Commit 657b747b authored by Tim Peters's avatar Tim Peters

Merge _data_find comment repair from 3.3 branch.

parent dfbde966
...@@ -681,9 +681,18 @@ class FileStorage(BaseStorage.BaseStorage, ...@@ -681,9 +681,18 @@ class FileStorage(BaseStorage.BaseStorage,
self._lock_release() self._lock_release()
def _data_find(self, tpos, oid, data): def _data_find(self, tpos, oid, data):
# Return backpointer to oid in data record for in transaction at tpos. # Return backpointer for oid. Must call with the lock held.
# It should contain a pickle identical to data. Returns 0 on failure. # This is a file offset to oid's data record if found, else 0.
# Must call with lock held. # The data records in the transaction at tpos are searched for oid.
# If a data record for oid isn't found, returns 0.
# Else if oid's data record contains a backpointer, that
# backpointer is returned.
# Else oid's data record contains the data, and the file offset of
# oid's data record is returned. This data record should contain
# a pickle identical to the 'data' argument.
# XXX If the length of the stored data doesn't match len(data),
# XXX an exception is raised. If the lengths match but the data
# XXX isn't the same, 0 is returned. Why the discrepancy?
self._file.seek(tpos) self._file.seek(tpos)
h = self._file.read(TRANS_HDR_LEN) h = self._file.read(TRANS_HDR_LEN)
tid, tl, status, ul, dl, el = struct.unpack(TRANS_HDR, h) tid, tl, status, ul, dl, el = struct.unpack(TRANS_HDR, h)
......
...@@ -73,9 +73,18 @@ class DataCopier(FileStorageFormatter): ...@@ -73,9 +73,18 @@ class DataCopier(FileStorageFormatter):
raise UndoError(None, "Invalid transaction id") raise UndoError(None, "Invalid transaction id")
def _data_find(self, tpos, oid, data): def _data_find(self, tpos, oid, data):
# Return backpointer to oid in data record for in transaction at tpos. # Return backpointer for oid. Must call with the lock held.
# It should contain a pickle identical to data. Returns 0 on failure. # This is a file offset to oid's data record if found, else 0.
# Must call with lock held. # The data records in the transaction at tpos are searched for oid.
# If a data record for oid isn't found, returns 0.
# Else if oid's data record contains a backpointer, that
# backpointer is returned.
# Else oid's data record contains the data, and the file offset of
# oid's data record is returned. This data record should contain
# a pickle identical to the 'data' argument.
# XXX If the length of the stored data doesn't match len(data),
# XXX an exception is raised. If the lengths match but the data
# XXX isn't the same, 0 is returned. Why the discrepancy?
h = self._read_txn_header(tpos) h = self._read_txn_header(tpos)
tend = tpos + h.tlen tend = tpos + h.tlen
pos = self._file.tell() pos = self._file.tell()
......
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