Synnefo

from bitarray import bitarray

from base64 import b64encode, b64decode

import ipaddr

AVAILABLE = True

UNAVAILABLE = False

class PoolManager(object):

    """PoolManager for DB PoolTable models.

    This class implements a persistent Pool mechanism based on rows of

    PoolTable objects. Values that are pooled by this class, are mapped to an

    index on a bitarray, which is the one that is stored on the DB.

    The object that will be used in order to initialize this pool, must have

    two string attributes (available_map and reserved_map) and the size of the

    pool.

    Subclasses of PoolManager must implement value_to_index and index_to_value

    method's in order to denote how the value will be mapped to the index in

    the bitarray.

    Important!!: Updates on a PoolManager object are not reflected to the DB,

    until save() method is called.

    """

    def __init__(self, pool_table):

        self.pool_table = pool_table

        self.pool_size = pool_table.size

        if pool_table.available_map:

            self.available = _bitarray_from_string(pool_table.available_map)

            self.reserved = _bitarray_from_string(pool_table.reserved_map)

        else:

            self.available = self._create_empty_pool(self.pool_size)

            self.reserved = self._create_empty_pool(self.pool_size)

            self.add_padding(self.pool_size)

    def _create_empty_pool(self, size):

        ba = bitarray(size)

        ba.setall(AVAILABLE)

        return ba

    def add_padding(self, pool_size):

        bits = find_padding(pool_size)

        self.available.extend([UNAVAILABLE] * bits)

        self.reserved.extend([UNAVAILABLE] * bits)

    def cut_padding(self, pool_size):

        bits = find_padding(pool_size)

        self.available = self.available[:-bits]

        self.reserved = self.reserved[:-bits]

    @property

    def pool(self):

        return (self.available & self.reserved)

    def get(self):

        """Get a value from the pool."""

        if self.empty():

            raise EmptyPool

        # Get the first available index

        index = int(self.pool.index(AVAILABLE))

        assert(index < self.pool_size)

        self._reserve(index)

        return self.index_to_value(index)

    def put(self, value, external=False):

        """Return a value to the pool."""

        if value is None:

            raise ValueError

        index = self.value_to_index(value)

        self._release(index, external)

    def reserve(self, value, external=False):

        """Reserve a value."""

        index = self.value_to_index(value)

        self._reserve(index, external)

        return True

    def save(self, db=True):

        """Save changes to the DB."""

        self.pool_table.available_map = _bitarray_to_string(self.available)

        self.pool_table.reserved_map = _bitarray_to_string(self.reserved)

        if db:

            self.pool_table.save()

    def empty(self):

        """Return True when pool is empty."""

        return not self.pool.any()

    def size(self):

        """Return the size of the bitarray(original size + padding)."""

        return self.pool.length()

    def _reserve(self, index, external=False):

        if external:

            self.reserved[index] = UNAVAILABLE

        else:

            self.available[index] = UNAVAILABLE

    def _release(self, index, external=False):

        if external:

            self.reserved[index] = AVAILABLE

        else:

            self.available[index] = AVAILABLE

    def count_available(self):

        return self.pool.count(AVAILABLE)

    def count_unavailable(self):

        return self.pool_size - self.count_available()

    def count_reserved(self):

        return self.reserved[:self.pool_size].count(UNAVAILABLE)

    def count_unreserved(self):

        return self.pool_size - self.count_reserved()

    def is_available(self, value, index=False):

        if not index:

            idx = self.value_to_index(value)

        else:

            idx = value

        return self.pool[idx] == AVAILABLE

    def is_reserved(self, value, index=False):

        if not index:

            idx = self.value_to_index(value)

        else:

            idx = value

        return self.reserved[idx] == UNAVAILABLE

    def to_01(self):

        return self.pool[:self.pool_size].to01()

    def to_map(self):

        return self.to_01().replace("0", "X").replace("1", ".")

    def extend(self, bits_num):

        assert(bits_num >= 0)

        self.resize(bits_num)

    def shrink(self, bits_num):

        assert(bits_num >= 0)

        size = self.pool_size

        tmp = self.available[(size - bits_num): size]

        if tmp.count(UNAVAILABLE):

            raise Exception("Can not shrink. In use")

        self.resize(-bits_num)

    def resize(self, bits_num):

        if bits_num == 0:

            return

        # Cut old padding

        self.cut_padding(self.pool_size)

        # Do the resize

        if bits_num > 0:

            self.available.extend([AVAILABLE] * bits_num)

            self.reserved.extend([AVAILABLE] * bits_num)

        else:

            self.available = self.available[:bits_num]

            self.reserved = self.reserved[:bits_num]

        # Add new padding

        self.pool_size = self.pool_size + bits_num

        self.add_padding(self.pool_size)

        self.pool_table.size = self.pool_size

    def index_to_value(self, index):

        raise NotImplementedError

    def value_to_index(self, value):

        raise NotImplementedError

class EmptyPool(Exception):

    pass

def find_padding(size):

    extra = size % 8

    return extra and (8 - extra) or 0

def bitarray_to_01(bitarray_):

    return bitarray_.to01()

def bitarray_to_map(bitarray_):

    return bitarray_to_01(bitarray_).replace("0", "X").replace("1", ".")

def _bitarray_from_string(bitarray_):

    ba = bitarray()

    ba.frombytes(b64decode(bitarray_))

    return ba

def _bitarray_to_string(bitarray_):

    return b64encode(bitarray_.tobytes())

##

## Custom pools

##

class BridgePool(PoolManager):

    def index_to_value(self, index):

        # Bridge indexes should start from 1

        return self.pool_table.base + str(index + 1)

    def value_to_index(self, value):

        return int(value.replace(self.pool_table.base, "")) - 1

class MacPrefixPool(PoolManager):

    def __init__(self, pool_table):

        do_init = False if pool_table.available_map else True

        super(MacPrefixPool, self).__init__(pool_table)

        if do_init:

            for i in xrange(1, self.pool_size):

                if not self.validate_mac(self.index_to_value(i)):

                    self._reserve(i, external=True)

            # Reserve the first mac-prefix for public-networks

            self._reserve(0, external=True)

    def index_to_value(self, index):

        """Convert index to mac_prefix"""

        base = self.pool_table.base

        a = hex(int(base.replace(":", ""), 16) + index).replace("0x", '')

        mac_prefix = ":".join([a[x:x + 2] for x in xrange(0, len(a), 2)])

        return mac_prefix

    def value_to_index(self, value):

        base = self.pool_table.base

        return int(value.replace(":", ""), 16) - int(base.replace(":", ""), 16)

    @staticmethod

    def validate_mac(value):

        hex_ = value.replace(":", "")

        bin_ = bin(int(hex_, 16))[2:].zfill(8)

        return bin_[6] == '1' and bin_[7] == '0'

class IPPool(PoolManager):

    def __init__(self, pool_table):

        do_init = False if pool_table.available_map else True

        network = pool_table.network

        self.net = ipaddr.IPNetwork(network.subnet)

        if not pool_table.size:

            pool_table.size = self.net.numhosts

        super(IPPool, self).__init__(pool_table)

        gateway = network.gateway

        self.gateway = gateway and ipaddr.IPAddress(gateway) or None

        if do_init:

            self._reserve(0, external=True)

            if gateway:

                self.reserve(gateway, external=True)

            self._reserve(self.pool_size - 1, external=True)

    def value_to_index(self, value):

        addr = ipaddr.IPAddress(value)

        return int(addr) - int(self.net.network)

    def index_to_value(self, index):

        return str(self.net[index])