The Hand of FuManChu

Update: I forgot to address buffering.

As I mentioned, I threw together an WSGI wrapper (gateway) for ASP. Here it is. Feedback welcome.

It blanks out SCRIPT_NAME to behave more like Apache. It also handles URL-rewriting, since that's pretty much the only sane way to use ASP with WSGI (or any framework, for that matter).

"""
WSGI wrapper for ASP.


Example Global.asa for a CherryPy app called "mcontrol":

<script language=Python runat=Server> 
def Application_OnStart():
    Application.Contents("multiprocess") = False
    Application.Contents("multithread") = True
    from mcontrol import chpy
</script>


Example handler.asp:

<%@Language=Python%>
<%
from wsgiref.asp_gateway import handler
from cherrypy.wsgiapp import wsgiApp

handler(Application, Request, Response).run(wsgiApp)
%>

"""

import sys
from wsgiref.handlers import BaseCGIHandler


class ASPInputWrapper(object):
    
    def __init__(self, Request):
        self.stream = Request.BinaryRead
        size = Request.ServerVariables('CONTENT_LENGTH')
        self.remainder = self.size = int(size)
    
    def read(self, size=-1):
        if size lt; 0:
            size = self.remainder
        content, size = self.stream(size)
        self.remainder -= size
        return content
    
    def readline(self):
        output = []
        while True:
            # Use an internal buffer instead? Still have to check for \n
            char = self.read(1)
            if not char:
                break
            output.append(char)
            if char in ('\n', '\r'):
                break
        return ''.join(output)
    
    def readlines(self, hint=-1):
        lines = []
        while True:
            line = self.readline()
            if not line:
                break
            lines.append(line)
        return lines
    
    def __iter__(self):
        line = self.readline()
        while line:
            yield line
            # Notice this won't prefetch the next line; it only
            # gets called if the generator is resumed.
            line = self.readline()


class handler(BaseCGIHandler):
    
    def __init__(self, Application, Request, Response, buffering=True):
        # If you set buffering to False, you must not "Enable Buffering" in
        # the current Virtual Directory, NOR in any of its parent containers
        # (directory, site, or server). IIS 5 and 6 buffer by default.
        # See http://support.microsoft.com/default.aspx?scid=kb;en-us;Q306805
        # and http://www.aspfaq.com/show.asp?id=2262
        Response.Buffer = buffering
        
        env = {}
        for name in Request.ServerVariables:
            try:
                # names and values are both probably unicode. coerce them.
                env[str(name)] = str(Request.ServerVariables(name))
            except UnicodeEncodeError, x:
                # There's a potential problem lurking here, since some ASP
                # server var's which are required by WSGI may be high ASCII.
                x.args += ((u"Server Variable '%s'" % name),)
                raise x
        
        multiprocess = str(Application.Contents("multiprocess"))
        multithread = str(Application.Contents("multithread"))
        
        # You will probably need *some* form of rewriter to use ASP
        # with WSGI, since ASP requires one physical .asp file
        # per requestable-URL; so far, we support one:
        
        # Handle URL rewriting done by ISAPI_Rewrite Lite.
        # http://www.isapirewrite.com/
        # Note that PATH_TRANSLATED is also rewritten, but we
        # don't make any provision for unmunging that.
        old_path = env.get("HTTP_X_REWRITE_URL", None)
        if old_path:
            # Tear off any params.
            env["PATH_INFO"] = old_path.split("?")[0]
        
        # ASP puts the same values in SCRIPT_NAME and PATH_INFO,
        # for some odd reason. Empty one of them.
        env["SCRIPT_NAME"] = ""
        
        BaseCGIHandler.__init__(self,
                                stdin=ASPInputWrapper(Request),
                                stdout=None,
                                stderr=sys.stderr,
                                environ=env,
                                multiprocess=multiprocess,
                                multithread=multithread
                                )
        
        self.Response = Response
        self._write = Response.Write
    
    def _flush(self):
        self.Response.Flush()
    
    def send_headers(self):
        self.cleanup_headers()
        self.headers_sent = True
        for key, val in self.headers.items():
            self.Response.AddHeader(key, val)