root / tea4cups / trunk / tea4cups @ 677

#! /usr/bin/env python
# -*- coding: ISO-8859-15 -*-

# Tea4CUPS : Tee for CUPS
#
# (c) 2005, 2006 Jerome Alet <alet@librelogiciel.com>
# (c) 2005 Peter Stuge <stuge-tea4cups@cdy.org>
# 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.
#
# $Id$
#
#

import sys
import os
import time
import pwd
import errno
import md5
import cStringIO
import shlex
import tempfile
import ConfigParser
import signal
import socket
import urllib2
from struct import pack, unpack

__version__ = "3.12alpha_unofficial"

class TeeError(Exception):
    """Base exception for Tea4CUPS related stuff."""
    def __init__(self, message = ""):
        self.message = message
        Exception.__init__(self, message)
    def __repr__(self):
        return self.message
    __str__ = __repr__

class ConfigError(TeeError) :
    """Configuration related exceptions."""
    pass

class IPPError(TeeError) :
    """IPP related exceptions."""
    pass
    
IPP_VERSION = "1.1"     # default version number

IPP_PORT = 631

IPP_MAX_NAME = 256
IPP_MAX_VALUES = 8

IPP_TAG_ZERO = 0x00
IPP_TAG_OPERATION = 0x01
IPP_TAG_JOB = 0x02
IPP_TAG_END = 0x03
IPP_TAG_PRINTER = 0x04
IPP_TAG_UNSUPPORTED_GROUP = 0x05
IPP_TAG_SUBSCRIPTION = 0x06
IPP_TAG_EVENT_NOTIFICATION = 0x07
IPP_TAG_UNSUPPORTED_VALUE = 0x10
IPP_TAG_DEFAULT = 0x11
IPP_TAG_UNKNOWN = 0x12
IPP_TAG_NOVALUE = 0x13
IPP_TAG_NOTSETTABLE = 0x15
IPP_TAG_DELETEATTR = 0x16
IPP_TAG_ADMINDEFINE = 0x17
IPP_TAG_INTEGER = 0x21
IPP_TAG_BOOLEAN = 0x22
IPP_TAG_ENUM = 0x23
IPP_TAG_STRING = 0x30
IPP_TAG_DATE = 0x31
IPP_TAG_RESOLUTION = 0x32
IPP_TAG_RANGE = 0x33
IPP_TAG_BEGIN_COLLECTION = 0x34
IPP_TAG_TEXTLANG = 0x35
IPP_TAG_NAMELANG = 0x36
IPP_TAG_END_COLLECTION = 0x37
IPP_TAG_TEXT = 0x41
IPP_TAG_NAME = 0x42
IPP_TAG_KEYWORD = 0x44
IPP_TAG_URI = 0x45
IPP_TAG_URISCHEME = 0x46
IPP_TAG_CHARSET = 0x47
IPP_TAG_LANGUAGE = 0x48
IPP_TAG_MIMETYPE = 0x49
IPP_TAG_MEMBERNAME = 0x4a
IPP_TAG_MASK = 0x7fffffff
IPP_TAG_COPY = -0x7fffffff-1

IPP_RES_PER_INCH = 3
IPP_RES_PER_CM = 4

IPP_FINISHINGS_NONE = 3
IPP_FINISHINGS_STAPLE = 4
IPP_FINISHINGS_PUNCH = 5
IPP_FINISHINGS_COVER = 6
IPP_FINISHINGS_BIND = 7
IPP_FINISHINGS_SADDLE_STITCH = 8
IPP_FINISHINGS_EDGE_STITCH = 9
IPP_FINISHINGS_FOLD = 10
IPP_FINISHINGS_TRIM = 11
IPP_FINISHINGS_BALE = 12
IPP_FINISHINGS_BOOKLET_MAKER = 13
IPP_FINISHINGS_JOB_OFFSET = 14
IPP_FINISHINGS_STAPLE_TOP_LEFT = 20
IPP_FINISHINGS_STAPLE_BOTTOM_LEFT = 21
IPP_FINISHINGS_STAPLE_TOP_RIGHT = 22
IPP_FINISHINGS_STAPLE_BOTTOM_RIGHT = 23
IPP_FINISHINGS_EDGE_STITCH_LEFT = 24
IPP_FINISHINGS_EDGE_STITCH_TOP = 25
IPP_FINISHINGS_EDGE_STITCH_RIGHT = 26
IPP_FINISHINGS_EDGE_STITCH_BOTTOM = 27
IPP_FINISHINGS_STAPLE_DUAL_LEFT = 28
IPP_FINISHINGS_STAPLE_DUAL_TOP = 29
IPP_FINISHINGS_STAPLE_DUAL_RIGHT = 30
IPP_FINISHINGS_STAPLE_DUAL_BOTTOM = 31
IPP_FINISHINGS_BIND_LEFT = 50
IPP_FINISHINGS_BIND_TOP = 51
IPP_FINISHINGS_BIND_RIGHT = 52
IPP_FINISHINGS_BIND_BOTTO = 53

IPP_PORTRAIT = 3
IPP_LANDSCAPE = 4
IPP_REVERSE_LANDSCAPE = 5
IPP_REVERSE_PORTRAIT = 6

IPP_QUALITY_DRAFT = 3
IPP_QUALITY_NORMAL = 4
IPP_QUALITY_HIGH = 5

IPP_JOB_PENDING = 3
IPP_JOB_HELD = 4
IPP_JOB_PROCESSING = 5
IPP_JOB_STOPPED = 6
IPP_JOB_CANCELLED = 7
IPP_JOB_ABORTED = 8
IPP_JOB_COMPLETE = 9

IPP_PRINTER_IDLE = 3
IPP_PRINTER_PROCESSING = 4
IPP_PRINTER_STOPPED = 5

IPP_ERROR = -1
IPP_IDLE = 0
IPP_HEADER = 1
IPP_ATTRIBUTE = 2
IPP_DATA = 3

IPP_PRINT_JOB = 0x0002
IPP_PRINT_URI = 0x0003
IPP_VALIDATE_JOB = 0x0004
IPP_CREATE_JOB = 0x0005
IPP_SEND_DOCUMENT = 0x0006
IPP_SEND_URI = 0x0007
IPP_CANCEL_JOB = 0x0008
IPP_GET_JOB_ATTRIBUTES = 0x0009
IPP_GET_JOBS = 0x000a
IPP_GET_PRINTER_ATTRIBUTES = 0x000b
IPP_HOLD_JOB = 0x000c
IPP_RELEASE_JOB = 0x000d
IPP_RESTART_JOB = 0x000e
IPP_PAUSE_PRINTER = 0x0010
IPP_RESUME_PRINTER = 0x0011
IPP_PURGE_JOBS = 0x0012
IPP_SET_PRINTER_ATTRIBUTES = 0x0013
IPP_SET_JOB_ATTRIBUTES = 0x0014
IPP_GET_PRINTER_SUPPORTED_VALUES = 0x0015
IPP_CREATE_PRINTER_SUBSCRIPTION = 0x0016
IPP_CREATE_JOB_SUBSCRIPTION = 0x0017
IPP_GET_SUBSCRIPTION_ATTRIBUTES = 0x0018
IPP_GET_SUBSCRIPTIONS = 0x0019
IPP_RENEW_SUBSCRIPTION = 0x001a
IPP_CANCEL_SUBSCRIPTION = 0x001b
IPP_GET_NOTIFICATIONS = 0x001c
IPP_SEND_NOTIFICATIONS = 0x001d
IPP_GET_PRINT_SUPPORT_FILES = 0x0021
IPP_ENABLE_PRINTER = 0x0022
IPP_DISABLE_PRINTER = 0x0023
IPP_PAUSE_PRINTER_AFTER_CURRENT_JOB = 0x0024
IPP_HOLD_NEW_JOBS = 0x0025
IPP_RELEASE_HELD_NEW_JOBS = 0x0026
IPP_DEACTIVATE_PRINTER = 0x0027
IPP_ACTIVATE_PRINTER = 0x0028
IPP_RESTART_PRINTER = 0x0029
IPP_SHUTDOWN_PRINTER = 0x002a
IPP_STARTUP_PRINTER = 0x002b
IPP_REPROCESS_JOB = 0x002c
IPP_CANCEL_CURRENT_JOB = 0x002d
IPP_SUSPEND_CURRENT_JOB = 0x002e
IPP_RESUME_JOB = 0x002f
IPP_PROMOTE_JOB = 0x0030
IPP_SCHEDULE_JOB_AFTER = 0x0031
IPP_PRIVATE = 0x4000
CUPS_GET_DEFAULT = 0x4001
CUPS_GET_PRINTERS = 0x4002
CUPS_ADD_PRINTER = 0x4003
CUPS_DELETE_PRINTER = 0x4004
CUPS_GET_CLASSES = 0x4005
CUPS_ADD_CLASS = 0x4006
CUPS_DELETE_CLASS = 0x4007
CUPS_ACCEPT_JOBS = 0x4008
CUPS_REJECT_JOBS = 0x4009
CUPS_SET_DEFAULT = 0x400a
CUPS_GET_DEVICES = 0x400b
CUPS_GET_PPDS = 0x400c
CUPS_MOVE_JOB = 0x400d
CUPS_AUTHENTICATE_JOB = 0x400e

IPP_OK = 0x0000
IPP_OK_SUBST = 0x0001
IPP_OK_CONFLICT = 0x0002
IPP_OK_IGNORED_SUBSCRIPTIONS = 0x0003
IPP_OK_IGNORED_NOTIFICATIONS = 0x0004
IPP_OK_TOO_MANY_EVENTS = 0x0005
IPP_OK_BUT_CANCEL_SUBSCRIPTION = 0x0006
IPP_REDIRECTION_OTHER_SITE = 0x0300
IPP_BAD_REQUEST = 0x0400
IPP_FORBIDDEN = 0x0401
IPP_NOT_AUTHENTICATED = 0x0402
IPP_NOT_AUTHORIZED = 0x0403
IPP_NOT_POSSIBLE = 0x0404
IPP_TIMEOUT = 0x0405
IPP_NOT_FOUND = 0x0406
IPP_GONE = 0x0407
IPP_REQUEST_ENTITY = 0x0408
IPP_REQUEST_VALUE = 0x0409
IPP_DOCUMENT_FORMAT = 0x040a
IPP_ATTRIBUTES = 0x040b
IPP_URI_SCHEME = 0x040c
IPP_CHARSET = 0x040d
IPP_CONFLICT = 0x040e
IPP_COMPRESSION_NOT_SUPPORTED = 0x040f
IPP_COMPRESSION_ERROR = 0x0410
IPP_DOCUMENT_FORMAT_ERROR = 0x0411
IPP_DOCUMENT_ACCESS_ERROR = 0x0412
IPP_ATTRIBUTES_NOT_SETTABLE = 0x0413
IPP_IGNORED_ALL_SUBSCRIPTIONS = 0x0414
IPP_TOO_MANY_SUBSCRIPTIONS = 0x0415
IPP_IGNORED_ALL_NOTIFICATIONS = 0x0416
IPP_PRINT_SUPPORT_FILE_NOT_FOUND = 0x0417

IPP_INTERNAL_ERROR = 0x0500
IPP_OPERATION_NOT_SUPPORTED = 0x0501
IPP_SERVICE_UNAVAILABLE = 0x0502
IPP_VERSION_NOT_SUPPORTED = 0x0503
IPP_DEVICE_ERROR = 0x0504
IPP_TEMPORARY_ERROR = 0x0505
IPP_NOT_ACCEPTING = 0x0506
IPP_PRINTER_BUSY = 0x0507
IPP_ERROR_JOB_CANCELLED = 0x0508
IPP_MULTIPLE_JOBS_NOT_SUPPORTED = 0x0509
IPP_PRINTER_IS_DEACTIVATED = 0x50a
  
CUPS_PRINTER_LOCAL = 0x0000
CUPS_PRINTER_CLASS = 0x0001
CUPS_PRINTER_REMOTE = 0x0002
CUPS_PRINTER_BW = 0x0004
CUPS_PRINTER_COLOR = 0x0008
CUPS_PRINTER_DUPLEX = 0x0010
CUPS_PRINTER_STAPLE = 0x0020
CUPS_PRINTER_COPIES = 0x0040
CUPS_PRINTER_COLLATE = 0x0080
CUPS_PRINTER_PUNCH = 0x0100
CUPS_PRINTER_COVER = 0x0200
CUPS_PRINTER_BIND = 0x0400
CUPS_PRINTER_SORT = 0x0800
CUPS_PRINTER_SMALL = 0x1000
CUPS_PRINTER_MEDIUM = 0x2000
CUPS_PRINTER_LARGE = 0x4000
CUPS_PRINTER_VARIABLE = 0x8000
CUPS_PRINTER_IMPLICIT = 0x1000
CUPS_PRINTER_DEFAULT = 0x2000
CUPS_PRINTER_FAX = 0x4000
CUPS_PRINTER_REJECTING = 0x8000
CUPS_PRINTER_DELETE = 0x1000
CUPS_PRINTER_NOT_SHARED = 0x2000
CUPS_PRINTER_AUTHENTICATED = 0x4000
CUPS_PRINTER_COMMANDS = 0x8000
CUPS_PRINTER_OPTIONS = 0xe6ff
  
class FakeAttribute :
    """Fakes an IPPRequest attribute to simplify usage syntax."""
    def __init__(self, request, name) :
        """Initializes the fake attribute."""
        self.request = request
        self.name = name
        
    def __setitem__(self, key, value) :
        """Appends the value to the real attribute."""
        attributeslist = getattr(self.request, "_%s_attributes" % self.name)
        for i in range(len(attributeslist)) :
            attribute = attributeslist[i]
            for j in range(len(attribute)) :
                (attrname, attrvalue) = attribute[j]
                if attrname == key :
                    attribute[j][1].append(value)
                    return
            attribute.append((key, [value]))        
            
    def __getitem__(self, key) :
        """Returns an attribute's value."""
        answer = []
        attributeslist = getattr(self.request, "_%s_attributes" % self.name)
        for i in range(len(attributeslist)) :
            attribute = attributeslist[i]
            for j in range(len(attribute)) :
                (attrname, attrvalue) = attribute[j]
                if attrname == key :
                    answer.extend(attrvalue)
        if answer :
            return answer
        raise KeyError, key            
    
class IPPRequest :
    """A class for IPP requests."""
    attributes_types = ("operation", "job", "printer", "unsupported", \
                                     "subscription", "event_notification")
    def __init__(self, data="", version=IPP_VERSION, 
                                operation_id=None, \
                                request_id=None, \
                                debug=False) :
        """Initializes an IPP Message object.
        
           Parameters :
           
             data : the complete IPP Message's content.
             debug : a boolean value to output debug info on stderr.
        """
        self.debug = debug
        self._data = data
        self.parsed = False
        
        # Initializes message
        self.setVersion(version)                
        self.setOperationId(operation_id)
        self.setRequestId(request_id)
        self.data = ""
        
        for attrtype in self.attributes_types :
            setattr(self, "_%s_attributes" % attrtype, [[]])
        
        # Initialize tags    
        self.tags = [ None ] * 256 # by default all tags reserved
        
        # Delimiter tags
        self.tags[0x01] = "operation-attributes-tag"
        self.tags[0x02] = "job-attributes-tag"
        self.tags[0x03] = "end-of-attributes-tag"
        self.tags[0x04] = "printer-attributes-tag"
        self.tags[0x05] = "unsupported-attributes-tag"
        self.tags[0x06] = "subscription-attributes-tag"
        self.tags[0x07] = "event_notification-attributes-tag"
        
        # out of band values
        self.tags[0x10] = "unsupported"
        self.tags[0x11] = "reserved-for-future-default"
        self.tags[0x12] = "unknown"
        self.tags[0x13] = "no-value"
        self.tags[0x15] = "not-settable"
        self.tags[0x16] = "delete-attribute"
        self.tags[0x17] = "admin-define"
  
        # integer values
        self.tags[0x20] = "generic-integer"
        self.tags[0x21] = "integer"
        self.tags[0x22] = "boolean"
        self.tags[0x23] = "enum"
        
        # octetString
        self.tags[0x30] = "octetString-with-an-unspecified-format"
        self.tags[0x31] = "dateTime"
        self.tags[0x32] = "resolution"
        self.tags[0x33] = "rangeOfInteger"
        self.tags[0x34] = "begCollection" # TODO : find sample files for testing
        self.tags[0x35] = "textWithLanguage"
        self.tags[0x36] = "nameWithLanguage"
        self.tags[0x37] = "endCollection"
        
        # character strings
        self.tags[0x40] = "generic-character-string"
        self.tags[0x41] = "textWithoutLanguage"
        self.tags[0x42] = "nameWithoutLanguage"
        self.tags[0x44] = "keyword"
        self.tags[0x45] = "uri"
        self.tags[0x46] = "uriScheme"
        self.tags[0x47] = "charset"
        self.tags[0x48] = "naturalLanguage"
        self.tags[0x49] = "mimeMediaType"
        self.tags[0x4a] = "memberAttrName"
        
        # Reverse mapping to generate IPP messages
        self.tagvalues = {}
        for i in range(len(self.tags)) :
            value = self.tags[i]
            if value is not None :
                self.tagvalues[value] = i
                                     
    def __getattr__(self, name) :                                 
        """Fakes attribute access."""
        if name in self.attributes_types :
            return FakeAttribute(self, name)
        else :
            raise AttributeError, name
            
    def __str__(self) :        
        """Returns the parsed IPP message in a readable form."""
        if not self.parsed :
            return ""
        mybuffer = []
        mybuffer.append("IPP version : %s.%s" % self.version)
        mybuffer.append("IPP operation Id : 0x%04x" % self.operation_id)
        mybuffer.append("IPP request Id : 0x%08x" % self.request_id)
        for attrtype in self.attributes_types :
            for attribute in getattr(self, "_%s_attributes" % attrtype) :
                if attribute :
                    mybuffer.append("%s attributes :" % attrtype.title())
                for (name, value) in attribute :
                    mybuffer.append("  %s : %s" % (name, value))
        if self.data :            
            mybuffer.append("IPP datas : %s" % repr(self.data))
        return "\n".join(mybuffer)
        
    def logDebug(self, msg) :    
        """Prints a debug message."""
        if self.debug :
            sys.stderr.write("%s\n" % msg)
            sys.stderr.flush()
            
    def setVersion(self, version) :
        """Sets the request's operation id."""
        if version is not None :
            try :
                self.version = [int(p) for p in version.split(".")]
            except AttributeError :
                if len(version) == 2 : # 2-tuple
                    self.version = version
                else :    
                    try :
                        self.version = [int(p) for p in str(float(version)).split(".")]
                    except :
                        self.version = [int(p) for p in IPP_VERSION.split(".")]
        
    def setOperationId(self, opid) :        
        """Sets the request's operation id."""
        self.operation_id = opid
        
    def setRequestId(self, reqid) :        
        """Sets the request's request id."""
        self.request_id = reqid
        
    def dump(self) :    
        """Generates an IPP Message.
        
           Returns the message as a string of text.
        """    
        mybuffer = []
        if None not in (self.version, self.operation_id) :
            mybuffer.append(chr(self.version[0]) + chr(self.version[1]))
            mybuffer.append(pack(">H", self.operation_id))
            mybuffer.append(pack(">I", self.request_id or 1))
            for attrtype in self.attributes_types :
                for attribute in getattr(self, "_%s_attributes" % attrtype) :
                    if attribute :
                        mybuffer.append(chr(self.tagvalues["%s-attributes-tag" % attrtype]))
                    for (attrname, value) in attribute :
                        nameprinted = 0
                        for (vtype, val) in value :
                            mybuffer.append(chr(self.tagvalues[vtype]))
                            if not nameprinted :
                                mybuffer.append(pack(">H", len(attrname)))
                                mybuffer.append(attrname)
                                nameprinted = 1
                            else :     
                                mybuffer.append(pack(">H", 0))
                            if vtype in ("integer", "enum") :
                                mybuffer.append(pack(">H", 4))
                                mybuffer.append(pack(">I", val))
                            elif vtype == "boolean" :
                                mybuffer.append(pack(">H", 1))
                                mybuffer.append(chr(val))
                            else :    
                                mybuffer.append(pack(">H", len(val)))
                                mybuffer.append(val)
            mybuffer.append(chr(self.tagvalues["end-of-attributes-tag"]))
        mybuffer.append(self.data)    
        return "".join(mybuffer)
            
    def parse(self) :
        """Parses an IPP Request.
        
           NB : Only a subset of RFC2910 is implemented.
        """
        self._curname = None
        self._curattributes = None
        
        self.setVersion((ord(self._data[0]), ord(self._data[1])))
        self.setOperationId(unpack(">H", self._data[2:4])[0])
        self.setRequestId(unpack(">I", self._data[4:8])[0])
        self.position = 8
        endofattributes = self.tagvalues["end-of-attributes-tag"]
        maxdelimiter = self.tagvalues["event_notification-attributes-tag"]
        nulloffset = lambda : 0
        try :
            tag = ord(self._data[self.position])
            while tag != endofattributes :
                self.position += 1
                name = self.tags[tag]
                if name is not None :
                    func = getattr(self, name.replace("-", "_"), nulloffset)
                    self.position += func()
                    if ord(self._data[self.position]) > maxdelimiter :
                        self.position -= 1
                        continue
                oldtag = tag        
                tag = ord(self._data[self.position])
                if tag == oldtag :
                    self._curattributes.append([])
        except IndexError :
            raise IPPError, "Unexpected end of IPP message."
            
        self.data = self._data[self.position+1:]            
        self.parsed = True
        
    def parseTag(self) :    
        """Extracts information from an IPP tag."""
        pos = self.position
        tagtype = self.tags[ord(self._data[pos])]
        pos += 1
        posend = pos2 = pos + 2
        namelength = unpack(">H", self._data[pos:pos2])[0]
        if not namelength :
            name = self._curname
        else :    
            posend += namelength
            self._curname = name = self._data[pos2:posend]
        pos2 = posend + 2
        valuelength = unpack(">H", self._data[posend:pos2])[0]
        posend = pos2 + valuelength
        value = self._data[pos2:posend]
        if tagtype in ("integer", "enum") :
            value = unpack(">I", value)[0]
        elif tagtype == "boolean" :    
            value = ord(value)
        try :    
            (oldname, oldval) = self._curattributes[-1][-1]
            if oldname == name :
                oldval.append((tagtype, value))
            else :    
                raise IndexError
        except IndexError :    
            self._curattributes[-1].append((name, [(tagtype, value)]))
        self.logDebug("%s(%s) : %s" % (name, tagtype, value))
        return posend - self.position
        
    def operation_attributes_tag(self) : 
        """Indicates that the parser enters into an operation-attributes-tag group."""
        self._curattributes = self._operation_attributes
        return self.parseTag()
        
    def job_attributes_tag(self) : 
        """Indicates that the parser enters into a job-attributes-tag group."""
        self._curattributes = self._job_attributes
        return self.parseTag()
        
    def printer_attributes_tag(self) : 
        """Indicates that the parser enters into a printer-attributes-tag group."""
        self._curattributes = self._printer_attributes
        return self.parseTag()
        
    def unsupported_attributes_tag(self) : 
        """Indicates that the parser enters into an unsupported-attributes-tag group."""
        self._curattributes = self._unsupported_attributes
        return self.parseTag()
        
    def subscription_attributes_tag(self) : 
        """Indicates that the parser enters into a subscription-attributes-tag group."""
        self._curattributes = self._subscription_attributes
        return self.parseTag()
        
    def event_notification_attributes_tag(self) : 
        """Indicates that the parser enters into an event-notification-attributes-tag group."""
        self._curattributes = self._event_notification_attributes
        return self.parseTag()
        
            
class CUPS :
    """A class for a CUPS instance."""
    def __init__(self, url=None, username=None, password=None, charset="utf-8", language="en-us", debug=False) :
        """Initializes the CUPS instance."""
        if url is not None :
            self.url = url.replace("ipp://", "http://")
            if self.url.endswith("/") :
                self.url = self.url[:-1]
        else :        
            self.url = self.getDefaultURL()
        self.username = username
        self.password = password
        self.charset = charset
        self.language = language
        self.debug = debug
        self.lastError = None
        self.lastErrorMessage = None
        self.requestId = None
        
    def getDefaultURL(self) :    
        """Builds a default URL."""
        # TODO : encryption methods.
        server = os.environ.get("CUPS_SERVER") or "localhost"
        port = os.environ.get("IPP_PORT") or 631
        if server.startswith("/") :
            # it seems it's a unix domain socket.
            # we can't handle this right now, so we use the default instead.
            return "http://localhost:%s" % port
        else :    
            return "http://%s:%s" % (server, port)
            
    def identifierToURI(self, service, ident) :
        """Transforms an identifier into a particular URI depending on requested service."""
        return "%s/%s/%s" % (self.url.replace("http://", "ipp://"),
                             service,
                             ident)
        
    def nextRequestId(self) :        
        """Increments the current request id and returns the new value."""
        try :
            self.requestId += 1
        except TypeError :    
            self.requestId = 1
        return self.requestId
            
    def newRequest(self, operationid=None) :
        """Generates a new empty request."""
        if operationid is not None :
            req = IPPRequest(operation_id=operationid, \
                             request_id=self.nextRequestId(), \
                             debug=self.debug)
            req.operation["attributes-charset"] = ("charset", self.charset)
            req.operation["attributes-natural-language"] = ("naturalLanguage", self.language)
            return req
    
    def doRequest(self, req, url=None) :
        """Sends a request to the CUPS server.
           returns a new IPPRequest object, containing the parsed answer.
        """   
        connexion = urllib2.Request(url=url or self.url, \
                             data=req.dump())
        connexion.add_header("Content-Type", "application/ipp")
        if self.username :
            pwmanager = urllib2.HTTPPasswordMgrWithDefaultRealm()
            pwmanager.add_password(None, \
                                   "%s%s" % (connexion.get_host(), connexion.get_selector()), \
                                   self.username, \
                                   self.password or "")
            authhandler = urllib2.HTTPBasicAuthHandler(pwmanager)                       
            opener = urllib2.build_opener(authhandler)
            urllib2.install_opener(opener)
        self.lastError = None    
        self.lastErrorMessage = None
        try :    
            response = urllib2.urlopen(connexion)
        except (urllib2.URLError, urllib2.HTTPError, socket.error), error :    
            self.lastError = error
            self.lastErrorMessage = str(error)
            return None
        else :    
            datas = response.read()
            ippresponse = IPPRequest(datas)
            ippresponse.parse()
            return ippresponse
    
    def getPPD(self, queuename) :    
        """Retrieves the PPD for a particular queuename."""
        req = self.newRequest(IPP_GET_PRINTER_ATTRIBUTES)
        req.operation["printer-uri"] = ("uri", self.identifierToURI("printers", queuename))
        for attrib in ("printer-uri-supported", "printer-type", "member-uris") :
            req.operation["requested-attributes"] = ("nameWithoutLanguage", attrib)
        return self.doRequest(req)  # TODO : get the PPD from the actual print server
        
    def getDefault(self) :
        """Retrieves CUPS' default printer."""
        return self.doRequest(self.newRequest(CUPS_GET_DEFAULT))
    
    def getJobAttributes(self, jobid) :    
        """Retrieves a print job's attributes."""
        req = self.newRequest(IPP_GET_JOB_ATTRIBUTES)
        req.operation["job-uri"] = ("uri", self.identifierToURI("jobs", jobid))
        return self.doRequest(req)
        
    def getPrinters(self) :    
        """Returns the list of print queues names."""
        req = self.newRequest(CUPS_GET_PRINTERS)
        req.operation["requested-attributes"] = ("keyword", "printer-name")
        req.operation["printer-type"] = ("enum", 0)
        req.operation["printer-type-mask"] = ("enum", CUPS_PRINTER_CLASS)
        return [printer[1] for printer in self.doRequest(req).printer["printer-name"]]
        
    def getDevices(self) :    
        """Returns a list of devices as (deviceclass, deviceinfo, devicemakeandmodel, deviceuri) tuples."""
        answer = self.doRequest(self.newRequest(CUPS_GET_DEVICES))
        return zip([d[1] for d in answer.printer["device-class"]], \
                   [d[1] for d in answer.printer["device-info"]], \
                   [d[1] for d in answer.printer["device-make-and-model"]], \
                   [d[1] for d in answer.printer["device-uri"]])
                   
    def getPPDs(self) :    
        """Returns a list of PPDs as (ppdnaturallanguage, ppdmake, ppdmakeandmodel, ppdname) tuples."""
        answer = self.doRequest(self.newRequest(CUPS_GET_PPDS))
        return zip([d[1] for d in answer.printer["ppd-natural-language"]], \
                   [d[1] for d in answer.printer["ppd-make"]], \
                   [d[1] for d in answer.printer["ppd-make-and-model"]], \
                   [d[1] for d in answer.printer["ppd-name"]])
                   
    def createSubscription(self, uri, events=["all"],
                                      userdata=None,
                                      recipient=None,
                                      pullmethod=None,
                                      charset=None,
                                      naturallanguage=None,
                                      leaseduration=None,
                                      timeinterval=None,
                                      jobid=None) :
        """Creates a job, printer or server subscription.
         
           uri : the subscription's uri, e.g. ipp://server
           events : a list of events to subscribe to, e.g. ["printer-added", "printer-deleted"]
           recipient : the notifier's uri
           pullmethod : the pull method to use
           charset : the charset to use when sending notifications
           naturallanguage : the language to use when sending notifications
           leaseduration : the duration of the lease in seconds
           timeinterval : the interval of time during notifications
           jobid : the optional job id in case of a job subscription
        """   
        if jobid is not None :
            opid = IPP_CREATE_JOB_SUBSCRIPTION
            uritype = "job-uri"
        else :
            opid = IPP_CREATE_PRINTER_SUBSCRIPTION
            uritype = "printer-uri"
        req = self.newRequest(opid)
        req.operation[uritype] = ("uri", uri)
        for event in events :
            req.subscription["notify-events"] = ("keyword", event)
        if userdata is not None :    
            req.subscription["notify-user-data"] = ("octetString-with-an-unspecified-format", userdata)
        if recipient is not None :    
            req.subscription["notify-recipient"] = ("uri", recipient)
        if pullmethod is not None :
            req.subscription["notify-pull-method"] = ("keyword", pullmethod)
        if charset is not None :
            req.subscription["notify-charset"] = ("charset", charset)
        if naturallanguage is not None :
            req.subscription["notify-natural-language"] = ("naturalLanguage", naturallanguage)
        if leaseduration is not None :
            req.subscription["notify-lease-duration"] = ("integer", leaseduration)
        if timeinterval is not None :
            req.subscription["notify-time-interval"] = ("integer", timeinterval)
        if jobid is not None :
            req.subscription["notify-job-id"] = ("integer", jobid)
        return self.doRequest(req)
            
    def cancelSubscription(self, uri, subscriptionid, jobid=None) :    
        """Cancels a subscription.
        
           uri : the subscription's uri.
           subscriptionid : the subscription's id.
           jobid : the optional job's id.
        """
        req = self.newRequest(IPP_CANCEL_SUBSCRIPTION)
        if jobid is not None :
            uritype = "job-uri"
        else :
            uritype = "printer-uri"
        req.operation[uritype] = ("uri", uri)
        req.event_notification["notify-subscription-id"] = ("integer", subscriptionid)
        return self.doRequest(req)
        

class FakeConfig :
    """Fakes a configuration file parser."""
    def get(self, section, option, raw=0) :
        """Fakes the retrieval of an option."""
        raise ConfigError, "Invalid configuration file : no option %s in section [%s]" % (option, section)

class CupsBackend :
    """Base class for tools with no database access."""
    def __init__(self) :
        """Initializes the CUPS backend wrapper."""
        signal.signal(signal.SIGTERM, signal.SIG_IGN)
        signal.signal(signal.SIGPIPE, signal.SIG_IGN)
        self.MyName = "Tea4CUPS"
        self.myname = "tea4cups"
        self.pid = os.getpid()

    def readConfig(self) :
        """Reads the configuration file."""
        confdir = os.environ.get("CUPS_SERVERROOT", ".")
        self.conffile = os.path.join(confdir, "%s.conf" % self.myname)
        if os.path.isfile(self.conffile) :
            self.config = ConfigParser.ConfigParser()
            self.config.read([self.conffile])
            self.debug = self.isTrue(self.getGlobalOption("debug", ignore=1))
        else :
            self.config = FakeConfig()
            self.debug = 1      # no config, so force debug mode !

    def logInfo(self, message, level="info") :
        """Logs a message to CUPS' error_log file."""
        try :
            sys.stderr.write("%s: %s v%s (PID %i) : %s\n" % (level.upper(), self.MyName, __version__, os.getpid(), message))
            sys.stderr.flush()
        except IOError :
            pass

    def logDebug(self, message) :
        """Logs something to debug output if debug is enabled."""
        if self.debug :
            self.logInfo(message, level="debug")

    def isTrue(self, option) :
        """Returns 1 if option is set to true, else 0."""
        if (option is not None) and (option.upper().strip() in ['Y', 'YES', '1', 'ON', 'T', 'TRUE']) :
            return 1
        else :
            return 0

    def getGlobalOption(self, option, ignore=0) :
        """Returns an option from the global section, or raises a ConfigError if ignore is not set, else returns None."""
        try :
            return self.config.get("global", option, raw=1)
        except (ConfigParser.NoSectionError, ConfigParser.NoOptionError) :
            if not ignore :
                raise ConfigError, "Option %s not found in section global of %s" % (option, self.conffile)

    def getPrintQueueOption(self, printqueuename, option, ignore=0) :
        """Returns an option from the printer section, or the global section, or raises a ConfigError."""
        globaloption = self.getGlobalOption(option, ignore=1)
        try :
            return self.config.get(printqueuename, option, raw=1)
        except (ConfigParser.NoSectionError, ConfigParser.NoOptionError) :
            if globaloption is not None :
                return globaloption
            elif not ignore :
                raise ConfigError, "Option %s not found in section [%s] of %s" % (option, printqueuename, self.conffile)

    def enumBranches(self, printqueuename, branchtype="tee") :
        """Returns the list of branchtypes branches for a particular section's."""
        branchbasename = "%s_" % branchtype.lower()
        try :
            globalbranches = [ (k, self.config.get("global", k)) for k in self.config.options("global") if k.startswith(branchbasename) ]
        except ConfigParser.NoSectionError, msg :
            raise ConfigError, "Invalid configuration file : %s" % msg
        try :
            sectionbranches = [ (k, self.config.get(printqueuename, k)) for k in self.config.options(printqueuename) if k.startswith(branchbasename) ]
        except ConfigParser.NoSectionError, msg :
            self.logInfo("No section for print queue %s : %s" % (printqueuename, msg))
            sectionbranches = []
        branches = {}
        for (k, v) in globalbranches :
            value = v.strip()
            if value :
                branches[k] = value
        for (k, v) in sectionbranches :
            value = v.strip()
            if value :
                branches[k] = value # overwrite any global option or set a new value
            else :
                del branches[k] # empty value disables a global option
        return branches

    def discoverOtherBackends(self) :
        """Discovers the other CUPS backends.

           Executes each existing backend in turn in device enumeration mode.
           Returns the list of available backends.
        """
        # Unfortunately this method can't output any debug information
        # to stdout or stderr, else CUPS considers that the device is
        # not available.
        available = []
        (directory, myname) = os.path.split(sys.argv[0])
        if not directory :
            directory = "./"
        tmpdir = tempfile.gettempdir()
        lockfilename = os.path.join(tmpdir, "%s..LCK" % myname)
        if os.path.exists(lockfilename) :
            lockfile = open(lockfilename, "r")
            pid = int(lockfile.read())
            lockfile.close()
            try :
                # see if the pid contained in the lock file is still running
                os.kill(pid, 0)
            except OSError, e :
                if e.errno != errno.EPERM :
                    # process doesn't exist anymore
                    os.remove(lockfilename)

        if not os.path.exists(lockfilename) :
            lockfile = open(lockfilename, "w")
            lockfile.write("%i" % self.pid)
            lockfile.close()
            allbackends = [ os.path.join(directory, b) \
                                for b in os.listdir(directory)
                                    if os.access(os.path.join(directory, b), os.X_OK) \
                                        and (b != myname)]
            for backend in allbackends :
                answer = os.popen(backend, "r")
                try :
                    devices = [line.strip() for line in answer.readlines()]
                except :
                    devices = []
                status = answer.close()
                if status is None :
                    for d in devices :
                        # each line is of the form :
                        # 'xxxx xxxx "xxxx xxx" "xxxx xxx"'
                        # so we have to decompose it carefully
                        fdevice = cStringIO.StringIO(d)
                        tokenizer = shlex.shlex(fdevice)
                        tokenizer.wordchars = tokenizer.wordchars + \
                                                        r".:,?!~/\_$*-+={}[]()#"
                        arguments = []
                        while 1 :
                            token = tokenizer.get_token()
                            if token :
                                arguments.append(token)
                            else :
                                break
                        fdevice.close()
                        try :
                            (devicetype, device, name, fullname) = arguments
                        except ValueError :
                            pass    # ignore this 'bizarre' device
                        else :
                            if name.startswith('"') and name.endswith('"') :
                                name = name[1:-1]
                            if fullname.startswith('"') and fullname.endswith('"') :
                                fullname = fullname[1:-1]
                            available.append('%s %s:%s "%s+%s" "%s managed %s"' \
                                                 % (devicetype, self.myname, device, self.MyName, name, self.MyName, fullname))
            os.remove(lockfilename)
        available.append('direct %s:// "%s+Nothing" "%s managed Virtual Printer"' \
                             % (self.myname, self.MyName, self.MyName))
        return available

    def initBackend(self) :
        """Initializes the backend's attributes."""
        self.JobId = sys.argv[1].strip()
        self.UserName = sys.argv[2].strip() or pwd.getpwuid(os.geteuid())[0] # use CUPS' user when printing test pages from CUPS' web interface
        self.Title = sys.argv[3].strip()
        self.Copies = int(sys.argv[4].strip())
        self.Options = sys.argv[5].strip()
        if len(sys.argv) == 7 :
            self.InputFile = sys.argv[6] # read job's datas from file
        else :
            self.InputFile = None        # read job's datas from stdin
        self.PrinterName = os.environ.get("PRINTER", "")
        self.Directory = self.getPrintQueueOption(self.PrinterName, "directory", ignore=1) or tempfile.gettempdir()
        self.DataFile = os.path.join(self.Directory, "%s-%s-%s-%s" % (self.myname, self.PrinterName, self.UserName, self.JobId))
        
        # check that the DEVICE_URI environment variable's value is
        # prefixed with self.myname otherwise don't touch it.
        # If this is the case, we have to remove the prefix from
        # the environment before launching the real backend
        muststartwith = "%s:" % self.myname
        device_uri = os.environ.get("DEVICE_URI", "")
        if device_uri.startswith(muststartwith) :
            fulldevice_uri = device_uri[:]
            device_uri = fulldevice_uri[len(muststartwith):]
            for i in range(2) :
                if device_uri.startswith("/") :
                    device_uri = device_uri[1:]
        try :
            (backend, destination) = device_uri.split(":", 1)
        except ValueError :
            if not device_uri :
                self.logDebug("Not attached to an existing print queue.")
                backend = ""
            else :
                raise TeeError, "Invalid DEVICE_URI : %s\n" % device_uri

        self.RealBackend = backend
        self.DeviceURI = device_uri
        
        try :
            cupsserver = CUPS() # TODO : username and password and/or encryption
            answer = cupsserver.getJobAttributes(self.JobId)
            self.ControlFile = "NotUsedAnymore"
        except :    
            (ippfilename, answer) = self.parseIPPRequestFile()
            self.ControlFile = ippfilename
        
        try :
            john = answer.job["job-originating-host-name"]
        except KeyError :    
            try :
                john = answer.operation["job-originating-host-name"]
            except KeyError :    
                john = (None, None)
        if type(john) == type([]) :                          
            john = john[-1]
        (chtype, self.ClientHost) = john                          
        try :        
            jbing = answer.job["job-billing"]
        except KeyError :    
            jbing = (None, None)
        if type(jbing) == type([]) : 
            jbing = jbing[-1]
        (jbtype, self.JobBilling) = jbing

    def getCupsConfigDirectives(self, directives=[]) :
        """Retrieves some CUPS directives from its configuration file.

           Returns a mapping with lowercased directives as keys and
           their setting as values.
        """
        dirvalues = {}
        cupsroot = os.environ.get("CUPS_SERVERROOT", "/etc/cups")
        cupsdconf = os.path.join(cupsroot, "cupsd.conf")
        try :
            conffile = open(cupsdconf, "r")
        except IOError :
            raise TeeError, "Unable to open %s" % cupsdconf
        else :
            for line in conffile.readlines() :
                linecopy = line.strip().lower()
                for di in [d.lower() for d in directives] :
                    if linecopy.startswith("%s " % di) :
                        try :
                            val = line.split()[1]
                        except :
                            pass # ignore errors, we take the last value in any case.
                        else :
                            dirvalues[di] = val
            conffile.close()
        return dirvalues

    def parseIPPRequestFile(self) :
        """Parses the IPP message file and returns a tuple (filename, parsedvalue)."""
        requestroot = os.environ.get("CUPS_REQUESTROOT")
        if requestroot is None :
            cupsdconf = self.getCupsConfigDirectives(["RequestRoot"])
            requestroot = cupsdconf.get("requestroot", "/var/spool/cups")
        if (len(self.JobId) < 5) and self.JobId.isdigit() :
            ippmessagefile = "c%05i" % int(self.JobId)
        else :
            ippmessagefile = "c%s" % self.JobId
        ippmessagefile = os.path.join(requestroot, ippmessagefile)
        ippmessage = {}
        try :
            ippdatafile = open(ippmessagefile)
        except :
            self.logInfo("Unable to open IPP message file %s" % ippmessagefile, "warn")
        else :
            self.logDebug("Parsing of IPP message file %s begins." % ippmessagefile)
            try :
                ippmessage = IPPRequest(ippdatafile.read())
                ippmessage.parse()
            except IPPError, msg :
                self.logInfo("Error while parsing %s : %s" % (ippmessagefile, msg), "warn")
            else :
                self.logDebug("Parsing of IPP message file %s ends." % ippmessagefile)
            ippdatafile.close()
        return (ippmessagefile, ippmessage)

    def exportAttributes(self) :
        """Exports our backend's attributes to the environment."""
        os.environ["DEVICE_URI"] = self.DeviceURI       # WARNING !
        os.environ["TEAPRINTERNAME"] = self.PrinterName
        os.environ["TEADIRECTORY"] = self.Directory
        os.environ["TEADATAFILE"] = self.DataFile
        os.environ["TEAJOBSIZE"] = str(self.JobSize)
        os.environ["TEAMD5SUM"] = self.JobMD5Sum
        os.environ["TEACLIENTHOST"] = self.ClientHost or ""
        os.environ["TEAJOBID"] = self.JobId
        os.environ["TEAUSERNAME"] = self.UserName
        os.environ["TEATITLE"] = self.Title
        os.environ["TEACOPIES"] = str(self.Copies)
        os.environ["TEAOPTIONS"] = self.Options
        os.environ["TEAINPUTFILE"] = self.InputFile or ""
        os.environ["TEABILLING"] = self.JobBilling or ""
        os.environ["TEACONTROLFILE"] = self.ControlFile

    def saveDatasAndCheckSum(self) :
        """Saves the input datas into a static file."""
        self.logDebug("Duplicating data stream into %s" % self.DataFile)
        mustclose = 0
        if self.InputFile is not None :
            infile = open(self.InputFile, "rb")
            mustclose = 1
        else :
            infile = sys.stdin
            
        filtercommand = self.getPrintQueueOption(self.PrinterName, "filter", \
                                                 ignore=1)
        if filtercommand :                                                 
            self.logDebug("Data stream will be filtered through [%s]" % filtercommand)
            filteroutput = "%s.filteroutput" % self.DataFile
            outf = open(filteroutput, "wb")
            filterstatus = self.stdioRedirSystem(filtercommand, infile.fileno(), outf.fileno())
            outf.close()
            self.logDebug("Filter's output status : %s" % repr(filterstatus))
            if mustclose :
                infile.close()
            infile = open(filteroutput, "rb")
            mustclose = 1
        else :    
            self.logDebug("Data stream will be used as-is (no filter defined)")
            
        CHUNK = 64*1024         # read 64 Kb at a time
        dummy = 0
        sizeread = 0
        checksum = md5.new()
        outfile = open(self.DataFile, "wb")
        while 1 :
            data = infile.read(CHUNK)
            if not data :
                break
            sizeread += len(data)
            outfile.write(data)
            checksum.update(data)
            if not (dummy % 32) : # Only display every 2 Mb
                self.logDebug("%s bytes saved..." % sizeread)
            dummy += 1
        outfile.close()
        
        if filtercommand :
            self.logDebug("Removing filter's output file %s" % filteroutput)
            try :
                os.remove(filteroutput)
            except :    
                pass
                
        if mustclose :
            infile.close()
            
        self.logDebug("%s bytes saved..." % sizeread)
        self.JobSize = sizeread
        self.JobMD5Sum = checksum.hexdigest()
        self.logDebug("Job %s is %s bytes long." % (self.JobId, self.JobSize))
        self.logDebug("Job %s MD5 sum is %s" % (self.JobId, self.JobMD5Sum))

    def cleanUp(self) :
        """Cleans up the place."""
        if (not self.isTrue(self.getPrintQueueOption(self.PrinterName, "keepfiles", ignore=1))) \
            and os.path.exists(self.DataFile) :
            try :
                os.remove(self.DataFile)
            except OSError, msg :    
                self.logInfo("Problem when removing %s : %s" % (self.DataFile, msg), "error")

    def sigtermHandler(self, signum, frame) :
        """Sets an attribute whenever SIGTERM is received."""
        self.gotSigTerm = 1
        self.logInfo("SIGTERM received for Job %s." % self.JobId)

    def runBranches(self) :
        """Launches each hook defined for the current print queue."""
        self.isCancelled = 0    # did a prehook cancel the print job ?
        self.gotSigTerm = 0
        signal.signal(signal.SIGTERM, self.sigtermHandler)
        serialize = self.isTrue(self.getPrintQueueOption(self.PrinterName, "serialize", ignore=1))
        self.pipes = { 0: (0, 1) }
        branches = self.enumBranches(self.PrinterName, "prehook")
        for b in branches.keys() :
            self.pipes[b.split("_", 1)[1]] = os.pipe()
        retcode = self.runCommands("prehook", branches, serialize)
        for p in [ (k, v) for (k, v) in self.pipes.items() if k != 0 ] :
            os.close(p[1][1])
        if not self.isCancelled and not self.gotSigTerm :
            if self.RealBackend :
                retcode = self.launchOriginalBackend()
                if retcode :
                    onfail = self.getPrintQueueOption(self.PrinterName, \
                                                      "onfail", ignore=1)
                    if onfail :
                        self.logDebug("Launching onfail script %s" % onfail)
                        os.system(onfail)
            if not self.gotSigTerm :
                os.environ["TEASTATUS"] = str(retcode)
                branches = self.enumBranches(self.PrinterName, "posthook")
                if self.runCommands("posthook", branches, serialize) :
                    self.logInfo("An error occured during the execution of posthooks.", "warn")
        for p in [ (k, v) for (k, v) in self.pipes.items() if k != 0 ] :
            os.close(p[1][0])
        signal.signal(signal.SIGTERM, signal.SIG_IGN)
        if not retcode :
            self.logInfo("OK")
        else :
            self.logInfo("An error occured, please check CUPS' error_log file.")
        return retcode

    def stdioRedirSystem(self, cmd, stdin=0, stdout=1) :
        """Launches a command with stdio redirected."""
        # Code contributed by Peter Stuge on May 23rd and June 7th 2005
        pid = os.fork()
        if pid == 0 :
            if stdin != 0 :
                os.dup2(stdin, 0)
                os.close(stdin)
            if stdout != 1 :
                os.dup2(stdout, 1)
                os.close(stdout)
            try :
                os.execl("/bin/sh", "sh", "-c", cmd)
            except OSError, msg :
                self.logDebug("execl() failed: %s" % msg)
            os._exit(-1)
        status = os.waitpid(pid, 0)[1]
        if os.WIFEXITED(status) :
            return os.WEXITSTATUS(status)
        return -1

    def runCommand(self, branch, command) :
        """Runs a particular branch command."""
        # Code contributed by Peter Stuge on June 7th 2005
        self.logDebug("Launching %s : %s" % (branch, command))
        btype, bname = branch.split("_", 1)
        if bname not in self.pipes.keys() :
            bname = 0
        if btype == "prehook" :
            return self.stdioRedirSystem(command, 0, self.pipes[bname][1])
        else :
            return self.stdioRedirSystem(command, self.pipes[bname][0])

    def runCommands(self, btype, branches, serialize) :
        """Runs the commands for a particular branch type."""
        exitcode = 0
        btype = btype.lower()
        btypetitle = btype.title()
        branchlist = branches.keys()
        branchlist.sort()
        if serialize :
            self.logDebug("Begin serialized %ss" % btypetitle)
            for branch in branchlist :
                if self.gotSigTerm :
                    break
                retcode = self.runCommand(branch, branches[branch])
                self.logDebug("Exit code for %s %s on printer %s is %s" % (btype, branch, self.PrinterName, retcode))
                if retcode :
                    if (btype == "prehook") and (retcode == 255) : # -1
                        self.logInfo("Job %s cancelled by prehook %s" % (self.JobId, branch))
                        self.isCancelled = 1
                    else :
                        self.logInfo("%s %s on printer %s didn't exit successfully." % (btypetitle, branch, self.PrinterName), "error")
                        exitcode = 1
            self.logDebug("End serialized %ss" % btypetitle)
        else :
            self.logDebug("Begin forked %ss" % btypetitle)
            pids = {}
            for branch in branchlist :
                if self.gotSigTerm :
                    break
                pid = os.fork()
                if pid :
                    pids[branch] = pid
                else :
                    os._exit(self.runCommand(branch, branches[branch]))
            for (branch, pid) in pids.items() :
                retcode = os.waitpid(pid, 0)[1]
                if os.WIFEXITED(retcode) :
                    retcode = os.WEXITSTATUS(retcode)
                else :
                    retcode = -1
                self.logDebug("Exit code for %s %s (PID %s) on printer %s is %s" % (btype, branch, pid, self.PrinterName, retcode))
                if retcode :
                    if (btype == "prehook") and (retcode == 255) : # -1
                        self.logInfo("Job %s cancelled by prehook %s" % (self.JobId, branch))
                        self.isCancelled = 1
                    else :
                        self.logInfo("%s %s (PID %s) on printer %s didn't exit successfully." % (btypetitle, branch, pid, self.PrinterName), "error")
                        exitcode = 1
            self.logDebug("End forked %ss" % btypetitle)
        return exitcode

    def launchOriginalBackend(self) :
        """Launches the original backend, optionally retrying if needed."""
        number = 1
        delay = 0
        retry = self.getPrintQueueOption(self.PrinterName, "retry", ignore=1)
        if retry is not None :
            try :
                (number, delay) = [int(p) for p in retry.strip().split(",")]
            except (ValueError, AttributeError, TypeError) :    
                self.logInfo("Invalid value '%s' for the 'retry' directive for printer %s in %s." % (retry, self.PrinterName, self.conffile), "error")
                number = 1
                delay = 0
                
        loopcount = 1 
        while 1 :            
            retcode = self.runOriginalBackend()
            if not retcode :
                break
            else :
                if (not number) or (loopcount < number) :
                    self.logInfo("The real backend produced an error, we will try again in %s seconds." % delay, "warn")
                    time.sleep(delay)
                    loopcount += 1
                else :    
                    break
        return retcode            
        
    def runOriginalBackend(self) :
        """Launches the original backend."""
        originalbackend = os.path.join(os.path.split(sys.argv[0])[0], self.RealBackend)
        arguments = [os.environ["DEVICE_URI"]] + sys.argv[1:]
        self.logDebug("Starting original backend %s with args %s" % (originalbackend, " ".join(['"%s"' % a for a in arguments])))

        pid = os.fork()
        if pid == 0 :
            if self.InputFile is None :
                f = open(self.DataFile, "rb")
                os.dup2(f.fileno(), 0)
                f.close()
            else :    
                arguments[6] = self.DataFile # in case a tea4cups filter was applied
            try :
                os.execve(originalbackend, arguments, os.environ)
            except OSError, msg :
                self.logDebug("execve() failed: %s" % msg)
            os._exit(-1)
        killed = 0
        status = -1
        while status == -1 :
            try :
                status = os.waitpid(pid, 0)[1]
            except OSError, (err, msg) :
                if (err == 4) and self.gotSigTerm :
                    os.kill(pid, signal.SIGTERM)
                    killed = 1
        if os.WIFEXITED(status) :
            status = os.WEXITSTATUS(status)
            if status :
                self.logInfo("CUPS backend %s returned %d." % (originalbackend,\
                                                             status), "error")
            return status
        elif not killed :
            self.logInfo("CUPS backend %s died abnormally." % originalbackend,\
                                                              "error")
            return -1
        else :
            return 1

if __name__ == "__main__" :
    # This is a CUPS backend, we should act and die like a CUPS backend
    wrapper = CupsBackend()
    if len(sys.argv) == 1 :
        print "\n".join(wrapper.discoverOtherBackends())
        sys.exit(0)
    elif len(sys.argv) not in (6, 7) :
        sys.stderr.write("ERROR: %s job-id user title copies options [file]\n"\
                              % sys.argv[0])
        sys.exit(1)
    else :
        retcode = 1
        try :
            try :
                wrapper.readConfig()
                wrapper.initBackend()
                wrapper.saveDatasAndCheckSum()
                wrapper.exportAttributes()
                retcode = wrapper.runBranches()
            except SystemExit, e :
                retcode = e.code
            except :
                import traceback
                lines = []
                for line in traceback.format_exception(*sys.exc_info()) :
                    lines.extend([l for l in line.split("\n") if l])
                msg = "ERROR: ".join(["%s (PID %s) : %s\n" % (wrapper.MyName, \
                                                              wrapper.pid, l) \
                            for l in (["ERROR: Tea4CUPS v%s" % __version__] + lines)])
                sys.stderr.write(msg)
                sys.stderr.flush()
                retcode = 1
        finally :        
            wrapper.cleanUp()
        sys.exit(retcode)