hashfile: add HashFile obj

Author: efiop

src/dvc_objects/hashfile/db.py

@@ -9,6 +9,7 @@
 from dvc_objects.errors import ObjectFormatError
 
 from .hash_info import HashInfo
+from .obj import HashFile
 
 if TYPE_CHECKING:
     from dvc_objects.fs.base import AnyFSPath, FileSystem
@@ -47,6 +48,13 @@ def config(self):
             "read_only": self.read_only,
         }
 
+    def get(self, oid: str):
+        return HashFile(
+            self.oid_to_path(oid),
+            self.fs,
+            HashInfo(self.hash_name, oid),
+        )
+
     def add(
         self,
         path: "AnyFSPath",

src/dvc_objects/hashfile/obj.py

@@ -0,0 +1,17 @@
+from typing import TYPE_CHECKING
+
+from dvc_objects.obj import Object
+
+if TYPE_CHECKING:
+    from .fs.base import AnyFSPath, FileSystem
+    from .hash_info import HashInfo
+
+
+class HashFile(Object):
+    def __init__(
+        self, path: "AnyFSPath", fs: "FileSystem", hash_info: "HashInfo"
+    ):
+        assert hash_info.value
+        oid = hash_info.value
+        super().__init__(path, fs, oid)
+        self.hash_info = hash_info