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# This module is part of GitDB and is released under

# the New BSD License: https://opensource.org/license/bsd-3-clause/

"""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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