plc_config.py

   1 #!/usr/bin/python
   2 #
   3 # Merge PlanetLab Central (PLC) configuration files into a variety of
   4 # output formats. These files represent the global configuration for a
   5 # PLC installation.
   6 #
   7 # Mark Huang <mlhuang@cs.princeton.edu>
   8 # Copyright (C) 2006 The Trustees of Princeton University
   9 #
  10 # $Id$
  11 #
  12
  13 import xml.dom.minidom
  14 from StringIO import StringIO
  15 import time
  16 import re
  17 import textwrap
  18 import codecs
  19 import os
  20 import types
  21
  22
  23 class ConfigurationException(Exception): pass
  24
  25 class PLCConfiguration:
  26     """
  27     Configuration file store. Optionally instantiate with a file path
  28     or object:
  29
  30     plc = PLCConfiguration()
  31     plc = PLCConfiguration(fileobj)
  32     plc = PLCConfiguration("/etc/planetlab/plc_config.xml")
  33
  34     You may load() additional files later, which will be merged into
  35     the current configuration:
  36
  37     plc.load("/etc/planetlab/local.xml")
  38
  39     You may also save() the configuration. If a file path or object is
  40     not specified, the configuration will be written to the file path
  41     or object that was first loaded.
  42
  43     plc.save()
  44     plc.save("/etc/planetlab/plc_config.xml")
  45     """
  46
  47     def __init__(self, file = None):
  48         impl = xml.dom.minidom.getDOMImplementation()
  49         self._dom = impl.createDocument(None, "configuration", None)
  50         self._variables = {}
  51         self._packages = {}
  52         self._files = []
  53
  54         if file is not None:
  55             self.load(file)
  56
  57
  58     def _get_text(self, node):
  59         """
  60         Get the text of a text node.
  61         """
  62
  63         if node.firstChild and \
  64            node.firstChild.nodeType == node.TEXT_NODE:
  65             if node.firstChild.data is None:
  66                 # Interpret simple presence of node as "", not NULL
  67                 return ""
  68             else:
  69                 return node.firstChild.data
  70
  71         return None
  72
  73
  74     def _get_text_of_child(self, parent, name):
  75         """
  76         Get the text of a (direct) child text node.
  77         """
  78
  79         for node in parent.childNodes:
  80             if node.nodeType == node.ELEMENT_NODE and \
  81                node.tagName == name:
  82                 return self._get_text(node)
  83
  84         return None
  85
  86
  87     def _set_text(self, node, data):
  88         """
  89         Set the text of a text node.
  90         """
  91
  92         if node.firstChild and \
  93            node.firstChild.nodeType == node.TEXT_NODE:
  94             if data is None:
  95                 node.removeChild(node.firstChild)
  96             else:
  97                 node.firstChild.data = data
  98         elif data is not None:
  99             text = TrimText()
 100             text.data = data
 101             node.appendChild(text)
 102
 103
 104     def _set_text_of_child(self, parent, name, data):
 105         """
 106         Set the text of a (direct) child text node.
 107         """
 108
 109         for node in parent.childNodes:
 110             if node.nodeType == node.ELEMENT_NODE and \
 111                node.tagName == name:
 112                 self._set_text(node, data)
 113                 return
 114
 115         child = TrimTextElement(name)
 116         self._set_text(child, data)
 117         parent.appendChild(child)
 118
 119
 120     def _category_element_to_dict(self, category_element):
 121         """
 122         Turn a <category> element into a dictionary of its attributes
 123         and child text nodes.
 124         """
 125
 126         category = {}
 127         category['id'] = category_element.getAttribute('id').lower()
 128         for node in category_element.childNodes:
 129             if node.nodeType == node.ELEMENT_NODE and \
 130                node.tagName in ['name', 'description']:
 131                 category[node.tagName] = self._get_text_of_child(category_element, node.tagName)
 132         category['element'] = category_element
 133
 134         return category
 135
 136
 137     def _variable_element_to_dict(self, variable_element):
 138         """
 139         Turn a <variable> element into a dictionary of its attributes
 140         and child text nodes.
 141         """
 142
 143         variable = {}
 144         variable['id'] = variable_element.getAttribute('id').lower()
 145         if variable_element.hasAttribute('type'):
 146             variable['type'] = variable_element.getAttribute('type')
 147         for node in variable_element.childNodes:
 148             if node.nodeType == node.ELEMENT_NODE and \
 149                node.tagName in ['name', 'value', 'description']:
 150                 variable[node.tagName] = self._get_text_of_child(variable_element, node.tagName)
 151         variable['element'] = variable_element
 152
 153         return variable
 154
 155
 156     def _group_element_to_dict(self, group_element):
 157         """
 158         Turn a <group> element into a dictionary of its attributes
 159         and child text nodes.
 160         """
 161
 162         group = {}
 163         for node in group_element.childNodes:
 164             if node.nodeType == node.ELEMENT_NODE and \
 165                node.tagName in ['id', 'name', 'default', 'description', 'uservisible']:
 166                 group[node.tagName] = self._get_text_of_child(group_element, node.tagName)
 167         group['element'] = group_element
 168
 169         return group
 170
 171
 172     def _packagereq_element_to_dict(self, packagereq_element):
 173         """
 174         Turns a <packagereq> element into a dictionary of its attributes
 175         and child text nodes.
 176         """
 177
 178         package = {}
 179         if packagereq_element.hasAttribute('type'):
 180             package['type'] = packagereq_element.getAttribute('type')
 181         package['name'] = self._get_text(packagereq_element)
 182         package['element'] = packagereq_element
 183
 184         return package
 185
 186
 187     def load(self, file = "/etc/planetlab/plc_config.xml"):
 188         """
 189         Merge file into configuration store.
 190         """
 191
 192         dom = xml.dom.minidom.parse(file)
 193         if type(file) in types.StringTypes:
 194             self._files.append(os.path.abspath(file))
 195
 196         # Parse <variables> section
 197         for variables_element in dom.getElementsByTagName('variables'):
 198             for category_element in variables_element.getElementsByTagName('category'):
 199                 category = self._category_element_to_dict(category_element)
 200                 self.set(category, None)
 201
 202                 for variablelist_element in category_element.getElementsByTagName('variablelist'):
 203                     for variable_element in variablelist_element.getElementsByTagName('variable'):
 204                         variable = self._variable_element_to_dict(variable_element)
 205                         self.set(category, variable)
 206
 207         # Parse <comps> section
 208         for comps_element in dom.getElementsByTagName('comps'):
 209             for group_element in comps_element.getElementsByTagName('group'):
 210                 group = self._group_element_to_dict(group_element)
 211                 self.add_package(group, None)
 212
 213                 for packagereq_element in group_element.getElementsByTagName('packagereq'):
 214                     package = self._packagereq_element_to_dict(packagereq_element)
 215                     self.add_package(group, package)
 216
 217
 218     def save(self, file = None):
 219         """
 220         Write configuration store to file.
 221         """
 222
 223         if file is None:
 224             if self._files:
 225                 file = self._files[0]
 226             else:
 227                 file = "/etc/planetlab/plc_config.xml"
 228
 229         if type(file) in types.StringTypes:
 230             fileobj = open(file, 'w')
 231         else:
 232             fileobj = file
 233
 234         fileobj.seek(0)
 235         fileobj.write(self.output_xml())
 236         fileobj.truncate()
 237
 238         fileobj.close()
 239
 240     def verify(self, default, read):
 241         """ Confirm that the existing configuration is consistent according to
 242         the checks below.
 243
 244             It looks for filled-in values in the order of, local object (self),
 245             followed by cread (read values), and finally default values.
 246
 247         Arguments:
 248
 249             None
 250
 251         Returns:
 252
 253             None.  If an exception is found, ConfigurationException is raised.
 254
 255         """
 256
 257         maint_user = self.get('plc_api', 'maintenance_user')
 258         if maint_user == (None, None):
 259             maint_user = read.get('plc_api', 'maintenance_user')
 260             if maint_user == (None, None):
 261                 maint_user = default.get('plc_api', 'maintenance_user')
 262
 263         root_user = self.get('plc', 'root_user')
 264         if root_user == (None, None):
 265             root_user = read.get('plc', 'root_user')
 266             if root_user == (None, None):
 267                 root_user = default.get('plc', 'root_user')
 268
 269         muser= maint_user[1]['value']
 270         ruser= root_user[1]['value']
 271
 272         if muser == ruser:
 273             raise ConfigurationException("The Maintenance Account email address cannot be the same as the Root User email address")
 274         return
 275
 276
 277     def get(self, category_id, variable_id):
 278         """
 279         Get the specified variable in the specified category.
 280
 281         Arguments:
 282
 283         category_id = unique category identifier (e.g., 'plc_www')
 284         variable_id = unique variable identifier (e.g., 'port')
 285
 286         Returns:
 287
 288         variable = { 'id': "variable_identifier",
 289                      'type': "variable_type",
 290                      'value': "variable_value",
 291                      'name': "Variable name",
 292                      'description': "Variable description" }
 293         """
 294
 295         if self._variables.has_key(category_id.lower()):
 296             (category, variables) = self._variables[category_id]
 297             if variables.has_key(variable_id.lower()):
 298                 variable = variables[variable_id]
 299             else:
 300                 variable = None
 301         else:
 302             category = None
 303             variable = None
 304
 305         return (category, variable)
 306
 307
 308     def delete(self, category_id, variable_id):
 309         """
 310         Delete the specified variable from the specified category. If
 311         variable_id is None, deletes all variables from the specified
 312         category as well as the category itself.
 313
 314         Arguments:
 315
 316         category_id = unique category identifier (e.g., 'plc_www')
 317         variable_id = unique variable identifier (e.g., 'port')
 318         """
 319
 320         if self._variables.has_key(category_id.lower()):
 321             (category, variables) = self._variables[category_id]
 322             if variable_id is None:
 323                 category['element'].parentNode.removeChild(category['element'])
 324                 del self._variables[category_id]
 325             elif variables.has_key(variable_id.lower()):
 326                 variable = variables[variable_id]
 327                 variable['element'].parentNode.removeChild(variable['element'])
 328                 del variables[variable_id]
 329
 330
 331     def set(self, category, variable):
 332         """
 333         Add and/or update the specified variable. The 'id' fields are
 334         mandatory. If a field is not specified and the category and/or
 335         variable already exists, the field will not be updated. If
 336         'variable' is None, only adds and/or updates the specified
 337         category.
 338
 339         Arguments:
 340
 341         category = { 'id': "category_identifier",
 342                      'name': "Category name",
 343                      'description': "Category description" }
 344
 345         variable = { 'id': "variable_identifier",
 346                      'type': "variable_type",
 347                      'value': "variable_value",
 348                      'name': "Variable name",
 349                      'description': "Variable description" }
 350         """
 351
 352         if not category.has_key('id') or type(category['id']) not in types.StringTypes:
 353             return
 354
 355         category_id = category['id'].lower()
 356
 357         if self._variables.has_key(category_id):
 358             # Existing category
 359             (old_category, variables) = self._variables[category_id]
 360
 361             # Merge category attributes
 362             for tag in ['name', 'description']:
 363                 if category.has_key(tag):
 364                     old_category[tag] = category[tag]
 365                     self._set_text_of_child(old_category['element'], tag, category[tag])
 366
 367             category_element = old_category['element']
 368         else:
 369             # Merge into DOM
 370             category_element = self._dom.createElement('category')
 371             category_element.setAttribute('id', category_id)
 372             for tag in ['name', 'description']:
 373                 if category.has_key(tag):
 374                     self._set_text_of_child(category_element, tag, category[tag])
 375
 376             if self._dom.documentElement.getElementsByTagName('variables'):
 377                 variables_element = self._dom.documentElement.getElementsByTagName('variables')[0]
 378             else:
 379                 variables_element = self._dom.createElement('variables')
 380                 self._dom.documentElement.appendChild(variables_element)
 381             variables_element.appendChild(category_element)
 382
 383             # Cache it
 384             category['element'] = category_element
 385             variables = {}
 386             self._variables[category_id] = (category, variables)
 387
 388         if variable is None or not variable.has_key('id') or type(variable['id']) not in types.StringTypes:
 389             return
 390
 391         variable_id = variable['id'].lower()
 392
 393         if variables.has_key(variable_id):
 394             # Existing variable
 395             old_variable = variables[variable_id]
 396
 397             # Merge variable attributes
 398             for attribute in ['type']:
 399                 if variable.has_key(attribute):
 400                     old_variable[attribute] = variable[attribute]
 401                     old_variable['element'].setAttribute(attribute, variable[attribute])
 402             for tag in ['name', 'value', 'description']:
 403                 if variable.has_key(tag):
 404                     old_variable[tag] = variable[tag]
 405                     self._set_text_of_child(old_variable['element'], tag, variable[tag])
 406         else:
 407             # Merge into DOM
 408             variable_element = self._dom.createElement('variable')
 409             variable_element.setAttribute('id', variable_id)
 410             for attribute in ['type']:
 411                 if variable.has_key(attribute):
 412                     variable_element.setAttribute(attribute, variable[attribute])
 413             for tag in ['name', 'value', 'description']:
 414                 if variable.has_key(tag):
 415                     self._set_text_of_child(variable_element, tag, variable[tag])
 416
 417             if category_element.getElementsByTagName('variablelist'):
 418                 variablelist_element = category_element.getElementsByTagName('variablelist')[0]
 419             else:
 420                 variablelist_element = self._dom.createElement('variablelist')
 421                 category_element.appendChild(variablelist_element)
 422             variablelist_element.appendChild(variable_element)
 423
 424             # Cache it
 425             variable['element'] = variable_element
 426             variables[variable_id] = variable
 427
 428
 429     def locate_varname (self, varname):
 430         """
 431         Locates category and variable from a variable's (shell) name
 432
 433         Returns:
 434         (variable, category) when found
 435         (None, None) otherwise
 436         """
 437
 438         for (category_id, (category, variables)) in self._variables.iteritems():
 439             for variable in variables.values():
 440                 (id, name, value, comments) = self._sanitize_variable(category_id, variable)
 441                 if (id == varname):
 442                     return (category,variable)
 443         return (None,None)
 444
 445     def get_package(self, group_id, package_name):
 446         """
 447         Get the specified package in the specified package group.
 448
 449         Arguments:
 450
 451         group_id - unique group id (e.g., 'plc')
 452         package_name - unique package name (e.g., 'postgresql')
 453
 454         Returns:
 455
 456         package = { 'name': "package_name",
 457                     'type': "mandatory|optional" }
 458         """
 459
 460         if self._packages.has_key(group_id.lower()):
 461             (group, packages) = self._packages[group_id]
 462             if packages.has_key(package_name):
 463                 package = packages[package_name]
 464             else:
 465                 package = None
 466         else:
 467             group = None
 468             package = None
 469
 470         return (group, package)
 471
 472
 473     def delete_package(self, group_id, package_name):
 474         """
 475         Deletes the specified variable from the specified category. If
 476         variable_id is None, deletes all variables from the specified
 477         category as well as the category itself.
 478
 479         Arguments:
 480
 481         group_id - unique group id (e.g., 'plc')
 482         package_name - unique package name (e.g., 'postgresql')
 483         """
 484
 485         if self._packages.has_key(group_id):
 486             (group, packages) = self._packages[group_id]
 487             if package_name is None:
 488                 group['element'].parentNode.removeChild(group['element'])
 489                 del self._packages[group_id]
 490             elif packages.has_key(package_name.lower()):
 491                 package = packages[package_name]
 492                 package['element'].parentNode.removeChild(package['element'])
 493                 del packages[package_name]
 494
 495
 496     def add_package(self, group, package):
 497         """
 498         Add and/or update the specified package. The 'id' and 'name'
 499         fields are mandatory. If a field is not specified and the
 500         package or group already exists, the field will not be
 501         updated. If package is None, only adds/or updates the
 502         specified group.
 503
 504         Arguments:
 505
 506         group = { 'id': "group_identifier",
 507                   'name': "Group name",
 508                   'default': "true|false",
 509                   'description': "Group description",
 510                   'uservisible': "true|false" }
 511
 512         package = { 'name': "package_name",
 513                     'type': "mandatory|optional" }
 514         """
 515
 516         if not group.has_key('id'):
 517             return
 518
 519         group_id = group['id']
 520
 521         if self._packages.has_key(group_id):
 522             # Existing group
 523             (old_group, packages) = self._packages[group_id]
 524
 525             # Merge group attributes
 526             for tag in ['id', 'name', 'default', 'description', 'uservisible']:
 527                 if group.has_key(tag):
 528                     old_group[tag] = group[tag]
 529                     self._set_text_of_child(old_group['element'], tag, group[tag])
 530
 531             group_element = old_group['element']
 532         else:
 533             # Merge into DOM
 534             group_element = self._dom.createElement('group')
 535             for tag in ['id', 'name', 'default', 'description', 'uservisible']:
 536                 if group.has_key(tag):
 537                     self._set_text_of_child(group_element, tag, group[tag])
 538
 539             if self._dom.documentElement.getElementsByTagName('comps'):
 540                 comps_element = self._dom.documentElement.getElementsByTagName('comps')[0]
 541             else:
 542                 comps_element = self._dom.createElement('comps')
 543                 self._dom.documentElement.appendChild(comps_element)
 544             comps_element.appendChild(group_element)
 545
 546             # Cache it
 547             group['element'] = group_element
 548             packages = {}
 549             self._packages[group_id] = (group, packages)
 550
 551         if package is None or not package.has_key('name'):
 552             return
 553
 554         package_name = package['name']
 555         if packages.has_key(package_name):
 556             # Existing package
 557             old_package = packages[package_name]
 558
 559             # Merge variable attributes
 560             for attribute in ['type']:
 561                 if package.has_key(attribute):
 562                     old_package[attribute] = package[attribute]
 563                     old_package['element'].setAttribute(attribute, package[attribute])
 564         else:
 565             # Merge into DOM
 566             packagereq_element = TrimTextElement('packagereq')
 567             self._set_text(packagereq_element, package_name)
 568             for attribute in ['type']:
 569                 if package.has_key(attribute):
 570                     packagereq_element.setAttribute(attribute, package[attribute])
 571
 572             if group_element.getElementsByTagName('packagelist'):
 573                 packagelist_element = group_element.getElementsByTagName('packagelist')[0]
 574             else:
 575                 packagelist_element = self._dom.createElement('packagelist')
 576                 group_element.appendChild(packagelist_element)
 577             packagelist_element.appendChild(packagereq_element)
 578
 579             # Cache it
 580             package['element'] = packagereq_element
 581             packages[package_name] = package
 582
 583
 584     def variables(self):
 585         """
 586         Return all variables.
 587
 588         Returns:
 589
 590         variables = { 'category_id': (category, variablelist) }
 591
 592         category = { 'id': "category_identifier",
 593                      'name': "Category name",
 594                      'description': "Category description" }
 595
 596         variablelist = { 'variable_id': variable }
 597
 598         variable = { 'id': "variable_identifier",
 599                      'type': "variable_type",
 600                      'value': "variable_value",
 601                      'name': "Variable name",
 602                      'description': "Variable description" }
 603         """
 604
 605         return self._variables
 606
 607
 608     def packages(self):
 609         """
 610         Return all packages.
 611
 612         Returns:
 613
 614         packages = { 'group_id': (group, packagelist) }
 615
 616         group = { 'id': "group_identifier",
 617                   'name': "Group name",
 618                   'default': "true|false",
 619                   'description': "Group description",
 620                   'uservisible': "true|false" }
 621
 622         packagelist = { 'package_name': package }
 623
 624         package = { 'name': "package_name",
 625                     'type': "mandatory|optional" }
 626         """
 627
 628         return self._packages
 629
 630
 631     def _sanitize_variable(self, category_id, variable):
 632         assert variable.has_key('id')
 633         # Prepend variable name with category label
 634         id = category_id + "_" + variable['id']
 635         # And uppercase it
 636         id = id.upper()
 637
 638         if variable.has_key('type'):
 639             type = variable['type']
 640         else:
 641             type = None
 642
 643         if variable.has_key('name'):
 644             name = variable['name']
 645         else:
 646             name = None
 647
 648         if variable.has_key('value') and variable['value'] is not None:
 649             value = variable['value']
 650             if type == "int" or type == "double":
 651                 # bash, Python, and PHP do not require that numbers be quoted
 652                 pass
 653             elif type == "boolean":
 654                 # bash, Python, and PHP can all agree on 0 and 1
 655                 if value == "true":
 656                     value = "1"
 657                 else:
 658                     value = "0"
 659             else:
 660                 # bash, Python, and PHP all support strong single quoting
 661                 value = "'" + value.replace("'", "\\'") + "'"
 662         else:
 663             value = None
 664
 665         if variable.has_key('description') and variable['description'] is not None:
 666             description = variable['description']
 667             # Collapse consecutive whitespace
 668             description = re.sub(r'\s+', ' ', description)
 669             # Wrap comments at 70 columns
 670             wrapper = textwrap.TextWrapper()
 671             comments = wrapper.wrap(description)
 672         else:
 673             comments = None
 674
 675         return (id, name, value, comments)
 676
 677
 678     def _header(self):
 679         header = """
 680 DO NOT EDIT. This file was automatically generated at
 681 %s from:
 682
 683 %s
 684 """ % (time.asctime(), os.linesep.join(self._files))
 685
 686         # Get rid of the surrounding newlines
 687         return header.strip().split(os.linesep)
 688
 689
 690     def output_shell(self, show_comments = True, encoding = "utf-8"):
 691         """
 692         Return variables as a shell script.
 693         """
 694
 695         buf = codecs.lookup(encoding)[3](StringIO())
 696         buf.writelines(["# " + line + os.linesep for line in self._header()])
 697
 698         for (category_id, (category, variables)) in self._variables.iteritems():
 699             for variable in variables.values():
 700                 (id, name, value, comments) = self._sanitize_variable(category_id, variable)
 701                 if show_comments:
 702                     buf.write(os.linesep)
 703                     if name is not None:
 704                         buf.write("# " + name + os.linesep)
 705                     if comments is not None:
 706                         buf.writelines(["# " + line + os.linesep for line in comments])
 707                 # bash does not have the concept of NULL
 708                 if value is not None:
 709                     buf.write(id + "=" + value + os.linesep)
 710
 711         return buf.getvalue()
 712
 713
 714     def output_php(self, encoding = "utf-8"):
 715         """
 716         Return variables as a PHP script.
 717         """
 718
 719         buf = codecs.lookup(encoding)[3](StringIO())
 720         buf.write("<?php" + os.linesep)
 721         buf.writelines(["// " + line + os.linesep for line in self._header()])
 722
 723         for (category_id, (category, variables)) in self._variables.iteritems():
 724             for variable in variables.values():
 725                 (id, name, value, comments) = self._sanitize_variable(category_id, variable)
 726                 buf.write(os.linesep)
 727                 if name is not None:
 728                     buf.write("// " + name + os.linesep)
 729                 if comments is not None:
 730                     buf.writelines(["// " + line + os.linesep for line in comments])
 731                 if value is None:
 732                     value = 'NULL'
 733                 buf.write("define('%s', %s);" % (id, value) + os.linesep)
 734
 735         buf.write("?>" + os.linesep)
 736
 737         return buf.getvalue()
 738
 739
 740     def output_xml(self, encoding = "utf-8"):
 741         """
 742         Return variables in original XML format.
 743         """
 744
 745         buf = codecs.lookup(encoding)[3](StringIO())
 746         self._dom.writexml(buf, addindent = "  ", indent = "", newl = "\n", encoding = encoding)
 747
 748         return buf.getvalue()
 749
 750
 751     def output_variables(self, encoding = "utf-8"):
 752         """
 753         Return list of all variable names.
 754         """
 755
 756         buf = codecs.lookup(encoding)[3](StringIO())
 757
 758         for (category_id, (category, variables)) in self._variables.iteritems():
 759             for variable in variables.values():
 760                 (id, name, value, comments) = self._sanitize_variable(category_id, variable)
 761                 buf.write(id + os.linesep)
 762
 763         return buf.getvalue()
 764
 765
 766     def output_packages(self, encoding = "utf-8"):
 767         """
 768         Return list of all packages.
 769         """
 770
 771         buf = codecs.lookup(encoding)[3](StringIO())
 772
 773         for (group, packages) in self._packages.values():
 774             buf.write(os.linesep.join(packages.keys()))
 775
 776         if buf.tell():
 777             buf.write(os.linesep)
 778
 779         return buf.getvalue()
 780
 781
 782     def output_groups(self, encoding = "utf-8"):
 783         """
 784         Return list of all package group names.
 785         """
 786
 787         buf = codecs.lookup(encoding)[3](StringIO())
 788
 789         for (group, packages) in self._packages.values():
 790             buf.write(group['name'] + os.linesep)
 791
 792         return buf.getvalue()
 793
 794
 795     def output_comps(self, encoding = "utf-8"):
 796         """
 797         Return <comps> section of configuration.
 798         """
 799
 800         if self._dom is None or \
 801            not self._dom.getElementsByTagName("comps"):
 802             return
 803         comps = self._dom.getElementsByTagName("comps")[0]
 804
 805         impl = xml.dom.minidom.getDOMImplementation()
 806         doc = impl.createDocument(None, "comps", None)
 807
 808         buf = codecs.lookup(encoding)[3](StringIO())
 809
 810         # Pop it off the DOM temporarily
 811         parent = comps.parentNode
 812         parent.removeChild(comps)
 813
 814         doc.replaceChild(comps, doc.documentElement)
 815         doc.writexml(buf, encoding = encoding)
 816
 817         # Put it back
 818         parent.appendChild(comps)
 819
 820         return buf.getvalue()
 821
 822
 823 # xml.dom.minidom.Text.writexml adds surrounding whitespace to textual
 824 # data when pretty-printing. Override this behavior.
 825 class TrimText(xml.dom.minidom.Text):
 826     def writexml(self, writer, indent="", addindent="", newl=""):
 827         xml.dom.minidom.Text.writexml(self, writer, "", "", "")
 828
 829
 830 class TrimTextElement(xml.dom.minidom.Element):
 831     def writexml(self, writer, indent="", addindent="", newl=""):
 832         writer.write(indent)
 833         xml.dom.minidom.Element.writexml(self, writer, "", "", "")
 834         writer.write(newl)
 835
 836
 837 if __name__ == '__main__':
 838     import sys
 839     if len(sys.argv) > 1 and sys.argv[1] in ['build', 'install', 'uninstall']:
 840         from distutils.core import setup
 841         setup(py_modules=["plc_config"])