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+# Copyright 2011 Canonical Ltd.
+#
+# This file is part of u1db.
+#
+# u1db is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License version 3
+# as published by the Free Software Foundation.
+#
+# u1db is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with u1db. If not, see <http://www.gnu.org/licenses/>.
+
+"""Abstract classes and common implementations for the backends."""
+
+import re
+try:
+ import simplejson as json
+except ImportError:
+ import json # noqa
+import uuid
+
+import u1db
+from u1db import (
+ errors,
+)
+import u1db.sync
+from u1db.vectorclock import VectorClockRev
+
+
+check_doc_id_re = re.compile("^" + u1db.DOC_ID_CONSTRAINTS + "$", re.UNICODE)
+
+
+class CommonSyncTarget(u1db.sync.LocalSyncTarget):
+ pass
+
+
+class CommonBackend(u1db.Database):
+
+ document_size_limit = 0
+
+ def _allocate_doc_id(self):
+ """Generate a unique identifier for this document."""
+ return 'D-' + uuid.uuid4().hex # 'D-' stands for document
+
+ def _allocate_transaction_id(self):
+ return 'T-' + uuid.uuid4().hex # 'T-' stands for transaction
+
+ def _allocate_doc_rev(self, old_doc_rev):
+ vcr = VectorClockRev(old_doc_rev)
+ vcr.increment(self._replica_uid)
+ return vcr.as_str()
+
+ def _check_doc_id(self, doc_id):
+ if not check_doc_id_re.match(doc_id):
+ raise errors.InvalidDocId()
+
+ def _check_doc_size(self, doc):
+ if not self.document_size_limit:
+ return
+ if doc.get_size() > self.document_size_limit:
+ raise errors.DocumentTooBig
+
+ def _get_generation(self):
+ """Return the current generation.
+
+ """
+ raise NotImplementedError(self._get_generation)
+
+ def _get_generation_info(self):
+ """Return the current generation and transaction id.
+
+ """
+ raise NotImplementedError(self._get_generation_info)
+
+ def _get_doc(self, doc_id, check_for_conflicts=False):
+ """Extract the document from storage.
+
+ This can return None if the document doesn't exist.
+ """
+ raise NotImplementedError(self._get_doc)
+
+ def _has_conflicts(self, doc_id):
+ """Return True if the doc has conflicts, False otherwise."""
+ raise NotImplementedError(self._has_conflicts)
+
+ def create_doc(self, content, doc_id=None):
+ json_string = json.dumps(content)
+ if doc_id is None:
+ doc_id = self._allocate_doc_id()
+ doc = self._factory(doc_id, None, json_string)
+ self.put_doc(doc)
+ return doc
+
+ def create_doc_from_json(self, json, doc_id=None):
+ if doc_id is None:
+ doc_id = self._allocate_doc_id()
+ doc = self._factory(doc_id, None, json)
+ self.put_doc(doc)
+ return doc
+
+ def _get_transaction_log(self):
+ """This is only for the test suite, it is not part of the api."""
+ raise NotImplementedError(self._get_transaction_log)
+
+ def _put_and_update_indexes(self, doc_id, old_doc, new_rev, content):
+ raise NotImplementedError(self._put_and_update_indexes)
+
+ def get_docs(self, doc_ids, check_for_conflicts=True,
+ include_deleted=False):
+ for doc_id in doc_ids:
+ doc = self._get_doc(
+ doc_id, check_for_conflicts=check_for_conflicts)
+ if doc.is_tombstone() and not include_deleted:
+ continue
+ yield doc
+
+ def _get_trans_id_for_gen(self, generation):
+ """Get the transaction id corresponding to a particular generation.
+
+ Raises an InvalidGeneration when the generation does not exist.
+
+ """
+ raise NotImplementedError(self._get_trans_id_for_gen)
+
+ def validate_gen_and_trans_id(self, generation, trans_id):
+ """Validate the generation and transaction id.
+
+ Raises an InvalidGeneration when the generation does not exist, and an
+ InvalidTransactionId when it does but with a different transaction id.
+
+ """
+ if generation == 0:
+ return
+ known_trans_id = self._get_trans_id_for_gen(generation)
+ if known_trans_id != trans_id:
+ raise errors.InvalidTransactionId
+
+ def _validate_source(self, other_replica_uid, other_generation,
+ other_transaction_id):
+ """Validate the new generation and transaction id.
+
+ other_generation must be greater than what we have stored for this
+ replica, *or* it must be the same and the transaction_id must be the
+ same as well.
+ """
+ (old_generation,
+ old_transaction_id) = self._get_replica_gen_and_trans_id(
+ other_replica_uid)
+ if other_generation < old_generation:
+ raise errors.InvalidGeneration
+ if other_generation > old_generation:
+ return
+ if other_transaction_id == old_transaction_id:
+ return
+ raise errors.InvalidTransactionId
+
+ def _put_doc_if_newer(self, doc, save_conflict, replica_uid, replica_gen,
+ replica_trans_id=''):
+ cur_doc = self._get_doc(doc.doc_id)
+ doc_vcr = VectorClockRev(doc.rev)
+ if cur_doc is None:
+ cur_vcr = VectorClockRev(None)
+ else:
+ cur_vcr = VectorClockRev(cur_doc.rev)
+ self._validate_source(replica_uid, replica_gen, replica_trans_id)
+ if doc_vcr.is_newer(cur_vcr):
+ rev = doc.rev
+ self._prune_conflicts(doc, doc_vcr)
+ if doc.rev != rev:
+ # conflicts have been autoresolved
+ state = 'superseded'
+ else:
+ state = 'inserted'
+ self._put_and_update_indexes(cur_doc, doc)
+ elif doc.rev == cur_doc.rev:
+ # magical convergence
+ state = 'converged'
+ elif cur_vcr.is_newer(doc_vcr):
+ # Don't add this to seen_ids, because we have something newer,
+ # so we should send it back, and we should not generate a
+ # conflict
+ state = 'superseded'
+ elif cur_doc.same_content_as(doc):
+ # the documents have been edited to the same thing at both ends
+ doc_vcr.maximize(cur_vcr)
+ doc_vcr.increment(self._replica_uid)
+ doc.rev = doc_vcr.as_str()
+ self._put_and_update_indexes(cur_doc, doc)
+ state = 'superseded'
+ else:
+ state = 'conflicted'
+ if save_conflict:
+ self._force_doc_sync_conflict(doc)
+ if replica_uid is not None and replica_gen is not None:
+ self._do_set_replica_gen_and_trans_id(
+ replica_uid, replica_gen, replica_trans_id)
+ return state, self._get_generation()
+
+ def _ensure_maximal_rev(self, cur_rev, extra_revs):
+ vcr = VectorClockRev(cur_rev)
+ for rev in extra_revs:
+ vcr.maximize(VectorClockRev(rev))
+ vcr.increment(self._replica_uid)
+ return vcr.as_str()
+
+ def set_document_size_limit(self, limit):
+ self.document_size_limit = limit