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""" |
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An implementation of PEP 333: Python Web Server Gateway Interface (WSGI). |
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""" |
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import os, threading |
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from zope.interface import implements |
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from twisted.internet import defer, threads |
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from twisted.internet import reactor |
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from twisted.python import log, failure |
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from twisted.web2 import http |
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from twisted.web2 import iweb |
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from twisted.web2 import server |
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from twisted.web2 import stream |
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from twisted.web2.twcgi import createCGIEnvironment |
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class AlreadyStartedResponse(Exception): |
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pass |
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class WSGIResource(object): |
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""" |
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A web2 Resource which wraps the given WSGI application callable. |
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The WSGI application will be called in a separate thread (using |
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the reactor threadpool) whenever a request for this resource or |
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any lower part of the url hierarchy is received. |
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""" |
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implements(iweb.IResource) |
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def __init__(self, application): |
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self.application = application |
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def renderHTTP(self, req): |
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handler = WSGIHandler(self.application, req) |
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d = handler.responseDeferred |
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reactor.callInThread(handler.run) |
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return d |
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def locateChild(self, request, segments): |
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return self, server.StopTraversal |
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class InputStream(object): |
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""" |
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This class implements the 'wsgi.input' object. The methods are |
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expected to have the same behavior as the same-named methods for |
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python's builtin file object. |
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""" |
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def __init__(self, newstream): |
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self.stream = stream.BufferedStream(newstream) |
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def read(self, size=None): |
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""" |
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Read at most size bytes from the input, or less if EOF is |
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encountered. If size is ommitted or negative, read until EOF. |
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""" |
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if size < 0: |
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size = None |
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return threads.blockingCallFromThread( |
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reactor, self.stream.readExactly, size) |
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def readline(self, size=None): |
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""" |
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Read a line, delimited by a newline. If the stream reaches EOF |
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or size bytes have been read before reaching a newline (if |
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size is given), the partial line is returned. |
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COMPATIBILITY NOTE: the size argument is excluded from the |
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WSGI specification, but is provided here anyhow, because |
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useful libraries such as python stdlib's cgi.py assume their |
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input file-like-object supports readline with a size |
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argument. If you use it, be aware your application may not be |
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portable to other conformant WSGI servers. |
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""" |
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if size < 0: |
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size = None |
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return threads.blockingCallFromThread( |
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reactor, self.stream.readline, '\n', size=size) |
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def readlines(self, hint=None): |
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""" |
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Read until EOF, collecting all lines in a list, and returns |
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that list. The hint argument is ignored (as is allowed in the |
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API specification) |
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""" |
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data = self.read() |
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lines = data.split('\n') |
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last = lines.pop() |
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lines = [s+'\n' for s in lines] |
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if last != '': |
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lines.append(last) |
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return lines |
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def __iter__(self): |
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""" |
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Returns an iterator, each iteration of which returns the |
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result of readline(), and stops when readline() returns an |
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empty string. |
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""" |
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while 1: |
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line = self.readline() |
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if not line: |
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return |
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yield line |
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class ErrorStream(object): |
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""" |
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This class implements the 'wsgi.error' object. |
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""" |
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def flush(self): |
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return |
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def write(self, s): |
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log.msg("WSGI app error: "+s, isError=True) |
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def writelines(self, seq): |
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s = ''.join(seq) |
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log.msg("WSGI app error: "+s, isError=True) |
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class WSGIHandler(object): |
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headersSent = False |
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stopped = False |
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stream = None |
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def __init__(self, application, request): |
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self.setupEnvironment(request) |
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self.application = application |
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self.request = request |
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self.response = None |
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self.responseDeferred = defer.Deferred() |
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def setupEnvironment(self, request): |
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env = createCGIEnvironment(request) |
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env['wsgi.version'] = (1, 0) |
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env['wsgi.url_scheme'] = env['REQUEST_SCHEME'] |
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env['wsgi.input'] = InputStream(request.stream) |
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env['wsgi.errors'] = ErrorStream() |
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env['wsgi.multithread'] = True |
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env['wsgi.multiprocess'] = False |
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env['wsgi.run_once'] = False |
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env['wsgi.file_wrapper'] = FileWrapper |
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self.environment = env |
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def startWSGIResponse(self, status, response_headers, exc_info=None): |
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if exc_info is not None: |
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try: |
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if self.headersSent: |
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raise exc_info[0], exc_info[1], exc_info[2] |
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finally: |
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exc_info = None |
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elif self.response is not None: |
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raise AlreadyStartedResponse, 'startWSGIResponse(%r)' % status |
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status = int(status.split(' ')[0]) |
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self.response = http.Response(status) |
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for key, value in response_headers: |
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self.response.headers.addRawHeader(key, value) |
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return self.write |
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def run(self): |
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try: |
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result = self.application(self.environment, self.startWSGIResponse) |
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self.handleResult(result) |
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except: |
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if not self.headersSent: |
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reactor.callFromThread(self.__error, failure.Failure()) |
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else: |
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reactor.callFromThread(self.stream.finish, failure.Failure()) |
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def __callback(self): |
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self.responseDeferred.callback(self.response) |
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self.responseDeferred = None |
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def __error(self, f): |
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self.responseDeferred.errback(f) |
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self.responseDeferred = None |
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def write(self, output): |
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if self.response is None: |
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raise RuntimeError( |
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"Application didn't call startResponse before writing data!") |
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if not self.headersSent: |
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self.stream=self.response.stream=stream.ProducerStream() |
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self.headersSent = True |
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self.unpaused = threading.Event() |
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def _start(): |
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self.stream.registerProducer(self, True) |
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self.__callback() |
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self.unpaused.set() |
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reactor.callFromThread(_start) |
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self.unpaused.wait() |
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reactor.callFromThread(self.stream.write, output) |
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def writeAll(self, result): |
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if not self.headersSent: |
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if self.response is None: |
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raise RuntimeError( |
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"Application didn't call startResponse before writing data!") |
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l = 0 |
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for item in result: |
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l += len(item) |
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self.response.stream=stream.ProducerStream(length=l) |
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self.response.stream.buffer = list(result) |
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self.response.stream.finish() |
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reactor.callFromThread(self.__callback) |
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else: |
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def _write(): |
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for s in result: |
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self.stream.write(s) |
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self.stream.finish() |
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reactor.callFromThread(_write) |
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def handleResult(self, result): |
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try: |
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if (isinstance(result, FileWrapper) and |
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hasattr(result.filelike, 'fileno') and |
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not self.headersSent): |
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if self.response is None: |
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raise RuntimeError( |
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"Application didn't call startResponse before writing data!") |
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self.headersSent = True |
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self.response.stream = stream.FileStream( |
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os.fdopen(os.dup(result.filelike.fileno()))) |
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reactor.callFromThread(self.__callback) |
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return |
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if type(result) in (list,tuple): |
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self.writeAll(result) |
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return |
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for data in result: |
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if self.stopped: |
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return |
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self.write(data) |
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if not self.headersSent: |
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if self.response is None: |
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raise RuntimeError( |
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"Application didn't call startResponse, and didn't send any data!") |
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self.headersSent = True |
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reactor.callFromThread(self.__callback) |
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else: |
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reactor.callFromThread(self.stream.finish) |
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finally: |
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if hasattr(result,'close'): |
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result.close() |
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def pauseProducing(self): |
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self.unpaused.set() |
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def resumeProducing(self): |
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self.unpaused.clear() |
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def stopProducing(self): |
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self.stopped = True |
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class FileWrapper(object): |
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""" |
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Wrapper to convert file-like objects to iterables, to implement |
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the optional 'wsgi.file_wrapper' object. |
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""" |
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def __init__(self, filelike, blksize=8192): |
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self.filelike = filelike |
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self.blksize = blksize |
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if hasattr(filelike,'close'): |
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self.close = filelike.close |
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def __iter__(self): |
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return self |
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def next(self): |
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data = self.filelike.read(self.blksize) |
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if data: |
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return data |
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raise StopIteration |
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__all__ = ['WSGIResource'] |
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