selinux-policy/refpolicy/support/pyplate.py

"""PyPlate : a simple Python-based templating program

PyPlate parses a file and replaces directives (in double square brackets [[ ... ]])
by various means using a given dictionary of variables.  Arbitrary Python code
can be run inside many of the directives, making this system highly flexible.

Usage:
# Load and parse template file
template = pyplate.Template("output") (filename or string)
# Execute it with a dictionary of variables
template.execute_file(output_stream, locals())

PyPlate defines the following directives:
  [[...]]       evaluate the arbitrary Python expression and insert the
                result into the output

  [[# ... #]]   comment.

  [[exec ...]]  execute arbitrary Python code in the sandbox namespace

  [[if ...]]    conditional expressions with usual Python semantics
  [[elif ...]]
  [[else]]
  [[end]]

  [[for ... in ...]]  for-loop with usual Python semantics
  [[end]]

  [[def ...(...)]]  define a "function" out of other templating elements
  [[end]]

  [[call ...]]  call a templating function (not a regular Python function)
"""

#
# Copyright (C) 2002 Michael Droettboom
#
# 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
#

from __future__ import nested_scopes
import sys, string, re, cStringIO

re_directive = re.compile("\[\[(.*)\]\]")
re_for_loop = re.compile("for (.*) in (.*)")
re_if = re.compile("if (.*)")
re_elif = re.compile("elif (.*)")
re_def = re.compile("def (.*?)\((.*)\)")
re_call = re.compile("call (.*?)\((.*)\)")
re_exec = re.compile("exec (.*)")
re_comment = re.compile("#(.*)#")

############################################################
# Template parser
class ParserException(Exception):
  def __init__(self, lineno, s):
    Exception.__init__(self, "line %d: %s" % (lineno, s))

class Template:
  def __init__(self, filename=None):
    if filename != None:
      try:
        self.parse_file(filename)
      except:
        self.parse_string(filename)

  def parse_file(self, filename):
    file = open(filename, 'r')
    self.parse(file)
    file.close()

  def parse_string(self, template):
    file = cStringIO.StringIO(template)
    self.parse(file)
    file.close()

  def parse(self, file):
    self.file = file
    self.line = self.file.read()
    self.lineno = 0
    self.functions = {}
    self.tree = TopLevelTemplateNode(self)

  def parser_get(self):
    if self.line == '':
      return None
    return self.line

  def parser_eat(self, chars):
    self.lineno = self.lineno + self.line[:chars].count("\n")
    self.line = self.line[chars:]

  def parser_exception(self, s):
    raise ParserException(self.lineno, s)

  def execute_file(self, filename, data):
    file = open(filename, 'w')
    self.execute(file, data)
    file.close()

  def execute_string(self, data):
    s = cStringIO.StringIO()
    self.execute(s, data)
    return s.getvalue()

  def execute_stdout(self, data):
    self.execute(sys.stdout, data)

  def execute(self, stream=sys.stdout, data={}):
    self.tree.execute(stream, data)

  def __repr__(self):
    return repr(self.tree)


############################################################
# NODES
class TemplateNode:
  def __init__(self, parent, s):
    self.parent = parent
    self.s = s
    self.node_list = []
    while 1:
      new_node = TemplateNodeFactory(parent)
      if self.add_node(new_node):
        break

  def add_node(self, node):
    if node == 'end':
      return 1
    elif node != None:
      self.node_list.append(node)
    else:
      raise self.parent.parser_exception(
        "[[%s]] does not have a matching [[end]]" % self.s)

  def execute(self, stream, data):
    for node in self.node_list:
      node.execute(stream, data)

  def __repr__(self):
    r = "<" + self.__class__.__name__ + " "
    for i in self.node_list:
      r = r + repr(i)
    r = r + ">"
    return r

class TopLevelTemplateNode(TemplateNode):
  def __init__(self, parent):
    TemplateNode.__init__(self, parent, '')

  def add_node(self, node):
    if node != None:
      self.node_list.append(node)
    else:
      return 1

class ForTemplateNode(TemplateNode):
  def __init__(self, parent, s):
    TemplateNode.__init__(self, parent, s)
    match = re_for_loop.match(s)
    if match == None:
      raise self.parent.parser_exception(
        "[[%s]] is not a valid for-loop expression" % self.s)
    else:
      self.vars_temp = match.group(1).split(",")
      self.vars = []
      for v in self.vars_temp:
        self.vars.append(v.strip())
      #print self.vars
      self.expression = match.group(2)

  def execute(self, stream, data):
    remember_vars = {}
    for var in self.vars:
      if data.has_key(var):
        remember_vars[var] = data[var]
    for list in eval(self.expression, globals(), data):
      if is_sequence(list):
        for index, value in enumerate(list):
          data[self.vars[index]] = value
      else:
        data[self.vars[0]] = list
      TemplateNode.execute(self, stream, data)
    for key, value in remember_vars.items():
      data[key] = value

class IfTemplateNode(TemplateNode):
  def __init__(self, parent, s):
    self.else_node = None
    TemplateNode.__init__(self, parent, s)
    match = re_if.match(s)
    if match == None:
      raise self.parent.parser_exception(
        "[[%s]] is not a valid if expression" % self.s)
    else:
      self.expression = match.group(1)

  def add_node(self, node):
    if node == 'end':
      return 1
    elif isinstance(node, ElseTemplateNode):
      self.else_node = node
      return 1
    elif isinstance(node, ElifTemplateNode):
      self.else_node = node
      return 1
    elif node != None:
      self.node_list.append(node)
    else:
      raise self.parent.parser_exception(
        "[[%s]] does not have a matching [[end]]" % self.s)

  def execute(self, stream, data):
    if eval(self.expression, globals(), data):
      TemplateNode.execute(self, stream, data)
    elif self.else_node != None:
      self.else_node.execute(stream, data)

class ElifTemplateNode(IfTemplateNode):
  def __init__(self, parent, s):
    self.else_node = None
    TemplateNode.__init__(self, parent, s)
    match = re_elif.match(s)
    if match == None:
      self.parent.parser_exception(
        "[[%s]] is not a valid elif expression" % self.s)
    else:
      self.expression = match.group(1)

class ElseTemplateNode(TemplateNode):
  pass

class FunctionTemplateNode(TemplateNode):
  def __init__(self, parent, s):
    TemplateNode.__init__(self, parent, s)
    match = re_def.match(s)
    if match == None:
      self.parent.parser_exception(
        "[[%s]] is not a valid function definition" % self.s)
    self.function_name = match.group(1)
    self.vars_temp = match.group(2).split(",")
    self.vars = []
    for v in self.vars_temp:
      self.vars.append(v.strip())
    #print self.vars
    self.parent.functions[self.function_name] = self

  def execute(self, stream, data):
    pass

  def call(self, args, stream, data):
    remember_vars = {}
    for index, var in enumerate(self.vars):
      if data.has_key(var):
        remember_vars[var] = data[var]
      data[var] = args[index]
    TemplateNode.execute(self, stream, data)
    for key, value in remember_vars.items():
      data[key] = value
      
class LeafTemplateNode(TemplateNode):
  def __init__(self, parent, s):
    self.parent = parent
    self.s = s

  def execute(self, stream, data):
    stream.write(self.s)

  def __repr__(self):
    return "<" + self.__class__.__name__ + ">"

class CommentTemplateNode(LeafTemplateNode):
  def execute(self, stream, data):
    pass

class ExpressionTemplateNode(LeafTemplateNode):
  def execute(self, stream, data):
    stream.write(str(eval(self.s, globals(), data)))

class ExecTemplateNode(LeafTemplateNode):
  def __init__(self, parent, s):
    LeafTemplateNode.__init__(self, parent, s)
    match = re_exec.match(s)
    if match == None:
      self.parent.parser_exception(
        "[[%s]] is not a valid statement" % self.s)
    self.s = match.group(1)

  def execute(self, stream, data):
    exec(self.s, globals(), data)
    pass
    
class CallTemplateNode(LeafTemplateNode):
  def __init__(self, parent, s):
    LeafTemplateNode.__init__(self, parent, s)
    match = re_call.match(s)
    if match == None:
      self.parent.parser_exception(
        "[[%s]] is not a valid function call" % self.s)
    self.function_name = match.group(1)
    self.vars = "(" + match.group(2).strip() + ",)"
  
  def execute(self, stream, data):
    self.parent.functions[self.function_name].call(
      eval(self.vars, globals(), data), stream, data)


############################################################
# Node factory
template_factory_type_map = {
  'if'   : IfTemplateNode,
  'for'  : ForTemplateNode,
  'elif' : ElifTemplateNode,
  'else' : ElseTemplateNode,
  'def'  : FunctionTemplateNode,
  'call' : CallTemplateNode,
  'exec' : ExecTemplateNode }
template_factory_types = template_factory_type_map.keys()

def TemplateNodeFactory(parent):
  src = parent.parser_get()

  if src == None:
    return None
  match = re_directive.search(src)
  if match == None:
    parent.parser_eat(len(src))
    return LeafTemplateNode(parent, src)
  elif src == '' or match.start() != 0:
    parent.parser_eat(match.start())
    return LeafTemplateNode(parent, src[:match.start()])
  else:
    directive = match.group()[2:-2].strip()
    parent.parser_eat(match.end())
    if directive == 'end':
      return 'end'
    elif re_comment.match(directive):
      return CommentTemplateNode(parent, directive)
    else:
      for i in template_factory_types:
        if directive[0:len(i)] == i:
          return template_factory_type_map[i](parent, directive)
      return ExpressionTemplateNode(parent, directive)

def is_sequence(object):
  try:
    test = object[0:0]
  except:
    return False
  else:
    return True