Demo/classes/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

error = 'bitvec.error'


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 'FATAL', '(param, l) = ' + `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' + `self._data, self._len`

	def __cmp__(self, other, *rest):
		#rprt(`self`+'.__cmp__'+`(other, ) + rest`+'\n')
		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(`self`+'.__len__()\n')
		return self._len

	def __getitem__(self, key):
		#rprt(`self`+'.__getitem__('+`key`+')\n')
		key = _check_key(self._len, key)
		return self._data & (1L << key) != 0

	def __setitem__(self, key, value):
		#rprt(`self`+'.__setitem__'+`key, value`+'\n')
		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(`self`+'.__delitem__('+`key`+')\n')
		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(`self`+'.__getslice__'+`i, j`+'\n')
		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(`self`+'.__setslice__'+`(i, j, sequence) + rest`+'\n')
		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(`self`+'.__delslice__'+`i, j`+'\n')
		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(`self`+'.__add__('+`other`+')\n')
		retval = self.copy()
		retval[self._len:self._len] = other
		return retval

	def __mul__(self, multiplier):
		#rprt(`self`+'.__mul__('+`multiplier`+')\n')
		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(`self`+'.__and__'+`(otherseq, ) + rest`+'\n')
		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(`self`+'.__xor__'+`(otherseq, ) + rest`+'\n')
		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(`self`+'.__or__'+`(otherseq, ) + rest`+'\n')
		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(`self`+'.__invert__()\n')
		return BitVec(~self._data & ((1L << self._len) - 1), \
			  self._len)

	def __coerce__(self, otherseq, *rest):
		#needed for *some* of the arithmetic operations
		#rprt(`self`+'.__coerce__'+`(otherseq, ) + rest`+'\n')
		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