Inital version of PCGI support. Still a bit buggy.

ZServer/ZServerPCGI.py

+##############################################################################
+# 
+# Zope Public License (ZPL) Version 0.9.6
+# ---------------------------------------
+# 
+# Copyright (c) Digital Creations.  All rights reserved.
+# 
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+# 
+# 1. Redistributions in source code must retain the above copyright
+#    notice, this list of conditions, and the following disclaimer.
+# 
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions, and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 
+# 3. Any use, including use of the Zope software to operate a website,
+#    must either comply with the terms described below under
+#    "Attribution" or alternatively secure a separate license from
+#    Digital Creations.  Digital Creations will not unreasonably
+#    deny such a separate license in the event that the request
+#    explains in detail a valid reason for withholding attribution.
+# 
+# 4. All advertising materials and documentation mentioning
+#    features derived from or use of this software must display
+#    the following acknowledgement:
+# 
+#      "This product includes software developed by Digital Creations
+#      for use in the Z Object Publishing Environment
+#      (http://www.zope.org/)."
+# 
+#    In the event that the product being advertised includes an
+#    intact Zope distribution (with copyright and license included)
+#    then this clause is waived.
+# 
+# 5. Names associated with Zope or Digital Creations must not be used to
+#    endorse or promote products derived from this software without
+#    prior written permission from Digital Creations.
+# 
+# 6. Modified redistributions of any form whatsoever must retain
+#    the following acknowledgment:
+# 
+#      "This product includes software developed by Digital Creations
+#      for use in the Z Object Publishing Environment
+#      (http://www.zope.org/)."
+# 
+#    Intact (re-)distributions of any official Zope release do not
+#    require an external acknowledgement.
+# 
+# 7. Modifications are encouraged but must be packaged separately as
+#    patches to official Zope releases.  Distributions that do not
+#    clearly separate the patches from the original work must be clearly
+#    labeled as unofficial distributions.  Modifications which do not
+#    carry the name Zope may be packaged in any form, as long as they
+#    conform to all of the clauses above.
+# 
+# 
+# Disclaimer
+# 
+#   THIS SOFTWARE IS PROVIDED BY DIGITAL CREATIONS ``AS IS'' AND ANY
+#   EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+#   PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DIGITAL CREATIONS OR ITS
+#   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+#   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+#   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+#   USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+#   ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+#   OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+#   OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+#   SUCH DAMAGE.
+# 
+# Attribution
+# 
+#   Individuals or organizations using this software as a web
+#   site ("the web site") must provide attribution by placing
+#   the accompanying "button" on the website's main entry
+#   point.  By default, the button links to a "credits page"
+#   on the Digital Creations' web site. The "credits page" may
+#   be copied to "the web site" in order to add other credits,
+#   or keep users "on site". In that case, the "button" link
+#   may be updated to point to the "on site" "credits page".
+#   In cases where this placement of attribution is not
+#   feasible, a separate arrangment must be concluded with
+#   Digital Creations.  Those using the software for purposes
+#   other than web sites must provide a corresponding
+#   attribution in locations that include a copyright using a
+#   manner best suited to the application environment.  Where
+#   attribution is not possible, or is considered to be
+#   onerous for some other reason, a request should be made to
+#   Digital Creations to waive this requirement in writing.
+#   As stated above, for valid requests, Digital Creations
+#   will not unreasonably deny such requests.
+# 
+# This software consists of contributions made by Digital Creations and
+# many individuals on behalf of Digital Creations.  Specific
+# attributions are listed in the accompanying credits file.
+# 
+##############################################################################
+
+"""First cut at a Medusa PCGI server.
+
+This server functions as the PCGI publisher--it accepts the request
+from the PCGI wrapper CGI program, services the request, and sends
+back the response.
+
+It should work with both inet and unix domain sockets.
+
+Why would you want to use it? Using PCGI to connect to ZServer from
+another webserver is similar to using the web server as a proxy,
+with the difference, that the web server gets to control the 
+environment and headers completely.
+
+Note that ZServer can operate multiple PCGI servers.
+"""
+
+from medusa import asynchat, asyncore, logger
+from medusa.counter import counter
+from medusa.producers import NotReady, hooked_producer
+
+from PubCore import handle
+
+from cStringIO import StringIO
+from tempfile import TemporaryFile
+import socket
+import string
+import os
+
+class PCGIChannel(asynchat.async_chat):    
+    """Processes a PCGI request by collecting the env and stdin and
+    then passing them to ZPublisher. The result is wrapped in a
+    producer and sent back."""
+    
+    def __init__(self,server,sock,addr):
+        self.server = server
+        self.addr = addr
+        asynchat.async_chat.__init__ (self, sock)
+        self.data=StringIO()
+        self.set_terminator(10)
+        self.size=None
+        self.env={}
+        self.done=None
+        
+    def found_terminator(self):
+        if self.size is None:
+            # read the next size header
+            # and prepare to read env or stdin
+            self.data.seek(0)
+            self.size=string.atoi(self.data.read())
+            self.set_terminator(self.size)
+            if self.size==0:
+                self.set_terminator('\r\n') 
+                self.data=StringIO()
+                self.send_response()
+            elif self.size > 1048576:
+                self.data=TemporaryFile('w+b')
+            else:
+                self.data=StringIO()
+        elif not self.env:
+            # read env
+            self.size=None
+            self.data.seek(0)
+            buff=self.data.read()
+            for line in string.split(buff,'\000'):
+                try:
+                    k,v = string.split(line,'=',1)
+                    self.env[k] = v
+                except:
+                    pass
+            # Hack around broken IIS PATH_INFO
+            # maybe, this should go in ZPublisher...      
+            if self.env.has_key('SERVER_SOFTWARE') and \
+                    string.find(self.env['SERVER_SOFTWARE'],
+                    'Microsoft-IIS') != -1:
+                script = filter(None,string.split(
+                        string.strip(self.env['SCRIPT_NAME']),'/'))
+                path = filter(None,string.split(
+                        string.strip(self.env['PATH_INFO']),'/'))
+                self.env['PATH_INFO'] = string.join(path[len(script):],'/')
+            
+            self.data=StringIO()
+            # now read the next size header
+            self.set_terminator(10)
+        else:
+            # we're done, we've got both env and stdin
+            self.set_terminator('\r\n')
+            self.data.seek(0)
+            self.send_response()
+        
+    def send_response(self):
+        # create an output pipe by passing request to ZPublisher,
+        # and requesting a callback of self.log with the module
+        # name and PATH_INFO as an argument.
+        self.done=1        
+        outpipe=handle(self.server.module, self.env, self.data)
+        self.push_with_producer(
+            hooked_producer(PCGIProducer(outpipe), self.log_request)
+            )
+        self.close_when_done()        
+        
+    def collect_incoming_data(self, data):
+        self.data.write(data)
+
+    def readable(self):
+        if not self.done:
+            return 1
+     
+    def log_request(self, bytes):
+        if self.env.has_key('PATH_INFO'):
+            path='%s/%s' % (self.server.module, self.env['PATH_INFO'])
+        else:
+            path='%s/' % self.server.module
+        self.server.logger.log (
+            self.addr[0],
+            '%d - - [time goes here] "%s" %d' % (
+                self.addr[1], path, bytes
+                )
+            )
+
+    def writable(self):
+        return len(self.ac_out_buffer) or self.producer_fifo.ready() \
+            or (not self.connected)
+
+
+class PCGIServer(asyncore.dispatcher):
+    """Accepts PCGI requests and hands them off to the PCGIChannel for
+    handling.
+        
+    PCGIServer can be configured with either a PCGI info file or by
+    directly specifying the module, pid_file, and either port (for
+    inet sockets) or socket_file (for unix domain sockets.)
+
+    For inet sockets, the ip argument specifies the address from which
+    the server will accept connections, '' indicates all addresses. If
+    you only want to accept connections from the localhost, set ip to
+    '127.0.0.1'."""
+        
+    channel_class=PCGIChannel
+
+    def __init__ (self,
+            module='Main',
+            ip='127.0.0.1',
+            port=None,
+            socket_file=None,
+            pid_file=None,
+            pcgi_file=None,
+            resolver=None,
+            logger_object=None):
+
+        self.ip = ip
+        asyncore.dispatcher.__init__(self)
+        self.count=counter()
+        if not logger_object:
+            logger_object = logger.file_logger (sys.stdout)
+        if resolver:
+            self.logger = logger.resolving_logger (resolver, logger_object)
+        else:
+            self.logger = logger.unresolving_logger (logger_object)
+        
+        # get configuration
+        if pcgi_file is None:
+            self.module=module    
+            self.port=port
+            self.pid_file=pid_file
+            self.socket_file=socket_file
+        else:
+            self.read_info(pcgi_file)
+        
+        # write pid file
+        try:
+           f = open(self.pid_file, 'wb')
+           f.write(str(os.getpid()))
+           f.close()
+        except IOError:
+            self.log("Error, cannot write PID file.")
+        
+        # setup sockets
+        if self.port:
+            self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
+            self.set_reuse_addr()
+            self.bind((self.ip, self.port))
+        else:
+            try:
+                os.unlink(self.socket_file)
+            except os.error:
+                pass
+            self.create_socket(socket.AF_UNIX, socket.SOCK_STREAM)
+            self.set_reuse_addr()
+            self.bind(self.socket_file)
+            try:
+                os.chmod(self.socket_file,0777)
+            except os.error:
+                pass
+        self.listen(5)
+
+    def read_info(self,info_file):
+        "read configuration information from a PCGI info file"
+        lines=open(info_file).readlines()
+        directives={}
+        for line in lines:
+            if not len(line) or line[0]=='#':
+                continue
+            k,v=string.split(line,'=',1)
+            directives[string.strip(k)]=string.strip(v)
+        self.pid_file=directives['PCGI_PID_FILE']
+        self.socket_file=directives.get('PCGI_SOCKET_FILE',None)
+        self.port=directives.get('PCGI_PORT',None)
+        if directives.has_key('PCGI_MODULE'):
+            self.module=directives['PCGI_MODULE']
+        else:
+            path=directives['PCGI_MODULE_PATH']
+            path,module=os.path.split(path)
+            module,ext=os.path.splitext(module)
+            self.module=module
+        
+    def handle_accept (self):
+        self.count.increment()
+        try:
+            conn, addr = self.accept()
+        except socket.error:
+            sys.stderr.write('warning: server accept() threw an exception\n')
+            return
+        self.channel_class(self, conn, addr)
+    
+    def writable (self):
+        return 0
+    
+        
+class PCGIProducer:
+    """Producer wrapper over output pipe
+    
+    output format is in PCGI format: 10 digits indicating len of
+    STDOUT followed by STDOUT.
+    
+    Note: no STDERR is returned.
+    Note: streaming is not supported, since PCGI requires the length
+    of the STDOUT be known before it is sent.
+    """
+    
+    def __init__(self,pipe):
+        self.pipe=pipe
+        self.buffer=StringIO()
+        self.buffer.write('0'*10) #this will hold length header
+        self.chunk_size=512
+        self.done=None
+    
+    def ready(self):
+        if self.done:
+            return 1
+        data=self.pipe.read()
+        if data is not None:
+            self.buffer.write(data)
+        if data=='':
+            self.buffer.write('0'*10) #write stderr header
+            self.buffer.seek(0)
+            size=len(self.buffer.getvalue())-20
+            self.buffer.write('%010d' % size)
+            self.buffer.seek(0)
+            self.done=1
+            return 1    
+        
+    def more(self):
+        if not self.done:
+            raise NotReady
+        else:
+            return self.buffer.read(self.chunk_size)
+

lib/python/ZServer/ZServerPCGI.py

+##############################################################################
+# 
+# Zope Public License (ZPL) Version 0.9.6
+# ---------------------------------------
+# 
+# Copyright (c) Digital Creations.  All rights reserved.
+# 
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+# 
+# 1. Redistributions in source code must retain the above copyright
+#    notice, this list of conditions, and the following disclaimer.
+# 
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions, and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 
+# 3. Any use, including use of the Zope software to operate a website,
+#    must either comply with the terms described below under
+#    "Attribution" or alternatively secure a separate license from
+#    Digital Creations.  Digital Creations will not unreasonably
+#    deny such a separate license in the event that the request
+#    explains in detail a valid reason for withholding attribution.
+# 
+# 4. All advertising materials and documentation mentioning
+#    features derived from or use of this software must display
+#    the following acknowledgement:
+# 
+#      "This product includes software developed by Digital Creations
+#      for use in the Z Object Publishing Environment
+#      (http://www.zope.org/)."
+# 
+#    In the event that the product being advertised includes an
+#    intact Zope distribution (with copyright and license included)
+#    then this clause is waived.
+# 
+# 5. Names associated with Zope or Digital Creations must not be used to
+#    endorse or promote products derived from this software without
+#    prior written permission from Digital Creations.
+# 
+# 6. Modified redistributions of any form whatsoever must retain
+#    the following acknowledgment:
+# 
+#      "This product includes software developed by Digital Creations
+#      for use in the Z Object Publishing Environment
+#      (http://www.zope.org/)."
+# 
+#    Intact (re-)distributions of any official Zope release do not
+#    require an external acknowledgement.
+# 
+# 7. Modifications are encouraged but must be packaged separately as
+#    patches to official Zope releases.  Distributions that do not
+#    clearly separate the patches from the original work must be clearly
+#    labeled as unofficial distributions.  Modifications which do not
+#    carry the name Zope may be packaged in any form, as long as they
+#    conform to all of the clauses above.
+# 
+# 
+# Disclaimer
+# 
+#   THIS SOFTWARE IS PROVIDED BY DIGITAL CREATIONS ``AS IS'' AND ANY
+#   EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+#   PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DIGITAL CREATIONS OR ITS
+#   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+#   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+#   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+#   USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+#   ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+#   OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+#   OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+#   SUCH DAMAGE.
+# 
+# Attribution
+# 
+#   Individuals or organizations using this software as a web
+#   site ("the web site") must provide attribution by placing
+#   the accompanying "button" on the website's main entry
+#   point.  By default, the button links to a "credits page"
+#   on the Digital Creations' web site. The "credits page" may
+#   be copied to "the web site" in order to add other credits,
+#   or keep users "on site". In that case, the "button" link
+#   may be updated to point to the "on site" "credits page".
+#   In cases where this placement of attribution is not
+#   feasible, a separate arrangment must be concluded with
+#   Digital Creations.  Those using the software for purposes
+#   other than web sites must provide a corresponding
+#   attribution in locations that include a copyright using a
+#   manner best suited to the application environment.  Where
+#   attribution is not possible, or is considered to be
+#   onerous for some other reason, a request should be made to
+#   Digital Creations to waive this requirement in writing.
+#   As stated above, for valid requests, Digital Creations
+#   will not unreasonably deny such requests.
+# 
+# This software consists of contributions made by Digital Creations and
+# many individuals on behalf of Digital Creations.  Specific
+# attributions are listed in the accompanying credits file.
+# 
+##############################################################################
+
+"""First cut at a Medusa PCGI server.
+
+This server functions as the PCGI publisher--it accepts the request
+from the PCGI wrapper CGI program, services the request, and sends
+back the response.
+
+It should work with both inet and unix domain sockets.
+
+Why would you want to use it? Using PCGI to connect to ZServer from
+another webserver is similar to using the web server as a proxy,
+with the difference, that the web server gets to control the 
+environment and headers completely.
+
+Note that ZServer can operate multiple PCGI servers.
+"""
+
+from medusa import asynchat, asyncore, logger
+from medusa.counter import counter
+from medusa.producers import NotReady, hooked_producer
+
+from PubCore import handle
+
+from cStringIO import StringIO
+from tempfile import TemporaryFile
+import socket
+import string
+import os
+
+class PCGIChannel(asynchat.async_chat):    
+    """Processes a PCGI request by collecting the env and stdin and
+    then passing them to ZPublisher. The result is wrapped in a
+    producer and sent back."""
+    
+    def __init__(self,server,sock,addr):
+        self.server = server
+        self.addr = addr
+        asynchat.async_chat.__init__ (self, sock)
+        self.data=StringIO()
+        self.set_terminator(10)
+        self.size=None
+        self.env={}
+        self.done=None
+        
+    def found_terminator(self):
+        if self.size is None:
+            # read the next size header
+            # and prepare to read env or stdin
+            self.data.seek(0)
+            self.size=string.atoi(self.data.read())
+            self.set_terminator(self.size)
+            if self.size==0:
+                self.set_terminator('\r\n') 
+                self.data=StringIO()
+                self.send_response()
+            elif self.size > 1048576:
+                self.data=TemporaryFile('w+b')
+            else:
+                self.data=StringIO()
+        elif not self.env:
+            # read env
+            self.size=None
+            self.data.seek(0)
+            buff=self.data.read()
+            for line in string.split(buff,'\000'):
+                try:
+                    k,v = string.split(line,'=',1)
+                    self.env[k] = v
+                except:
+                    pass
+            # Hack around broken IIS PATH_INFO
+            # maybe, this should go in ZPublisher...      
+            if self.env.has_key('SERVER_SOFTWARE') and \
+                    string.find(self.env['SERVER_SOFTWARE'],
+                    'Microsoft-IIS') != -1:
+                script = filter(None,string.split(
+                        string.strip(self.env['SCRIPT_NAME']),'/'))
+                path = filter(None,string.split(
+                        string.strip(self.env['PATH_INFO']),'/'))
+                self.env['PATH_INFO'] = string.join(path[len(script):],'/')
+            
+            self.data=StringIO()
+            # now read the next size header
+            self.set_terminator(10)
+        else:
+            # we're done, we've got both env and stdin
+            self.set_terminator('\r\n')
+            self.data.seek(0)
+            self.send_response()
+        
+    def send_response(self):
+        # create an output pipe by passing request to ZPublisher,
+        # and requesting a callback of self.log with the module
+        # name and PATH_INFO as an argument.
+        self.done=1        
+        outpipe=handle(self.server.module, self.env, self.data)
+        self.push_with_producer(
+            hooked_producer(PCGIProducer(outpipe), self.log_request)
+            )
+        self.close_when_done()        
+        
+    def collect_incoming_data(self, data):
+        self.data.write(data)
+
+    def readable(self):
+        if not self.done:
+            return 1
+     
+    def log_request(self, bytes):
+        if self.env.has_key('PATH_INFO'):
+            path='%s/%s' % (self.server.module, self.env['PATH_INFO'])
+        else:
+            path='%s/' % self.server.module
+        self.server.logger.log (
+            self.addr[0],
+            '%d - - [time goes here] "%s" %d' % (
+                self.addr[1], path, bytes
+                )
+            )
+
+    def writable(self):
+        return len(self.ac_out_buffer) or self.producer_fifo.ready() \
+            or (not self.connected)
+
+
+class PCGIServer(asyncore.dispatcher):
+    """Accepts PCGI requests and hands them off to the PCGIChannel for
+    handling.
+        
+    PCGIServer can be configured with either a PCGI info file or by
+    directly specifying the module, pid_file, and either port (for
+    inet sockets) or socket_file (for unix domain sockets.)
+
+    For inet sockets, the ip argument specifies the address from which
+    the server will accept connections, '' indicates all addresses. If
+    you only want to accept connections from the localhost, set ip to
+    '127.0.0.1'."""
+        
+    channel_class=PCGIChannel
+
+    def __init__ (self,
+            module='Main',
+            ip='127.0.0.1',
+            port=None,
+            socket_file=None,
+            pid_file=None,
+            pcgi_file=None,
+            resolver=None,
+            logger_object=None):
+
+        self.ip = ip
+        asyncore.dispatcher.__init__(self)
+        self.count=counter()
+        if not logger_object:
+            logger_object = logger.file_logger (sys.stdout)
+        if resolver:
+            self.logger = logger.resolving_logger (resolver, logger_object)
+        else:
+            self.logger = logger.unresolving_logger (logger_object)
+        
+        # get configuration
+        if pcgi_file is None:
+            self.module=module    
+            self.port=port
+            self.pid_file=pid_file
+            self.socket_file=socket_file
+        else:
+            self.read_info(pcgi_file)
+        
+        # write pid file
+        try:
+           f = open(self.pid_file, 'wb')
+           f.write(str(os.getpid()))
+           f.close()
+        except IOError:
+            self.log("Error, cannot write PID file.")
+        
+        # setup sockets
+        if self.port:
+            self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
+            self.set_reuse_addr()
+            self.bind((self.ip, self.port))
+        else:
+            try:
+                os.unlink(self.socket_file)
+            except os.error:
+                pass
+            self.create_socket(socket.AF_UNIX, socket.SOCK_STREAM)
+            self.set_reuse_addr()
+            self.bind(self.socket_file)
+            try:
+                os.chmod(self.socket_file,0777)
+            except os.error:
+                pass
+        self.listen(5)
+
+    def read_info(self,info_file):
+        "read configuration information from a PCGI info file"
+        lines=open(info_file).readlines()
+        directives={}
+        for line in lines:
+            if not len(line) or line[0]=='#':
+                continue
+            k,v=string.split(line,'=',1)
+            directives[string.strip(k)]=string.strip(v)
+        self.pid_file=directives['PCGI_PID_FILE']
+        self.socket_file=directives.get('PCGI_SOCKET_FILE',None)
+        self.port=directives.get('PCGI_PORT',None)
+        if directives.has_key('PCGI_MODULE'):
+            self.module=directives['PCGI_MODULE']
+        else:
+            path=directives['PCGI_MODULE_PATH']
+            path,module=os.path.split(path)
+            module,ext=os.path.splitext(module)
+            self.module=module
+        
+    def handle_accept (self):
+        self.count.increment()
+        try:
+            conn, addr = self.accept()
+        except socket.error:
+            sys.stderr.write('warning: server accept() threw an exception\n')
+            return
+        self.channel_class(self, conn, addr)
+    
+    def writable (self):
+        return 0
+    
+        
+class PCGIProducer:
+    """Producer wrapper over output pipe
+    
+    output format is in PCGI format: 10 digits indicating len of
+    STDOUT followed by STDOUT.
+    
+    Note: no STDERR is returned.
+    Note: streaming is not supported, since PCGI requires the length
+    of the STDOUT be known before it is sent.
+    """
+    
+    def __init__(self,pipe):
+        self.pipe=pipe
+        self.buffer=StringIO()
+        self.buffer.write('0'*10) #this will hold length header
+        self.chunk_size=512
+        self.done=None
+    
+    def ready(self):
+        if self.done:
+            return 1
+        data=self.pipe.read()
+        if data is not None:
+            self.buffer.write(data)
+        if data=='':
+            self.buffer.write('0'*10) #write stderr header
+            self.buffer.seek(0)
+            size=len(self.buffer.getvalue())-20
+            self.buffer.write('%010d' % size)
+            self.buffer.seek(0)
+            self.done=1
+            return 1    
+        
+    def more(self):
+        if not self.done:
+            raise NotReady
+        else:
+            return self.buffer.read(self.chunk_size)
+