Synnefo » snf-ganeti

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#

# Copyright (C) 2010, 2011 Google Inc.

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# 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.

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# 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.

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# 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.

"""Module for a simple query language

A query filter is always a list. The first item in the list is the operator

(e.g. C{[OP_AND, ...]}), while the other items depend on the operator. For

logic operators (e.g. L{OP_AND}, L{OP_OR}), they are subfilters whose results

are combined. Unary operators take exactly one other item (e.g. a subfilter for

L{OP_NOT} and a field name for L{OP_TRUE}). Binary operators take exactly two

operands, usually a field name and a value to compare against. Filters are

converted to callable functions by L{query._CompileFilter}.

"""

from ganeti import errors

# Logic operators with one or more operands, each of which is a filter on its

# own

OP_OR = "|"

OP_AND = "&"

# Unary operators with exactly one operand

OP_NOT = "!"

OP_TRUE = "?"

# Binary operators with exactly two operands, the field name and an

# operator-specific value

OP_EQUAL = "="

OP_NOT_EQUAL = "!="

OP_GLOB = "=*"

OP_REGEXP = "=~"

OP_CONTAINS = "=[]"

def ReadSimpleFilter(namefield, filter_):

  """Function extracting wanted names from restricted filter.

  This should only be used until proper filtering is implemented. The filter

  must either be empty or of the format C{["|", ["=", field, "name1"], ["=",

  field, "name2"], ...]}.

  """

  if filter_ is None:

    return []

  if not isinstance(filter_, list):

    raise errors.ParameterError("Filter should be list")

  if not filter_ or filter_[0] != OP_OR:

    raise errors.ParameterError("Filter should start with OR operator")

  if len(filter_) < 2:

    raise errors.ParameterError("Invalid filter, OR operator should have"

                                " operands")

  result = []

  for idx, item in enumerate(filter_[1:]):

    if not isinstance(item, list):

      raise errors.ParameterError("Invalid OR operator, operand %s not a"

                                  " list" % idx)

    if len(item) != 3 or item[0] != OP_EQUAL:

      raise errors.ParameterError("Invalid OR operator, operand %s is not an"

                                  " equality filter" % idx)

    (_, name, value) = item

    if not isinstance(value, basestring):

      raise errors.ParameterError("Operand %s for OR should compare against a"

                                  " string" % idx)

    if name != namefield:

      raise errors.ParameterError("Operand %s for OR should filter field '%s',"

                                  " not '%s'" % (idx, namefield, name))

    result.append(value)

  return result

def MakeSimpleFilter(namefield, values):

  """Builds a filter for use with L{ReadSimpleFilter}.

  @param namefield: Name of field containing item name

  @param values: List of names

  """

  if values:

    return [OP_OR] + [[OP_EQUAL, namefield, i] for i in values]

  return None