root / tea4cups / trunk / tea4cups @ 674

#! /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 pwd
import errno
import md5
import cStringIO
import shlex
import tempfile
import ConfigParser
import signal
from struct import pack, unpack

__version__ = "3.11_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

class IPPRequest :
    """A class for IPP requests.
    
       Usage :
       
         fp = open("/var/spool/cups/c00001", "rb")
         message = IPPRequest(fp.read())
         fp.close()
         message.parse()
         # print message.dump() # dumps an equivalent to the original IPP message
         # print str(message)   # returns a string of text with the same content as below
         print "IPP version : %s.%s" % message.version
         print "IPP operation Id : 0x%04x" % message.operation_id
         print "IPP request Id : 0x%08x" % message.request_id
         for attrtype in message.attributes_types :
             attrdict = getattr(message, "%s_attributes" % attrtype)
             if attrdict :
                 print "%s attributes :" % attrtype.title()
                 for key in attrdict.keys() :
                     print "  %s : %s" % (key, attrdict[key])
         if message.data :            
             print "IPP datas : ", repr(message.data)            
    """
    attributes_types = ("operation", "job", "printer", "unsupported", \
                                     "subscription", "event_notification")
    def __init__(self, data="", version=None, operation_id=None, \
                                              request_id=None, debug=0) :
        """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 = 0
        
        # Initializes message
        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 = (1, 1) # default version number
        self.operation_id = operation_id
        self.request_id = request_id
        self.data = ""
        
        # Initialize attributes mappings
        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.dictags = {}
        for i in range(len(self.tags)) :
            value = self.tags[i]
            if value is not None :
                self.dictags[value] = i
        
    def logDebug(self, msg) :    
        """Prints a debug message."""
        if self.debug :
            sys.stderr.write("%s\n" % msg)
            sys.stderr.flush()
            
    def __str__(self) :        
        """Returns the parsed IPP message in a readable form."""
        if not self.parsed :
            return ""
        else :    
            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 :
                attrdict = getattr(self, "%s_attributes" % attrtype)
                if attrdict :
                    mybuffer.append("%s attributes :" % attrtype.title())
                    for key in attrdict.keys() :
                        mybuffer.append("  %s : %s" % (key, attrdict[key]))
            if self.data :            
                mybuffer.append("IPP datas : %s" % repr(self.data))
            return "\n".join(mybuffer)
        
    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, self.request_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))
            for attrtype in self.attributes_types :
                tagprinted = 0
                for (attrname, value) in getattr(self, "%s_attributes" % attrtype).items() :
                    if not tagprinted :
                        mybuffer.append(chr(self.dictags["%s-attributes-tag" % attrtype]))
                        tagprinted = 1
                    if type(value) != type([]) :
                        value = [ value ]
                    for (vtype, val) in value :
                        mybuffer.append(chr(self.dictags[vtype]))
                        mybuffer.append(pack(">H", len(attrname)))
                        mybuffer.append(attrname)
                        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.dictags["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._curdict = None
        self.version = (ord(self._data[0]), ord(self._data[1]))
        self.operation_id = unpack(">H", self._data[2:4])[0]
        self.request_id = unpack(">I", self._data[4:8])[0]
        self.position = 8
        endofattributes = self.dictags["end-of-attributes-tag"]
        maxdelimiter = self.dictags["event-notification-attributes-tag"]
        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("-", "_"), None)
                    if func is not None :
                        self.position += func()
                        if ord(self._data[self.position]) > maxdelimiter :
                            self.position -= 1
                            continue
                tag = ord(self._data[self.position])
        except IndexError :
            raise IPPError, "Unexpected end of IPP message."
            
        # Now transform all one-element lists into single values
        for attrtype in self.attributes_types :
            attrdict = getattr(self, "%s_attributes" % attrtype)
            for (key, value) in attrdict.items() :
                if len(value) == 1 :
                    attrdict[key] = value[0]
        self.data = self._data[self.position+1:]            
        self.parsed = 1            
        
    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)
        oldval = self._curdict.setdefault(name, [])
        oldval.append((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.logDebug("Start of operation_attributes_tag")
        self._curdict = self.operation_attributes
        return self.parseTag()
        
    def job_attributes_tag(self) : 
        """Indicates that the parser enters into a job-attributes-tag group."""
        self.logDebug("Start of job_attributes_tag")
        self._curdict = self.job_attributes
        return self.parseTag()
        
    def printer_attributes_tag(self) : 
        """Indicates that the parser enters into a printer-attributes-tag group."""
        self.logDebug("Start of printer_attributes_tag")
        self._curdict = self.printer_attributes
        return self.parseTag()
        
    def unsupported_attributes_tag(self) : 
        """Indicates that the parser enters into an unsupported-attributes-tag group."""
        self.logDebug("Start of unsupported_attributes_tag")
        self._curdict = self.unsupported_attributes
        return self.parseTag()
        
    def subscription_attributes_tag(self) : 
        """Indicates that the parser enters into a subscription-attributes-tag group."""
        self.logDebug("Start of subscription_attributes_tag")
        self._curdict = 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.logDebug("Start of event_notification_attributes_tag")
        self._curdict = self.event_notification_attributes
        return self.parseTag()

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."""
        # 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.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.RealBackend = backend
        self.DeviceURI = device_uri
        self.PrinterName = os.environ.get("PRINTER", "")
        self.Directory = self.getPrintQueueOption(self.PrinterName, "directory")
        self.DataFile = os.path.join(self.Directory, "%s-%s-%s-%s" % (self.myname, self.PrinterName, self.UserName, self.JobId))
        (ippfilename, ippmessage) = self.parseIPPRequestFile()
        self.ControlFile = ippfilename
        john = ippmessage.operation_attributes.get("job-originating-host-name", \
               ippmessage.job_attributes.get("job-originating-host-name", \
               (None, None)))
        if type(john) == type([]) :                          
            john = john[-1]
        (chtype, self.ClientHost) = john                          
        (jbtype, self.JobBilling) = ippmessage.job_attributes.get("job-billing", (None, None))

    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)."""
        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)) :
            os.remove(self.DataFile)

    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.runOriginalBackend()
                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 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()
            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 :
        try :
            wrapper.readConfig()
            wrapper.initBackend()
            wrapper.saveDatasAndCheckSum()
            wrapper.exportAttributes()
            retcode = wrapper.runBranches()
            wrapper.cleanUp()
        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
        sys.exit(retcode)