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lib.data: improve annotation handling for Struct and Union.

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* Annotations like `s: unsigned(4) = 1` are recognized and
  the assigned value is used as the reset value for the implicitly
  created `Signal`.
* Base classes inheriting from `Struct` and `Union` without
  specifying a layout are recognized.
* Classes that both inherit from a base class with a layout and
  specify a layout are rejected.
This commit is contained in:
Catherine 2023-02-28 15:18:49 +00:00
parent 0ee5de036c
commit c7ef05c894
2 changed files with 99 additions and 12 deletions
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45
amaranth/lib/data.py
View file

@ -323,7 +323,7 @@ class View(ValueCastable):
try:
cast_layout = Layout.cast(layout)
except TypeError as e:
raise TypeError("View layout must be a Layout instance, not {!r}"
raise TypeError("View layout must be a layout, not {!r}"
.format(layout)) from e
if target is not None:
if (name is not None or reset is not None or reset_less is not None or
@ -398,28 +398,51 @@ class View(ValueCastable):
class _AggregateMeta(ShapeCastable, type):
def __new__(metacls, name, bases, namespace, *, _layout_cls=None, **kwargs):
cls = type.__new__(metacls, name, bases, namespace, **kwargs)
if _layout_cls is not None:
cls.__layout_cls = _layout_cls
if "__annotations__" in namespace:
def __new__(metacls, name, bases, namespace):
if "__annotations__" not in namespace:
# This is a base class without its own layout. It is not shape-castable, and cannot
# be instantiated. It can be used to share behavior.
return type.__new__(metacls, name, bases, namespace)
elif all(not hasattr(base, "_AggregateMeta__layout") for base in bases):
# This is a leaf class with its own layout. It is shape-castable and can
# be instantiated. It can also be subclassed, and used to share layout and behavior.
reset = dict()
for name in namespace["__annotations__"]:
if name in namespace:
reset[name] = namespace.pop(name)
cls = type.__new__(metacls, name, bases, namespace)
cls.__layout = cls.__layout_cls(namespace["__annotations__"])
return cls
cls.__reset = reset
return cls
else:
# This is a class that has a base class with a layout and annotations. Such a class
# is not well-formed.
raise TypeError("Aggregate class '{}' must either inherits or specify a layout, "
"not both"
.format(name))
def as_shape(cls):
if not hasattr(cls, "_AggregateMeta__layout"):
raise TypeError("Aggregate class '{}.{}' does not have a defined shape"
.format(cls.__module__, cls.__qualname__))
return cls.__layout
class _Aggregate(View, metaclass=_AggregateMeta):
def __init__(self, target=None, *, name=None, reset=None, reset_less=None,
attrs=None, decoder=None, src_loc_at=0):
if target is None and hasattr(self.__class__, "_AggregateMeta__reset"):
if reset is None:
reset = self.__class__._AggregateMeta__reset
else:
reset = {**self.__class__._AggregateMeta__reset, **reset}
super().__init__(self.__class__, target, name=name, reset=reset, reset_less=reset_less,
attrs=attrs, decoder=decoder, src_loc_at=src_loc_at + 1)
class Struct(_Aggregate, _layout_cls=StructLayout):
pass
class Struct(_Aggregate):
_AggregateMeta__layout_cls = StructLayout
class Union(_Aggregate, _layout_cls=UnionLayout):
pass
class Union(_Aggregate):
_AggregateMeta__layout_cls = UnionLayout