Add a function related to fp submodule

Author: arithy

python/src/simuhw/fp/__init__.py

@@ -47,7 +47,7 @@
 
     __all__ += [
         'TininessMode', 'RoundingMode', 'ExceptionFlag',
-        'Float', 'Float16', 'Float32', 'Float64', 'Float128',
+        'Float', 'Float16', 'Float32', 'Float64', 'Float128', 'dsize_to_dtype',
         'FPState', 'FPUnaryOperator', 'FPBinaryOperator', 'FPTernaryOperator',
         'SIMD_FPUnaryOperator', 'SIMD_FPBinaryOperator', 'SIMD_FPTernaryOperator',
         'FPNegator', 'SIMD_FPNegator',
@@ -70,7 +70,7 @@
 
     from softfloatpy import TininessMode, RoundingMode, ExceptionFlag
     from ._operator import (
-        Float, Float16, Float32, Float64, Float128,
+        Float, Float16, Float32, Float64, Float128, dsize_to_dtype,
         FPState, FPUnaryOperator, FPBinaryOperator, FPTernaryOperator,
         SIMD_FPUnaryOperator, SIMD_FPBinaryOperator, SIMD_FPTernaryOperator
     )

python/src/simuhw/fp/_operator.py

@@ -55,6 +55,30 @@ class Float128(sf.Float128, metaclass=ABCMeta):
 Float = type[Float16 | Float32 | Float64 | Float128]
 
 
+def dsize_to_dtype(dsize: int) -> Float:
+    """Returns a floating-point type that has the specified data size.
+
+    Args:
+        dsize: The data size in bits.
+
+    Returns:
+        A floating-point type that has the specified data size.
+
+    Raises:
+        ValueError: If no floating-point type that has the specified data size.
+
+    """
+    if dsize == 16:
+        return Float16
+    if dsize == 32:
+        return Float32
+    if dsize == 64:
+        return Float64
+    if dsize == 128:
+        return Float128
+    raise ValueError(f'No floating-point type with {dsize} bits')
+
+
 class FPState(metaclass=ABCMeta):
     """A class that manipulates the floating-point states."""