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+"""Base classes for server/gateway implementations"""
+
+from types import StringType
+from util import FileWrapper, guess_scheme, is_hop_by_hop
+from headers import Headers
+
+import sys, os, time
+
+__all__ = ['BaseHandler', 'SimpleHandler', 'BaseCGIHandler', 'CGIHandler']
+
+try:
+ dict
+except NameError:
+ def dict(items):
+ d = {}
+ for k,v in items:
+ d[k] = v
+ return d
+
+# Uncomment for 2.2 compatibility.
+#try:
+# True
+# False
+#except NameError:
+# True = not None
+# False = not True
+
+
+# Weekday and month names for HTTP date/time formatting; always English!
+_weekdayname = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]
+_monthname = [None, # Dummy so we can use 1-based month numbers
+ "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+ "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
+
+def format_date_time(timestamp):
+ year, month, day, hh, mm, ss, wd, y, z = time.gmtime(timestamp)
+ return "%s, %02d %3s %4d %02d:%02d:%02d GMT" % (
+ _weekdayname[wd], day, _monthname[month], year, hh, mm, ss
+ )
+
+
+class BaseHandler:
+ """Manage the invocation of a WSGI application"""
+
+ # Configuration parameters; can override per-subclass or per-instance
+ wsgi_version = (1,0)
+ wsgi_multithread = True
+ wsgi_multiprocess = True
+ wsgi_run_once = False
+
+ origin_server = True # We are transmitting direct to client
+ http_version = "1.0" # Version that should be used for response
+ server_software = None # String name of server software, if any
+
+ # os_environ is used to supply configuration from the OS environment:
+ # by default it's a copy of 'os.environ' as of import time, but you can
+ # override this in e.g. your __init__ method.
+ os_environ = dict(os.environ.items())
+
+ # Collaborator classes
+ wsgi_file_wrapper = FileWrapper # set to None to disable
+ headers_class = Headers # must be a Headers-like class
+
+ # Error handling (also per-subclass or per-instance)
+ traceback_limit = None # Print entire traceback to self.get_stderr()
+ error_status = "500 Internal Server Error"
+ error_headers = [('Content-Type','text/plain')]
+ error_body = "A server error occurred. Please contact the administrator."
+
+ # State variables (don't mess with these)
+ status = result = None
+ headers_sent = False
+ headers = None
+ bytes_sent = 0
+
+ def run(self, application):
+ """Invoke the application"""
+ # Note to self: don't move the close()! Asynchronous servers shouldn't
+ # call close() from finish_response(), so if you close() anywhere but
+ # the double-error branch here, you'll break asynchronous servers by
+ # prematurely closing. Async servers must return from 'run()' without
+ # closing if there might still be output to iterate over.
+ try:
+ self.setup_environ()
+ self.result = application(self.environ, self.start_response)
+ self.finish_response()
+ except:
+ try:
+ self.handle_error()
+ except:
+ # If we get an error handling an error, just give up already!
+ self.close()
+ raise # ...and let the actual server figure it out.
+
+
+ def setup_environ(self):
+ """Set up the environment for one request"""
+
+ env = self.environ = self.os_environ.copy()
+ self.add_cgi_vars()
+
+ env['wsgi.input'] = self.get_stdin()
+ env['wsgi.errors'] = self.get_stderr()
+ env['wsgi.version'] = self.wsgi_version
+ env['wsgi.run_once'] = self.wsgi_run_once
+ env['wsgi.url_scheme'] = self.get_scheme()
+ env['wsgi.multithread'] = self.wsgi_multithread
+ env['wsgi.multiprocess'] = self.wsgi_multiprocess
+
+ if self.wsgi_file_wrapper is not None:
+ env['wsgi.file_wrapper'] = self.wsgi_file_wrapper
+
+ if self.origin_server and self.server_software:
+ env.setdefault('SERVER_SOFTWARE',self.server_software)
+
+
+ def finish_response(self):
+ """Send any iterable data, then close self and the iterable
+
+ Subclasses intended for use in asynchronous servers will
+ want to redefine this method, such that it sets up callbacks
+ in the event loop to iterate over the data, and to call
+ 'self.close()' once the response is finished.
+ """
+ try:
+ if not self.result_is_file() or not self.sendfile():
+ for data in self.result:
+ self.write(data)
+ self.finish_content()
+ finally:
+ self.close()
+
+
+ def get_scheme(self):
+ """Return the URL scheme being used"""
+ return guess_scheme(self.environ)
+
+
+ def set_content_length(self):
+ """Compute Content-Length or switch to chunked encoding if possible"""
+ try:
+ blocks = len(self.result)
+ except (TypeError,AttributeError,NotImplementedError):
+ pass
+ else:
+ if blocks==1:
+ self.headers['Content-Length'] = str(self.bytes_sent)
+ return
+ # XXX Try for chunked encoding if origin server and client is 1.1
+
+
+ def cleanup_headers(self):
+ """Make any necessary header changes or defaults
+
+ Subclasses can extend this to add other defaults.
+ """
+ if 'Content-Length' not in self.headers:
+ self.set_content_length()
+
+ def start_response(self, status, headers,exc_info=None):
+ """'start_response()' callable as specified by PEP 333"""
+
+ if exc_info:
+ try:
+ if self.headers_sent:
+ # Re-raise original exception if headers sent
+ raise exc_info[0], exc_info[1], exc_info[2]
+ finally:
+ exc_info = None # avoid dangling circular ref
+ elif self.headers is not None:
+ raise AssertionError("Headers already set!")
+
+ assert type(status) is StringType,"Status must be a string"
+ assert len(status)>=4,"Status must be at least 4 characters"
+ assert int(status[:3]),"Status message must begin w/3-digit code"
+ assert status[3]==" ", "Status message must have a space after code"
+ if __debug__:
+ for name,val in headers:
+ assert type(name) is StringType,"Header names must be strings"
+ assert type(val) is StringType,"Header values must be strings"
+ assert not is_hop_by_hop(name),"Hop-by-hop headers not allowed"
+ self.status = status
+ self.headers = self.headers_class(headers)
+ return self.write
+
+
+ def send_preamble(self):
+ """Transmit version/status/date/server, via self._write()"""
+ if self.origin_server:
+ if self.client_is_modern():
+ self._write('HTTP/%s %s\r\n' % (self.http_version,self.status))
+ if 'Date' not in self.headers:
+ self._write(
+ 'Date: %s\r\n' % format_date_time(time.time())
+ )
+ if self.server_software and 'Server' not in self.headers:
+ self._write('Server: %s\r\n' % self.server_software)
+ else:
+ self._write('Status: %s\r\n' % self.status)
+
+ def write(self, data):
+ """'write()' callable as specified by PEP 333"""
+
+ assert type(data) is StringType,"write() argument must be string"
+
+ if not self.status:
+ raise AssertionError("write() before start_response()")
+
+ elif not self.headers_sent:
+ # Before the first output, send the stored headers
+ self.bytes_sent = len(data) # make sure we know content-length
+ self.send_headers()
+ else:
+ self.bytes_sent += len(data)
+
+ # XXX check Content-Length and truncate if too many bytes written?
+ self._write(data)
+ self._flush()
+
+
+ def sendfile(self):
+ """Platform-specific file transmission
+
+ Override this method in subclasses to support platform-specific
+ file transmission. It is only called if the application's
+ return iterable ('self.result') is an instance of
+ 'self.wsgi_file_wrapper'.
+
+ This method should return a true value if it was able to actually
+ transmit the wrapped file-like object using a platform-specific
+ approach. It should return a false value if normal iteration
+ should be used instead. An exception can be raised to indicate
+ that transmission was attempted, but failed.
+
+ NOTE: this method should call 'self.send_headers()' if
+ 'self.headers_sent' is false and it is going to attempt direct
+ transmission of the file.
+ """
+ return False # No platform-specific transmission by default
+
+
+ def finish_content(self):
+ """Ensure headers and content have both been sent"""
+ if not self.headers_sent:
+ # Only zero Content-Length if not set by the application (so
+ # that HEAD requests can be satisfied properly, see #3839)
+ self.headers.setdefault('Content-Length', "0")
+ self.send_headers()
+ else:
+ pass # XXX check if content-length was too short?
+
+ def close(self):
+ """Close the iterable (if needed) and reset all instance vars
+
+ Subclasses may want to also drop the client connection.
+ """
+ try:
+ if hasattr(self.result,'close'):
+ self.result.close()
+ finally:
+ self.result = self.headers = self.status = self.environ = None
+ self.bytes_sent = 0; self.headers_sent = False
+
+
+ def send_headers(self):
+ """Transmit headers to the client, via self._write()"""
+ self.cleanup_headers()
+ self.headers_sent = True
+ if not self.origin_server or self.client_is_modern():
+ self.send_preamble()
+ self._write(str(self.headers))
+
+
+ def result_is_file(self):
+ """True if 'self.result' is an instance of 'self.wsgi_file_wrapper'"""
+ wrapper = self.wsgi_file_wrapper
+ return wrapper is not None and isinstance(self.result,wrapper)
+
+
+ def client_is_modern(self):
+ """True if client can accept status and headers"""
+ return self.environ['SERVER_PROTOCOL'].upper() != 'HTTP/0.9'
+
+
+ def log_exception(self,exc_info):
+ """Log the 'exc_info' tuple in the server log
+
+ Subclasses may override to retarget the output or change its format.
+ """
+ try:
+ from traceback import print_exception
+ stderr = self.get_stderr()
+ print_exception(
+ exc_info[0], exc_info[1], exc_info[2],
+ self.traceback_limit, stderr
+ )
+ stderr.flush()
+ finally:
+ exc_info = None
+
+ def handle_error(self):
+ """Log current error, and send error output to client if possible"""
+ self.log_exception(sys.exc_info())
+ if not self.headers_sent:
+ self.result = self.error_output(self.environ, self.start_response)
+ self.finish_response()
+ # XXX else: attempt advanced recovery techniques for HTML or text?
+
+ def error_output(self, environ, start_response):
+ """WSGI mini-app to create error output
+
+ By default, this just uses the 'error_status', 'error_headers',
+ and 'error_body' attributes to generate an output page. It can
+ be overridden in a subclass to dynamically generate diagnostics,
+ choose an appropriate message for the user's preferred language, etc.
+
+ Note, however, that it's not recommended from a security perspective to
+ spit out diagnostics to any old user; ideally, you should have to do
+ something special to enable diagnostic output, which is why we don't
+ include any here!
+ """
+ start_response(self.error_status,self.error_headers[:],sys.exc_info())
+ return [self.error_body]
+
+
+ # Pure abstract methods; *must* be overridden in subclasses
+
+ def _write(self,data):
+ """Override in subclass to buffer data for send to client
+
+ It's okay if this method actually transmits the data; BaseHandler
+ just separates write and flush operations for greater efficiency
+ when the underlying system actually has such a distinction.
+ """
+ raise NotImplementedError
+
+ def _flush(self):
+ """Override in subclass to force sending of recent '_write()' calls
+
+ It's okay if this method is a no-op (i.e., if '_write()' actually
+ sends the data.
+ """
+ raise NotImplementedError
+
+ def get_stdin(self):
+ """Override in subclass to return suitable 'wsgi.input'"""
+ raise NotImplementedError
+
+ def get_stderr(self):
+ """Override in subclass to return suitable 'wsgi.errors'"""
+ raise NotImplementedError
+
+ def add_cgi_vars(self):
+ """Override in subclass to insert CGI variables in 'self.environ'"""
+ raise NotImplementedError
+
+
+class SimpleHandler(BaseHandler):
+ """Handler that's just initialized with streams, environment, etc.
+
+ This handler subclass is intended for synchronous HTTP/1.0 origin servers,
+ and handles sending the entire response output, given the correct inputs.
+
+ Usage::
+
+ handler = SimpleHandler(
+ inp,out,err,env, multithread=False, multiprocess=True
+ )
+ handler.run(app)"""
+
+ def __init__(self,stdin,stdout,stderr,environ,
+ multithread=True, multiprocess=False
+ ):
+ self.stdin = stdin
+ self.stdout = stdout
+ self.stderr = stderr
+ self.base_env = environ
+ self.wsgi_multithread = multithread
+ self.wsgi_multiprocess = multiprocess
+
+ def get_stdin(self):
+ return self.stdin
+
+ def get_stderr(self):
+ return self.stderr
+
+ def add_cgi_vars(self):
+ self.environ.update(self.base_env)
+
+ def _write(self,data):
+ self.stdout.write(data)
+ self._write = self.stdout.write
+
+ def _flush(self):
+ self.stdout.flush()
+ self._flush = self.stdout.flush
+
+
+class BaseCGIHandler(SimpleHandler):
+
+ """CGI-like systems using input/output/error streams and environ mapping
+
+ Usage::
+
+ handler = BaseCGIHandler(inp,out,err,env)
+ handler.run(app)
+
+ This handler class is useful for gateway protocols like ReadyExec and
+ FastCGI, that have usable input/output/error streams and an environment
+ mapping. It's also the base class for CGIHandler, which just uses
+ sys.stdin, os.environ, and so on.
+
+ The constructor also takes keyword arguments 'multithread' and
+ 'multiprocess' (defaulting to 'True' and 'False' respectively) to control
+ the configuration sent to the application. It sets 'origin_server' to
+ False (to enable CGI-like output), and assumes that 'wsgi.run_once' is
+ False.
+ """
+
+ origin_server = False
+
+
+class CGIHandler(BaseCGIHandler):
+
+ """CGI-based invocation via sys.stdin/stdout/stderr and os.environ
+
+ Usage::
+
+ CGIHandler().run(app)
+
+ The difference between this class and BaseCGIHandler is that it always
+ uses 'wsgi.run_once' of 'True', 'wsgi.multithread' of 'False', and
+ 'wsgi.multiprocess' of 'True'. It does not take any initialization
+ parameters, but always uses 'sys.stdin', 'os.environ', and friends.
+
+ If you need to override any of these parameters, use BaseCGIHandler
+ instead.
+ """
+
+ wsgi_run_once = True
+ # Do not allow os.environ to leak between requests in Google App Engine
+ # and other multi-run CGI use cases. This is not easily testable.
+ # See http://bugs.python.org/issue7250
+ os_environ = {}
+
+ def __init__(self):
+ BaseCGIHandler.__init__(
+ self, sys.stdin, sys.stdout, sys.stderr, dict(os.environ.items()),
+ multithread=False, multiprocess=True
+ )