Add db method to determine recovered records using sequence number

dfindexeddb/leveldb/log.py

@@ -152,7 +152,7 @@ class PhysicalRecord(utils.FromDecoderMixin):
   @classmethod
   def FromDecoder(
       cls, decoder: utils.LevelDBDecoder, base_offset: int = 0
-  ) -> PhysicalRecord:
+  ) -> Optional[PhysicalRecord]:
     """Decodes a PhysicalRecord from the current position of a LevelDBDecoder.
 
     Args:
@@ -161,11 +161,13 @@ def FromDecoder(
           read from.
 
     Returns:
-      A PhysicalRecord.
+      A PhysicalRecord or None if the parsed header is 0.
     """
     offset, checksum = decoder.DecodeUint32()
     _, length = decoder.DecodeUint16()
     _, record_type_byte = decoder.DecodeUint8()
+    if checksum == 0 or length == 0 or record_type_byte == 0:
+      return None
     try:
       record_type = definitions.LogFilePhysicalRecordType(record_type_byte)
     except ValueError as error:
@@ -206,7 +208,11 @@ def GetPhysicalRecords(self) -> Generator[PhysicalRecord, None, None]:
     buffer_length = len(self.data)
 
     while buffer.tell() + PhysicalRecord.PHYSICAL_HEADER_LENGTH < buffer_length:
-      yield PhysicalRecord.FromStream(buffer, base_offset=self.offset)
+      record = PhysicalRecord.FromStream(buffer, base_offset=self.offset)
+      if record:
+        yield record
+      else:
+        return
 
   @classmethod
   def FromStream(cls, stream: BinaryIO) -> Optional[Block]:

dfindexeddb/leveldb/record.py

@@ -14,6 +14,7 @@
 # limitations under the License.
 """A module for records from LevelDB files."""
 from __future__ import annotations
+from collections import defaultdict
 import dataclasses
 import pathlib
 import re
@@ -297,6 +298,34 @@ def _RecordsByManifest(self) -> Generator[LevelDBRecord, None, None]:
         record.recovered = True
         yield record
 
+  def _RecordsBySequenceNumber(self) -> Generator[LevelDBRecord, None, None]:
+    """Yields LevelDBRecords using the sequence number to determine if a record
+    is active.
+
+    Yields:
+      LevelDBRecords.
+    """
+    unsorted_records = defaultdict(list)
+
+    for filename in self.foldername.iterdir():
+      for leveldb_record in LevelDBRecord.FromFile(filename):
+        if leveldb_record:
+          unsorted_records[leveldb_record.record.key].append(leveldb_record)
+    for key, unsorted_records in unsorted_records.items():
+      num_unsorted_records = len(unsorted_records)
+      if num_unsorted_records == 1:
+        unsorted_records[0].recovered = False
+        yield unsorted_records[0]
+      else:
+        for i, record in enumerate(sorted(
+            unsorted_records, key=lambda x: (
+                x.record.sequence_number, x.record.offset))):
+          if i == num_unsorted_records:
+            record.recovered = False
+          else:
+            record.recovered = True
+          yield record
+
   def GetRecords(
       self,
       use_manifest: bool = False
@@ -313,5 +342,4 @@ def GetRecords(
     if use_manifest:
       yield from self._RecordsByManifest()
     else:
-      for filename in self.foldername.iterdir():
-        yield from LevelDBRecord.FromFile(filename)
+      yield from self._RecordsBySequenceNumber()