Re: [myhdl-list] intbv wrap
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Re: [myhdl-list] intbv wrap
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From: Christopher F. <chr...@gm...> - 2011-05-10 11:27:56
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I made a couple of minor adjustments to this patch.
1. Made the wrap function private (_wrap) and moved _wrap to __wrap.
The wrap function should not be used directly because it will not
covert correctly. I think for a future (todo) enhancement the wrap
function can be made public and handled by the converter. This is an
involved modification. For now I think it is good to advertise the wrap
function was private.
2. Added myrange to a slot, _range.
3. Modified a couple comments.
wrap4.patch is the text version.
Thanks
Chris Felton
On 5/5/11 4:25 PM, Christopher Felton wrote:
> On 5/5/2011 9:21 AM, Ben wrote:
>> Hi Christopher,
>>
>> I took the liberty to review and edit your patch.
>>
>> As you can see, I added some tests, and removed the inclusion of the
>> val property. It became quite smaller ! I left your name in it as the
>> idea and the logic is from you.
>>
>> I also moved the check from the wrap function to the constructor (no
>> need to check every time.).
>
> Perfect! Thanks for the contributions and for the additional test
> cases, very nice. Also, good catch on the range checking!
>
> Is there an opinion if 'myrange' should be a class member so that it
> doesn't need to be recalculated on each check? I don't know if there is
> a down side to having too many slots (_range)?
>
> In the future we will need to address if wrap() can be converted or
> changed to a private function? As discussed in previous threads.
>
> Thanks again Benoît.
>
> Chris
>
>>
>> Here is a text version, enclosed a bundle. All tests pass fine.
>>
>> # HG changeset patch
>> # User cfelton
>> # Date 1303212809 18000
>> # Node ID 145d558e234f363c3e43e9a79ab48ad7e20d7b9b
>> # Parent f77cf2c4a5894013ceb2f5c184d84136ea4f04a3
>> Add a wrap parameter to intbv. When set, no overflow will occur.
>>
>> diff -r f77cf2c4a589 -r 145d558e234f myhdl/_intbv.py
>> --- a/myhdl/_intbv.py Wed May 04 21:33:14 2011 +0200
>> +++ b/myhdl/_intbv.py Tue Apr 19 06:33:29 2011 -0500
>> @@ -31,37 +31,46 @@
>> from __builtin__ import max as maxfunc
>>
>> class intbv(object):
>> - __slots__ = ('_val', '_min', '_max', '_nrbits')
>> + __slots__ = ('_min', '_max', '_nrbits', '_wrap', '__val')
>>
>> - def __init__(self, val=0, min=None, max=None, _nrbits=0):
>> + def __init__(self, val=0, min=None, max=None, wrap=False, _nrbits=0):
>> if _nrbits:
>> self._min = 0
>> self._max = 2**_nrbits
>> + self._nrbits = _nrbits
>> else:
>> self._min = min
>> self._max = max
>> if max is not None and min is not None:
>> if min>= 0:
>> - _nrbits = len(bin(max-1))
>> + self._nrbits = len(bin(max-1))
>> elif max<= 1:
>> - _nrbits = len(bin(min))
>> + self._nrbits = len(bin(min))
>> else:
>> # make sure there is a leading zero bit in positive numbers
>> - _nrbits = maxfunc(len(bin(max-1))+1, len(bin(min)))
>> + self._nrbits = maxfunc(len(bin(max-1))+1, len(bin(min)))
>> + else:
>> + self._nrbits = 0
>> +
>> + if wrap:
>> + myrange = self._nrbits**2
>> + if (abs(self.min) != self.max) or ((abs(self.min) +
>> self.max) != myrange):
>> + raise ValueError, "Cannot use wrapping if -min != max
>> (%d != %d)" % (-self.min, self.max)
>> + self._wrap = wrap
>> if isinstance(val, (int, long)):
>> self._val = val
>> elif isinstance(val, StringType):
>> mval = val.replace('_', '')
>> + self._nrbits = len(mval)
>> self._val = long(mval, 2)
>> - _nrbits = len(val)
>> elif isinstance(val, intbv):
>> self._val = val._val
>> self._min = val._min
>> self._max = val._max
>> - _nrbits = val._nrbits
>> + self._wrap = val._wrap
>> + self._nrbits = val._nrbits
>> else:
>> raise TypeError("intbv constructor arg should be int or string")
>> - self._nrbits = _nrbits
>> self._checkBounds()
>>
>> # support for the 'min' and 'max' attribute
>> @@ -82,6 +91,20 @@
>> raise ValueError("intbv value %s< minimum %s" %
>> (self._val, self._min))
>>
>> + # val property
>> + def _get_val(self):
>> + return self.__val
>> +
>> + def _set_val(self, pval):
>> +
>> + if self._wrap:
>> + self.__val = self.wrap(pval)
>> + else:
>> + self.__val = pval
>> +
>> + self._checkBounds()
>> +
>> + _val = property(_get_val, _set_val)
>>
>> # hash
>> def __hash__(self):
>> @@ -433,6 +456,21 @@
>> return "intbv(" + repr(self._val) + ")"
>>
>>
>> + def wrap(self, val):
>> + """ Wrap the value back to the range of the inbv
>> +
>> + The following will check that the defined min-max is the full
>> + range of the binary word. If the full range is specified if
>> + the value is outside the bounds of the range it will be adjusted
>> + to the proper value in bounds.
>> + """
>> + myrange = 2**self._nrbits
>> +
>> + rval = self.min + ((val +self.max) % myrange)
>> +
>> + return rval
>> +
>> +
>> def signed(self):
>> ''' return integer with the signed value of the intbv instance
>>
>> diff -r f77cf2c4a589 -r 145d558e234f myhdl/test/core/test_intbv.py
>> --- a/myhdl/test/core/test_intbv.py Wed May 04 21:33:14 2011 +0200
>> +++ b/myhdl/test/core/test_intbv.py Tue Apr 19 06:33:29 2011 -0500
>> @@ -576,8 +576,50 @@
>> self.assertEqual(n.max, m.max)
>> self.assertEqual(len(n), len(m))
>>
>> +class TestIntbvWrap(TestCase):
>> +
>> + def testWrap(self):
>> + x = intbv(0, min=-8, max=8, wrap=True)
>> + x[:] = x + 1
>> + self.assertEqual(1, x)
>> + x[:] = x + 2
>> + self.assertEqual(3, x)
>> + x[:] = x + 5
>> + self.assertEqual(-8, x)
>> + x[:] = x + 1
>> + self.assertEqual(-7, x)
>> + x[:] = x - 5
>> + self.assertEqual(4, x)
>> + x[:] = x - 4
>> + self.assertEqual(0, x)
>> + x[:] += 15
>> + x[:] = x - 1
>> + self.assertEqual(-2, x)
>> +
>> + def testInit(self):
>> + self.assertRaises(ValueError, intbv, 15, min=-8, max=8)
>> + x = intbv(15, min=-8, max=8, wrap=True)
>> + self.assertEqual(-1, x)
>> +
>> + self.assertRaises(ValueError, intbv, 5, min=-3, max=8, wrap=True)
>> + intbv(5, min=-3, max=8)
>>
>>
>> + def testNoWrap(self):
>> + x = intbv(0, min=-8, max=8, wrap=False)
>> + try:
>> + x[:] += 15
>> + self.fail()
>> + except ValueError:
>> + pass
>> +
>> + x = intbv(0, min=-8, max=8)
>> + try:
>> + x[:] += 15
>> + self.fail()
>> + except ValueError:
>> + pass
>> +
>> if __name__ == "__main__":
>> unittest.main()
>>
>>
>>
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>
>
>
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