make crc more dynamic

src/smllib/reader.py

@@ -12,8 +12,13 @@ class SmlStreamReader:
     def __init__(self, build_ctx: Optional[CTX_HINT] = None, crc: Literal['kermit', 'x25'] = 'x25') -> None:
         self.bytes: bytes = b''
         self.build_ctx: CTX_HINT = build_ctx if build_ctx is not None else create_context()
-        self.crc_func: Callable[[Union[memoryview, bytes]], int] = {
-            'x25': crc_module.x25.get_crc, 'kermit': crc_module.kermit.get_crc}[crc]
+
+        # This makes it easy to patch additional crc functions to the module
+        try:
+            self.crc_func: Callable[[Union[memoryview, bytes]], int] = getattr(crc_module, crc).get_crc
+        except AttributeError:
+            available = [f'"{n:s}"' for n in dir(crc_module) if not n.startswith('_')]
+            raise ValueError(f'Unsupported CRC "{crc}"! Available: {", ".join(available):s}')
 
     def add(self, _bytes: bytes) -> None:
         self.bytes += _bytes

tests/test_crc.py

@@ -1,7 +1,12 @@
+import inspect
+import typing
 from binascii import a2b_hex
+from typing import Union
 
 import pytest
 
+from smllib import SmlStreamReader
+from smllib import crc as crc_module
 from smllib.crc.x25 import get_crc as x25_get_crc
 
 
@@ -17,3 +22,38 @@ def test_crc_x25(msg) -> None:
     crc_msg = f'{_msg[-3]:02x}{_msg[-2]:02x}'
     crc_calc = f'{x25_get_crc(_msg[:-4]):04x}'
     assert crc_msg == crc_calc
+
+
+def _get_signature() -> inspect.Signature:
+    return inspect.Signature(
+        parameters=[
+            inspect.Parameter('buf', kind=inspect.Parameter.POSITIONAL_OR_KEYWORD, annotation=Union[memoryview, bytes])
+        ],
+        return_annotation=int
+    )
+
+
+@pytest.mark.parametrize('name', (n for n in dir(crc_module) if not n.startswith('_')))
+def test_signature_crc_funcs(name: str) -> None:
+    crc_impl = getattr(crc_module, name)
+    crc_sig = inspect.signature(crc_impl.get_crc)
+    assert crc_sig == _get_signature()
+
+
+def test_type_hint_reader() -> None:
+    signature = _get_signature()
+
+    a = SmlStreamReader()
+    hint = typing.get_type_hints(a.crc_func)
+    assert hint.pop('return') is signature.return_annotation
+
+    assert hint
+    for name in hint:
+        assert hint[name] == signature.parameters[name].annotation
+
+
+def test_invalid_crc_name() -> None:
+
+    with pytest.raises(ValueError) as e:
+        SmlStreamReader(crc='asfd')
+    assert str(e.value) == 'Unsupported CRC "asfd"! Available: "kermit", "x25"'