path/doesnt/matter")
# maps 20 byte shas to their OStream objects
self._cache = dict()
def set_ostream(self, stream):
raise UnsupportedOperation("MemoryDB'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 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 as e:
raise BadObject(sha) from e
# END exception handling
def size(self):
return len(self._cache)
def sha_iter(self):
return self._cache.keys()
#{ 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 existence
ostream = self.stream(sha)
# compressed data including header
sio = BytesIO(ostream.stream.data())
istream = IStream(ostream.type, ostream.size, sio, sha)
odb.store(istream)
count += 1
# END for each sha
return count
#} END interface
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