Synnefo » snf-ganeti

#

#

# Copyright (C) 2006, 2007, 2010, 2011 Google Inc.

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful, but

# WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

# General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Utility functions with algorithms.

"""

import re

import time

import itertools

from ganeti import compat

from ganeti.utils import text

_SORTER_GROUPS = 8

_SORTER_RE = re.compile("^%s(.*)$" % (_SORTER_GROUPS * "(\D+|\d+)?"))

def UniqueSequence(seq):

  """Returns a list with unique elements.

  Element order is preserved.

  @type seq: sequence

  @param seq: the sequence with the source elements

  @rtype: list

  @return: list of unique elements from seq

  """

  seen = set()

  return [i for i in seq if i not in seen and not seen.add(i)]

def JoinDisjointDicts(dict_a, dict_b):

  """Joins dictionaries with no conflicting keys.

  Enforces the constraint that the two key sets must be disjoint, and then

  merges the two dictionaries in a new dictionary that is returned to the

  caller.

  @type dict_a: dict

  @param dict_a: the first dictionary

  @type dict_b: dict

  @param dict_b: the second dictionary

  @rtype: dict

  @return: a new dictionary containing all the key/value pairs contained in the

  two dictionaries.

  """

  assert not (set(dict_a) & set(dict_b)), ("Duplicate keys found while joining"

                                           " %s and %s" % (dict_a, dict_b))

  result = dict_a.copy()

  result.update(dict_b)

  return result

def FindDuplicates(seq):

  """Identifies duplicates in a list.

  Does not preserve element order.

  @type seq: sequence

  @param seq: Sequence with source elements

  @rtype: list

  @return: List of duplicate elements from seq

  """

  dup = set()

  seen = set()

  for item in seq:

    if item in seen:

      dup.add(item)

    else:

      seen.add(item)

  return list(dup)

def _NiceSortTryInt(val):

  """Attempts to convert a string to an integer.

  """

  if val and val.isdigit():

    return int(val)

  else:

    return val

def NiceSortKey(value):

  """Extract key for sorting.

  """

  return [_NiceSortTryInt(grp)

          for grp in _SORTER_RE.match(value).groups()]

def NiceSort(values, key=None):

  """Sort a list of strings based on digit and non-digit groupings.

  Given a list of names C{['a1', 'a10', 'a11', 'a2']} this function

  will sort the list in the logical order C{['a1', 'a2', 'a10',

  'a11']}.

  The sort algorithm breaks each name in groups of either only-digits

  or no-digits. Only the first eight such groups are considered, and

  after that we just use what's left of the string.

  @type values: list

  @param values: the names to be sorted

  @type key: callable or None

  @param key: function of one argument to extract a comparison key from each

    list element, must return string

  @rtype: list

  @return: a copy of the name list sorted with our algorithm

  """

  if key is None:

    keyfunc = NiceSortKey

  else:

    keyfunc = lambda value: NiceSortKey(key(value))

  return sorted(values, key=keyfunc)

def InvertDict(dict_in):

  """Inverts the key/value mapping of a dict.

  @param dict_in: The dict to invert

  @return: the inverted dict

  """

  return dict(zip(dict_in.values(), dict_in.keys()))

def InsertAtPos(src, pos, other):

  """Inserts C{other} at given C{pos} into C{src}.

  @note: This function does not modify C{src} in place but returns a new copy

  @type src: list

  @param src: The source list in which we want insert elements

  @type pos: int

  @param pos: The position where we want to start insert C{other}

  @type other: list

  @param other: The other list to insert into C{src}

  @return: A copy of C{src} with C{other} inserted at C{pos}

  """

  new = src[:pos]

  new.extend(other)

  new.extend(src[pos:])

  return new

def SequenceToDict(seq, key=compat.fst):

  """Converts a sequence to a dictionary with duplicate detection.

  @type seq: sequen

  @param seq: Input sequence

  @type key: callable

  @param key: Function for retrieving dictionary key from sequence element

  @rtype: dict

  """

  keys = map(key, seq)

  duplicates = FindDuplicates(keys)

  if duplicates:

    raise ValueError("Duplicate keys found: %s" % text.CommaJoin(duplicates))

  assert len(keys) == len(seq)

  return dict(zip(keys, seq))

def _MakeFlatToDict(data):

  """Helper function for C{FlatToDict}.

  This function is recursively called

  @param data: The input data as described in C{FlatToDict}, already splitted

  @returns: The so far converted dict

  """

  if not compat.fst(compat.fst(data)):

    assert len(data) == 1, \

      "not bottom most element, found %d elements, expected 1" % len(data)

    return compat.snd(compat.fst(data))

  keyfn = lambda e: compat.fst(e).pop(0)

  return dict([(k, _MakeFlatToDict(list(g)))

               for (k, g) in itertools.groupby(sorted(data), keyfn)])

def FlatToDict(data, field_sep="/"):

  """Converts a flat structure to a fully fledged dict.

  It accept a list of tuples in the form::

    [

      ("foo/bar", {"key1": "data1", "key2": "data2"}),

      ("foo/baz", {"key3" :"data3" }),

    ]

  where the first element is the key separated by C{field_sep}.

  This would then return::

    {

      "foo": {

        "bar": {"key1": "data1", "key2": "data2"},

        "baz": {"key3" :"data3" },

        },

    }

  @type data: list of tuple

  @param data: Input list to convert

  @type field_sep: str

  @param field_sep: The separator for the first field of the tuple

  @returns: A dict based on the input list

  """

  return _MakeFlatToDict([(keys.split(field_sep), value)

                          for (keys, value) in data])

class RunningTimeout(object):

  """Class to calculate remaining timeout when doing several operations.

  """

  __slots__ = [

    "_allow_negative",

    "_start_time",

    "_time_fn",

    "_timeout",

    ]

  def __init__(self, timeout, allow_negative, _time_fn=time.time):

    """Initializes this class.

    @type timeout: float

    @param timeout: Timeout duration

    @type allow_negative: bool

    @param allow_negative: Whether to return values below zero

    @param _time_fn: Time function for unittests

    """

    object.__init__(self)

    if timeout is not None and timeout < 0.0:

      raise ValueError("Timeout must not be negative")

    self._timeout = timeout

    self._allow_negative = allow_negative

    self._time_fn = _time_fn

    self._start_time = None

  def Remaining(self):

    """Returns the remaining timeout.

    """

    if self._timeout is None:

      return None

    # Get start time on first calculation

    if self._start_time is None:

      self._start_time = self._time_fn()

    # Calculate remaining time

    remaining_timeout = self._start_time + self._timeout - self._time_fn()

    if not self._allow_negative:

      # Ensure timeout is always >= 0

      return max(0.0, remaining_timeout)

    return remaining_timeout