Ejemplo n.º 1
0
def decode_sets(bytes):
    """
    Decodes a set of sets encoded using encode_sets (see above). 
    
    >>> b = BitStream(hex='0x00000000000000010503').tobytes(); write_sets(decode_sets(b))
    '{{0,2},{0,1}}'
    
    >>> b = BitStream(hex='0x000000000000000100').tobytes(); write_sets(decode_sets(b))
    '{{}}'
    
    >>> b = BitStream(hex='0x0000000000000001').tobytes(); write_sets(decode_sets(b))
    '{}'
    """
    from bitstring.bitstream import BitStream, pack
    bs = BitStream(bytes=bytes)
    bytesperset, content = bs.readlist('uint:64, bits')
    setOfSets = set()
    for bits in content.cut(bytesperset * 8):
        aSet = set()
        bits.reverse()
        for i, b in enumerate(bits):
            if b is True:
                aSet.add(i)
        setOfSets.add(frozenset(aSet))
    return setOfSets
def decode_sets(bytes):
    """
    Decodes a set of sets encoded using encode_sets (see above). 
    
    >>> b = BitStream(hex='0x00000000000000010503').tobytes(); write_sets(decode_sets(b))
    '{{0,2},{0,1}}'
    
    >>> b = BitStream(hex='0x000000000000000100').tobytes(); write_sets(decode_sets(b))
    '{{}}'
    
    >>> b = BitStream(hex='0x0000000000000001').tobytes(); write_sets(decode_sets(b))
    '{}'
    """
    from bitstring.bitstream import BitStream, pack
    bs = BitStream(bytes=bytes)
    bytesperset, content = bs.readlist('uint:64, bits')
    setOfSets = set()
    for bits in content.cut(bytesperset*8):
        aSet = set()
        bits.reverse()
        for i,b in enumerate(bits):
            if b is True:
                aSet.add(i)
        setOfSets.add(frozenset(aSet))
    return setOfSets
Ejemplo n.º 3
0
def encode_sets(setOfSets):
    """
    Encode a set of sets (e.g., a set of conflict sets or a set of hitting sets) in a binary format, where each 
    of the sets is represented as a word whose bits indicate which elements are part of the set. 
    The first 64bit unsigned big-endian integer indicates the number of bytes used per set. 
    
    For example, the set of sets {{a,c},{a,b}} contains three components: [a, b, c]. 
    As we only use full bytes (i.e. 8 bits, 16 bits, ...), we use 1 byte to encode each set in this example. 
    Therefore, the first 64 bit of the encoded value are 0x0000000000000001. 
    
    The set {a,c} contains components number 1 and 3:
    a = 0b001
    c = 0b100
    ---------
      = 0b101 = 0x5 = 0x05
    
    The set {a,b} contains components number 1 and 2:
    a = 0b001
    b = 0b010
    ---------
      = 0b011 = 0x3 = 0x03
    
    Thus, the encoded value of {{a,c},{a,b}} is 0x00000000000000010503.
    
    Examples:
    
    >>> b = encode_sets(read_sets('{{a,c},{a,b}}')); BitStream(bytes=b).hex
    '0x00000000000000010503'
    
    >>> b = encode_sets(read_sets('{{0,2},{0,1}}')); BitStream(bytes=b).hex
    '0x00000000000000010503'
    
    Corner case: setOfSets contains just one empty set:
    >>> b = encode_sets(frozenset([frozenset([])])); BitStream(bytes=b).hex
    '0x000000000000000100'
    
    Corner case: setOfSets is empty itself:
    >>> b = encode_sets(frozenset([])); BitStream(bytes=b).hex
    '0x0000000000000001'
    """
    from bitstring.bitstream import BitStream, pack
    comp = sorted(list(set().union(*setOfSets)))
    bytesperset = max(1, int(ceil(float(len(comp)) / 8)))
    bs = BitStream()
    bs.append(pack('uint:64', bytesperset))
    for aSet in setOfSets:
        result = 0
        for element in aSet:
            result |= 2**(comp.index(element))
        bs.append(pack('uint:%d' % (bytesperset * 8), result))
    return bs.tobytes()
def encode_sets(setOfSets):
    """
    Encode a set of sets (e.g., a set of conflict sets or a set of hitting sets) in a binary format, where each 
    of the sets is represented as a word whose bits indicate which elements are part of the set. 
    The first 64bit unsigned big-endian integer indicates the number of bytes used per set. 
    
    For example, the set of sets {{a,c},{a,b}} contains three components: [a, b, c]. 
    As we only use full bytes (i.e. 8 bits, 16 bits, ...), we use 1 byte to encode each set in this example. 
    Therefore, the first 64 bit of the encoded value are 0x0000000000000001. 
    
    The set {a,c} contains components number 1 and 3:
    a = 0b001
    c = 0b100
    ---------
      = 0b101 = 0x5 = 0x05
    
    The set {a,b} contains components number 1 and 2:
    a = 0b001
    b = 0b010
    ---------
      = 0b011 = 0x3 = 0x03
    
    Thus, the encoded value of {{a,c},{a,b}} is 0x00000000000000010503.
    
    Examples:
    
    >>> b = encode_sets(read_sets('{{a,c},{a,b}}')); BitStream(bytes=b).hex
    '0x00000000000000010503'
    
    >>> b = encode_sets(read_sets('{{0,2},{0,1}}')); BitStream(bytes=b).hex
    '0x00000000000000010503'
    
    Corner case: setOfSets contains just one empty set:
    >>> b = encode_sets(frozenset([frozenset([])])); BitStream(bytes=b).hex
    '0x000000000000000100'
    
    Corner case: setOfSets is empty itself:
    >>> b = encode_sets(frozenset([])); BitStream(bytes=b).hex
    '0x0000000000000001'
    """
    from bitstring.bitstream import BitStream, pack
    comp = sorted(list(set().union(*setOfSets)))
    bytesperset = max(1,int(ceil(float(len(comp))/8)))
    bs = BitStream()
    bs.append(pack('uint:64', bytesperset))
    for aSet in setOfSets:
        result = 0
        for element in aSet:
            result |= 2**(comp.index(element))
        bs.append(pack('uint:%d' % (bytesperset*8), result))
    return bs.tobytes()