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78 lines
1.9 KiB
Python
78 lines
1.9 KiB
Python
# A bitset represents a fixed number of bits and have some helper methods for
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# manipulating them.
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class bitset:
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def __init__(self, n, val):
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assert n > 0
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assert val < pow(2, n) # number should fit within the available bits
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self.n = n
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self.data = val
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def size(self):
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return self.n
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def get(self, i):
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assert i >= 0 and i < self.n
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return (self.data >> i) & 1
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def get_msb(self):
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return self.get(self.n-1)
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def get_lsb(self):
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return self.get(0)
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def set(self, i, x):
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assert isinstance(x, bool) or isinstance(x, int)
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assert i >= 0 and i < self.n
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self.data ^= (-x ^ self.data) & (1 << i)
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def substr(self, msb, lsb):
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assert msb >= lsb
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assert lsb >= 0
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assert msb < self.n
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count = msb - lsb + 1
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newdata = self.data >> lsb & ((1 << count) - 1)
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return bitset(count, newdata)
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def number(self):
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return self.data
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def bits(self):
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return [self.get(i) for i in range(self.n-1, -1, -1)]
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def __eq__(self, other):
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assert isinstance(other, bitset)
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return self.n == other.n and self.data == other.data
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def __str__(self):
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return ''.join('1' if x else '0' for x in self.bits())
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def __repr__(self):
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return "bitset(%d, 0b%s)" % (self.n, self.__str__())
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@staticmethod
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def from_list(lst):
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num = 0
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n = len(lst) - 1
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for x in lst:
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assert x >= 0 and x <= 1
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num = num | (x << n)
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n = n - 1
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return bitset(len(lst), num)
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@staticmethod
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def from_args(*args):
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return bitset.from_list(list(args))
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@staticmethod
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def join(a, b):
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assert isinstance(a, bitset)
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assert isinstance(b, bitset)
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count = a.size()+b.size()
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number = b.number() | (a.number() << b.size())
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return bitset(count, number)
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