Source code for hwt.hdl.types.bitsCastUtils

from typing import Union

from hwt.hdl.types.bits import HBits
from hwt.synthesizer.exceptions import TypeConversionErr




class BitWidthErr(TypeConversionErr):
    """
    Wrong bit width of signal/value
    """





def fitTo_t(what: Union["HBitsRtlSignal", "HBitsConst"], where_t: HBits,
            extend: bool=True, shrink: bool=True) -> Union["HBitsRtlSignal", "HBitsConst"]:
    """
    Slice signal "what" to fit in "where"
    or
    arithmetically (for signed by MSB / unsigned, vector with 0) extend
    "what" to same width as "where"

    little-endian impl.

    :param extend: allow increasing of the signal width
    :param shrink: allow shrinking of the signal width
    """

    whatWidth = what._dtype.bit_length()
    toWidth = where_t.bit_length()
    if toWidth == whatWidth:
        return what
    elif toWidth < whatWidth:
        # slice
        if not shrink:
            raise BitWidthErr()

        return what._trunc(toWidth)
    else:
        if not extend:
            raise BitWidthErr()

        res = what._ext(toWidth)
        if where_t.signed is not None:
            return res._reinterpret_cast(where_t)
        return res





def fitTo(what: Union["HBitsRtlSignal", "HBitsConst"], where: Union["HBitsRtlSignal", "HBitsConst"],
          extend: bool=True, shrink: bool=True) -> Union["HBitsRtlSignal", "HBitsConst"]:
    return fitTo_t(what, where._dtype, extend, shrink)