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# 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 implementations of database retrieveing objects"""
from gitdb.util import (
join,
LazyMixin,
hex_to_bin
)
from gitdb.utils.encoding import force_text
from gitdb.exc import (
BadObject,
AmbiguousObjectName
)
from itertools import chain
from functools import reduce
__all__ = ('ObjectDBR', 'ObjectDBW', 'FileDBBase', 'CompoundDB', 'CachingDB')
class ObjectDBR(object):
"""Defines an interface for object database lookup.
Objects are identified either by their 20 byte bin sha"""
def __contains__(self, sha):
return self.has_obj
#{ Query Interface
def has_object(self, sha):
"""
:return: True if the object identified by the given 20 bytes
binary sha is contained in the database"""
raise NotImplementedError("To be implemented in subclass")
def info(self, sha):
""" :return: OInfo instance
:param sha: bytes binary sha
:raise BadObject:"""
raise NotImplementedError("To be implemented in subclass")
def stream(self, sha):
""":return: OStream instance
:param sha: 20 bytes binary sha
:raise BadObject:"""
raise NotImplementedError("To be implemented in subclass")
def size(self):
""":return: amount of objects in this database"""
raise NotImplementedError()
def sha_iter(self):
"""Return iterator yielding 20 byte shas for all objects in this data base"""
raise NotImplementedError()
#} END query interface
class ObjectDBW(object):
"""Defines an interface to create objects in the database"""
def __init__(self, *args, **kwargs):
self._ostream = None
#{ Edit Interface
def set_ostream(self, stream):
"""
Adjusts the stream to which all data should be sent when storing new objects
:param stream: if not None, the stream to use, if None the default stream
will be used.
:return: previously installed stream, or None if there was no override
:raise TypeError: if the stream doesn't have the supported functionality"""
cstream = self._ostream
self._ostream = stream
return cstream
def ostream(self):
"""
:return: overridden output stream this instance will write to, or None
if it will write to the default stream"""
return self._ostream
def store(self, istream):
"""
Create a new object in the database
:return: the input istream object with its sha set to its corresponding value
:param istream: IStream compatible instance. If its sha is already set
to a value, the object will just be stored in the our database format,
in which case the input stream is expected to be in object format ( header + contents ).
:raise IOError: if data could not be written"""
raise NotImplementedError("To be implemented in subclass")
#} END edit interface
class FileDBBase(object):
"""Provides basic facilities to retrieve files of interest, including
caching facilities to help mapping hexsha's to objects"""
def __init__(self, root_path):
"""Initialize this instance to look for its files at the given root path
All subsequent operations will be relative to this path
:raise InvalidDBRoot:
**Note:** The base will not perform any accessablity checking as the base
might not yet be accessible, but become accessible before the first
access."""
super(FileDBBase, self).__init__()
self._root_path = root_path
#{ Interface
def root_path(self):
""":return: path at which this db operates"""
return self._root_path
def db_path(self, rela_path):
"""
:return: the given relative path relative to our database root, allowing
to pontentially access datafiles"""
return join(self._root_path, force_text(rela_path))
#} END interface
class CachingDB(object):
"""A database which uses caches to speed-up access"""
#{ Interface
def update_cache(self, force=False):
"""
Call this method if the underlying data changed to trigger an update
of the internal caching structures.
:param force: if True, the update must be performed. Otherwise the implementation
may decide not to perform an update if it thinks nothing has changed.
:return: True if an update was performed as something change indeed"""
# END interface
def _databases_recursive(database, output):
"""Fill output list with database from db, in order. Deals with Loose, Packed
and compound databases."""
if isinstance(database, CompoundDB):
dbs = database.databases()
output.extend(db for db in dbs if not isinstance(db, CompoundDB))
for cdb in (db for db in dbs if isinstance(db, CompoundDB)):
_databases_recursive(cdb, output)
else:
output.append(database)
# END handle database type
class CompoundDB(ObjectDBR, LazyMixin, CachingDB):
"""A database which delegates calls to sub-databases.
Databases are stored in the lazy-loaded _dbs attribute.
Define _set_cache_ to update it with your databases"""
def _set_cache_(self, attr):
if attr == '_dbs':
self._dbs = list()
elif attr == '_db_cache':
self._db_cache = dict()
else:
super(CompoundDB, self)._set_cache_(attr)
def _db_query(self, sha):
""":return: database containing the given 20 byte sha
:raise BadObject:"""
# most databases use binary representations, prevent converting
# it every time a database is being queried
try:
return self._db_cache[sha]
except KeyError:
pass
# END first level cache
for db in self._dbs:
if db.has_object(sha):
self._db_cache[sha] = db
return db
# END for each database
raise BadObject(sha)
#{ ObjectDBR interface
def has_object(self, sha):
try:
self._db_query(sha)
return True
except BadObject:
return False
# END handle exceptions
def info(self, sha):
return self._db_query(sha).info(sha)
def stream(self, sha):
return self._db_query(sha).stream(sha)
def size(self):
""":return: total size of all contained databases"""
return reduce(lambda x, y: x + y, (db.size() for db in self._dbs), 0)
def sha_iter(self):
return chain(*(db.sha_iter() for db in self._dbs))
#} END object DBR Interface
#{ Interface
def databases(self):
""":return: tuple of database instances we use for lookups"""
return tuple(self._dbs)
def update_cache(self, force=False):
# something might have changed, clear everything
self._db_cache.clear()
stat = False
for db in self._dbs:
if isinstance(db, CachingDB):
stat |= db.update_cache(force)
# END if is caching db
# END for each database to update
return stat
def partial_to_complete_sha_hex(self, partial_hexsha):
"""
:return: 20 byte binary sha1 from the given less-than-40 byte hexsha (bytes or str)
:param partial_hexsha: hexsha with less than 40 byte
:raise AmbiguousObjectName: """
databases = list()
_databases_recursive(self, databases)
partial_hexsha = force_text(partial_hexsha)
len_partial_hexsha = len(partial_hexsha)
if len_partial_hexsha % 2 != 0:
partial_binsha = hex_to_bin(partial_hexsha + "0")
else:
partial_binsha = hex_to_bin(partial_hexsha)
# END assure successful binary conversion
candidate = None
for db in databases:
full_bin_sha = None
try:
if hasattr(db, 'partial_to_complete_sha_hex'):
full_bin_sha = db.partial_to_complete_sha_hex(partial_hexsha)
else:
full_bin_sha = db.partial_to_complete_sha(partial_binsha, len_partial_hexsha)
# END handle database type
except BadObject:
continue
# END ignore bad objects
if full_bin_sha:
if candidate and candidate != full_bin_sha:
raise AmbiguousObjectName(partial_hexsha)
candidate = full_bin_sha
# END handle candidate
# END for each db
if not candidate:
raise BadObject(partial_binsha)
return candidate
#} END interface