src/snakia/field/__init__.py

@@ -3,6 +3,7 @@ from .bool import BoolField
 from .field import Field
 from .float import FloatField
 from .int import IntField
+from .list import ListField
 from .str import StrField
 
 __all__ = [
@@ -11,5 +12,6 @@ __all__ = [
     "BoolField",
     "FloatField",
     "IntField",
+    "ListField",
     "StrField",
 ]

src/snakia/field/list.py

@@ -0,0 +1,38 @@
+from typing import Callable, Final, Iterable, TypeVar
+
+from typing_extensions import Self
+
+from .field import Field
+
+T = TypeVar("T")
+
+
+class ListField(Field[list[T]]):
+    def __init__(
+        self,
+        field: Field[T],
+        *,
+        length_size: int = 1,
+        default_factory: Callable[[Self], Iterable[T]] = lambda _: (),
+    ) -> None:
+        self.length_size: Final[int] = length_size
+        self.field: Final = field
+        super().__init__(default_factory=lambda s: [*default_factory(s)])
+
+    def serialize(self, items: list[T], /) -> bytes:
+        result = b""
+        for item in items:
+            value = self.field.serialize(item)
+            length_prefix = len(value).to_bytes(self.length_size, "big")
+            result += length_prefix + value
+        return result
+
+    def deserialize(self, serialized: bytes, /) -> list[T]:
+        result = []
+        while serialized:
+            length = int.from_bytes(serialized[: self.length_size], "big")
+            serialized = serialized[self.length_size :]
+            item = self.field.deserialize(serialized[:length])
+            serialized = serialized[length:]
+            result.append(item)
+        return result

src/snakia/field/t.py

@@ -4,6 +4,7 @@ from .bool import BoolField as bool
 from .field import Field as field
 from .float import FloatField as float
 from .int import IntField as int
+from .list import ListField as list
 from .str import StrField as str
 
 __all__ = [
@@ -12,5 +13,6 @@ __all__ = [
     "field",
     "float",
     "int",
+    "list",
     "str",
 ]