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Editing: bitvec.py
# # this is a rather strict implementation of a bit vector class # it is accessed the same way as an array of python-ints, except # the value must be 0 or 1 # import sys; rprt = sys.stderr.write #for debugging class error(Exception): pass def _check_value(value): if type(value) != type(0) or not 0 <= value < 2: raise error, 'bitvec() items must have int value 0 or 1' import math def _compute_len(param): mant, l = math.frexp(float(param)) bitmask = 1L << l if bitmask <= param: raise RuntimeError('(param, l) = %r' % ((param, l),)) while l: bitmask = bitmask >> 1 if param & bitmask: break l = l - 1 return l def _check_key(len, key): if type(key) != type(0): raise TypeError, 'sequence subscript not int' if key < 0: key = key + len if not 0 <= key < len: raise IndexError, 'list index out of range' return key def _check_slice(len, i, j): #the type is ok, Python already checked that i, j = max(i, 0), min(len, j) if i > j: i = j return i, j class BitVec: def __init__(self, *params): self._data = 0L self._len = 0 if not len(params): pass elif len(params) == 1: param, = params if type(param) == type([]): value = 0L bit_mask = 1L for item in param: # strict check #_check_value(item) if item: value = value | bit_mask bit_mask = bit_mask << 1 self._data = value self._len = len(param) elif type(param) == type(0L): if param < 0: raise error, 'bitvec() can\'t handle negative longs' self._data = param self._len = _compute_len(param) else: raise error, 'bitvec() requires array or long parameter' elif len(params) == 2: param, length = params if type(param) == type(0L): if param < 0: raise error, \ 'can\'t handle negative longs' self._data = param if type(length) != type(0): raise error, 'bitvec()\'s 2nd parameter must be int' computed_length = _compute_len(param) if computed_length > length: print 'warning: bitvec() value is longer than the length indicates, truncating value' self._data = self._data & \ ((1L << length) - 1) self._len = length else: raise error, 'bitvec() requires array or long parameter' else: raise error, 'bitvec() requires 0 -- 2 parameter(s)' def append(self, item): #_check_value(item) #self[self._len:self._len] = [item] self[self._len:self._len] = \ BitVec(long(not not item), 1) def count(self, value): #_check_value(value) if value: data = self._data else: data = (~self)._data count = 0 while data: data, count = data >> 1, count + (data & 1 != 0) return count def index(self, value): #_check_value(value): if value: data = self._data else: data = (~self)._data index = 0 if not data: raise ValueError, 'list.index(x): x not in list' while not (data & 1): data, index = data >> 1, index + 1 return index def insert(self, index, item): #_check_value(item) #self[index:index] = [item] self[index:index] = BitVec(long(not not item), 1) def remove(self, value): del self[self.index(value)] def reverse(self): #ouch, this one is expensive! #for i in self._len>>1: self[i], self[l-i] = self[l-i], self[i] data, result = self._data, 0L for i in range(self._len): if not data: result = result << (self._len - i) break result, data = (result << 1) | (data & 1), data >> 1 self._data = result def sort(self): c = self.count(1) self._data = ((1L << c) - 1) << (self._len - c) def copy(self): return BitVec(self._data, self._len) def seq(self): result = [] for i in self: result.append(i) return result def __repr__(self): ##rprt('<bitvec class instance object>.' + '__repr__()\n') return 'bitvec(%r, %r)' % (self._data, self._len) def __cmp__(self, other, *rest): #rprt('%r.__cmp__%r\n' % (self, (other,) + rest)) if type(other) != type(self): other = apply(bitvec, (other, ) + rest) #expensive solution... recursive binary, with slicing length = self._len if length == 0 or other._len == 0: return cmp(length, other._len) if length != other._len: min_length = min(length, other._len) return cmp(self[:min_length], other[:min_length]) or \ cmp(self[min_length:], other[min_length:]) #the lengths are the same now... if self._data == other._data: return 0 if length == 1: return cmp(self[0], other[0]) else: length = length >> 1 return cmp(self[:length], other[:length]) or \ cmp(self[length:], other[length:]) def __len__(self): #rprt('%r.__len__()\n' % (self,)) return self._len def __getitem__(self, key): #rprt('%r.__getitem__(%r)\n' % (self, key)) key = _check_key(self._len, key) return self._data & (1L << key) != 0 def __setitem__(self, key, value): #rprt('%r.__setitem__(%r, %r)\n' % (self, key, value)) key = _check_key(self._len, key) #_check_value(value) if value: self._data = self._data | (1L << key) else: self._data = self._data & ~(1L << key) def __delitem__(self, key): #rprt('%r.__delitem__(%r)\n' % (self, key)) key = _check_key(self._len, key) #el cheapo solution... self._data = self[:key]._data | self[key+1:]._data >> key self._len = self._len - 1 def __getslice__(self, i, j): #rprt('%r.__getslice__(%r, %r)\n' % (self, i, j)) i, j = _check_slice(self._len, i, j) if i >= j: return BitVec(0L, 0) if i: ndata = self._data >> i else: ndata = self._data nlength = j - i if j != self._len: #we'll have to invent faster variants here #e.g. mod_2exp ndata = ndata & ((1L << nlength) - 1) return BitVec(ndata, nlength) def __setslice__(self, i, j, sequence, *rest): #rprt('%s.__setslice__%r\n' % (self, (i, j, sequence) + rest)) i, j = _check_slice(self._len, i, j) if type(sequence) != type(self): sequence = apply(bitvec, (sequence, ) + rest) #sequence is now of our own type ls_part = self[:i] ms_part = self[j:] self._data = ls_part._data | \ ((sequence._data | \ (ms_part._data << sequence._len)) << ls_part._len) self._len = self._len - j + i + sequence._len def __delslice__(self, i, j): #rprt('%r.__delslice__(%r, %r)\n' % (self, i, j)) i, j = _check_slice(self._len, i, j) if i == 0 and j == self._len: self._data, self._len = 0L, 0 elif i < j: self._data = self[:i]._data | (self[j:]._data >> i) self._len = self._len - j + i def __add__(self, other): #rprt('%r.__add__(%r)\n' % (self, other)) retval = self.copy() retval[self._len:self._len] = other return retval def __mul__(self, multiplier): #rprt('%r.__mul__(%r)\n' % (self, multiplier)) if type(multiplier) != type(0): raise TypeError, 'sequence subscript not int' if multiplier <= 0: return BitVec(0L, 0) elif multiplier == 1: return self.copy() #handle special cases all 0 or all 1... if self._data == 0L: return BitVec(0L, self._len * multiplier) elif (~self)._data == 0L: return ~BitVec(0L, self._len * multiplier) #otherwise el cheapo again... retval = BitVec(0L, 0) while multiplier: retval, multiplier = retval + self, multiplier - 1 return retval def __and__(self, otherseq, *rest): #rprt('%r.__and__%r\n' % (self, (otherseq,) + rest)) if type(otherseq) != type(self): otherseq = apply(bitvec, (otherseq, ) + rest) #sequence is now of our own type return BitVec(self._data & otherseq._data, \ min(self._len, otherseq._len)) def __xor__(self, otherseq, *rest): #rprt('%r.__xor__%r\n' % (self, (otherseq,) + rest)) if type(otherseq) != type(self): otherseq = apply(bitvec, (otherseq, ) + rest) #sequence is now of our own type return BitVec(self._data ^ otherseq._data, \ max(self._len, otherseq._len)) def __or__(self, otherseq, *rest): #rprt('%r.__or__%r\n' % (self, (otherseq,) + rest)) if type(otherseq) != type(self): otherseq = apply(bitvec, (otherseq, ) + rest) #sequence is now of our own type return BitVec(self._data | otherseq._data, \ max(self._len, otherseq._len)) def __invert__(self): #rprt('%r.__invert__()\n' % (self,)) return BitVec(~self._data & ((1L << self._len) - 1), \ self._len) def __coerce__(self, otherseq, *rest): #needed for *some* of the arithmetic operations #rprt('%r.__coerce__%r\n' % (self, (otherseq,) + rest)) if type(otherseq) != type(self): otherseq = apply(bitvec, (otherseq, ) + rest) return self, otherseq def __int__(self): return int(self._data) def __long__(self): return long(self._data) def __float__(self): return float(self._data) bitvec = BitVec
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