Synnefo » snf-ganeti

#

#

# Copyright (C) 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.

"""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}.

"""

import re

import pyparsing as pyp

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_REGEXP = "=~"

OP_CONTAINS = "=[]"

def MakeSimpleFilter(namefield, values):

  """Builds simple a filter.

  @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

def _ConvertLogicOp(op):

  """Creates parsing action function for logic operator.

  @type op: string

  @param op: Operator for data structure, e.g. L{OP_AND}

  """

  def fn(toks):

    """Converts parser tokens to query operator structure.

    @rtype: list

    @return: Query operator structure, e.g. C{[OP_AND, ["=", "foo", "bar"]]}

    """

    operands = toks[0]

    if len(operands) == 1:

      return operands[0]

    # Build query operator structure

    return [[op] + operands.asList()]

  return fn

_KNOWN_REGEXP_DELIM = "/#^|"

_KNOWN_REGEXP_FLAGS = frozenset("si")

def _ConvertRegexpValue(_, loc, toks):

  """Regular expression value for condition.

  """

  (regexp, flags) = toks[0]

  # Ensure only whitelisted flags are used

  unknown_flags = (frozenset(flags) - _KNOWN_REGEXP_FLAGS)

  if unknown_flags:

    raise pyp.ParseFatalException("Unknown regular expression flags: '%s'" %

                                  "".join(unknown_flags), loc)

  if flags:

    re_flags = "(?%s)" % "".join(sorted(flags))

  else:

    re_flags = ""

  re_cond = re_flags + regexp

  # Test if valid

  try:

    re.compile(re_cond)

  except re.error, err:

    raise pyp.ParseFatalException("Invalid regular expression (%s)" % err, loc)

  return [re_cond]

def BuildFilterParser():

  """Builds a parser for query filter strings.

  @rtype: pyparsing.ParserElement

  """

  field_name = pyp.Word(pyp.alphas, pyp.alphanums + "_/.")

  # Integer

  num_sign = pyp.Word("-+", exact=1)

  number = pyp.Combine(pyp.Optional(num_sign) + pyp.Word(pyp.nums))

  number.setParseAction(lambda toks: int(toks[0]))

  # Right-hand-side value

  rval = (number | pyp.quotedString.setParseAction(pyp.removeQuotes))

  # Boolean condition

  bool_cond = field_name.copy()

  bool_cond.setParseAction(lambda (fname, ): [[OP_TRUE, fname]])

  # Simple binary conditions

  binopstbl = {

    "==": OP_EQUAL,

    "!=": OP_NOT_EQUAL,

    }

  binary_cond = (field_name + pyp.oneOf(binopstbl.keys()) + rval)

  binary_cond.setParseAction(lambda (lhs, op, rhs): [[binopstbl[op], lhs, rhs]])

  # "in" condition

  in_cond = (rval + pyp.Suppress("in") + field_name)

  in_cond.setParseAction(lambda (value, field): [[OP_CONTAINS, field, value]])

  # "not in" condition

  not_in_cond = (rval + pyp.Suppress("not") + pyp.Suppress("in") + field_name)

  not_in_cond.setParseAction(lambda (value, field): [[OP_NOT, [OP_CONTAINS,

                                                               field, value]]])

  # Regular expression, e.g. m/foobar/i

  regexp_val = pyp.Group(pyp.Optional("m").suppress() +

                         pyp.MatchFirst([pyp.QuotedString(i, escChar="\\")

                                         for i in _KNOWN_REGEXP_DELIM]) +

                         pyp.Optional(pyp.Word(pyp.alphas), default=""))

  regexp_val.setParseAction(_ConvertRegexpValue)

  regexp_cond = (field_name + pyp.Suppress("=~") + regexp_val)

  regexp_cond.setParseAction(lambda (field, value): [[OP_REGEXP, field, value]])

  not_regexp_cond = (field_name + pyp.Suppress("!~") + regexp_val)

  not_regexp_cond.setParseAction(lambda (field, value):

                                 [[OP_NOT, [OP_REGEXP, field, value]]])

  # All possible conditions

  condition = (binary_cond ^ bool_cond ^

               in_cond ^ not_in_cond ^

               regexp_cond ^ not_regexp_cond)

  # Associativity operators

  filter_expr = pyp.operatorPrecedence(condition, [

    (pyp.Keyword("not").suppress(), 1, pyp.opAssoc.RIGHT,

     lambda toks: [[OP_NOT, toks[0][0]]]),

    (pyp.Keyword("and").suppress(), 2, pyp.opAssoc.LEFT,

     _ConvertLogicOp(OP_AND)),

    (pyp.Keyword("or").suppress(), 2, pyp.opAssoc.LEFT,

     _ConvertLogicOp(OP_OR)),

    ])

  parser = pyp.StringStart() + filter_expr + pyp.StringEnd()

  parser.parseWithTabs()

  # Originally C{parser.validate} was called here, but there seems to be some

  # issue causing it to fail whenever the "not" operator is included above.

  return parser

def ParseFilter(text, parser=None):

  """Parses a query filter.

  @type text: string

  @param text: Query filter

  @type parser: pyparsing.ParserElement

  @param parser: Pyparsing object

  @rtype: list

  """

  if parser is None:

    parser = BuildFilterParser()

  try:

    return parser.parseString(text)[0]

  except pyp.ParseBaseException, err:

    raise errors.QueryFilterParseError("Failed to parse query filter"

                                       " '%s': %s" % (text, err), err)