read individual files rather than all at once

Sparserestore/backup.py

@@ -23,19 +23,35 @@ class BackupFile:
 @dataclass
 class ConcreteFile(BackupFile):
     contents: bytes
+    src_path: Optional[str] = None
     owner: int = 0
     group: int = 0
     inode: Optional[int] = None
     mode: _FileMode = DEFAULT
 
+    hash: bytes = None
+    size: int = None
+
+    def read_contents(self) -> bytes:
+        contents = self.contents
+        if self.contents == None:
+            with open(self.src_path, "rb") as in_file:
+                contents = in_file.read()
+        # prepopulate hash and size
+        self.hash = sha1(contents).digest()
+        self.size = len(contents)
+        return contents
+
     def to_record(self) -> mbdb.MbdbRecord:
         if self.inode is None:
             self.inode = int.from_bytes(randbytes(8), "big")
+        if self.hash == None or self.size == None:
+            self.read_contents()
         return mbdb.MbdbRecord(
             domain=self.domain,
             filename=self.path,
             link="",
-            hash=sha1(self.contents).digest(),
+            hash=self.hash,
             key=b"",
             mode=self.mode | _FileMode.S_IFREG,
             #unknown2=0,
@@ -46,7 +62,7 @@ class ConcreteFile(BackupFile):
             mtime=int(datetime.now().timestamp()),
             atime=int(datetime.now().timestamp()),
             ctime=int(datetime.now().timestamp()),
-            size=len(self.contents),
+            size=self.size,
             flags=4,
             properties=[]
         )
@@ -126,7 +142,7 @@ class Backup:
             if isinstance(file, ConcreteFile):
                 #print("Writing", file.path, "to", directory / sha1((file.domain + "-" + file.path).encode()).digest().hex())
                 with open(directory / sha1((file.domain + "-" + file.path).encode()).digest().hex(), "wb") as f:
-                    f.write(file.contents)
+                    f.write(file.read_contents())
             
         with open(directory / "Manifest.mbdb", "wb") as f:
             f.write(self.generate_manifest_db().to_bytes())